Corneal Asphericity Preservation via Spatially Selective Peripheral Stromal Volume Ablation Following Ray-tracing-Guided LASIK.

PURPOSE: To quantitatively appraise postoperative visual quality and to delineate the spatial corneal morphological changes occurring within the central and pericentral optical zones subsequent to ray-tracing-guided laser in situ keratomileusis (RTLASIK) compared to Q-value-guided LASIK (Q-LASIK).

METHODS

Sixty eyes from 60 patients were enrolled: 30 eyes in the RT-LASIK group and 30 eyes in the Q-LASIK group with a mean preoperative spherical equivalent of -5.029 ± 1.532 diopters (D) versus -5.279 ± 1.779 D. The cornea was partitioned into three vertex-centered concentric regions: a central 0- to 3-mm optical zone, a paracentral 3- to 5-mm annulus, and a pericentral 5- to 7-mm annulus. The corneal ablation ratio (CAR) was calculated as the quotient of the preoperative-to-postoperative reduction in either corneal thickness (tCAR) or stromal volume (vCAR) divided by the absolute value of the preoperative SE.

RESULTS

Relative to the Q-LASIK group, the RT-LASIK group exhibited significantly superior uncorrected distance visual acuity, spherical equivalent, and 3-mm Strehl ratio 3 months postoperatively. The vCAR within the same 3- to 5-mm zone was significantly elevated in the RT-LASIK group, whereas the tCAR did not differ between groups. Furthermore, RTLASIK was associated with a significantly attenuated postoperative change in Q-value within the 5-mm zone, a more pronounced reduction in spherical aberration across all of the optical zones.

CONCLUSIONS

RT-LASIK conferred superior postoperative visual performance by conserving native corneal asphericity and effecting a significant reduction in spherical aberration across the entire optical zone. This optical advantage was mediated by a proportionally greater ablation of stromal volume within the paracentral 3- to 5-mm annulus.