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

Abstract

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 ( p = 0.809). In the epi-on group, this change was significantly correlated with the preoperative apical (r = −0.375, p = 0.045) and central corneal thickness (r = −0.402, p = 0.031). In the epi-off group, the CDVA change was significantly correlated with not only the preoperative apical (r = 0.402, p = 0.028) and central corneal thickness (r = 0.367, p = 0.046) but also with some topometric and aberrometric indices (r ≤ −0.374, p ≤ 0.042). Furthermore, the change in CDVA in the epi-on group could be predicted from age, preoperative refractive astigmatism J45 component, anterior corneal asphericity, and posterior corneal high order aberration root mean square ( p = 0.002, R2 = 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 ( p = 0.001, R2 = 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.

Analysis of Tear Function Outcomes following Collagen Cross-Linking Treatment in Ectatic Corneas

“…Considering the ocular morbidity that dry eye can cause, therapeutic approaches to managing keratoconus should not worsen any underlying dry eye. Few studies have compared epi-on and epi-off surgery in terms of visual and tear film functional changes, or even in terms of the progression of keratoconus [ 18 , 19 ]. Therefore, we studied the effects of two surgical methods on BCVA, which are described as decimal visual acuity style and tear film function of patients with keratoconus.…”

Binocular Visual Function Changes After Corneal Collagen Cross-linking in Patients With Keratoconus

“…28 As a consequence, visual improvement with epi-off CXL is related to the severity of the disease, while the mechanism of improvement with an epi-on CXL technique are potentially independent from it. 28 The effects of CXL on HOAs have been postulated to be a consequence of the flattening of the corneal apex. 29 By contrast, posterior corneal surface seems to be negatively affected by CXL as concerns the burden of HOAs.…”

“…By contrast, epi-off CXL has better effects on CDVA in eyes with thinner corneas and significant levels of primary coma on the anterior corneal surface. 28 As a consequence, visual improvement with epi-off CXL is related to the severity of the disease, while the mechanism of improvement with an epi-on CXL technique are potentially independent from it. 28 The effects of CXL on HOAs have been postulated to be a consequence of the flattening of the corneal apex.…”