Astigmatic Vectorial Analysis in Pediatric Keratoconus After Unilateral Cross-Linking Treatment

The aims of this study were to evaluate the treatment response of pediatric keratoconus (KC) patients to unilateral corneal collagen cross-linking (CXL) in treated eyes, disease progression in untreated eyes, and define the predictive value of astigmatic parameters by astigmatic vectorial analysis.

Pediatric patients with KC with CXL-treated progressive eye and untreated fellow eye were included. Patients with other ocular conditions and a history of previous ocular surgery were excluded. Astigmatic changes in anterior and posterior corneal surfaces were evaluated with vectorial analysis. The receiver operating characteristic curves were analyzed to detect the best parameter that discriminates treated and untreated groups.

Thirty-two eyes of 16 patients with at least 2-year follow-up were analyzed. The maximum keratometry (K) in CXL-treated eyes remained stable (from 53.51 ± 2.86-53.41 ± 2.84 diopter (D), P = 0.84) while the steepest K increased in untreated eyes (from 47.82 ± 1.71-49.59 ± 3.32 D, P = 0.03). The oblique components of corneal astigmatism in CXL-treated eyes were higher than those of fellow eyes (all P < 0.05), which significantly decreased in the anterior 3-mm zone after treatment (P = 0.048). The mean differential astigmatism magnitudes were significantly higher in treated eyes (all P < 0.05). The refractive centroid remained unchanged in treated eyes (P = 0.553) and shifted in the oblique direction in untreated eyes (P = 0.04). The oblique differential astigmatism in the anterior 7-mm zone showed the highest area under the curve value in predicting treatment efficacy (0.813, 95% confidence interval: 0.646-0.981, P < 0.001).

Astigmatic vectorial analysis is an objective tool for longitudinal assessment of clinical outcomes in KC. Changes in the oblique components of corneal astigmatism might predict progression and treatment efficacy.