Thresholds for Interface Haze Formation After Thin-Flap Femtosecond Laser In Situ Keratomileusis for Myopia

Purpose: To evaluate the risk factors for interface haze formation after thin-flap femtosecond laser - laser in situ keratomileusis (LASIK). Design: Prospective case series. Methods: One hundred and ninety-nine consecutive eyes that underwent femtosecond laser LASIK with a LADAR 4000 excimer laser (Alcon Laboratories, Fort Worth, Texas, USA), were analyzed from January 1 to April 30, 2008. Treated eyes were divided into 2 groups according to desired flap thickness: 90 μm (106 eyes), and 100 to 110 μm (93 eyes). Cycloplegic refraction, spherical equivalent (SE), uncorrected visual acuity, best spectacle-corrected visual acuity (BSCVA), depth of ablation, central corneal thickness, flap thickness (optical coherence tomography), Scheimpflug images (Pentacam; Oculus Inc, Lynnwood, Washington, USA), and light scattering were assessed in all eyes that developed haze postoperatively. Results: Haze was observed in 32 eyes treated for moderate to high myopia (SE -6.23 ± 1.67 diopters and depth of ablation 94.6 ± 22.9μm) at 3 months postoperatively. Ultra-thin IntraLASIK flaps (≤90 μm) and younger age were strongly associated with risk of postoperative haze (P = .003 and P = .01, respectively). SE, depth of ablation, and self-reported history of dry eyes were not independently associated with an increased risk of corneal haze. Patients who developed any degree of haze had significantly higher logarithmic value of scatter (log S) values (mean difference =0.24 units, P < .0005) compared with those who did not develop haze. The mean postoperative BSCVA was good in all eyes with haze (logarithm of the minimal angle of resolution 0.05 ± 0.04). Conclusion: Interface haze is associated with an ultra-thin femtosecond laser flap setting of 90 μm and younger age among eyes following LASIK for myopia.