Flattening effect of corneal cross-linking depends on the preoperative severity of keratoconus

Abstract

A retrospective observational study was conducted to validate the effect of corneal cross-linking (CXL) on eyes with progressing keratoconus, depending on severity.In total, 45 eyes of 33 patients (age: 23.9 ± 6.8 years, range: 14–42 years) with progressive keratoconus who underwent CXL were enrolled. Examinations were performed at pre-, 1, 3, 6, and 12 months after surgery. In addition to a slit lamp microscopy, measurement of visual acuity, the steepest keratometric value (Kmax), the thinnest corneal thickness (TCT), and the corneal endothelial cell density (ECD) were assessed. Change in Kmax (ΔKmax) was calculated by subtracting the preoperative Kmax from the 12-month postoperative Kmax.CDVA, TCT, and ECD did not change significantly throughout the follow-up period. Kmax was 56.4 ± 7.2 D preoperatively and 54.3 ± 5.6 D at 12 months after CXL (P = .174). The average value of ΔKmax was −2.23 ± 4.31 D at 12 months after CXL. ΔKmax was negatively correlated with preoperative Kmax (ρ = −0.5517, P = .0001), and positively correlated with preoperative TCT (ρ = 0.4791, P = .0012). However, no correlation was observed between Kmax and patient age or the decrease ratio of ECD.The more flattening was obtained after CXL in cases with the more advanced keratoconus. No complication, including corneal endothelial damage, was observed even in advanced cases.

Epithelium-Off vs. transepithelial corneal collagen crosslinking in progressive keratoconus: 3 years of follow-up

“…The two most significant indicators of improvement in vision after corneal CXL were the preoperative values of low CDVA (≤ 20/40) and high K-max values (≥ 55 D). 1 , 8 , 20 , 21 In the current study, the central KCs exhibited lower average values for the preoperative CDVA, with higher K-max values (0.25 ± 0.04 log MAR and 56.6 D) compared to paracentral KC (0.1 ± 0.2 log MAR and 53.84 D), which could explain these results. The greater improvement in the CDVA in the central cones is in accordance with what has been published by other authors, 22 , 23 and this may be due to the fact that the central area is closer to the radiation of the CXL, so the intensity of radiation is higher than in the paracentral region, plus the depth does not appear to be homogeneous within the treatment area, exhibiting a decrease towards the periphery of the cornea.…”

Factors influencing haze formation and corneal flattening, and the impact of haze on visual acuity after conventional collagen cross-linking: a 12-month retrospective study

“…Preoperative K max was the only preoperative factor which correlated significantly with changes in haze and with changes in keratometry. Recently, several studies [ 29 – 31 ] have highlighted the prognostic significance of preoperative keratometry in determining the amount of topographic flattening after CXL. Our study has also demonstrated that a greater flattening might be expected in corneas with higher preoperative keratomtery readings.…”

Corneal flattening following collagen crosslinking for keratoconus: Findings at 5-year follow-up

“…Few authors studied risk factors for corneal flattening, concluding that preoperative Kmax was the only important risk factor for the decrease in corneal curvature, unlike age, gender, visual acuity, and corneal shape factors that weren't significantly associated with the flattening effect. 17,27 In addition, corneal flattening occurred more frequently in advanced keratoconus with a higher Kmax in comparison to mild to moderate disease. 18,19 In the current study, we found similar results showing that ΔKmax was positively correlated with preoperative Kmax, while no significant correlation of ΔKmax was found with age, gender, thinnest corneal pachymetry, corneal asphericity, keratoconus index, and the index of surface variance.…”