Biometric Parameters Variation After Corneal Collagen Cross-Linking In Pediatric Patients

Corneal collagen cross-linking is often performed in children and adolescents. The developmental trajectory of the axial length is a crucial determinant of the refractive state and visual function of children and teenagers. Despite being a potential modifier of the ocular anatomy, there is limited data to document the impact of CXL in the evolution of the anterior chamber depth (ACD) and axial length (AL) in pediatric keratoconus patients. We compared biometric parameters of pediatric patients submitted to unilateral CXL.

- Department of Ophthalmology, Coimbra Hospital and University Center (CHUC), Coimbra, Portugal;

- Clinical Academic Center of Coimbra (CACC), Coimbra, Portugal;

- Faculty of Medicine, University of Coimbra (FMUC), Coimbra, Portugal

Patients diagnosed with keratoconus (KC) and submitted to unilateral CXL in pediatric age were included for analysis. Corneal tomography (Oculus Pentacam, Optikgerate GmbH, Wetzlar, Germany) and biometry (IOLMaster 700, Carl-Zeiss company, Germany) were performed in every patient. AL and ACD indices were compared between eyes submitted to CXL and not. The length of the posterior segment (PS), here calculated as the difference between AL and ACD was also analyzed. All parameters were compared between eyes intra-individually using Mann-Whitney U test. Results were analyzed in the overall data and then correlated with age at surgery and follow-up duration using Spearman correlation.

We have enrolled 20 eyes of 10 patients, 8 (80%) males, mean age at surgery of 15.15±2.17 years; 10 eyes (one of each patient) were submitted to CXL. Mean age of follow-up until analysis was 4.86±1.40 years.

Mean AL for all cases was 24.01±0,64 mm, mean ACD was 3.82±0.28 mm and mean PS was 20.19±0.55 mm. AL in eyes submitted to CXL was 23.95±0.75 mm while AL in the fellow eye was 24.06±0.53 mm (p=0.91). ACD was 3.79±0.26 and 3.84±0.32 mm (p=0.70) in eyes with and without CXL, respectively. The PS of CXL eyes was 20.16±0.71 mm and the PS of the fellow eyes was 20.22±0.38 mm (p=0.97).

The differences for PS length were not significantly correlated with neither age at the time of surgery (p=0.12) nor duration of follow-up (p=0.47).

There is ongoing controversy regarding the potential anatomical impact of CXL in keratoconus eyes. Previous data has shown a continued modifier effect that can extend for more than a decade.  In our data, no statistically significant impact on AL, ACD or PS measurements was noted. Despite the limitations related to our narrow sample size, our results strengthen the hypothesis that the effect of UV radiation in CXL is limited to the corneal stroma and highlight the favorable safety profile of CXL.