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

PURPOSE: To describe a novel technique for cutting asym-metric 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 coher-ence tomography (OCT) sections were measured preoperatively and 6 months postoperatively. Evaluations included slit-lamp ex-amination, manifest refraction, uncorrected (UDVA) and corrected (CDVA) distance visual acuity, and simulated and maximum ante-rior keratometry (Kmax) using anterior segment OCT.RESULTS: Spherical and cylindrical refractive errors de-creased from2.38 +/- 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 allogen-ic 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.