Method of the Cyclotorsion Error Compensation for Myopic Astigmatism during SMILE Surgery

Abstract

Purpose: to develop an effective and safe method of cyclotorsion compensation, to improve the clinical and functional results of the of myopic astigmatism correction with SMILE surgery.Patients and methods: Two equivalent groups of 30 people (30 eyes) were formed with cyclotorsion from ±5 degrees («Standard» and «Verion»). The correction for cyclotorsion was carried out only in the «Verion» group. Before the laser-refraction surgery, all eyes were examined using «Verion» image guided system (Alcon, USA) to determine cyclotorsion. In the «Verion» group, the obtained cyclotorsion data was used to aligement the astigmatism axis by Introducing into the «Visumax» femtolaser system. Further, the operation was carried out according to the standard protocol. At 3 months after SMILE surgery, all patients were examined by a UDVA, CDVA, objective refraction. Furthermore, efficiency and safety, as well as vector analysis of corneal astigmatism according to Alpins were calculated indices at 3 months after surgery.Results: The mean and standard deviation of cyclotorsion of the «Standard» and «Verion» groups was 6.16 ± 1.31 D and 6.30 ± 1.36 degrees, respectively (p > 0.05). The increasement of 1 or more UDVA lines was noted at 20 % and 7 %, respectively after 3 months in the «Standard» and «Verion» groups. The safety index (postoperative UDVA / preoperative UDVA) in both groups was not statistically significantly different (p > 0.05). The predictability of the spherical equivalent within ±0.5 D relative to the target refraction (emmetropia) in the «Standard» and «Verion» groups was 70 % and 100 %, respectively. The predictability of the cylindrical component of refraction within ±0.5 D relative to the target refraction (emmetropia) was 40 % and 90 % for the «Standard» and «Verion» groups, respectively (p < 0.05). Difference vector was 1.01 ± 0.59 D in the group «Standard» and 0.64 ± 0.33 D in the «Verion» group (p < 0.05). Correction index was 0.80 ± 0.43 in the «Standard» group and 0.99 ± 0.04 in the «Verion» group (p < 0.05).Conclusions: Сyclotorsion compensation using the «Verion» image guided system is a safe method. It improves the efficiency and predictability of correction myopic astigmatism in patient undergoing to SMILE surgery. This method recommended for patients with cyclotorsion from ±5 degrees and myopic astigmatism from –0.75 D.