Asymmetric All-Femtosecond Laser–Cut Corneal Allogenic Intrastromal Ring Segments

Abstract

Purpose: To describe a novel technique for cutting asymmetric allogenic segments using the femtosecond laser for the management of cases of keratoconus with non-coinciding astigmatism and coma axes. Methods: Four eyes of 2 patients with irregular keratoconus and asymmetric allogenic segments were included. Visual, refractive, tomographic, and aberrometric outcomes, and optical coherence tomography (OCT) sections were measured preoperatively and 6 months postoperatively. Evaluations included slit-lamp examination, manifest refraction, uncorrected (UDVA) and corrected (CDVA) distance visual acuity, and simulated and maximum anterior keratometry (Kmax) using anterior segment OCT. Results: Spherical and cylindrical refractive errors decreased from −2.38 ± 2.96 and −2.94 ± 2.16 to −1.81 ± 2.77 ( P = .04) and −1.75 ± 2.07 ( P = .01) diopters (D), respectively, 6 months postoperatively. There was an average gain of three lines of CDVA. Kmax decreased from 50.02 ± 1.99 to 47.89 ± 3.05 D (P= .03) and coma from 1.05 ± 0.21 to 0.21 ± 0.19 D ( P = .01). Conclusions: Asymmetric femtosecond laser–cut allogenic segments allow a higher level of customization based on size, shape, and arc length, in contrast to the limited range of available synthetic asymmetrical segments. [ J Refract Surg . 2023;39(12):856–862.]