Characteristics influencing visual outcomes of corneal topography-guided excimer laser keratectomy combined with corneal cross-linking for keratoconus.

PURPOSE: To identify preoperative predictive factors for visual outcomes of corneal topography-guided excimer laser keratectomy (TG-PRK) combined with corneal collagen cross-linking (CXL) in keratoconic eyes, and to explore potential thresholds of these factors for optimizing patient selection.

METHODS

Keratoconic patients who underwent CXL combined with TG-PRK were enrolled and divided into the on-target group and off-target group based on the difference between the best spectacle-corrected visual acuity (BSCVA) at the last postoperative follow-up and the preoperative BSCVA. Preoperative parameters, including corneal topography (e.g., index of surface variance [ISV]), refraction (e.g., cylinder power), biomechanics, and aberrations, were compared between groups. Generalized estimating equations (GEE) were used to identify independent predictors, while receiver operating characteristic (ROC) curves and restricted cubic splines (RCS) were applied to assess predictive efficacy and potential thresholds.

RESULTS

A total of 107 participants (113 eyes) were enrolled, with 79 eyes in the on-target group and 34 eyes in the off-target group. GEE analysis showed that preoperative ISV (OR=1.04, 95% CI:1.01-1.08, P = 0.038) and preoperative cylinder power (OR=1.72, 95% CI:1.13-2.60, P = 0.011) were independent predictors of visual response. ROC analysis demonstrated modest discriminative ability for both parameters (ISV: AUC=0.671, P = 0.004; cylinder power: AUC=0.670, P = 0.005). RCS analysis identified ISV>96.37 and preoperative cylinder power>4.25 D were associated with an increased risk of off-target visual outcomes.

CONCLUSIONS

Preoperative ISV and cylinder power may help identify patients at increased risk of suboptimal BSCVA after TG-PRK-CXL. Further studies are required to validate these exploratory thresholds.