Tissue Saving by Reducing and Using Variable Optic Zone (VOZ) to Correct Myopia by Refractive Lenticule Extraction

Abstract

Purpose: The lenticular diameter was reduced to below standard 6.5 mm, in a stepwise manner up to 5.2 mm and report on the Residual Stromal Thickness (RST), refractive outcomes and subjective scotopic visual quality of patients compared to those who underwent Small Incision Lenticule Extraction (SMILE) with the conventional 6.5 mm lenticular diameter.

Study Design: Retrospective study

Methods: Patients undergoing SMILE in the first year of the study were subjected to lenticular diameter of standard 6.5 mm for lenticule extraction. In the second year, using the same nomogram, the lenticular diameter was gradually reduced from 6.4 to 6 mm, with 0.1 mm decrements in each subset. In the last 6 months, all cases were performed using the same nomogram but with lenticular diameter below 6 mm, again with 0.1 mm decrements in each subset.

Results: We included 100 eyes of 55 patients with a mean age of 26.18+ 6.6 years (median=25 years, IQR= 22 to 28 years). The mean preoperative best corrected visual acuity (BCVA) was 0.03+ 0.07 logMAR (range = 0 to 0.3 logMAR) and the mean preoperative spherical equivalent was -5.5D + 2.05D (median = -5.5D, IQR= -7.10 to -3.75D). The mean keratometry was 44.12D + 1.3D (range = 41.5 to 48D) and mean central corneal thickness was 532.24+
29.8 µ (median = 533 µ IQR= 511 to 552 µ, range = 449 to 629 µ). The pupillary size in the study group was 3.80+ 0.82 mm (median= 3.84 mm, IQR= 3.3 to 4.3mm). At 1 month follow up; the best corrected distance visual acuity (UCDVA) across groups was 0.02 + 0.06 logMAR (median = 0 logMAR, range= 0 – 0.3 logMAR). There were no differences in UCDVA and contrast sensitivity between groups with respect to the lenticular diameter. Univariate linear regression analysis showed that age, spherical equivalent, preoperative pachymetry and lenticular diameter size were significantly associated with residual stromal thickness.

Conclusion: We found that SMILE performed with a lenticular diameter of < 6 mm was effective in delivering excellent refractive correction and improving the corneal biomechanical strength by virtue of significantly greater RST.