Safety of laser in situ keratomileusis performed under ultra-thin corneal flaps

To report on the safety of laser in situ keratomileusis (LASIK) performed under ultra-thin corneal flaps (Micro-LASIK).

We performed a retrospective review of 1131 eyes that underwent LASIK for myopia with the Nidek MK-2000 microkeratome, and Nidek EC-5000 excimer laser. The 130-microm head and 8.5-mm ring were used in 1042 eyes and the 160-microm head and 9.5-mm ring were used in 89 eyes. For 175 eyes, intraoperative ultrasonic pachymetry was used to measure central corneal thickness and central bed thickness. Flap thickness was calculated by subtracting bed thickness prior to laser ablation from central corneal thickness. All 175 of these eyes had keratectomies using the 130-microm head and 8.5-mm ring.

At last follow-up, 455 eyes (40%) achieved 20/20 or better, 798 eyes (70%) achieved 20/25 or better, and 1077 eyes (95%) achieved 20/40 or better uncorrected visual acuity; 922 eyes (82%) achieved within 1 line of their best spectacle-corrected visual acuity. The following clinically significant complications were observed: four epithelial defects (3.5%), zero irregular flaps (0%), seven stria (0.6%), one diffuse lamellar keratitis (0.1%), one epithelial ingrowth (0.1%), and zero infections (0.0%). Two eyes (0.2%) with stria had 20/40 best spectacle-corrected visual acuity, but lost more than 2 lines of best spectacle-corrected visual acuity. The average measured flap thickness was 87.3 +/- 15.4 microm.

LASIK can be performed safely under ultra-thin corneal flaps.