Does Adjunctive Under-flap CXL Reduce Regression for Hyperopic LASIK?

Abstract

Purpose: To investigate whether adding accelerated under-flap corneal cross-linking to hyperopic laser in situ keratomileusis (LASIK-ufCXL) affects postoperative stability and regression, visual and refractive outcomes, and subjective quality of vision. Methods: This prospective comparative contralateral eye study included 51 patients with hyperopia (102 eyes) who received LASIK-ufCXL in the eye with highest defocus equivalent (DEQ) or randomized when DEQ equal, with the contralateral control eye receiving LASIK alone. After excimer ablation, 0.25% riboflavin was instilled on the stromal bed for 3 minutes. The flap was repositioned, followed by a total irradiation dose of 3.24 J ultraviolet A (UV-A) light administered to the corneal surface, using 18 mW/cm 2 UV-A for 3 minutes. Postoperative hyperopic regression (stability) was the primary outcome measure, defined by the difference in spherical equivalent (SEQ) at 1 week and 24 months postoperatively. Secondary measures reported uncorrected distance visual acuity, corrected distance visual acuity, cylinder vector analysis, subjective quality of vision, subjective night vision disturbances, and corneal haze. Results: At 24 months, the SEQ stability ( P = .4273) and the magnitude of hyperopic regression ( P = .5613) did not significantly differ between groups, with a small trend showing hyperopic regression of 0.50 diopters or greater being less frequent in LASIK-ufCXL eyes. There were no significant differences in accuracy, efficacy, and safety ( P > .05), with a small trend of more residual refractive astigmatism in the LASIK-ufCXL group ( P = .3216, Cohen's d : −0.29). Subjective quality of vision trended inferior in LASIK-ufCXL eyes ( P = .2237, Cohen's d : −0.25), with a greater haze grading ( P = .0466, Cohen's d : 0.41). Conclusions: Postoperative regression and stability were statistically equivalent between hyperopic LASIK vs LASIK-ufCXL, with identical safety. There were small clinical trends of lower efficacy, accuracy, and subjective quality of vision in LASIK-ufCXL eyes. [ J Refract Surg . 2022;38(12):770–779.]