The thickness of cornea do influence the results of ReLexSMILE
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First Author: E.Eskina RUSSIA
Co Author(s): K. Davtian O. Klokova R. Damashkauskas
To study the predictability, safety and stability of ReLexSMILE for patients with minimal cornea thickness less than 500 mkm in comparison to those with normal cornea.
Sphere clinic, Moscow, Russia, MNTK by the name of Fedorov, Krasnodar, Russia
“Thin corneas” group 35 patients (59 eyes), age from 18-44 years, planned RST > 290µ Minimal corneal thickness < 500µ , “Control” group 78 patients (156 eyes), age from 18-44 years, planned RST > 290µ, minimal corneal thickness > 500µ. Observation time up to 12 months. In all groups we performed SMILE correction following a standard protocol We analyzed: UDVA, BCVA, manifest refraction, efficacy, predictability, safety and stability, topography and posterior cornea with Scheimflug analysis. Statistical analysis was performed with 95% confidence interval and multilinear regression analyses started with full degrees of freedom and applied stepwise regression.
A significant difference in UCVA recovery at 1 and 3 months postop was found, at 1 month post-surgery UCVA 0,8 and better was only in 71% of eyes with “Thin corneas” and in 93% of eyes in “Control group”. In “Control group” the vision recovery was faster- at 1 month postop 80% of eyes had the same UCVA or better as BCVA preop in comparison to 55% in “Thin corneas” group. Difference in efficacy compared between groups was also significant at 1 and 3 months post-surgery and in safety 3 months postop. No ectasia occurred.
Vision recovery is slower in “Thin cornea” group. Thin and normal corneas requiring different nomograms for SMILE. Difference in posterior cornea reaction explains the difference in results. “Thin” corneas are reacting on SMILE procedure more remarkable and new depth and volume limitations for SMILE should be created. We strongly recommend to follow the “40% rule” while planning SMILE. Let us consider that CAP thickness should be also included into the calculation. Further development of PTA formula in SMILE is necessary. Thin corneas is a good in vivo model to study biomechanical reaction of the cornea on different refractive procedures.