Saturday, 18 February 2012

Recurrent Corneal Abrasion

Recurrent Corneal Abrasion
Corneal abrasion
(green when seen with fluorescein drops added)

Recurrent corneal abrasion is a painful eye condition, although your eye heals after a few hours or days. It is caused by a scratch on the surface of the eye in the previous months. Although the first injury heals, the healing is not perfect and the 'scratch' returns over the next months for no apparent reason. This page describes what is happening, and how you can reduce the number of recurrences.

Typically the condition starts when the surface of the eye is scratched, possibly by a finger nail. A patch of epithelium is scratched off or wrinkles up, leaving a bare patch of cornea.As the cornea has many nerves, this injury feels exquisitely painful, like a needle.The abrasion always heals and the pain goes.The healing takes 1mm a day from each side, so a large 7mm abrasion takes about 31/2 days, less in children, longer if you are older.
When a doctor looks into your eye, even with the microscope slit lamp in the Eye Department, it may be very difficult to see the injury.Sometimes it may not be apparent at the first examination. The doctor or nurse uses a yellow dye, called fluorescein, to examine your eye, and this dye sticks to a bare patch of cornea if there is one.There may not actually be a bare patch the cornea may just be wrinkled and very loosely attached.
Normally the epithelium sticks down to the layer underneath (the basement membrane) firmly. Tiny pegs underneath the cells that make up the epithelium keep the cells stuck on to the basement membrane.This is like painting on a wall: if you paint on the undercoat first, and then paint on the top coat, when the paint dries it will be well stuck down.However, these pegs may take 6-12 months to reform properly after the original injury. During this time the epithelium may be prone to slipping and sliding, and this slipping and sliding causes this condition.This is like painting on a bare surface with a 'top coat' of paint, when there is no 'undercoat'. The paint will dry but peel off really easily.A few people will this condition have inherited genes that make this sticking process faulty, but this is quite unusual.Certainly if your condition keeps happening year after a year a corneal specialist may detect this condition.

A second reason for the faulty sticking may lie in your tears.The glands in your eyelid, especially your lower lid, make secretions that help tears to spread. If these glands get blocked, your tears do not spread properly, and the eyelid may stick to the epithelium and pull it off before the pegs have firmly fixed it in position.If you clean your lids as below, the glands start to make their secretions again, and the process stops.In addition to the regular cleaning of the eyelids, sometimes using a cream at night can stop the sticking (the 'sticking' of the eyelid to the epithelium occurs when you wake up in the morning).


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