UV toxicity culprit in post-LASIK dry eye

Hypoesthesia is not the origin of post-LASIK punctuate epithelial keratopathy or the so-called dry eye syndrome. Rather, these sequelae may represent a phototoxic effect of treatment with the ultraviolet excimer laser, said Carmen Barraquer-Coll, MD.

"In our surgical and clinical experience we have never seen dry eye in recipients of penetrating or lamellar grafts or in eyes that have undergone freezing keratomileusis, epikeratophakia, planar keratomileusis, or in situ keratomileusis with and without a hinge. Nor have we found any publications on the so-called dry eye syndrome after these procedures," observed Dr Barraquer-Coll, head, refractive surgery department, Barraquer Clinic, Bogota, Colombia.

"Like LASIK, these are all corneal surgeries associated with nerve sectioning or tissue denervation," Dr Barraquer-Coll said. "Use of the excimer laser is the most obvious answer to the question of what is the difference between LASIK and these corneal surgeries."

Dr Barraquer-Coll hypothesized that every pulse of the laser produces an equal area of collateral damage. In addition, through a reaction with ambient oxygen, there is the potential for release of ozone.

This concept is being investigated in a prospective open-label clinical trial where eyes were allocated to undergo LASIK with a standard technique or a protected technique involving covering of the limbus, bulbar conjunctiva, and stromal side of the flap. A preliminary analysis was performed using data from a total of 143 eyes. The two surgical groups were nearly equally represented, and they were similar with respect to gender, age, preoperative Schirmer II and tear breakup time results, defocus, and total ablation depth.

In logistic regression analysis, eyes operated on with the protected technique had an approximately 70% lower risk of dry eye syndrome postoperatively. Females had a threefold greater risk than males.

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ASCRS 2008 meeting highlights.