Relationship of placido corneal topography data with scleral lens fitting parameters

Abstract

Purpose: To analyze the relationship between corneal sagittal height and asymmetry parameters derived from Placido-videokeratoscopy with the parameters of fitted scleral lenses (ScCLs). Methods: Corneal topographies were measured with MedmontE300 in a total of 126 eyes with irregular and regular corneas before ScCL fitting were analyzed. Measurements of sagittal height (OC-SAG) at steep and flat corneal meridians were obtained for 10mm and 12mm chords. Estimated Height (EHChord) parameters were taken for a chord equal to the diameter of the lens that each subject was wearing at different semi-meridians. Corneal asymmetry (difference in OC-SAG between steep and flat corneal meridians) was also assessed. These outcomes were correlated to ScCL parameters that subjects were wearing after 1 month. Results: The mean ScCL-SAG was 4696 ± 240μm, and the mean OC-SAG ranged from 1891μm (10mm), 2914μm (12mm), and between 4162μm and 4251μm for EH0-180º and EH30-210º. Stronger correlations (p < 0.001) between OC-SAG and ScCL-SAG were determined for EH0-180º (r=0.595) and EH30-210º (r=0.618). The mean differences between OC-SAG and ScCL-SAG were between 447 ± 290μm (EH0-180º) and 389 ± 360μm (EH30-210º). There was no relationship between corneal asymmetry and the need to fita ScCL with toric haptic design in irregular corneas. Orientation of flat corneal and scleral meridians were similar only in corneas with high regular astigmatism. Conclusions: EHChord attributes were the parameters that best correlated with the ScCL-SAG. The corneal asymmetry was shown to be a poor predictor for the need to fit a ScCL with toricity at landing zone in irregular corneas, but could have some predictive power in regular corneas.