History
For all patients who present with signs and symptoms of RCE syndrome, a careful history and examination of the cornea should be undertaken to ensure that no underlying factors have predisposed these patients to this condition. [2] This applies even in those cases where a history of injury to the cornea is present because a defect in the epithelial basement membrane complex may have been present before the initial trauma. [3]
Of patients with anterior basement membrane dystrophy, 80-90% are asymptomatic. The primary symptom of recurrent erosion syndrome is mild to severe eye pain. Symptoms, when they occur, consist of 1 or more of the following:
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Slightly blurred vision (when the epithelial and basement changes are in the visual axis)
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Visual acuity loss
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Astigmatism
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Epithelial blebs
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Foreign body sensation with recurrent erosion, when the epithelium loosens
Foreign body sensation with recurrent erosion, when the epithelium loosens, is commonly the first symptom of recurrent erosion, and, in some cases, patients who have previously experienced this pain on awakening are so fearful of the pain that they are unable to sleep well.
The pain is fleeting in most cases, lasting only for a few seconds, but it may last from minutes to 1-2 hours and is a warning that the epithelium has not healed.
Attacks of pain and ocular irritation occurring in the early morning hours or upon awakening are understandable because corneal hydration from lid closure may be a factor affecting epithelial adhesion. An abnormal adherence between lid and cornea may be a factor in setting the stage for an attack of epithelial erosion.
Sudden sharp pain often is felt in the early morning during sleep or on awakening when a frank epithelial defect occurs because of the eyelid movement across the loosened epithelium.
Recurrences affect the area of the cornea that was previously injured.
Physical
Depending on the severity of the erosion, corneal examination findings may be totally normal, or they may reveal telltale signs of RCE syndrome. A classic history of recurrent pain upon awakening is often more important than seeing classic signs of corneal irregularity in making the correct diagnosis of RCE syndrome.
During an acute attack, one may see epithelial loss, epithelial microcysts, bullae, lack of adherence of sheets of epithelium, and epithelial filament formation. In these instances, the visual acuity may be impaired severely if the pathogenic condition occurs in the pupillary area. The examination findings may be totally normal, or there may be barely visible epithelial irregularities (may have negative staining) where the erosion has almost completely resolved.
An external eye examination generally shows a corneal abrasion, often centrally located, that stains brightly with fluorescein. The abraded area tends to create loose edges with moderate-to-large epithelial flaps, which commonly form. A brownish granular edema (brawny edema) may occupy the underlying anterior stroma. The tendency toward a central location and dense secondary edema can cause a significant deterioration in vision.
Recurrent corneal erosions can be classified as either microform or macroform. With the latter, severe pain persists from hours to days as a result of a large area of the epithelium being separated from the cornea. In posttraumatic cases, the microform type of erosion always occurs at the site of the original abrasion. Microform recurrent erosions are characterized by intraepithelial microcysts with a minor break in the epithelium. These erosions usually are associated with brief episodes of pain, lasting from seconds to minutes.
Laibson et al have stated that in the interval between attacks, one can detect epithelial cysts, surface irregularity, and some subepithelial scarring on slit lamp examination. [1] The healed epithelial area may even resemble a dendritic figure, a pseudodendrite. This fact should be kept in mind to avoid prescribing unnecessary medication.
Causes
The corneal epithelial basement membrane complex is responsible for the tight adhesion of the epithelial basal cell layer to the underlying stroma. The primary abnormality with RCE syndrome is poor adhesion of the epithelium to the Bowman layer due to a failure to establish or maintain normal adhesion complexes. Multiple recurrences are common because the basal epithelial cells require at least 8-12 weeks to regenerate or repair the epithelial basement membrane.
Most cases of recurrent erosions are related to anterior basement membrane dystrophy or are caused by corneal injuries from fingernails and paper. Acquired recurrent erosions also are observed after the following:
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Alkali burns
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Foreign bodies
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Post infectious ulcers from herpes simplex
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Exposure
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Cockayne syndrome
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Reis-Bücklers dystrophy
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Vitrectomy
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Photocoagulation
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Secondary to other corneal dystrophies (eg, lattice, Fuchs, other anterior membrane dystrophies)
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Contact lenses
Contact lenses
Soft contact lenses have many uses and are made from a variety of materials. The most common pitfall in the matter of lens care is the inability to keep lenses clean of deposits. These deposits can consist of protein, lipid, or calcium. They can cause discomfort, pseudomyopia, loss of vision, displacement of lenses (usually in an upward direction), and corneal erosions.
Unfortunately, thimerosal (sodium ethylmercurithiosalicylate) is the major offender in producing a delayed hypersensitivity response. It causes recurrent corneal erosions, conjunctival hyperemia, or corneal deposits. Many thimerosal-free solutions are now being prepared.
Drying of the lenses can result in a change in lens curvature, which alters the fit and can cause conjunctival irritation and swelling or corneal epithelial erosions. Conjunctival swelling results in tightening of the lens, which can cause pain, corneal edema, and epithelial erosions.
A flat-fitting contact lens moves too much and is uncomfortable to wear. Such a lens can give rise to central corneal epithelial edema and erosions. If the lens is too tight, the eye becomes uncomfortable, there is circumcorneal injection, and there may be epithelial erosions.
Postoperative management of corneal transplants for severely alkali-burned corneas includes the protection of the epithelium with well-fitted bandage contact lenses. But if the lenses are not of proper fit, they can lead to recurrent corneal erosions.
Recurrent corneal erosion is an indication for the use of a therapeutic lens. However, with the advent of anterior stromal puncture and related procedures, many clinicians choose to definitively treat typical posttraumatic recurrent corneal erosions, thereby minimizing the number of such patients requiring therapeutic lenses. Bandage lens treatment, if used for this indication, must be continued for up to 8-26 weeks to facilitate repair of the corneal epithelial basement membrane.
Junctional epidermolysis bullosa
Patients with junctional epidermolysis bullosa, one of the rarest types, have more corneal problems (eg, recurrent corneal erosions) but relatively little conjunctival involvement.
In the acquired autoimmune form, the immune response is believed to be directed against the basement membrane proteins uncein and collagen VII. It may be associated with small subepithelial vesicles in the cornea, symblepharon, and scarring of the lacrimal puncta.
Topical neomycin produces contact hypersensitivity in 5-10% of patients. Eyelid edema, conjunctivitis, and punctate corneal erosions may be due to allergic and toxic effects of topical neomycin.
While the corneal epithelium is affected minimally by a low dose of topical neomycin, cytotoxicity occurs at concentrations greater than 5 mg/mL. Corneal sensation can be altered with very high levels of neomycin eye drops.
Topical paromomycin
The effects of topical paromomycin on the ocular surface have not been studied adequately. Frequent dosing and prolonged administration presumably can slow wound healing and may contribute to conjunctival hyperemia and punctate corneal erosions.
Topical diamidines
Topical diamidines can produce stinging and burning immediately after application. Conjunctival hyperemia and punctate corneal erosions have been attributed to its use.
Propamidine
Mast cell degranulation with histamine release is produced by propamidine. Contact hypersensitivity has been described.
Topical anesthetics
While some corneal epithelial damage occurs with all topical anesthetics, it is most exaggerated when cocaine is used, with epithelial loosening and corneal erosions. This may be an advantage when removing epithelium in the treatment of a dendritic ulcer.
Toxic effects on epithelial cell metabolism and ultrastructure include depressed cellular respiration and glycolysis with lactic acid accumulation; alterations in desmosomes, intracellular mitochondria, rough endoplasmic reticulum, and tonofibrils; and inhibition of cell mitosis and migration.
Epithelial microvilli loss results in instability and rapid breakup of the tear film. Thus, local anesthetics may retard healing of corneal erosions as epithelial cells round up and accumulate at the wound margin. The epithelium may totally lift off the basement membrane proteins and cell membrane permeability; destruction of mitochondria, rough endoplasmic reticulum, and tonofibrils; and inhibition of cell mitosis and migration.
Complications
Complications include corneal haze, corneal scarring, infectious keratitis, and permanently decreased vision.
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Corneal abrasion.
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Recurrent corneal erosion.
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Recurrent erosion with fluorescein in an area of staining.
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Map-dot-fingerprint dystrophy.
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Stromal puncture seen with fluorescein.
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Direct view with a slit lamp.
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Debriding of the epithelium. Poorly adherent epithelium with a second layer of basement membrane.
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Granular dystrophy before phototherapeutic keratectomy.
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Granular dystrophy after photorefractive keratectomy.
