Recurrent corneal erosion

Overview
Recurrent corneal erosion is a disorder of the eyes characterized by the failure of the cornea's outermost layer of epithelial cells to attach to the underlying basement membrane (Bowman's layer). The condition is frequently painful because the loss of these cells results in the exposure of sensitive corneal nerves.

Etiology
There is often a history of previous corneal injury (corneal abrasion or ulcer), but also may be due to corneal dystrophy or corneal disease. In other words, one may suffer from corneal erosions as a result of another disorder, such as map dot fingerprint disease.

Symptoms and signs
Symptoms include recurring attacks of acute ocular pain, foreign-body sensation, photophobia (i.e. sensitivity to bright lights), and tearing often at the time of awakening or during sleep when the eyelids are rubbed or opened. Signs of the condition include corneal abrasion or localized roughening of the corneal epithelium, sometimes with map-like lines, epithelial dots or microcyts, or fingerprint patterns.

Diagnosis
The erosion may be seen by a doctor using the magnification of an ophthalmoscope, although usually fluorescein stain must be applied first and a blue-light used. Opticians, optometrists and ophthalmologists have use of slit lamp microscopes that allow for more thorough evaluation under the higher magnification. Mis-diagnosis of a scratched cornea is fairly common, especially in younger patients.

Management of episodes
With the eye generally profusely watering, the type of tears being produced have little adhesive property. Water or saline eye drops tend therefore to be ineffective. Rather a 'better quality' of tear is required with higher 'wetting ability' (ie greater amount of glycoproteins) and so artificial tears (eg viscotears) are applied frequently.

Whilst individual episodes may settle within a few hours or days, additional episodes (as the name suggests) will recur at intervals.

Prevention
Given that episodes tend to occur on awakening and are sometimes managed by use of good 'wetting agents', approaches to be taken to help prevent episodes include:
 * avoiding dry or irritating environments (eg cigarette smoke)
 * drinking plenty fluids to help prevent drying of the eyes. This may also involve limiting alcohol intake in the evenings. Drinking heavily may cause an episode the morning after, known by some as "Drinker's Eye".
 * not sleeping-in late, as corneal hydration from lid closure may be a factor affecting epithelial adhesion.
 * use of long-lasting eye ointments (eg lacrilube) applied before going to bed.
 * learn to wake with eyes closed and still. Keep high quality artificial tears within reach at bedtime. If eyes feel 'stuck shut' upon awakening, insert the tip of tears bottle slightly into inner corner of eye, gently squirting the tears, which will seep under the eyelid, often allowing opening of eyes without an erosion episode. Several repeated applications of tears may be necessary, but with patience, eyes will very likely become 'unstuck' allowing painfree opening of eyes and erosion avoidance. (personal experience)
 * another method, after waking with eyes closed and still, is to gently rub the closed eyelids with fingers in a circular motion to "unstick" the eyelids before attempting to open them. (personal experience)
 * control air quality and humidity while sleeping. Avoid having an over ventilated room while you sleep. Having air flowing over your face, even with your eyes closed, can and will increase eye dryness. Cool, moist and still air is the best environment to prevent unnecessary evaporation of eye moisture. (personal experience)
 * limit your exposure to viruses (e.g. by getting an annual flu shot). Viruses like the flu (and gastro symptoms like diarrhea) seem to cause the eyes to dry out which can contribute to causing an episode. (personal experience)
 * wear glasses (sunglasses, prescription glasses or even "fake" glasses) especially when engaging in activities like gardening or playing with children. (personal experience)
 * since dryness can be a cause of episodes using the medication Restasis to increase tear production is considered a possible means of reducing erosions

Treatment
Where episodes frequently occur, or there is an underlying disorder, three types of curative procedures may be attempted: use of therapeutic contact lens, controlled puncturing of the surface layer of the eye (Anterior Stromal Puncture) and laser phototherapeutic keratectomy (PTK). These all essentially try to allow the surface epithelium to reestablish with normal binding to the underlying basement membrane, the method chosen depends upon the location & size of the erosion.

The use of contact lenses may help prevent the abrasion during blinking lifting off the surface layer and uses thin lenses that are gas permeable to minimise reduced oxygenation. However they need to be used for between 8-26 weeks and such persistent use both incurs frequent follow-up visits and may increase the risk of infections.

Alternatively, under local anaesthetic, the corneal layer may be gently removed with a fine needle, cauterised (heat or laser) or 'spot welding' attempted (again with lasers). The procedures are not guaranteed to work, and in a minority may exacerbate the problem.

Patients with recalcitrant recurrent corneal erosions often show increased levels of matrix metalloproteinase (MMP) enzymes. These enzymes dissolve the basement membrane and fibrils of the hemidesmosomes, which can lead to the separation of the epithelial layer. Treatment with oral tetracycline antibiotics (such as doxycycline or oxytetracycline) together with a topical corticosteroid (such as prednisolone), reduce MMP activity and may rapidly resolve and prevent further episodes in cases unresponsive to conventional therapies.