Femtolaser intrastromal implantation of corneal segments using a digital marking device in the surgical treatment of keratoconus

Abstract

Purpose. To develop a technology for topographically oriented positioning of intrastromal segments during femtolaser intrastromal keratoplasty (ISKP) in patients with keratoconus using a digital marking device and to evaluate its clinical efficacy. Material and methods. The study included 102 patients (102 eyes) with stage II keratoconus according to the Amsler – Krumeich classification. According to the type of surgery performed, the patients were divided into groups: the main group (53 patients (53 eyes) – femtolaser ISKP with implantation of polymethyl methacrylate (PMMA) segments was performed using a digital marking device and taking into account the cyclotorsion angle; control group (49 patients (49 eyes)) – femtolaser ISKP with implantation of PMMA segments was performed using the standard method (marking the geometric center of the cornea using the Purkenier – Sanson reflex without taking into account cyclotorsion). Results. The indices of the «success» index, the calculated vector of astigmatism close to the actual postoperative one and a smaller value of the vector of the difference in the axis of astigmatism, confirmed the higher accuracy of ISKP with the use of a digital marker compared to the standard one. The mean values of visual acuity and best corrected visual acuity 12 months after surgery in the main group were 0.58 ± 0.05 and 0.80 ± 0.04, respectively, and in the control group they were at the level of 0.49 ± 0.06 and 0.68 ± 0.05 respectively. After the surgery, there was a statistically significant decrease in the mean values of astigmatism: the main group – after 3 months to -1.8 ± 0.15 diopters (p <0.05), after 6 months – by another 1.7 ± 0.20 diopters (p <0.05); the control group – after 3 months to -2.43 ± 0.17 diopters (p <0.05), after 6 months – by another 2.42 ± 0.17 diopters. Conclusion. The proposed optimized ISKP technique with the use of a digital marking device provides precise positioning of segments during the surgical treatment of keratoconus and allows to obtain higher acuity of vision and best corrected visual acuity, as well as to correct corneal astigmatism more efficiently than using standard technique. Key words: surgical treatment of keratoconus, femtolaser intrastromal implantation of corneal segments, digital marking device.