Astigmatic vectorial analysis is a useful method for evaluating disease progression and efficacy of unilateral corneal collagen crosslinking (CXL) treatment in pediatric patients with keratoconus (KC), according to a study published in Cornea.

The investigators used vectorial analysis to examine astigmatic changes in anterior and posterior corneal surfaces. They analyzed receiver operating characteristic curves (ROC) to identify the best parameter that discriminates between treated and untreated groups. The researchers looked at 32 eyes of 16 patients (10 boys, 6 girls) with pediatric KC treated with CXL. The mean age of the participants was 15±2.8 years (range: 9-18 years). All patients underwent CXL treatment in 1 eye, while the other eye did not receive any intervention. 

According to the report, the maximum keratometry (K) in eyes treated with CXL remained stable (from 53.51±2.86 D to 53.41±2.84 D, P =.84), while the steepest K increased in the untreated eyes (from 47.82±1.71–49.59±3.32 D, P =.03). The oblique components of corneal astigmatism in treated eyes were higher than those in untreated eyes (all P <.05), which significantly decreased in the anterior 3 mm zone at follow-up (P =.048). The study also shows that mean differential astigmatism magnitudes were significantly higher in treated eyes (all P <.05). The refractive centroid did not change in treated eyes (P =.553) and shifted in the oblique direction in untreated eyes (P =.04). Longitudinal ROC analysis reveals that the anterior 7 mm zone had the highest area under the curve in all parameters (0.813, 95% CI: 0.646–0.981, P =.003).


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“Astigmatic vectorial analysis is an objective tool for longitudinal assessment of clinical outcomes in KC,” the researchers report. “The oblique vectorial astigmatic changes in the early stages of KC might be a promising biomarker to predict disease progression and to confirm treatment efficacy, which needs approval by further studies in larger populations.”

Study limitations include the retrospective design, limited sample size, possible bias, the inclusion of only pediatric patients, and no clinical data on patients before enrollment were available. According to the researchers, a more sufficient evaluation for the clinical utility of astigmatic vectorial analysis requires: “(1) a control group of untreated, nonprogressive KC eyes to compare with both untreated, progressive, and CXL-treated KC eyes for disease progression and (2) a group consisted of progressive KC eyes despite receiving CXL treatment to compare with CXL-treated eyes with halted progression for treatment efficacy.”

Reference

Kesim C, Öztürkmen C, Şahin A. Astigmatic vectorial analysis in pediatric keratoconus after unilateral cross-linking treatment. Cornea. 2022;41(3):272-279. doi:10.1097/ICO.0000000000002924