Refractive Coupling Effects in Keratorefractive Lenticule Extraction Procedures: A Machine Learning-Assisted Approach

Area of Science:

• Ophthalmology
• Refractive Surgery
• Corneal Surgery

Background:

• Myopia and myopic astigmatism are common refractive errors.
• Keratorefractive lenticule extraction (KLEx) is an advanced surgical technique for correcting these conditions.
• Understanding refractive couplings is crucial for optimizing surgical outcomes.

Purpose of the Study:

• To evaluate the impact of refractive couplings in myopia and myopic astigmatism.
• To compare coupling effects between two different keratorefractive lenticule extraction (KLEx) systems: small incision lenticule extraction (SMILE) and SmartSight.
• To determine the influence of sphere and cylinder on each other and on different types of astigmatism.

Main Methods:

• Retrospective evaluation of refractive outcomes in 2,841 eyes (SMILE) and 2,528 eyes (SmartSight).
• Calculation of coupling effects using the ratio between partial slopes for sphere, cylinder, spherical equivalent, cardinal, and oblique astigmatism.
• Analysis of coupling effects in cases with and without astigmatism plans, and in high astigmatism cases.

Main Results:

• Statistically significant coupling effects were observed for both VisuMax (SMILE) and ATOS (SmartSight) systems (P < .05).
• Observed coupling effects were consistently low, generally below 10%, even for high astigmatism.
• Specific coupling effects included cylinder into sphere (8%) and sphere into cylinder (2%) for VisuMax, and sphere into cylinder (1%) for ATOS.

Conclusions:

• The observed refractive coupling effects in KLEx procedures are low, despite statistical significance.
• These low coupling values are advantageous compared to non-aspheric excimer laser ablations.
• Optimizing nomograms may further refine surgical results by mitigating residual coupling effects.