Impact of Different Keratorefractive Lenticule Extraction Procedures on Corneal Deflection Characteristics During Air-puff.

Purpose: To compare corneal deflection characteristics during air-puff before and after keratorefractive procedures using a mathematical method.

Methods: The authors collected Corvis ST (Oculus Optikgeräte GmbH) corneal images from 86 eyes after photorefractive keratectomy (PRK), 93 eyes after laser in situ keratomileusis (LASIK), and 76 eyes after small incision lenticule extraction (SMILE). Using these images, corneal deflection was quantified and modal coefficients obtained over time through a decomposition method. The results were then compared among individual patients to identify differences before and after surgery.

Results: SMILE surgery increased corneal deflection by a quantifiable amount with less dependence on the depth of removed tissue, demonstrating up to 1.46 times (maximum) greater modal deflection changes compared with other surgeries. In contrast, in PRK and LASIK, corneal deflection was increased with greater ablation depth. Inter-patient variability was the largest in PRK, particularly in lower-order modes, which affected a large central area. Higher-order modes of the decomposition method in the central area demonstrated that SMILE and PRK exhibited similar patterns before air-puff, whereas SMILE and LASIK exhibited similar deflection patterns during air-puff. A significant difference between LASIK and SMILE was observed in transient deflection during the early air-puff phase and the ending phase.

Conclusions: This computational method could comprehensively analyze the overall corneal bending over time. The results suggest the use of LASIK and PRK for patients with low myopia and SMILE for patients with high myopia.