Retinoschisis is an uncommon eye disease characterized by the abnormal splitting of the retina's sensory layers, usually in the outer plexiform layer, with resulting loss of visual function.[1] The retina, which consists of multiple layers of interconnected nerve and pigment cells, separates into separate layers resulting in a loss of vision in the corresponding visual field.
It is estimated that retinoschisis affects one in 5,000 to 25,000 individuals, primarily young males. "Schisis" is derived from the Greek word meaning "splitting," describing the splitting of the retinal layers from each other. If the retinoschisis involves the macula, then the high-resolution central area of vision used to view detail is lost, and this one form of macular degeneration. Treatment is often aimed at restricting any worsening of the separation so that it does not encroach on the macula.
Retinoschisis can be caused by an X-linked genetic defect, affecting the vision of men who inherit the disease from their unaffected carrier mothers. The genetic form of this disease usually starts during childhood and is called Juvenile X-linked Retinoschisis. Affected males are usually identified in grade school, but occasionally are identified as young infants. Senile retinoschisis, on the other hand, is the splitting of the retina as a result of aging. It can affect both men and women and is not a genetic condition.
Very few affected individuals go completely blind from retinoschisis, but some sufferers have very limited reading vision and are "legally blind". Visual acuity can be reduced to less than 20/200 in both eyes.
Retinoschisis causes acuity loss in the center of the visual field through the formation of tiny cysts in the retina, often forming a "spoke-wheel" pattern that can be very subtle. The cysts are usually only detectable by a trained clinician. Vision cannot be improved by glasses, as the nerve tissue itself is damaged by these cysts. Furthermore, peripheral vision can be lost due to the splitting of the inner layer of nerve cells from the outer layer of cells.
If the anchoring of the outer layer of the retina to the eye wall is impaired, retinal detachments can occur. Retinal detachments can be treated surgically when detected early, but the root cause - the splitting of the retina - cannot be corrected by current medications or surgeries. Since retinoschisis can be confused with other eye diseases such as lazy eye, it is important that a thorough exam be done by an ophthalmologist to ensure that retinal detachment is not overlooked.
[edit] References
1. ^ Cassin, B. and Solomon, S. Dictionary of Eye Terminology. Gainsville, Florida: Triad Publishing Company, 1990.
* http://www.kellogg.umich.edu/patientcare/conditions/retinoschisis.html
* http://www.mrcophth.com/retinacases/retinoschisis.html
Tuesday, April 3, 2007
All About Retinoschisis
All About Retinal detachment
Retinal detachment is a disorder of the eye in which the retina peels away from its underlying layer of support tissue. Initial detachment may be localized, but without rapid treatment the entire retina may detach, leading to vision loss and blindness. It is a medical emergency. [1]
The retina is a thin disc-shaped layer of light-sensitive tissue on the back wall of the eye. Its job is to translate what we see into neural impulses and send them to the brain via the optic nerve. Occasionally, injury or trauma to the eye or head may cause a small tear in the retina, which allows fluid to seep through, and peel it away like a bubble in wallpaper.
Types
* Rhegmatogenous retinal detachment - A rhegmatogenous retinal detachment occurs due to a hole, tear, or break in the retina that allows fluid to pass into the subretinal space between the sensory retina and the retinal pigment epithelium.
* Exudative, serous, or secondary retinal detachment - An exudative retinal detachment occurs due to inflammation, injury or vascular abnormalities that results in fluid accumulating underneath the retina without the presence of a hole, tear, or break.
* Tractional retinal detachment - A tractional retinal detachment occurs when fibrovascular tissue, caused by an injury, inflammation or neovascularization, pulls the sensory retina from the retinal pigment epithelium.
Prevalence
The risk of retinal detachment in otherwise normal eyes is around 5 in 100,000 per year.[2] Detachment is more frequent in the middle-aged or elderly population with rates of around 20 in 100,000 per year [1]. The lifetime risk in normal eyes is about 1 in 300 [2].
* Retinal detachment is more common in those with severe or extreme myopia (above 5-6 diopters), as their eyes are longer and the retina is stretched thin. The lifetime risk increases to 1 in 20 [3]. Myopia is associated with 67% of retinal detachment cases. Patients suffering from a detachment related to myopia tend to be younger than non-myopic detachment patients.
* Retinal detachment can occur more frequently after surgery for cataracts. The estimate of risk of retinal detachment after cataract surgery is 5 to 16 per 1000 cataract operations.[4]. The risk may be much higher in those who are highly myopic, with a frequency of 7% reported in one study [5]. Young age at cataract removal further increased risk in this study.
* Tractional retinal detachments can also occur in patients with proliferative diabetic retinopathy [6]or those with proliferative retinopathy of sickle cell disease [7]. In proliferative retinopathy, abnormal blood vessels (neovascularization) grow within the retina and extend into the vitreous. In advanced disease, the vessels can pull the retina away from the back wall of the eye causing a traction retinal detachment.
Although retinal detachment usually occurs in one eye, there is a 15% chance of developing it in the other eye, and this risk increases to 25-30% in patients who had cataracts extracted from both eyes [8].
Symptoms
A retinal detachment is commonly preceded by a posterior vitreous detachment which gives rise to these symptoms:
* flashes of light (photopsia) - very brief in the extreme temporal (outside away from the nose) part of vision
* a sudden dramatic increase in the number of floaters
* a ring of floaters or hairs just to the temporal side of the central vision
* a slight feeling of heaviness in the eye
Although most posterior vitreous detachments do not progress to retinal detachments, those that do produce the following symptoms:
* a dense shadow that starts in the peripheral vision and slowly progresses towards the central vision
* the impression that a veil or curtain was drawn over the field of vision
* straight lines (scale, edge of the wall, road, etc.) that suddenly appear curved (positive Amsler grid test)
* central visual loss
Treatment
There are several methods of treating a detached retina which all depend on finding and closing the holes (tears) which have formed in the retina.
* Cryopexy and Laser Photocoagulation
Cryotherapy (freezing) and laser photocoagulation are treatments used to create a scar/adhesion around the retinal hole to prevent fluid from entering the hole and accumulating behind the retina and excacerbating the retinal detachment. Cryopexy and photocoagulation are generally interchangeable. However, cryopexy is generally used in instances where there is a lot of fluid behind the hole;laser retinopexy will not take.
* Scleral buckle surgery
Scleral buckle surgery is an established treatment in which the eye surgeon sews one or more silicone bands (bands , tyres) to the outside of the eyeball. The bands push the wall of the eye inward against the retinal hole, closing the hole and allowing the retina to re-attach. The bands do not usually have to be removed. The most common side effect of a scleral operation is myopic shift. The operated eye generally will be 3-5 diopters more near sighted after the scleral buckle operation.
* Pneumatic retinopexy
This operation is generally performed in the doctor's office under local anesthesia. It is another method of repairing a retinal detachment in which a gas bubble ( SF6 or C3F8 gas ) is injected into the eye after laser or freezing treatment is applied to surround the retinal hole. The patient's head is then positioned so that the bubble rests against the retinal hole. Patients may have to keep their heads tilted for several days to keep the gas bubble in contact with the retinal hole. The surface tension of the air/water interface seals the hole in the retina, and allows the retinal pigment epithelium to pump the subretinal space dry and pull the retina back into place. This strict positioning requirement makes the treatment of the retinal holes and detachments that occurs in the lower part of the eyeball impractical.
* Vitrectomy
Vitrectomy is an increasingly widely used treatment for retinal detachment in countries with modern healthcare systems. It involves the removal of the vitreous gel and is usually combined with filling the eye with a gas bubble (SF6 or C3F8 gas). Advantages of this operation is that there is no myopic shift after the operation. A disadvantage is that a vitrectomy always leads to more rapid progression of a cataract in the operated eye. Another major disadvantage of the operation is that , should a vitrectomy operation fail to work, the recurrent retinal detachment is much harder to repair. As such, except for special instances, the vitrectomy operation is not usually used as the initial operation to attempt to repair a rhegmatogenous retinal detachment.
* Ignipuncture
Ignipuncture is an outdated procedure that involves cauterization of the retina with a very hot pointed instrument.[3] It was pioneered and named by Jules Gonin in the early 1900s.[3]
After treatment, patients gradually regain their vision over a period of a few weeks, although the visual acuity may not be as good as it was prior to the detachment, particularly if the macula was involved in the area of the detachment. However, if left untreated, total blindness can occur in a matter of days.
Prevention
Retinal detachment can be prevented in some. The most effective way of preventing retinal detachment is educating people to seek ophthalmic medical attention if they suffer symptoms suggestive of a posterior vitreous detachment [9]. Early examination allows detection of retinal tears which can be treated with laser or cryotherapy. This reduces the risk of retinal detachment in those who have tears from around 1:3 to 1:20.
There are some known risk factors for retinal detachment. There are also many activities which at one time or another have been forbidden to those at risk of retinal detachment, with varying degrees of evidence supporting the restrictions.
Cataract surgery is a major cause, and can result in detachment even a long time after the operation. The risk is increased if there are complications during cataract surgery, but remains even in apparently uncomplicated surgery. The increasing rates of cataract surgery, and decreasing age at cataract surgery, will inevitably lead to an increased incidence of retinal detachment.
Trauma is a less frequent cause. Activities which cause direct trauma to the eye (boxing, kick-boxing, karate and others) can cause a particular type of retinal tear called a retinal dialysis. This type of tear can be detected and treated before it develops into a retinal detachment. For this reason governing bodies in some of these sports require regular ophthalmic examination.
Individuals prone to retinal detachment due to a high level of myopia are encouraged to avoid activities where there is a risk of shock to the head or eyes, although without direct trauma to the eye the evidence base for this may not be convincing [4]. Some doctors recommend avoiding activities that increase pressure in the eye, including diving, skydiving, again with little supporting evidence. Retinal detachment does not happen as a result of straining your eyes, bending or heavy lifting.[5] Therefore, heavy weightlifting is fine.
Activities that involve sudden acceleration or deceleration also increase eye pressure and are discouraged by some doctors. These include bungee jumping,[4] but may also include rollercoaster rides.
References
1. ^ Retinal detachment. MedlinePlus Medical Encyclopedia. National Institutes of Health (2005). Retrieved on 2006-07-18.
2. ^ Ivanisevic M, Bojic L, Eterovic D. "Epidemiological study of nontraumatic phakic rhegmatogenous retinal detachment." Ophthalmic Res. 2000 Sep-Oct;32(5):237-9. PMID 10971186.
3. ^ a b Wolfensberger TJ. "Jules Gonin. Pioneer of retinal detachment surgery." Indian J Ophthalmol. 2003 Dec;51(4):303-8. PMID 14750617.
4. ^ a b http://www.emedicine.com/emerg/topic504.htm
5. ^ http://www.rnib.org.uk/xpedio/groups/public/documents/PublicWebsite/public_rnib003661.hcsp
See also
* Lattice degeneration
* Retinoschisis
All About Cataracts
A cataract is an opacity that develops in the crystalline lens of the eye or in its envelope. Early on in the development of senile cataract the power of the crystaline lens may be increased, causing myopia, and the gradual yellowing and opacification of the lens may reduce the perception of blue colours. Cataracts typically progress slowly to cause vision loss and are potentially blinding if untreated.[1] Moreover, with time the cataract cortex liquefies to form a milky white fluid in a Morgagnian Cataract, and can cause severe inflammation if the lens capsule ruptures and leaks. Untreated, the cataract can cause phacomorphic glaucoma. Very advanced cataracts with weak zonules are liable to dislocation anteriorly or posteriorly. Such spontaneous posterior dislocations (akin to the earliest surgical procedure of couching) in ancient times were regarded as a blessing from the heavens, because it restored some perception of light in the bilaterally affected patients.
Cataract derives from the Latin cataracta meaning "waterfall" and the Greek kataraktes and katarrhaktes, from katarassein meaning "to dash down" (kata-, "down"; arassein, "to strike, dash"[2]). As rapidly running water turns white, the term may later have been used metaphorically to describe the similar appearance of mature ocular opacities. In Latin, cataracta had the alternate meaning, "portcullis"[3], so it is also possible that the name came about through the sense of "obstruction".
Causes
Normal vision. Courtesy National Institutes of Health, USA (NIH).
Normal vision. Courtesy National Institutes of Health, USA (NIH).
Hazy view as seen by a person with a cataract, Courtesy NIH
Hazy view as seen by a person with a cataract, Courtesy NIH
Cataracts develop from a variety of reasons, including long-term ultraviolet exposure, secondary effects of diseases such as diabetes, or simply due to advanced age; they are usually a result of denaturation of lens proteins. Genetic factors are often a cause of congenital cataracts and positive family history may also play a role in predisposing someone to cataracts at an earlier age, a phenomenon of "anticipation" in pre-senile cataracts. Cataracts can also be produced by eye injury or physical trauma. A study among Icelandair pilots showed commercial airline pilots as three times more likely to develop cataracts than people with non-flying jobs. This is thought to be caused by excessive exposure to radiation coming from outer space.[4] Cataracts are also unusually common in persons exposed to infrared radiation, such as glassblowers who suffer from "exfoliation syndrome". Exposure to microwave radiation can cause cataracts.
Cataracts may be partial or complete, stationary or progressive, hard or soft.
Some drugs can induce cataract development:
* Corticosteroids[5]
* Ezetimibe
There are various types of cataracts, e.g. nuclear, cortical, mature, hypermature. Cataracts are also classified by their location, e.g. posterior (classically due to steroid use[5][6]) and anterior (common (senile) cataract related to aging).
Epidemiology
Cataracts are the leading cause of blindness in the world.[7]
In the United States, age-related lenticular changes have been reported in 42% of those between the ages of 52 to 64[8], 60% of those between the ages 65 and 74[9], and 91% of those between the ages of 75 and 85[8].
Cataract surgery
Main article: Cataract surgery
Cataract surgery, using a temporal approach phacoemulsification probe (in right hand) and "chopper"(in left hand) being done under operating microscope at a Navy medical center
The most effective and common treatment is to surgically remove the cloudy lens. There are two types of surgery that can be used to remove cataracts, extra-capsular (extracapsular cataract extraction, or ECCE) and intra-capsular surgery (intracapsular cataract extraction, or ICCE). Extra-capsular surgery consists of removing the lens but leaving the majority of the lens capsule intact. High frequency sound waves (phacoemulsification) are sometimes used to break up the lens before extraction. Intra-capsular surgery involves removing the entire lens of the eye, including the lens capsule, but it is rarely performed in modern practice. In either extra-capsular surgery or intra-capsular surgery, the cataractous lens is removed and replaced with a plastic lens (an intraocular lens implant) which stays in the eye permanently.
Cataract operations are usually performed using a local anaesthetic and the patient will be allowed to go home the same day. Recent improvements in intraocular technology now allow cataract patients to choose a multifocal lens to create a visual environment where they are less dependent on glasses. Traditional intraocular lenses were monofocal. Medicare has allowed physicians, for the first time, to bill patients for this advanced lens design.
Complications after cataract surgery, including posterior capsular opacification and retinal detachment, are possible.
In ICCE there is the issue of the Jack in the box Phenomenon where the patient has to wear aphakic glasses...alternatives include contact lenses but these can prove to be high maintainance in dusty areas, which can lead to the complications of contact lenses.
Prevention
Although cataracts have no scientifically proven prevention, it is sometimes said that wearing ultraviolet-protecting sunglasses may slow the development of cataracts.[citation needed] Regular intake of antioxidants (such as vitamin C and E) is theoretically helpful, but this is also not proven.
Recent research
Although statins are known for their ability to lower lipids, they are also believed to have antioxidant qualities. It is believed that oxidative stress plays a role in the development of nuclear cataracts, which are the most common type of age-related cataract. To explore the relationship between nuclear cataracts and statin use, a group of researchers took a group of 1299 patients who were at risk of developing nuclear cataracts and gave some of them statins. Their results suggest that statin use in a general population may be associated with a lower risk of developing nuclear cataract. [10]
Types of cataracts
Bilateral cataracts in an infant due to Congenital rubella syndrome, courtesy CDC
The following is a classification of the various types of cataracts. This is not comprehensive and other unusual types may be noted.
* Classified by etiology
* Age-related cataract
* Immature Senile Cataract (IMSC) - partially opaque lens, disc view hazy
* Mature Senile Cataract (MSC) - Completely opaque lens, no disc view
* Hypermature Senile Cataract (HMSC) - Liquefied cortical matter: Morgagnian Cataract
* Congenital cataract
* Sutural cataract
* Lamellar cataract
* Zonular cataract
* Total cataract
* Secondary cataract
Slit lamp photo of Anterior capsular opacification visible few months after implantation of Intraocular lens in eye, magnified view
Slit lamp photo of Anterior capsular opacification visible few months after implantation of Intraocular lens in eye, magnified view
* Drug-induced cataract (e.g. Corticosteroids)
* Traumatic cataract
* Blunt trauma (capsule usually intact)
* Penetrating trauma (capsular rupture & leakage of lens material - calls for an emergency surgery for extraction of lens and leaked material to minimise further damage)
* Classified by location of opacity within lens structure (However, mixed morphology is quite commonly seen, e.g. PSC with nuclear changes & cortical spokes of cataract)
* Anterior cortical cataract
* Anterior polar cataract
* Anterior subcapsular cataract
Slit lamp photo of Posterior capsular opacification visible few months after implantation of Intraocular lens in eye, seen on retroillumination
Slit lamp photo of Posterior capsular opacification visible few months after implantation of Intraocular lens in eye, seen on retroillumination
* Nuclear cataract - Grading correlates with hardness & difficulty of surgical removal
* 1 - Grey
* 2 - Yellow
* 3 - Amber
* 4 - Brown/Black (Note: "Black cataract" translated in some languages (like Hindi) refers to Glaucoma, not the color of the lens nucleus)
* Posterior cortical cataract
* Posterior polar cataract (importance lies in higher risk of complication - posterior capuslar tears during surgery)
* Posterior subcapsular cataract (PSC) (clinically common)
* After-cataract - posterior capsular opacification subsequent to a successful extracapsular cataract surgery (usually within 3 months - 2 years) with or without IOL implantation. Requires a quick & painless office procedure with Nd:YAG laser capsulotomy to restore optical clarity.
Associations with systemic conditions
* Chromosomal disorders
* Alport's syndrome
* Cri-du-chat syndrome
* Conradi's syndrome
* Myotonia dystrophica
* Patau's syndrome
* Schmid-Fraccaro syndrome
* Trisomy 18 (Edward's syndrome)
* Turner's syndrome
* Disease of the skin and mucous membranes
* Atopic dermatitis
* Basal-cell nevus syndrome
* Ichthyosis
* Pemphigus
* Metabolic and nutrition diseases
* Aminoaciduria (Lowe's syndrome)
* Diabetes mellitus
* Fabry's disease
* Galactosemia
* Homocystinuria
* Hypervitaminosis D
* Hyperparathyroidism
* Hypothyroidism
* Mucopolysaccharidoses
* Wilson's disease
* Infectious diseases
* Congenital
* Congential herpes simplex
* Congenital syphilis
* Cytomegalic inclusion disease
* Rubella
* Others
* Cysticercosis
* Leprosy
* Onchocerciasis
* Toxoplasmosis
* Toxic substances introduced systemically
* Corticosteroids
* Haloperidol
* Miotics
* Triparanol
References
1. ^ http://www.aafp.org/afp/990700ap/99.html
2. ^ http://dictionary.reference.com/wordoftheday/archive/2003/10/29.html]
3. ^ http://www.etymonline.com/index.php?term=cataract
4. ^ Rafnsson, V; Olafsdottir E, Hrafnkelsson J, Sasaki H, Arnarsson A, Jonasson F. "Cosmic radiation increases the risk of nuclear cataract in airline pilots: a population-based case-control study". Arch Ophthalmol 123: 1102-1105.
5. ^ a b SPENCER R, ANDELMAN S. "STEROID CATARACTS. POSTERIOR SUBCAPSULAR CATARACT FORMATION IN RHEUMATOID ARTHRITIS PATIENTS ON LONG TERM STEROID THERAPY". Arch Ophthalmol 74: 38-41. PMID 14303339.
6. ^ Greiner J, Chylack L (1979). "Posterior subcapsular cataracts: histopathologic study of steroid-associated cataracts". Arch Ophthalmol 97 (1): 135-44. PMID 758890.
7. ^ https://web.emmes.com/study/areds/mopfiles/chp2_mop.pdf
8. ^ a b Sperduto RD, Seigel D. Sperduto RD, Seigel D. "Senile lens and senile macular changes in a population-based sample." Am J Ophthalmol. 1980 Jul;90(1):86-91. PMID 7395962.
9. ^ Kahn HA, Leibowitz HM, Ganley JP, Kini MM, Colton T, Nickerson RS, Dawber TR. "The Framingham Eye Study. I. Outline and major prevalence findings." Am J Epidemiol. 1977 Jul;106(1):17-32. PMID 879158.
10. ^ Klein, Barbara; Ronald Klein, Kristine Lee, and Lisa Grady. "Statin Use and Incident Nuclear Cataract". Journal of the American Medical Association 295 (23): 2752-2758.
* Pavan-Langston, Deborah (1990). Manual of Ocular Diagnosis and Therapy. Little, Brown and Company.
See also
* List of eye diseases and disorders
* List of systemic diseases with ocular manifestations
All About Uveitis
Uveitis specifically refers to inflammation of the middle layer of the eye, termed the "uvea" but in common usage may refer to any inflammatory process involving the interior of the eye.
Uveitis is estimated to be responsible for approximately 10% of the blindness in the United States.[citation needed] Uveitis requires an urgent referral and thorough examination by an optometrist or an ophthalmologist, along with urgent treatment to control the inflammation.
Types
Uveitis is usually categorized anatomically into anterior, intermediate, posterior and panuveitic forms.
* Anywhere from two-thirds to 90% of uveitis cases are anterior in location (anterior uveitis), frequently termed iritis - or inflammation of the iris and anterior chamber. This condition can occur as a single episode and subside with proper treatment or may take on a recurrent or chronic nature. Symptoms include red eye, injected conjunctiva, pain and decreased vision. Signs include dilated ciliary vessels, presence of cells and flare in the anterior chamber, and keratic precipitates ("KP") on the posterior surface of the cornea.
* Intermediate uveitis consists of vitritis - inflammatory cells in the vitreous cavity, sometimes with snowbanking, or deposition of inflammatory material on the pars plana.
* Posterior uveitis is the inflammation of the retina and choroid.
* Pan-uveitis is the inflammation of all the layers of the uvea.
Causes
A myriad of conditions can lead to the development of uveitis, including systemic diseases as well as syndromes confined to the eye. In anterior uveitis, no specific diagnosis is made in approximately one-half of cases. However, anterior uveitis is often one of the syndromes associated with HLA-B27.
Systemic disorders causing uveitis
Systemic disorders that can cause uveitis include: White G. "Uveitis." AllAboutVision.com. Retrieved August 20, 2006.
* Acute posterior multifocal placoid pigment epitheliopathy
* Ankylosing spondylitis
* Behçet's disease
* Birdshot retinochoroidopathy
* Brucellosis
* Herpes simplex
* Herpes zoster
* Inflammatory bowel disease
* Juvenile rheumatoid arthritis
* Kawasaki's disease
* Leptospirosis
* Lyme disease
* Multiple sclerosis
* Presumed ocular histoplasmosis syndrome
* Psoriatic arthritis
* Reiter's syndrome
* Sarcoidosis
* Syphilis
* Systemic lupus erythematosus
* Toxocariasis
* Toxoplasmosis
* Tuberculosis
* Vogt-Koyanagi-Harada syndrome
Masquerade syndromes
Masquerade syndromes are ophthalmic disorders that clinically present as either an anterior or posterior uveitis, but are not primarily inflammatory. The following are some of the most common:
* Anterior segment
* Intraocular foreign body
* Juvenile xanthogranuloma
* Leukemia
* Malignant melanoma
* Retinoblastoma
* Retinal detachment
* Posterior segment
* Lymphoma
* Malignant melanoma
* Multiple sclerosis
* Reticulum cell sarcoma
* Retinitis pigmentosa
* Retinoblastoma
Symptoms
* Redness of the eye
* Blurred vision
* Sensitivity to light
* Dark, floating spots along the visual field
* Eye pain
Treatment
The prognosis is generally good for those who receive prompt diagnosis and treatment, but serious complication (including cataracts, glaucoma, band keratopathy, retinal edema and permanent vision loss) may result if left untreated. The type of uveitis, as well as its severity, duration, and responsiveness to treatment or any associated illnesses, all factor in to the outlook.[1]
Uveitis is typically treated with glucocorticoid steroids, either as topical eye drops (such as betamethasone, dexamethasone or prednisolone) or oral therapy with prednisolone tablets. In addition topical cycloplegics, such as atropine or homatropine, may be used.[1]
Antimetabolite medications, such as methotrexate are often used for recalcitrant or more aggressive cases of uveitis. Experimental treatment with Infliximab infusions may prove helpful.
See also
* List of eye diseases and disorders
* List of systemic diseases with ocular manifestations
* intermediate Uveitis
Footnotes
1. ^ BNF 45 March 2003
All About Iritis
Iritis is a form of anterior uveitis and refers to the inflammation of the iris of the eye.
Types
There are two main types of iritis, which are called acute iritis and chronic iritis. Acute iritis is a type of iritis that can heal independantly within a few weeks. If treatment is provided, acute iritis improves quickly. Chronic iritis can exist for months or years before recovery occurs. Chronic iritis does not respond to treatment as well as acute iritis does. Chronic iritis is also accompanied by a higher risk of serious visual impairment.
Signs and symptoms
* Ocular and periorbital pain
* Photophobia
* Consensual photophobia (pain in affected eye when light is shone in unaffected eye)
* Blurred or cloudy vision
* White blood cells (leukocytes) (resulting in a grey or near-white haze) and protein (resulting in tiny white dots) in the anterior chamber, often called "cells and flare."
* Synechia or adhesion of iris to lens or cornea
Causes
People with ankylosing spondylitis and other HLA-B27 related disorders are prone to iritis, iridocyclitis, and other forms of uveal tract inflammation. Iritis is also found in those with rheumatoid arthritis, Behcet's disease, Crohn's disease, lupus, Reiter's disease, chronic psoriasis, psoriatic arthritis, sarcoidosis, scleroderma, and ulcerative colitis. Iritis is usually secondary to some other systemic condition, but can be the only apparent somatic symptom.
Complications
Complications of iritis may include the following: Cataract, glaucoma, corneal calcification, posterior uveitis, blindness, band keratopathy, and cystoid macular oedema.
Treatment
* Steroid anti-inflammatory eye drops (such as prednisolone acetate)
* Dilating eye drops (to help prevent synechia and reduce photophobia)
* Pressure-reducing eye drops (such as brimonidine tartrate)
* Oral steroids (such as prednisone)
* Subconjunctival steroid injections
* Steroid-sparing agents such as methotrexate (for prolonged, chronic iritis)
References
* Care of the Patient with Anterior Uveitis (CPG7) (PDF)
* Iritis Organization
* Assessment of the Red Eye - Iritis
* Medical Info on Iritis
All About Keratoconjunctivitis sicca
Keratoconjunctivitis sicca (KCS), also called keratitis sicca,[1] sicca syndrome,[1] xerophthalmia,[1] dry eye syndrome (DES),[1] or simply dry eyes,[1] is an eye disease caused by decreased tear production or increased tear film evaporation commonly found in humans and some animals[2]. Keratoconjunctivitis sicca is Latin and its literal translation is "dryness of the cornea and conjunctiva".
Symptoms
Typical symptoms of keratoconjunctivitis are dryness, burning[3] and a sandy-gritty eye irritation that gets worse as the day goes on.[1] Symptoms may also be described as itchy,[3] scratchy,[4] stingy[3] or tired[3] eyes. Other symptoms are pain,[5] redness,[5] a pulling sensation,[3] and pressure behind the eye[3]. There may be a feeling that something,[3] such as a speck of dirt,[5] is in the eye. The resultant damage to the eye surface increases discomfort and sensitivity to bright light.[3] Both eyes usually are affected.[6]
There may also be a stringy discharge from the eyes.[5] Although it may seem strange, dry eye can cause the eyes to water.[5] This can happen because the eyes are irritated.[5] One may experience excessive tearing in the same way as one would if something got into the eye.[5] These reflex tears will not necessarily make the eyes feel better.[5] This is because they are the watery type that are produced in response to injury, irritation, or emotion.[5] They do not have the lubricating qualities necessary to prevent dry eye.[5]
Because blinking coats the eye with tears,[5] symptoms are worsened by activities in which the rate of blinking is reduced due to prolonged use of the eyes[3]. These activities include prolonged reading,[1] computer usage,[1][5][3] driving,[3] or watching television[5][3]. Symptoms increase in windy,[5] dusty[5][3] or smoky (including cigarette smoke[5]) areas,[1][3] in dry environments[1][3], high altitudes including airplanes,[6] on days with low humidity,[3] and in areas where an air conditioner[5] (especially in a car[3]), fan,[3] heater,[3] or even a hair dryer[5] is being used. Symptoms reduce during cool, rainy, or foggy weather and in humid places, such as in the shower.[3]
Most people who have dry eyes experience mild irritation with no long-term effects.[5] However, if the condition is left untreated or becomes severe, it can produce complications that can cause eye damage,[5] resulting in impaired vision or (rarely[3]) in the loss of vision[5].
Symptom assessment is a key component of dry eye diagnosis - to the extent that many believe dry eye syndrome to be a symptom-based disease. Several questionnaires have been developed to determine a score that would allow for dry eye diagnosis. McMonnies & Ho dry eye questionnaire is the one that is often used in clinical studies of dry eyes. There are 14 questions that can give a score from 0 to 45. Scores above 14.5 are consistent with dry eye diagnosis.
Pathophysiology
Having dry eyes for a while can lead to tiny abrasions on the surface of the eyes.[4] In advanced cases, the epithelium undergoes pathologic changes, namely squamous metaplasia and loss of goblet cells.[1] Some severe cases result in thickening of the corneal surface,[3] corneal erosion,[1] punctate keratopathy,[1] epithelial defects,[1] corneal ulceration (sterile and infected),[1] corneal neovascularization,[1] corneal scarring,[1][3] corneal thinning,[1] and even corneal perforation[1].
Causes
Any abnormality of any one of the three layers of tears produces an unstable tear film, resulting in symptoms of keratitis sicca.[1]
Deficient tear production
Keratoconjunctivitis sicca is usually due to inadequate tear production.[1][3] The aqueous tear layer is affected, resulting in aqueous tear deficiency (ATD) or lacrimal hyposecretion.[1] The lacrimal gland does not produce sufficient tears to keep the entire conjunctiva and cornea covered by a complete layer.[3] This usually occurs in people who are otherwise healthy. Increased age is associated with decreased tearing.[1] This is the most common type found in postmenopausal women.[3][7]
Causes include idiopathic, congenital alacrima, xerophthalmia, lacrimal gland ablation, and sensory denervation.[1] In rare cases, it may be a symptom of collagen vascular diseases, including rheumatoid arthritis[3], Wegener's granulomatosis, and systemic lupus erythematosus.[1] Sjögren's syndrome[3] and autoimmune diseases associated with Sjögren's syndrome are also conditions associated with aqueous tear deficiency.[1] Drugs such as isotretinoin,[3] sedatives,[3][6] diuretics,[3] tricyclic antidepressants,[6] antihypertensives,[3] oral contraceptives,[1][3] antihistamines,[1][5][3] nasal decongestants,[5] beta-blockers,[1] phenothiazines,[1] atropine,[1], and pain relieving opiates such as morphine[6] can cause or worsen this condition. Infiltration of the lacrimal glands by sarcoidosis or tumors, or postradiation fibrosis of the lacrimal glands can also cause this condition.[1]
Abnormal tear composition
Keratoconjunctivitis sicca can also be caused by abnormal tear composition resulting in rapid evaporation[3] or premature destruction of the tears.[1] When caused by rapid evaporation, it is termed evaporative dry eyes.[3] In this, although the tear gland produces a sufficient amount of tears, the rate of evaporation of the tears is too rapid.[3] There is a loss of water from the tears that results in tears that are too "salty" or hypertonic. As a result, the entire conjunctiva and cornea cannot be kept covered with a complete layer of tears during certain activities or in certain environments.[3]
Additional causes
Aging is one of the most common causes of dry eyes.[5] This is because tear production decreases with age.[5] It may be caused by thermal or chemical burns, or (in epidemic cases) by adenoviruses. A number of studies have found that diabetics are at increased risk for the disease.[8][9]
An eye injury or other problem with the eyes or eyelids, such as bulging eyes or a drooping eyelid can cause keratoconjunctivitis sicca.[4] Disorders of the eyelid can impair the complex blinking motion required to spread tears.[6]
About half of all people who wear contact lenses complain of dry eyes.[5] This is because soft contact lenses, which float on the tear film that covers the cornea, absorb the tears in the eyes.[5] Dry eyes also occurs or gets worse after LASIK and other refractive surgeries, in which the corneal nerves are cut during the creation of a corneal flap.[5] The corneal nerves stimulate tear secretion.[5] Dry eyes caused by these procedures usually resolves after several months.[6] Persons who are thinking about refractive surgery should consider this.[5]
Abnormalities of the lipid tear layer caused by blepharitis and rosacea, and abnormalities of the mucin tear layer caused by vitamin A deficiency, trachoma, diphtheric keratoconjunctivitis, mucocutaneous disorders and certain topical medications are causes of keratoconjunctivitis sicca.[1]
Persons with keratoconjunctivitis sicca have elevated levels of tear nerve growth factor (NGF).[1] It is possible that this ocular surface NGF plays an important role in ocular surface inflammation associated with dry eyes.[1]
Diagnosis
Dry eyes can usually be diagnosed by the symptoms alone.[3] Tests can determine both the quantity and the quality of the tears.[6] A slit lamp examination can be performed to diagnose dry eyes and to document any damage to the eye.[1][3]
A Schirmer's test can measure the amount of moisture bathing the eye.[3] This test is useful for determining the severity of the condition.[5] A five-minute Schirmer's test with and without anesthesia using a Whatman #41 filter paper 5 mm wide by 35 mm long is performed.[1] For this test, wetting under 5 mm with or without anesthesia is considered diagnostic for dry eyes.[1]
If the results for the Schirmer's test are abnormal, a Schirmer II test can be performed to measure reflex secretion.[1] In this test, the nasal mucosa is irritated with a cotton-tipped applicator, after which tear production is measured with a Whatman #41 filter paper.[1] For this test, wetting under 15 mm after five minutes is considered abnormal.[1]
A tear breakup time (TBUT) test measures the time it takes for tears to break up in the eye.[5] The tear breakup time can be determined after placing a drop of fluorescein in the cul-de-sac.[1]
A tear protein analysis test measures the lysozyme contained within tears.[1] In tears, lysozyme accounts for approximately 20 to 40 percent of total protein content.[1]
A lactoferrin analysis test provides good correlation with other tests.[1]
Recently it was described a molecule - Ap4A- which is intrinsic component of the tears. The presence of this molecule is abnormally high in different states of the ocular dryness. This molecule could quantifyied biochemically simply taking one tear sample with a plain Schirmer test. Utilizing this technique is possible to determine the concentrations of Ap4A in the tear of the patients and such way to diagnose in an objective way if the samples are corresponding to dry eye[10].
Treatment
Purposefully blinking more often, and resting the eyes are basic steps one can take.[4] Rubbing one's eyes can irritate them further, so it should be avoided.[6] Persons with dry eyes caused by an eyelid disorder should undergo treatment for the underlying condition.[6]
Rehydration
For mild and moderate cases, supplemental lubrication is the most important part of treatment.[1]
Artificial tears
Main article: Artificial tears
Application of artificial tears every few hours[3] can provide temporary relief.
Additional options
Lubricating tear ointments can be used during the day, but they generally are used at bedtime due to poor vision after application.[1] They contain white petrolatum, mineral oil, and similar lubricants.[1] They serve as a lubricant and an emollient.[1] Application requires pulling down the eyelid and applying a small amount (0.25 in) inside.[1] Depending on the severity of the condition, it may be applied from every hour to just at bedtime.[1] It should not be used with contact lenses.[1]
Environmental control
Avoiding dry or drafty environments, or environments with smoke and dust may help.[3] This also includes avoiding environmental aggravation caused by hair dryers, heaters, air conditioners or fans, especially when directed toward the eyes.[6] Wearing wraparound glasses when outside can help reduce the drying effects of the wind.[6]
Using a humidifier,[3][4] especially in the winter,[4] adds moisture[6] to dry indoor air. Specially designed glasses that form a moisture chamber around the eye may be used to create additional humidity.[6]
Supplementation
Consumption of dietary omega-3 fatty acids is associated with a decreased incidence of dry eyes syndrome in women.[11] This finding is consistent with postulated biological mechanisms.[11]
Medication
Inflammation occurring in response to tears film hypertonicity can be suppressed by mild topical steroids or with topical immunosuppressants such as ciclosporin.[12][13] Elevated levels of tear NGF can be decreased with 0.1% prednisolone.[1]
Restasis
Topical ciclosporin A (tCSA) 0.05% ophthalmic emulsion, marketed in the United States by Allergan under the trade name Restasis[1], is the only prescription product for chronic dry eyes.[5] Approved by the U.S. Food and Drug Administration in 2002,[5] the drug decreases inflammation[6] on the eye surface. It increases healthy tear production,[6] which may be reduced because of inflammation on the eye surface.[5] In a clinical trial involving 1,200 individuals, Restasis increased tear production in 15 percent of patients, compared with 5 percent of patients in the placebo group.[5]
Usually, 1 gtt of Restasis is applied twice a day, 12 hours apart.[1] It should not be used when wearing contact lenses,[1] or by persons with eye infections[5] or hypersensitivity[5] to the ingredients. It has not been tested in people with herpes viral infections of the eye,[5] and it should not be used by anyone with a history[6] of such an infection. The most common side effect is a burning sensation.[5] Other side effects may be eye redness, discharge, watery eyes, eye pain, foreign body sensation, itching, stinging, and blurred vision.[1][5]
Generic alternatives
Cheaper generic alternatives to Restasis are available in some countries. In India, it is marketed as Cyclomune by Sun Pharma.[14]
Conserving tears
There are methods that allow both natural and artificial tears to stay longer.[6]
Blocking tear drainage
In each eye, there are two puncta[15] — little openings that drain tears into the tear ducts[5]. There are methods to partially or completely close the tear ducts.[6] This blocks the flow of tears into the nose, and thus more tears are available to the eyes.[3]
Punctal plugs
Punctal plugs are inserted into the puncta to block tear drainage.[5] For people who have not found dry eye relief with drugs, punctal plugs may help.[5] They are reserved for people with moderate or severe dry eye when other medical treatment has not been adequate.[5]
A temporary punctal occlusion can be inserted and tried first.[1][5] These are made of collagen and are dissolvable.[1][5] This is to ascertain that permanent ones will not cause excessive tearing.[5]
Permanent punctal plugs are usually made of silicone.[5] Some plugs are made of thermally reactive material.[5] Some of these are inserted into the punctum as a liquid and then they harden and conform to the individual's drainage system.[5] Others start out rigid and become soft and flexible, adapting to the individual's punctal size after they are inserted.[5]
Artificial tears are usually still required after punctal plug insertion.[5]
The risks of punctal plugs are fairly minimal.[5] There is a risk of eye irritation, excessive tearing, and, in rare cases, infection.[5]
Cauterization
If punctal plugs are effective, thermal[6] or electric[1] cauterization of puncti can be performed.
In thermal cauterization, a local anesthetic is used, and then a hot wire is applied.[6] This shrinks the drainage area tissues and causes scarring, which closes the tear duct.[6]
Customized contact lenses
Persons with severe dry eyes may benefit from the Boston Scleral Lens which is a customized contact lense.[6] Resting on the sclera, it creates a fluid filled layer over the cornea, thus preventing it from drying.[6]
Surgery
In severe cases of keratoconjunctivitis sicca, the eyelids may be partially sewn together to reduce tear evaporation.[3]
Prognosis
Keratoconjunctivitis sicca usually is a chronic problem.[6] Its prognosis shows considerable variance, depending upon the severity of the condition.[1] Most patients have mild-to-moderate cases, and can be treated symptomatically with lubricants.[1] This provides an adequate relief of symptoms.[1]
When dry eyes symptoms are severe, they can interfere with quality of life.[5] People sometimes feel their vision blurs with use,[3] or severe irritation[3] to the point that they have trouble keeping their eyes open[5] or they may not be able to work or drive[5].
Prevention
There is no way to prevent keratoconjunctivitis sicca.[16] Complications can be prevented by use of wetting and lubricating drops and ointments.[16]
Epidemiology
Keratoconjunctivitis sicca is relatively common within the United States, especially so in older patients.[1] Specifically, the persons most likely to be affected by dry eyes are those aged 40 or older.[6]
While persons with autoimmune diseases have a have a high likelihood of having dry eyes, most persons with dry eyes do not have an autoimmune disease.[6] Instances of Sjögren syndrome and keratoconjunctivitis sicca associated with it are present much more commonly in women, with a ratio of 9:1.[1] In addition, milder forms of keratoconjunctivitis sicca also are more common in women.[1] This is partly because hormonal changes,[6] such as those that occur in pregnancy, menstruation, and menopause,[6] can decrease tear production.[5]
In areas of the world where malnutrition is common, vitamin A deficiency is a common cause.[16] This is rare in the United States.[16]
Racial predilections do not exist for this disease.[1]
Occurrence in animals
Among animals, keratoconjunctivitis sicca occurs in dogs, cats, and horses.[2]
Dogs
Keratoconjunctivitis sicca is common in dogs. Most cases are caused by a genetic predisposition, but chronic conjunctivitis, canine distemper, and drugs such as sulfasalazine and trimethoprim-sulfonamide also cause the disease.[17] Symptoms include eye redness, a yellow or greenish discharge, ulceration of the cornea, pigmented cornea, and blood vessels on the cornea. Diagnosis is made by measuring tear production with a Schirmer tear test. Less than 15 millimeters of tears produced in a minute is abnormal.[17]
Tear replacers are a mainstay of treatment, preferably containing methylcellulose or carboxymethyl cellulose.[17] Ciclosporin stimulates tear production and acts as a suppressant on the immune-mediated processes that cause the disease. Topical antibiotics and corticosteroids are sometimes used to treat secondary infections and inflammation. A surgery known as parotid duct transposition is used in some extreme cases where medical treatment has not helped. This redirects the duct from the parotid salivary gland to the eye. Saliva replaces the tears. Dogs suffering from cherry eye should have the condition corrected to help prevent this disease.
Commonly affected breeds include:
* Cavalier King Charles Spaniel
* English Bulldog
* Chinese Shar-Pei
* Lhasa Apso
* Shih Tzu
* West Highland White Terrier
* Pug
* Bloodhound
* Cocker Spaniel
* Pekingese
* Boston Terrier
* Miniature Schnauzer
* Samoyed[17]
Cats
Keratoconjunctivitis sicca is uncommon in cats. Most cases seem to be caused by chronic conjunctivitis, especially secondary to feline herpesvirus.[17] Diagnosis, symptoms, and treatment are similar to those for dogs.
See also
* Keratoconjunctivitis
* List of eye diseases and disorders
References
1. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao ap aq ar as at au av aw ax ay az ba bb bc bd be bf bg bh bi bj bk bl bm bn bo bp Keratoconjunctivitis, Sicca. eMedicine. WebMD, Inc. (2006-04-21). Retrieved on 2006-11-12.
2. ^ a b Keratoconjunctivitis, Sicca. The Merck Veterinary Manual. Merck & Co., Inc.. Retrieved on 2006-11-18.
3. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao ap aq ar as at au av Keratoconjunctivitis Sicca. The Merck Manual, Home Edition. Merck & Co., Inc. (2003-02-01). Retrieved on 2006-11-12.
4. ^ a b c d e f Dry eyes. MedlinePlus Medical Encyclopedia. U.S. National Library of Medicine (2006-10-04). Retrieved on 2006-11-16.
5. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao ap aq ar as at au av aw ax ay az ba bb bc bd be bf bg Meadows, Michelle (May-June 2005). Dealing with Dry Eye. FDA Consumer Magazine. U.S. Food and Drug Administration. Retrieved on 2006-11-16.
6. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac Dry eyes. Mayo Clinic. Mayo Foundation for Medical Education and Research (2006-06-14). Retrieved on 2006-11-17.
7. ^ Sendecka M, Baryluk A, Polz-Dacewicz M (2004). "Prevalence and risk factors of dry eye syndrome". Przegl Epidemiol 58 (1): 227-33. PMID 15218664.
8. ^ Kaiserman I, Kaiserman N, Nakar S, Vinker S (2005). "Dry eye in diabetic patients.". Am J Ophthalmol 139 (3): 498-503. PMID 15767060.
9. ^ Li H, Pang G, Xu Z (2004). "Tear film function of patients with type 2 diabetes". Zhongguo Yi Xue Ke Xue Yuan Xue Bao 26 (6): 682-6. PMID 15663232.
10. ^ A. Peral, G. Carracedo, M.C. Acosta, J. Gallar, J. Pintor."Increasing Levels of Diadenosine Polyphosphates in Dry Eye" (2006)Invest.Ophthalmol. Vis. Sci.47 (9):4053–4058 http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?CMD=search&DB=pubmed]
11. ^ a b Miljanović B, Trivedi K, Dana M, Gilbard J, Buring J, Schaumberg D (2005). "Relation between dietary n-3 and n-6 fatty acids and clinically diagnosed dry eye syndrome in women.". Am J Clin Nutr 82 (4): 887-93. PMID 16210721.
12. ^ Tatlipinar S, Akpek E (2005). "Topical ciclosporin in the treatment of ocular surface disorders.". Br J Ophthalmol 89 (10): 1363-7. PMID 16170133.
13. ^ Barber L, Pflugfelder S, Tauber J, Foulks G (2005). "Phase III safety evaluation of cyclosporine 0.1% ophthalmic emulsion administered twice daily to dry eye disease patients for up to 3 years.". Ophthalmology 112 (10): 1790-4. PMID 16102833.
14. ^ Sun Pharma Product List. Sun Pharma. Retrieved on 2006-11-27.
15. ^ Dry eye syndrome. Health encyclopaedia. NHS Direct (2006-04-10). Retrieved on 2007-02-26.
16. ^ a b c d Dry eyes syndrome. MedlinePlus Medical Encyclopedia. U.S. National Library of Medicine (2006-10-04). Retrieved on 2006-11-16.
17. ^ a b c d e Gelatt, Kirk N. (ed.) (1999). Veterinary Ophthalmology, 3rd ed., Lippincott, Williams & Wilkins. ISBN 0-683-30076-8.
Further reading
* The Dry Eye: A Practical Approach, by Sudi Patel, Kenny Blades, 2003, Butterworth-Heinemann, ISBN 0-7506-4978-X
* Dry Eye Disease: The Clinician's Guide to Diagnosis And Treatment, by Penny A. Asbell, Michael A. Lemp, 2006, Thieme Medical Publishers, ISBN 1-58890-412-1
Monday, April 2, 2007
All About Keratoconus
Keratoconus (from Greek: kerato- horn, cornea; and konos cone), is a degenerative non-inflammatory disorder of the eye in which structural changes within the cornea cause it to thin and change to a more conical shape than its normal gradual curve. Keratoconus can cause substantial distortion of vision, with multiple images, streaking and sensitivity to light all often reported by the patient. Keratoconus is the most common dystrophy of the cornea, affecting around one person in a thousand, and it seems to occur in all ethnic groups worldwide, although for some groups the prevalence of keratoconus is greater than others. It is typically diagnosed in the patient's adolescent years and attains its most severe state in the twenties and thirties.
Keratoconus is a little-understood disease with an uncertain cause, and its progression following diagnosis is unpredictable. If afflicting both eyes, the deterioration in vision can affect the patient's ability to drive a car or read normal print. It does not however lead to blindness, and in most cases, corrective lenses are effective enough to allow the patient to continue to drive legally and likewise function normally. Further progression of the disease may lead to a need for surgery. Despite its uncertainties, keratoconus can be successfully managed with a variety of clinical and surgical techniques, and often with little or no impairment to the patient's quality of life.
In a 1748 doctoral dissertation, the German oculist Burchard Mauchart provided an early description of a case of keratoconus, which he called staphyloma diaphanum. However, it was not until 1854 that British physician John Nottingham clearly described keratoconus and distinguished it from other ectasias of the cornea.[1] Nottingham reported the cases of "conical cornea" that had come to his attention, and described several classic features of the disease, including polyopia, weakness of the cornea, and difficulty matching corrective lenses to the patient's vision. In 1859 British surgeon William Bowman used an ophthalmoscope (recently invented by German physician and physicist Hermann von Helmholtz) to diagnose keratoconus, and described how to angle the instrument's mirror so as to best see the conical shape of the cornea.[2] Bowman also attempted to restore the vision by pulling on the iris with a fine hook inserted through the cornea and stretching the pupil into a vertical stenopeic slit like that of a cat. He reported that he had had a measure of success with the technique, restoring vision to an 18-year old woman who had previously been unable to count fingers at a distance of 8 inches (20 cm). By 1869, when the pioneering Swiss ophthalmologist Johann Horner wrote a thesis entitled On the treatment of keratoconus,[3] the disorder had acquired its current name. The treatment at that time, endorsed by the leading German ophthalmologist Albrecht von Gräfe, was an attempt to physically reshape the cornea by chemical cauterization with a silver nitrate solution and application of a miosis-causing agent with a pressure dressing. In 1888 the treatment of keratoconus became one of the first practical applications of the then newly-invented contact lens, when the French physician Eugène Kalt manufactured a glass scleral shell which improved vision by compressing the cornea into a more regular shape.[4] Since the start of the twentieth century, research on keratoconus has both improved understanding of the disease and greatly expanded the range of treatment options.
Features
Symptoms
A simulation of the multiple images seen by a person with keratoconus. "... a candle, when looked at, appears like a number of lights, confusedly running into one another" — Nottingham
A simulation of the multiple images seen by a person with keratoconus.
"... a candle, when looked at, appears like a number of lights, confusedly running into one another" — Nottingham[1]
People with early keratoconus typically notice a minor blurring of their vision and come to their clinician seeking corrective lenses for reading or driving. At early stages, the symptoms of keratoconus may be no different from those of any other refractive defect of the eye. As the disease progresses, vision deteriorates, sometimes rapidly. Visual acuity becomes impaired at all distances, and night vision is often quite poor. Some individuals have vision in one eye that is markedly worse than that in the other eye. Some develop photophobia (sensitivity to bright light), eye strain from squinting in order to read, or itching in the eye. There is usually little or no sensation of pain.
The classic symptom of keratoconus is the perception of multiple 'ghost' images, known as monocular polyopia. This effect is most clearly seen with a high contrast field, such as a point of light on a dark background. Instead of seeing just one point, a person with keratoconus sees many images of the point, spread out in a chaotic pattern. This pattern does not typically change from day to day, but over time it often takes on new forms. Patients also commonly notice streaking and flaring distortion around light sources. Some even notice the images moving relative to one another in time with their heart beat.
Signs and diagnosis
Prior to any physical examination, the diagnosis of keratoconus frequently begins with an ophthalmologist's or optometrist's assessment of the patient's medical history, particularly the chief complaint and other visual symptoms, the presence of any history of ocular disease or injury which might affect vision, and the presence of any family history of ocular disease. An eye chart, such as a standard Snellen chart of progressively smaller letters, is then used to determine the patient's visual acuity. The eye examination may proceed to measurement of the localised curvature of the cornea with a manual keratometer,[5] with detection of irregular astigmatism suggesting a possibility of keratoconus. Severe cases can exceed the instrument's measuring ability. A further indication can be provided by retinoscopy, in which a light beam is focused on the patient's retina and the reflection, or reflex, observed as the examiner tilts the light source back and forth. Keratoconus is amongst the ophthalmic conditions that exhibit a scissor reflex action of two bands moving toward and away from each other like the blades of a pair of scissors.[6]
If keratoconus is suspected, the ophthalmologist or optometrist will search for other characteristic findings of the disease by means of slit lamp examination of the cornea. An advanced case is usually readily apparent to the examiner, and can provide for an unambiguous diagnosis prior to more specialised testing. Under close examination, a ring of yellow-brown to olive-green pigmentation known as a Fleischer ring can be observed in around half of keratoconic eyes.[7] The Fleischer ring, caused by deposition of the iron oxide hemosiderin within the corneal epithelium, is subtle and may not be readily detectable in all cases, but becomes more evident when viewed under a cobalt blue filter. Similarly, around 50% of subjects exhibit Vogt's striae, fine stress lines within the cornea caused by stretching and thinning.[7] The striae temporarily disappear while slight pressure is applied to the eyeball. A highly pronounced cone can create a V-shaped indentation in the lower eyelid when the patient's gaze is directed downwards, known as Munson's sign. Other clinical signs of keratoconus will normally have presented themselves long before Munson's sign becomes apparent,[8] and so this finding, though a classic sign of the disease, tends not to be of primary diagnostic importance.
Corneal topogram of a keratoconic eye
A handheld keratoscope, sometimes known as Placido's disk, can provide a simple non-invasive visualization of the surface of the cornea by projecting a series of concentric rings of light onto the cornea. A more definitive diagnosis can be obtained using corneal topography, in which an automated instrument projects the illuminated pattern onto the cornea and determines its topology from analysis of the digital image. The topographical map indicates any distortions or scarring in the cornea, with keratoconus revealed by a characteristic steepening of curvature which is usually below the centreline of the eye. The technique can record a snapshot of the degree and extent of the deformation as a benchmark for assessing its rate of progression. It is of particular value in detecting the disorder in its early stages when other signs have not yet presented.[9]
Once keratoconus has been diagnosed, its degree may be classified by several metrics:[10][11]
* The steepness of greatest curvature from mild (< 45 D), advanced (up to 52 D) or severe (> 52 D);
* The morphology of the cone: nipple (small: 5 mm and near-central), oval (larger, below-center and often sagging), or globus (more than 75% of cornea affected);
* The corneal thickness from mild (> 506 μm) to advanced (< 446 μm).
Increasing use of corneal topography has led to a decline in use of these terms.[11]
Epidemiology
The National Eye Institute reports that keratoconus is the most common corneal dystrophy in the United States, affecting approximately 1 in 2,000 Americans,[12][13] but some reports place the figure as high as 1 in 500.[14] The inconsistency may be due to variations in diagnostic criteria, with some cases of severe astigmatism interpreted as those of keratoconus, and vice versa.[8] A long-term study found a mean incidence rate of 2.0 new cases per 100,000 population per year.[13] It is suggested that males and females, and all ethnicities appear equally susceptible, though some recent studies have cast doubt upon this,[15] suggesting a higher prevalence amongst females; the literature however varying as to its extent. Also, a study carried out in the UK[16] suggests that people of an Asian heritage are 4.4 times as likely to suffer from keratoconus as Caucasians, and are also more likely to be affected with the condition earlier.
Keratoconus is normally bilateral[13] (affecting both eyes) although the distortion is usually asymmetric and is rarely completely identical in both corneas. Unilateral cases tend to be uncommon, and may in fact be very rare if a very mild condition in the better eye is simply below the limit of clinical detection.[8] It is common for keratoconus to be diagnosed first in one eye and not until later in the other. As the condition then progresses in both eyes, the vision in the earlier-diagnosed eye will often persist to be poorer than that in its fellow.
Prognosis
Patients with keratoconus typically present initially with mild astigmatism, commonly at the onset of puberty, and are diagnosed as having the disease by the late teenage years or early 20s. In rare cases keratoconus can occur in children or not present until later adulthood. A diagnosis of the disease at an early age may indicate a greater risk of severity in later life.[17] Patients' vision will seem to fluctuate over a period of months, driving them to change lens prescriptions frequently but as the condition worsens, contact lenses become required in the majority of cases. The course of the disorder can be quite variable, with some patients remaining stable for years or indefinitely, while others progress rapidly or experience occasional exacerbations over a long and otherwise steady course. Most commonly, keratoconus progresses for a period of ten to twenty years[8] before the course of the disease generally ceases.
Corneal hydrops
In advanced cases, bulging of the cornea can result in a localized rupture of Descemet's membrane, an inner layer of the cornea. Aqueous humor from the eye's anterior chamber seeps into the cornea before Descemet's membrane reseals. The patient experiences pain and a sudden severe clouding of vision, with the cornea taking on a translucent milky-white appearance known as a corneal hydrops.[18] Although disconcerting to the patient, the effect is normally temporary and after a period of six to eight weeks the cornea usually returns to its former transparency. The recovery can be aided non-surgically by bandaging with an osmotic saline solution. Although a hydrops usually causes increased scarring of the cornea, occasionally it will benefit a patient by creating a flatter cone, aiding the fitting of contact lenses.[18] Very occasionally, in extreme cases, the cornea thins to the point that a partial rupture occurs, resulting in a small, bead-like swelling on the cornea that has been filled with fluid. When this occurs, a corneal transplant can become urgently necessary to avoid complete rupture and resulting loss of the eye.[18]
Pathophysiology and cause
Despite considerable research, the etiology of keratoconus remains somewhat of a mystery. According to the United States National Keratoconus Foundation,[19] it is likely that keratoconus can arise from a number of different factors: genetic, environmental or cellular, any of which may form the trigger for the onset of the disease. Once initiated, the disease normally develops by progressive dissolution of Bowman's layer, the membrane lying between the corneal epithelium and stroma. As the two come into contact, cellular and structural changes in the cornea adversely affect its integrity and lead to the bulging and scarring that are characteristic of the disorder. Within any individual keratoconic cornea, there may be found regions of degenerative thinning coexisting with regions undergoing wound healing.
The visual distortion experienced by the patient comes from two sources, one being the irregular deformation of the surface of the cornea; the other being scarring that occurs on its exposed highpoints. These factors act to form regions on the cornea that map an image to different locations on the retina and give rise to the symptom of monocular polyopia. The effect can worsen in low light conditions as the dark-adapted pupil dilates to expose more of the irregular surface of the cornea. Scarring appears to be an aspect of the corneal degradation; however, a recent, large, multi-center study suggests that abrasion by contact lenses may increase the likelihood of this finding by a factor of over two.[20]
A number of studies have indicated that keratoconic corneas show signs of increased activity by proteases, a class of enzymes that break some of the collagen cross-linkages in the corneal stroma, with a simultaneous reduced expression of protease inhibitors.[21] Other studies have suggested that reduced activity by the enzyme aldehyde dehydrogenase may be responsible for a build-up of free radicals and oxidising species in the cornea.[22] It seems likely that, whatever the pathogenetical process, the damage caused by activity within the cornea results in a reduction in its thickness and biomechanical strength.
A genetic predisposition to keratoconus has been observed,[23] with the disease running in certain families,[24] and incidences reported of concordance in identical twins. The frequency of occurrence in close family members is not clearly defined, though it is known to be considerably higher than that in the general population, and studies have obtained estimates ranging between 6% and 19%.[25] A responsible gene has not been identified: two studies involving isolated, largely homogenetic communities have contrarily mapped putative gene locations to chromosomes 16q and 20q.[25] However, most genetic studies agree on an autosomal dominant model of inheritance. Keratoconus is also diagnosed more often in people with Down syndrome, though the reasons for this link have not yet been determined.[26] Keratoconus has been associated with atopic diseases, which include asthma, allergies, and eczema, and it is not uncommon for several or all of these diseases to affect one person. A number of studies suggest that vigorous eye rubbing may contribute to the progression of keratoconus, and that patients should be discouraged from the practice.[27][28][29][30][31]
Treatment
Contact lenses
Main article: Contact lens
In early stages of keratoconus, spectacles can suffice to correct for the mild astigmatism. As the condition progresses, spectacles may no longer provide the patient with a satisfactory degree of visual acuity, and most clinical practitioners will move to managing the condition with contact lenses.
Rigid gas permeable lens for keratoconus
In keratoconic patients, contact lenses improve vision by means of tear fluid filling the gap between the irregular corneal surface and the smooth regular inner surface of the lens, thereby creating the effect of a smoother cornea. Many specialized types of contact lenses have been developed for keratoconus, and affected people may seek out both doctors specialized in conditions of the cornea, and contact-lens fitters who have experience managing patients with keratoconus. The irregular cone presents a challenge and the fitter will endeavour to produce a lens with the optimal contact, stability and steepness. Some trial-and-error fitting may prove necessary.[8]
Traditionally, contact lenses for keratoconus have been the 'hard' or rigid gas-permeable variety, although manufacturers have also produced specialized 'soft' or hydrophilic lenses. A soft lens has a tendency to conform to the conical shape of the cornea, thus diminishing its effect. To counter this, hybrid lenses have been developed which are hard in the centre and encompassed by a soft skirt. Soft or hybrid lenses do not however prove effective for every patient.[32]
Some patients also find good vision correction and comfort with a "piggyback" lens combination, in which gas permeable rigid lenses are worn over soft lenses, both providing a degree of vision correction.[33] One form of piggyback lens makes use of a soft lens with a countersunk central area to accept the rigid lens. Fitting a piggyback lens combination requires experience on the part of the lens fitter, and tolerance on the part of the keratoconic patient.
Scleral lenses are sometimes prescribed for cases of advanced or very irregular keratoconus; these lenses cover a greater proportion of the surface of the eye and hence can offer improved stability.[34] The larger size of the lenses may make them unappealing or uncomfortable to some, however their easier handling can find favour with patients with reduced dexterity, such as the elderly.
Surgical options
Corneal transplant
Main article: Cornea transplant
Corneal transplant for keratoconus, approximately 1 week after surgery. Multiple light reflections indicate folds in the cornea which later resolved.
Corneal transplant for keratoconus, approximately 1 week after surgery. Multiple light reflections indicate folds in the cornea which later resolved.
Between 10% and 25% of cases of keratoconus[19][35][36] will progress to a point where vision correction is no longer possible, thinning of the cornea becomes excessive, or scarring as a result of contact lens wear causes problems of its own, and a corneal transplantation or penetrating keratoplasty becomes required. Keratoconus is the most common grounds for conducting a penetrating keratoplasty, generally accounting for around a quarter of such procedures.[37] The corneal transplant surgeon trephines a lenticule of corneal tissue and then grafts the donor cornea to the existing eye tissue, usually using a combination of running and individual sutures. The cornea does not have a direct blood supply, and so donor tissue is not required to be blood type matched. Eye banks check the donor corneas for any disease or cellular irregularities.
The acute recovery period can take four to six weeks and full post-operative vision stabilization often takes a year or more but most transplants are very stable in the long term.[36] The National Keratoconus Foundation reports that penetrating keratoplasty has the most successful outcome of all transplant procedures, and when performed for keratoconus in an otherwise healthy eye, its success rate can be 95% or greater.[19] The sutures used usually dissolve over a period of three to five years but individual sutures can be removed during the healing process if they are causing irritation to the patient.
In the USA, corneal transplants (also known as corneal grafts) for keratoconus are usually performed under sedation as outpatient surgery. In other countries, such as Australia and the UK, the operation is commonly performed with the patient undergoing a general anaesthetic. All cases a require careful follow-up with an eye surgeon (ophthalmologist) for a number of years. Frequently, vision is greatly improved after the surgery, but even if the actual visual acuity does not improve, because the cornea is a more normal shape after the healing is completed, patients can more easily be fitted with corrective lenses. Complications of corneal transplants are mostly related to vascularization of the corneal tissue and rejection of the donor cornea. Vision loss is very rare, though difficult-to-correct vision is possible. When rejection is severe, repeat transplants are often attempted, and are frequently successful.[38] Keratoconus will not normally reoccur in the transplanted cornea; incidences of this have been observed, but are usually attributed to incomplete excision of the original cornea or inadequate screening of the donor tissue.[39] The long-term outlook for corneal transplants performed for keratoconus is usually favorable once the initial healing period is completed and a few years have elapsed without problems.
DALK transplants
One way of reducing the risk of rejection is to use a newer technique called a Deep Anterior Lamellar Keratoplasty, referred to as DALK. In a DALK graft, only the outermost epithelium and the main bulk of the cornea, the stroma, are replaced; the patient's rearmost endothelium layer is retained, giving some additional structural integrity to the post-graft cornea. Because a graft rejection usually begins in the endothelium, the chance of a rejection episode is greatly reduced.
Furthermore, it is possible to transplant tissue from a donor which has been freeze-dried. The freeze-drying process ensures that this tissue is dead, so there is no chance at all of a rejection.
Some surgeons prefer to remove the donor epithelium, others leave the donor's cells in place. Removing it can cause a slight improvement in overall vision, but a corresponding increase in visual recovery time.
Epikeratophakia
Rarely, a non-penetrating keratoplasty known as an epikeratophakia (or epikeratoplasty) may be performed in cases of keratoconus. The corneal epithelium is removed and a lenticule of donor cornea grafted on top of it. The procedure requires a greater level of skill on the part of the surgeon, and is less frequently performed than a penetrating keratoplasty as the outcome is generally less favorable. It may however be seen as an option in a number of cases, particularly for young patients.[40]
Corneal ring segment inserts
Main article: Intrastromal corneal ring segments
A pair of Intacs inserts.
A recent surgical alternative to corneal transplant is the insertion of intrastromal corneal ring segments. A small incision is made in the periphery of the cornea and two thin arcs of polymethyl methacrylate are slid between the layers of the corneal stroma on either side of the pupil, the incision then being closed. The segments push out against the curvature of the cornea, flattening the peak of the cone and returning it to a more natural shape. The procedure, carried out on an outpatient basis under local anaesthesia, offers the benefit of being reversible and even potentially exchangeable as it involves no removal of eye tissue.
The two principal types of intrastromal rings available are known by the trade names of Intacs and Ferrara rings. Intacs are flatter and less centrally placed than the prismatic Ferrara rings. Intacs were first approved by the Food and Drug Administration (FDA) in the United States in 1999 for myopia; this was extended to the treatment of keratoconus in July 2004.[41] Ferrara rings await FDA approval for keratoconus. A development on the concept involves the injection of a transparent synthetic gel into a channel bored through the stroma. As the gel polymerises, it stiffens and takes on similar properties to the pre-formed rings.[42]
Clinical studies on the effectiveness of intrastromal rings on keratoconus are in their early stages, and results have so far been generally encouraging,[43][44] though they have yet to enter into wide acceptance with all refractive surgeons. In common with a penetrating keratoplasty, the requirement for some vision correction in the form of hydrophilic (soft) contact lenses or spectacles may remain subsequent to the operation. Potential complications of intrastromal rings include accidental penetration through to the anterior chamber when forming the channel, post-operative infection of the cornea, and migration or extrusion of the segments.[44] The rings offer a good chance of vision improvement even in otherwise hard to manage eyes, but it is not guaranteed and in a few cases may worsen.
Radial keratotomy
Main article: Radial keratotomy
Radial keratotomy is a refractive surgery procedure where the surgeon makes a spoke-like pattern of incisions into the cornea to modify its shape. This early surgical option for myopia has been largely superseded by LASIK and other similar procedures. LASIK itself is absolutely contraindicated in keratoconus and other corneal thinning conditions – it cannot be used for people with keratoconus because removal of corneal stromal tissue will further damage their already thin and weak corneas.[45]
For similar reasons, radial keratotomy has also generally not been used for keratoconic patients.[46][47] However, an Italian clinic has reported some success with a modified asymmetric radial keratotomy procedure,[48] in which the incisions are confined to one sector of the eye. The corneal thickness is first measured using a pachymeter, then the surgeon makes cuts to a depth of 70-80% of the measured thickness. The patient may initially experience photophobia and fluctuation of vision after radial keratotomy, just as with other forms of refractive surgery.[48]
Corneal Collagen Crosslinking with Riboflavin (C3-R)
A new treatment which has shown success but which has not yet been approved in all countries is Corneal Collagen Crosslinking with Riboflavin (C3-R), a one-time application of riboflavin eye drops to the eye.[21][49] The riboflavin, when activated by approximately 30 minutes illumination with UV-A light, augments the collagen cross-links within the stroma and so recovers some of the cornea's mechanical strength. C3-R, developed at the Technische Universität Dresden, has been shown to slow or arrest the progression of keratoconus, and in some cases even reverse it, particularly when applied in combination with intracorneal ring segments. Clinical trials are continuing, and to date relatively few procedures have been performed but the technique is showing promise in treating early cases of the disease.[50] Corrective lenses may still be required after the treatment but it is hoped that it could limit further deterioration in the patient's vision and reduce the case for keratoplasty.
Related disorders
Several other non-inflammatory eye disorders, generally rarer than keratoconus, also cause thinning of the cornea:[8]
Keratoglobus
Keratoglobus is a very rare condition that may be genetically related to keratoconus. It causes corneal thinning, primarily at the margins, resulting in a spherical, slightly enlarged eye.
Pellucid marginal degeneration
Pellucid marginal degeneration causes thinning of a narrow (1-2 mm) band of the cornea, usually along the inferior corneal margin. It causes an irregular astigmatism that can often be corrected by spectacles.
Posterior keratoconus
Keratoconus and posterior keratoconus are distinct disorders, despite their similar names. Posterior keratoconus is a rare abnormality, usually congenital, which causes a non-progressive thinning of the inner surface of the cornea. Posterior keratoconus generally affects only a single eye.
See also
* List of eye diseases and disorders
* Ophthalmology
References
* Arffa R (1997). Grayson's Diseases of the Cornea. Chap. 17. Mosby. ISBN 0-8151-3654-4.
* Brown D. Research Overview. National Keratoconus Foundation. Retrieved on 2006-03-12.
* Burger D, Shovlin J, Zadnik K (2003). Keratoconus: Diagnosis & Management. Pacific University College of Optometry. Retrieved on 2006-03-12.
* Caroline P, Andre M, Kinoshita B, and Choo, J. Etiology, Diagnosis, and Management of Keratoconus: New Thoughts and New Understandings. Pacific University College of Optometry. Retrieved on 2006-03-12.
* Epstein A (2000). Keratoconus and related disorders (PDF). North Shore Contact Lens. Retrieved on 2006-03-12.
* Feder R, Kshettry P (2005). "Chap 78: Non-inflammatory Ectactic Disorders", in Edited: Krachmer J: Cornea. Mosby. ISBN 0-323-02315-0.
* Heverly V, Lowther G. Keratoconus. School of Optometry, Indiana University. Retrieved on 2006-03-12.
* Rabonitz Y (2004). "Ectatic Disorders of the Cornea", in Edited: Foster C et al.: The Cornea, 4th Ed.. ISBN 0-7817-4206-4.
* Yanoff M, Duker J (2004). Ophthalmology, 2nd Ed., Mosby. ISBN 0-323-01634-0.
* Zadnik K, Barr J (1999). Diagnosis, Contact Lens Prescribing, and Care of the Keratoconus Patient. Butterworth Heinemann. ISBN 0-7506-9676-1.
Notes
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