TOPOGRAPHY, TOMOGRAPHY, AND ABERROMETRIC EVALUATION OF THE CORNEA IN THE PEDIATRIC POPULATION

To compare topographic, tomographic, and aberrometric parameters among children and adolescents with keratoconus and patients with known risk factors for developing this disease. A secondary purpose is to assess the repeatability and agreement of three different devices in those patients. 

Department of Ophthalmology of the Federal University of São Paulo, Brazil; Department of Ophthalmology of the University of Coimbra, Portugal.

This is a cross-sectional study. Patients were divided into 5 groups: Keratoconus (KC), ocular allergy, astigmatism higher than 2 diopters, Down´s Syndrome (DS), and a control group (CG). All patients were scanned by three devices, named the NIDEK OPD-Scan III, the Pentacam HR, and the Carl Zeiss Vision i.Profiler Plus. Corneal topography values of the anterior and posterior cornea, asphericity (Q value), and wavefront aberrometry were compared among these three devices in each group. Pachymetry and derived indices provided by Pentacam were also compared. The differences in measurements among groups were evaluated by multivariate mixed-effect models. The reproducibility between equipment was evaluated by Intraclass correlation (ICC) tests. P values <.05 were considered statistically significant. 

220 eyes of 114 patients were included in this study, with a median age of 12.78±3.78. Comparing the groups, the statistical analysis revealed that KC and DS had Km values 4.07 and 2.77 higher than CG respectively (p.value <0.05). Median thinner pachymetry was 555 in CG, 487 in KC, and 495 in DS (p.value <0.05). Down´s syndrome patients showed a higher K1 and K2, a thinner cornea, and more high-order aberration than all other groups except for the KC group. In these patients, ART-max and the BAD-D values surpassed the cut-off values for suspicious KC. Vertical coma, spherical aberration (SA), and trefoil were statistically different in the KC group. The ICC indicated that pentacam had excellent reliability in almost every parameter, except the trefoil. The OPD-Scan III and the I.Profiler Plus showed poor reliability in aberrometry values and asphericity but excellent reliability in keratometric parameters. When comparing the three devices, Pentacam showed lower values of K1 and K2 when compared to OPD and i.Profiler. No differences were observed for Q values. The aberrometry indices varied significantly among the three devices with no specific pattern. 

Down´s syndrome patients have a more curved and thinner cornea than the control group in a pattern that resembles keratoconus. KC patients have more vertical coma, trefoil, and SA aberration. Pentacam, OPD scan III, and i.Profiler Plus may be considered interchangeable for keratometric readings and asphericity. Pentacam had better repeatability than I.Profiler and OPD, especially in aberrometric measurements.