Purpose: To investigate the contribution of anterior corneal higher-order aberration ablation depth (HOA-AD) to topography-guided outcomes.
Methods: This was a retrospective comparative analysis of 9,722 consecutive eyes undergoing laser in situ keratomileusis (LASIK) treated on the clinically measured refractive cylinder with Contoura software (Alcon Laboratories, Inc., Fort Worth, TX). Outcomes of the 3,246 eyes with the shallowest HOA-AD (first tercile: 5.4 ± 0.9 µm) were compared to the 3,362 eyes with the deepest HOA-AD (last tercile: 11.0 ± 1.7 µm).
Results: The HOA-AD followed a left-skewed normal distribution (R2 = 0.98) with a mean ± standard deviation of 8.02 ± 3.00 µm, with 1.8% of eyes greater than 15 µm. The efficacy index of shallow versus deep HOA-AD eyes was identical (0.98 ± 0.07 vs 0.98 ± 0.09; P = .99), with a similar percentage having spherical equivalent within ±0.50 diopters (D) (95.2% vs 95.0%; P = .71) and within ±0.75 D (98.9% vs 98.7%; P = .46) of intended target. The safety index (1.00 ± 0.03 vs 1.00 ± 0.04; P = .19) and Alpins correction index (1.00 ± 0.39 vs 1.01 ± 0.43; P = .53) were also identical. The mean postoperative refractive astigmatism difference between the shallow (0.15 D) and deep (0.20 D) groups was 0.05 D. The 3-month laser re-treatment rate was greater in the deep group (0.83% vs 0.37%; P = .02), but less than 1% for both groups.
Conclusions: The contribution of topography-guided HOA-AD to clinical outcomes in most virgin eyes is negligible, with excellent efficacy, accuracy, and safety in both the deep and shallow ablation groups. Eyes with deep HOA-AD greater than 15 µm trend to lesser outcomes, but should not be excluded from topography-guided surgery. [J Refract Surg. 2019;35(12):754-762].
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