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Diamond burr polishing combined with PTK for anterior basement membrane dystrophy
Sometimes the combination of two or more well-established technologies yields a new and better treatment for an old problem. So I've found with phototherapeutic keratectomy combined with a diamond burr for the treatment of anterior basement membrane dystrophy.
Anterior basement membrane dystrophy (ABMD), also called map-dot-fingerprint dystrophy or Cogan's microcystic dystrophy, is the most common corneal epithelial dystrophy, occurring in up to 2% of the general population. This condition's presence makes itself known when patients have painful recurrent corneal erosions, but quite frequently it's missed as a cause of painless visual symptoms.
The best way to detect this condition is not with a fine slit beam and indirect illumination. Instead, use broad, direct slit lamp illumination directed from the patient's side to bring out the lines, map areas and microcysts that characterize ABMD.
Loss of acuity with ABMD happens when the basement membrane beneath the central corneal epithelium is thrown into folds. This may cause surface irregularity that the tear film simply can't smooth out, or it's possible that the basement membrane folds cause diffraction and light scatter that become symptomatic. Whatever the cause, the best way to eliminate the problem is to remove the offending basement membrane and epithelium.
Simple epithelial scraping can provide very satisfactory results after epithelial healing, but in my experience, many of these patients have a recurrence of aberrant basement membrane (with a return of erosions or visual symptoms or both) within months or years. Scraping plus PTK yields still less recurrence, but more recently I've employed a combined approach using both PTK and "polishing" of Bowman's membrane with a diamond burr.
In this procedure, after proparacaine drops are placed, I remove the epithelium with a blunt PRK spatula, then use a 3-mm diamond burr, polishing the entire surface of the stroma for a few seconds. PTK is then applied for 20 to 30 pulses, and a bandage contact lens is placed over Zymar (gatifloxacin 0.3%, Allergan), Xibrom (bromfenac ophthalmic solution 0.09%, Ista) and prednisolone acetate drops. The postoperative regimen includes these same three drops, discontinuing the first two when the epithelium has healed and continuing the prednisolone for about 4 weeks.
Over the past 2 years, I've used this regimen on nearly 30 patients with various manifestations of ABMD, some with painful erosions and some with visual symptoms. To date, none have recurred.
I invite readers to comment on any other pearls or suggestions for diagnosing and treating ABMD.