Preliminary Characterization of Predictive Factors of the Visual Change after Epi-On and Epi-Off Corneal Collagen Crosslinking Techniques.

Purpose: To investigate the potential predictive factors of the visual change achieved with accelerated epi-on and epi-off corneal collagen crosslinking (CXL) in keratoconus.

Methods: This retrospective comparative study analyzed 67 eyes treated with an accelerated epithelium-on (epi-on group) and epithelium-off (epi-off group) CXL. The clinical outcomes were evaluated and compared during a 1-year follow-up. Likewise, the relationship of the change achieved with both CXL techniques in the corrected distance visual acuity (CDVA) with different preoperative data was investigated.

Results: The mean CDVA change at 3 months postoperatively was -0.04 ± 0.19 and -0.07 ± 0.25 in the epi-on and epi-off groups, respectively ( = 0.809). In the epi-on group, this change was significantly correlated with the preoperative apical ( = -0.375,  = 0.045) and central corneal thickness ( = -0.402,  = 0.031). In the epi-off group, the CDVA change was significantly correlated with not only the preoperative apical ( = 0.402,  = 0.028) and central corneal thickness ( = 0.367,  = 0.046) but also with some topometric and aberrometric indices ( ≤ -0.374,  ≤ 0.042). Furthermore, the change in CDVA in the epi-on group could be predicted from age, preoperative refractive astigmatism J component, anterior corneal asphericity, and posterior corneal high order aberration root mean square ( = 0.002,  = 0.503). In the epi-off group, the CDVA change could be predicted from the preoperative minimum corneal thickness and magnitude of the vertical anterior corneal primary coma component ( = 0.001,  = 0.446).

Conclusions: Clearly, different predictive factors of the visual change induced with the accelerated epi-on and epi-off CXL techniques are present, suggesting a different mechanism of action for stiffening the cornea and inducing changes in this structure.