Evaluation of the effect of corneal collagen cross-linking for keratoconus on the ocular higher-order aberrations

Abstract

BackgroundCorneal collagen cross-linking (CXL) is the only treatment currently available to arrest the progression of keratoconus. The procedure consists of photopolymerization of stromal collagen fibers induced by combined action of a photosensitizing substance (riboflavin or vitamin B2) and ultraviolet-A light.PurposeTo determine changes in the ocular higher-order aberrations (HOAs) after CXL and its correlation with changes in visual acuity.DesignProspective interventional study.Subjects and methodsThis study was conducted on 30 eyes of 16 patients with progressive keratoconus documented between 2012 and 2014. Patients were treated with epithelium-off CXL and followed for a minimum of 6 months. The following ocular HOAs were measured and analyzed using I-Tracey Aberrometer: coma, trefoil, spherical aberration, astigmatism, and total HOAs.ResultsThere was statistically significant improvement in uncorrected visual acuity and best-corrected visual acuity between the preoperative and 6-month evaluations (P<0.001). Total HOAs and total coma were statistically significantly reduced at 6 months by 25% and 18%, respectively. Significant improvement was seen in spherical aberration by 8.71% (P<0.001), while no significant change was observed in trefoil and high order astigmatism (P=0.405 and 0.329, respectively). There was a statistically significant change in the average (K) value at the apex between the preoperative values and the 6-month values (P<0.05).ConclusionTotal HOAs, total coma, and spherical aberrations decreased after CXL. Coma has a direct relationship with the improvement of visual function.

<p>Accelerated Epithelium-Off Corneal Collagen Cross-Linking For Keratoconus: 12-Month Results</p>

“…In this work, we recorded the corneal thickness before and after the procedure. Statistically significant corneal thinning was found after the procedure as reported by many other previous studies 23,29. This thinning can be explained by postoperative keratocyte apoptosis and structural changes in corneal collagen fibrils and extracellular matrix in the anterior stroma.…”

“…These results are relatively different from the results found by El-Massry et al who found that total HOAs and total coma were significantly reduced at 6 months by 25% and 18%, respectively. Significant improvement was seen in spherical aberration by 8.71%, while no significant change was observed in trefoil 23. As stated before, the main changes in HOAs after corneal cross-linking were in the coma, particularly vertical coma, and spherical aberrations.…”

“…In a study done by El-Massry et al, they found a statistically significant reduction in mean K reading. The preoperative mean K was 47.21±3.18 D and changed to 44.14±2.09 D with a difference of means of about 3D 23. This finding was also addressed by Caporossi et al, who recorded topographic mean reduction in dioptric power of about 2 D, but they reported initial worsening of keratometric readings in the first month which might have been due to transient haze and corneal edema 24.…”

Delayed Topographical and Refractive Changes Following Corneal Cross-Linking for Keratoconus

“…This prompted us to investigate in our series a possible correlation between an improvement in corneal aberrations and corrected visual acuity, as previously reported by El-Massry et al [ 19 ]. If such an association was detected, one could have concluded that improved corneal aberrations, more than topographical flattening, would play a significant role in improving CDVA in the long term after CXL.…”

Predictors of Successful Outcome following Intrastromal Corneal Ring Segments Implantation

“…It should be considered that the i-Trace aberrometer was previously shown to be valid for characterizing ocular aberrations in keratoconus. 30,31 All measurements with the TMS-4, Pentacam, ORA and i-Trace were taken by the same experienced and qualified technician to avoid any bias.…”