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.
Highlights
Keratoconus (KC) is a progressive disease in which the cornea becomes thinner, inducing irregular astigmatism and reduced quality of vision [1,2,3]. e exact mechanism of KC development is not well understood, but it is commonly accepted that genetic susceptibility and environmental factors are necessary [2]
All of them had undergone the accelerated epithelial-on or accelerated epithelial-off CXL in the Torrecardenas University Hospital (Almeria, Spain) from May 2017 to January 2020. e classification of KC severity into four stages was performed in accordance with the Amsler–Krumeich grading criteria based on the mean corneal power, transparency, astigmatism, and the thinnest point of corneal thickness [19]. e research was carried out in accordance with the principles of the Declaration of Helsinki and was approved by the Clinical Research Ethics Committee of Torrecardenas Hospital
Two patients did not have a complete follow-up and were excluded from the analysis. erefore, the data from 67 patients (67 eyes) with a complete follow-up of 12 months after CXL were analyzed. e sample included a total of 71.0% of males and 29.0% of females. e epi-on group consisted of a total of 35 eyes of 35 patients (50.7%), while the epi-off group comprised a total of 32 eyes of 32 patients (46.4%). e mean ages of the epi-on and epi-off groups were 26.5 ± 1.0 and 23.5 ± 1.0 years (p 0.130) (Table 1)
Summary
Keratoconus (KC) is a progressive disease in which the cornea becomes thinner, inducing irregular astigmatism and reduced quality of vision [1,2,3]. e exact mechanism of KC development is not well understood, but it is commonly accepted that genetic susceptibility and environmental factors are necessary [2]. A successful CXL can prevent the progression of KC and can even cause the ectatic cornea to regress, and a non-effect or even worsening of the ocular parameters can occur [2]. For this reason, CXL research in recent years has attempted to define the predictive factors for the outcomes achieved with this technique with the aim of helping the clinicians manage the patients’ expectations and minimize the exposure to potential side effects. Multiple factors have been defined, including preoperative visual acuity, the eccentricity of the cone, pretreatment Kmax, age, and gender [2]
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