Corneal thickness, residual stromal thickness, and its effect on opaque bubble layer in small-incision lenticule extraction
To evaluate the effects of the central corneal thickness (CCT) and residual stromal thickness (RST) on the formation of opaque bubble layer (OBL) during small-incision lenticule extraction (SMILE).
A total of 345 eyes from Refractive Surgery Center database at Tianjin Eye Hospital that had been subjected to SMILE surgery and followed for 6 months were included in this study and divided into OBL and OBL-free groups. Preoperative, intraoperative, and postoperative data for all eyes were evaluated and analyzed using multivariate regression analysis. After adjustment for several confounding factors, potential associations of CCT and RST with OBL were elucidated by determining odds ratios (ORs) and 95% confidence intervals (CIs).
In total, 22 of the 345 eyes developed various degrees of OBL during the femtosecond laser scanning phase of SMILE surgery. After adjustment for age, sex, and refractive errors, significant relationships were detected between CCT and RST and OBL formation (OR 1.04; 95% CI 1.02–1.06; OR 1.03; 95% CI 1.02–1.05, respectively, P < 0.001). Smooth curve fitting revealed an increased risk of OBL in the presence of an increased CCT or RST. However, visual outcomes were comparable between the two groups at both 3 and 6 months postoperatively.
The results suggest that OBL formation during SMILE surgery is more likely in eyes with a thicker cornea. CCT and RST can be considered independent risk factors for OBL formation. Although this phenomenon may disturb the surgical procedure, it is unlikely to affect the postoperative visual outcome.
KeywordsCentral corneal thickness (CCT) Residual stromal thickness (RST) Opaque bubble layer (OBL) Small-incision lenticule extraction (SMILE)
The authors are grateful for the technical support of Tianjin Eye Hospital and Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science.
This study was supported by the National Natural Science Foundation of China (No. 81670884). The funding organization had no role in the design or conduct of this research.
Compliance with ethical standards
Conflict of interest
All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest or non-financial interest in the subject matter or materials discussed in this manuscript.
This study was adhered to the tenets of the Declaration of Helsinki and was approved by the ethics committee of Tianjin Eye Hospital.
Informed consent was obtained from all individual participants included in the study.
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