Gregory DeNaeyer, O.D. and Donald R. Sanders, M.D., Ph.D.
To determine repeatability of measurements using the sMap3D Corneo-Scleral Topographer in patients presenting for scleral lens fitting.
As part of our standard clinical evaluation, 25 eyes of 23 patients who presented for scleral lens fitting were examined twice in the same day with the sMap3D in this retrospective study. Sagittal height (SAG), sMap3D principal toricity magnitude (as calculated by the instrument software), and steep axis location were measured at a 16-mm chord diameter. Up gaze, primary, and down gaze positions of each eye were imaged and “stitched” by the instrument software into a single corneo-scleral topography map from which the measurements were derived.
The mean difference in SAG between the 2 examinations was 14 mm with an SD of 55 mm. Sixty-eight percent of cases had a difference of #50 mm, and 95% of cases had a difference of #100 mm. The mean difference in sMap3D principal toricity magnitude between examinations was 0.15 diopter (D) with an SD of 0.38 D. Eighty-four percent of cases had a difference of #0.5 D, and all cases had a difference of ,1 D. Mean toric axis difference between examinations was 2.5° with an SD of 18.4°. Sixty four percent of cases had an axis difference of #10°, and 84% had an axis difference of #15°.
The sMap3D measurements are repeatable with regard to scleral toricity and SAG values at a 16-mm diameter and thus would be suitable to use for scleral lens fitting.