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Dry eye or limbal stem cell deficiency?
Case presentation:
This 83-year-old man has a history of age-related macular degeneration, glaucoma, severe dry eye and IOLs in both eyes.
Ocular coherence tomography shows scarring from old, inactive exudative changes in the right eye and nonexudative retinal pigment epithelium changes in the left eye. This is stable, as seen by comparing to OCTs from 5 years ago that the patient provides. His has been taking Combigan (brimonidine tartrate and timolol maleate, Allergan) and Travatan (travoprost, Alcon) for his glaucoma for 10 years. His dry eye is being treated with artificial tears.
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This man has AMD, glaucoma, severe dry eye
and IOLs in both eyes.
Image: Hovanesian J |
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The patient regularly experiences a feeling of "gravel," especially in his right eye, and has more than once developed a condition diagnosed as a corneal abrasion that occurs spontaneously.
Discussion:
Limbal stem cell deficiency is a common defect in the limbal conjunctival cells that repopulate the surface epithelium of the cornea. Deficiency of these cells occurs in chemical injuries, vitamin A deficiency, scarring diseases such as ocular cicatricial pemphigoid and Stevens-Johnson syndrome, and in chronic use of topical medications with preservatives that damage these cells.
 BAK is an effective preservative because of its properties as a soap. These same properties make it somewhat toxic to ocular surface cells. Image: Wikipedia |
Benzalkonium chloride (BAK) is one of the most common causes of damage, as this preservative acts chemically like a soap that disrupts the phospholipid cell membrane of the limbal cells.
Patients who use glaucoma medications chronically (and even artificial tears that are preserved) are causing chronic insult to these limbal stem cells, and this can lead to permanent damage and a symptom pattern that mimics dry eye. Treatment for this condition can include switching the medications to the preservative-free variety (where available), use of preservative-free artificial tears or punctal plugs to improve ocular wetting, and treatment with autologous serum, an eye drop derived from the patients’ own blood plasma.
In some cases glaucoma surgery can reduce the need for topical medications and alleviate further insult from continued topical therapy. In Europe, where glaucoma surgery is considered at a much earlier stage of treatment, this phenomenon of limbal stem cell deficiency caused by chronic medications is probably much less common. With time, this trend may also occur here in the United States.
- Disclosure: Dr. Hovanesian is a consultant to Allergan.