Common Diseases Of the Cornea
Astigmatism
Distortion of the lens- shape of the cornea causes poor quality of focus. If the corneal shape is ovalled into a rugby ball shape then the focus of the eye will be distorted and this is called regular astigmatism. Usually this is mild and does not progress or change much during life. It is easily treated with glasses or contact lenses.
Surgical treatments are available now for more severe forms of regular astigmatism. ; the treatments include LASIK and lens implantation with astigmatic lenses.
If the cornea is scarred as a result of infection or injury then the disturbance to the shape will result in very poor sight but a contact lens can be tried. It acts as a new ‘front surface' of the eye and evens out these irregularities, with improvement in sight. If a contact lens doesn't work, then the cornea may have to be replaced, an operation called a corneal graft
Herpes simplex
About 60% of adults in the UK have been infected with Herpes simplex virus at some stage of their lives. For most of us this virus continues to live in our body causing absolutely no problems and we are unaware of its presence; others get sores around their lips, usually at the time of a cold - hence the term "cold sores".
In some patients however, the virus becomes active in the cornea causes a painful ulcer called a DENDRITIC ULCER. This is treated with antiviral ointment and usually resolves in about ten days, and usually without any later problems or scarring.
Corneal infection
Corneal infections are serious problems that need urgent specialist attention. They are usually caused by bacteria which attack and penetrate the surface of the cornea particularly if there is scratch or damage to the corneal surface. This tends to occur more frequently in people who are contact lens wearers (soft contact lens users and especially extended wear lens users); patients who have (very) dry eyes or who have lost corneal sensation . These high risk groups are more likely to develop an infection which leads on to an abscess (SUPPURATIVE KERATITIS) or deeper infection of the eye.
Symptoms include pain and watering of the eyes, blurred vision, sensitivity to light ( photophobia).
Untreated, the ulcers may go on to cause a deep infection of the whole of the eye. Loss of sight, dense scarring or even globe perforation with loss of the eye can occur.
Prompt treatment is required.
Acanthamoeba keratitis
Is a rare infection of the cornea found almost exclusively in soft contact lens wearers who contaminate their lenses by washing them in unclean water (usually using bathroom tap water and not mains water) or who have poor standards of contact lens hygiene. The amoebae have the ability to penetrate the normal ocular.
The condition is excruciatingly painful and vision is rapidly blurred If untreated this could lead to abscess formation, Iritis, Glaucoma or Scleritis. Urgent attention is required by an Ophthalmologist if severe pain is felt in the eye, particularly if you wear contact lenses regularly.
Keratoconus
Is a progressive condition of the cornea where its strength is reduced and the shape progressively changes resulting in increasing astigmatism. The cornea begins to bulge forwards causing irregular astigmatism, i.e. astigmatism which cannot be corrected by spectacles alone.
The disease tends to show itself in teenage or in the 20's; there may be long periods of stability. Initially the astigmatism is corrected by specialist contact lens fitting with gas permeable contact lenses; in the majority of patients the bulging of the cornea will continue and contact lens fitting becomes difficult or impossible. When this point is reached then the patient will usually need a corneal, though surgery is not needed in all cases.
Corneal oedema
The internal fluids of the eye ( aqueous humour) has a tendency to flood into the cornea which would make it opaque with an almost bluish colour. The cells that line the inner layer of the eye (CORNEAL ENDOTHELIUM) are specialised and have the special function of keeping the cornea transparent by actively pumping back this fluid and thus prevent the cornea from becoming waterlogged. If the cornea becomes waterlogged, it indicates that these cells are either not working properly or that they have been damaged.
Unlike most other cell types in the body, these corneal endothelial cells are unable to repair or replace themselves and if the oedema (swelling/ oedema) persists, cells will need to be replaced surgically by corneal grafting.
As this condition tends to occur in older patients, cataracts are frequently also seen. Cataract surgery could cause more damage to the dwindling population of the cells. Special care is needed to prevent further damage and corneal oedema, (corneal decompensatation). If this occurs then a corneal graft will be needed.
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