The post-LASIK cornea: what's the damage?

Globally, LASIK is a very popular refractive procedure, which provides excellent visual acuity and quality of vision in low to moderate myopia and hyperopia.1 In the mid-nineties, however, LASIK was performed even in extreme myopic errors (up to 23D) or in corneas that were too thin with or without Forme Fruste Keratoconus (FFKC).

The excimer laser used for the refractive procedures was the C217 Technolas with Planoscan software (Bausch & Lomb). The Automated Corneal Shaper (ACS) microkeratome (Chiron) was used from 1996 to 1999 while the Hansatome microkeratome (Bausch & Lomb) was used in procedures performed since 1999. Flap thickness was considered to be the same as the microkeratome plates (160 µm to 180 µm). In addition, we re-evaluated three eyes in which we had to remove the corneal flap (DLK in two eyes; epithelial ingrowth in one eye) resulting in a total residual corneal thickness <350 µm.

Residual Stromal Bed (RSB) thickness was calculated according to available data. If preoperative pachymetry were known, we subtracted predicted flap thickness and calculated ablation depth. If it were unknown, we would make a postoperative pachymetry measurement using Orbscan and subtract the predicted flap thickness.