Results of thin-cap small-incision lenticule extraction

Abstract

Purpose: To evaluate the influence of a thin cap in small-incision lenticule extraction (SMILE) for the correction of myopia or myopic astigmatism. Setting: Tertiary care private practice. Methods: A chart review of 102 eyes of 51 patients was performed. The effect of 120 µm vs 100 μm cap thickness on postoperative spherical equivalent refraction (SEQ), cylinder, corrected and uncorrected visual acuities, and ease of lenticule separation was assessed in a contralateral manner, whereas all other parameters were identical between eyes (including optical zone, minimum lenticule thickness, incision size, and energy and spot settings) using paired t test. Results: At 3 months postoperatively, SMILE with 120 μm cap thickness was undercorrected in SEQ relative to SMILE with 100 μm cap thickness in a cohort of 102 eyes of 51 consecutive patients. The difference of 0.06 ± 0.39 diopter (or 0.7% ± 5.7%) did not reach statistical significance. Postoperative cylinder was not statistically different in both groups. Visual acuity was similar in both groups. Ease of lenticule separation was identical in both groups. Suction time was shorter with a 100 μm cap (P < .005). Postoperative central residual stromal thickness was 20 ± 15 μm thicker with a 100 μm cap (P < .0001). Adverse events were comparable. Conclusions Postoperative refraction, visual acuity, ease of lenticule separation, and incidence of adverse events were not significantly affected by cap thickness. Surgeons might safely use 100 μm instead of 120 μm caps without nomogram adjustment. Alternatively, after suction loss during the lenticule cut, a second docking with a programmed cap thickness of 100 μm (and a larger optical zone) might be a rescue technique enabling surgeons to still perform the intended SMILE procedure.

Decision taking in corneal refractive surgery

“…Choosing a thin cap over the extracted lenticule may be an option to preserve more residual stromal thickness. 5 The mesopic pupil size of this patient is rather large as is typical for young women. However, large pupils are not associated with dysphotopsia if the lenticule diameter (or effective optical zone in LASIK) is 6.5 mm or larger.…”

Applying Information Gain to Explore Factors Affecting Small-Incision Lenticule Extraction: A Multicenter Retrospective Study

“…Liu et al ( 12 ) have demonstrated that a 110-μm cap thickness had better visual outcomes postoperatively compared with a 150-μm cap thickness. In contrast, another study found that postoperative refraction was not significantly affected by cap thickness of 100 and 120 μm in SMILE ( 11 ). In our study, cap thickness ranged from 110 to 140 μm, which may have led to different results.…”

“…There is a rising acceptance and recognition of SMILE surgery as a global surgical treatment option for refractive errors ( 4 ). Previous studies have reported that sex ( 5 ), age ( 6 , 7 ), preoperative spherical equivalent (SE) ( 8 ), corneal curvature ( 9 ), optical zone ( 10 ), central corneal thickness (CCT) ( 11 , 12 ), treatment nomogram ( 13 ), and laser energy ( 14 , 15 ) affect visual outcomes after SMILE. While previous studies mostly analyzed the influence of a single factor, in this study, machine learning was used to analyze 20 different factors to determine the most important factors affecting SMILE.…”

Twelve-month outcomes of a new refractive lenticular extraction procedure

“…Although, the literature is controversial as to whether thicker caps result in biomechanically stronger 40 or weaker corneas. 41 Some recent publications even suggest a nomogram compensation based on the planned cap thickness. 42 …”

“…Caps were 140-150 µm thick, 43 the optical zone ranged from 5.5 to 6.5 mm, 44 the incision was positioned pseudo-superior at 150° with entry angle of 120° and width of 3.0 mm. 45 …”