Three-Year Outcomes of Under-flap Stromal Bed CXL for Early Post-LASIK Ectasia

Abstract

PURPOSE: To investigate the 36-month clinical outcomes of under-flap stromal bed CXL (ufCXL) and report on its ability to stabilize post-laser in situ keratomileusis (LASIK) ectasia. METHODS: This case series included 20 eyes with diagnosed early post-LASIK ectasia treated with ufCXL. Inclusion criteria were early, mild post-LASIK ectasia, defined as new-onset postoperative manifest refraction cylinder of 1.50 diopters (D) or less, with new topographic inferior steepening consistent with ectasia, uncorrected distance visual acuity of 20/40 or better, and corrected distance visual acuity of 20/25 or better. The existing LASIK flap was lifted, 0.25% isotonic riboflavin was applied directly to the stromal bed, the flap was repositioned, and 18 mW/cm 2 ultraviolet light was applied for 5 minutes to the corneal flap surface. Post-ufCXL ophthalmic data were compared to pre-ufCXL baseline measurements. RESULTS: Visual outcomes were maintained pre-ufCXL to 36 months post-ufCXL, with preserved safety index ( P = .6545), efficacy index ( P = .4980), spherical equivalent accuracy ( P = .1536), defocus equivalent accuracy ( P = .1032), central corneal thickness ( P = .5196), and corneal irregularity indices at 3 mm ( P = .8548) and 5 mm ( P = .3399). Refractive astigmatism significantly decreased from 0.83 to 0.55 D pre-ufCXL to post-ufCXL ( P = .0439), as did maximum keratometry from 42.40 to 42.00 D pre-ufCXL to post-ufCXL ( P = .0420). The ufCXL demarcation line depth was 336 ± 21 µm post-ufCXL, with normal endothelial cell density (2,574 ± 203 cells/mm 2 ). Only 1 of 20 eyes showed evidence of progression of 1.00 D in maximum keratometry. CONCLUSIONS: The ufCXL procedure shows promise in stabilizing early post-LASIK ectasia. Visual function, refractive astigmatism, maximum keratometry, and corneal irregularity indices were statistically maintained at 36 months postoperatively. [ J Refract Surg . 2022;38(8):511–519.]