Q: A patient who has mild posterior polymorphous dystrophy (PPMD) wants LASIK. Is it contraindicated? What should I consider?

A: Posterior polymorphous dystrophy is a mild relative contraindication to LASIK; it is certainly not an absolute contraindication, says Eric D. Donnenfeld, M.D., of Ophthalmic Consultants of Connecticut and Long Island. These patients have an increased risk of endothelial dysfunction and are at risk of developing corneal edema over time. But, most patients who have PPMD are never diagnosed with the disease and function perfectly normally their entire lives.

PPMD is an autosomal-dominant disorder with no predilection based on race or sex.1 Affected patients may not even be aware that they have the dystrophy, and their functional vision may never be affected.

However, PPMD may cause corneal edema or may be a sign of another condition, such as glaucoma.1 So, examine the patient carefully to determine if he or she is a good candidate for LASIK.2 The major concern in evaluating these patients is whether the patient has active corneal edema during the preoperative evaluation, says Dr. Donnenfeld. If an endothelial cell count is taken, and if this cell count is significantly diminished, then LASIK would be a contraindicated procedure.

Corneal thickness may also determine whether a patient can undergo LASIK.2 Pachymetry and a Pentacam (Oculus) measurement or Orbscan (Bausch & Lomb) could determine the corneal thickness and if there are any local variations in thickness [that are] undetectable from an exam at the slit lamp or in the exam chair, says J. James Thimons, O.D., also of Ophthalmic Consultants of Connecticut and Long Island. If the pachymetry is normal, the patient has good corrected vision, and everything else falls under the normative pattern, then this patient with posterior polymorphous dystrophy should be able to undergo LASIK.

Dr. Thimons advice: Follow the patient for a few months before deciding if the patient can undergo LASIKespecially if there are any red flags, e.g., corneal edema or uneven corneal thickness. If the condition progresses over a six-month period, this patient isnt a good candidate. The procedure may interfere with the corneas ability to produce a normal fluid balance and could create some thickening and hazing of the cornea postoperatively, he adds.

In patients with PPMD, the endothelial cells may be normal, attenuated, degenerative or absent.1 And, resulting complications may impact post-LASIK recovery. One complication of endothelial dysfunction is reduced flap adherence, says Dr. Donnenfeld. Patients who have corneal edema or who have undergone previous corneal transplants are at risk of flap dislocation.

Q: What other conditions are relative contraindications to LASIK or affect the endothelium?

Interface fluid syndrome and edema in a post-LASIK patient with increased IOP following steroid usage. Courtesy: Farid Eghbali, O.D.

A: Other complications result from mild Fuchs dystrophy or pseudophakic bullous keratopathy, or following a corneal transplant, says Dr. Donnenfeld. Each presents with diminished endothelial cell counts, while only in severe cases [of PPMD] is the cell count diminished and is the patient at risk of corneal decompensation.

Watch for flap-related complications (e.g., interface fluid syndrome, which can happen in any eye that develops corneal edema). Surface treatment may be better for any patient with less-than-normal endothelial cell count or function.

A patient with Fuchs dystrophy is more likely to suffer corneal decompensation. When the corneal thickness of a patient with Fuchs is greater than 600m, suggest another procedure, such as endothelial keratoplasty, Dr. Thimons says.

 

1. Kiel J. Case report: posterior polymorphous dystrophy. Clin Exp Optom 1999 Jan-Feb;82(1):20-2.

2. Moshirfar M, Barsam CA, Tanner MC. LASIK in patients with PPMD. Cornea 2005 Mar;24(2):230-2.