Surface coverage with single vs. multiple gaze surface topography to fit scleral lenses.

BY Gregory DeNaeyera, Donald R. Sanders, Timothy S. Farajianc

To determine surface coverage of measurements using the sMap3D corneo-scleral topographer in patients presenting for scleral lens fitting.


Twenty-five eyes of 23 scleral lens patients were examined. Up-gaze, straight-gaze, and down- gaze positions of each eye were “stitched” into a single map. The percentage surface coverage between 10 mm and 20 mm diameter circles from corneal center was compared between the straight-gaze and stitched images. Scleral toricity magnitude was calculated at 100% coverage and at the same diameter after 50% of the data was removed.


At a 10 mm diameter from corneal center, the straight-gaze and stitched images both had 100% coverage. At the 14, 15, 16, 18 and 20 mm diameters, the straight-gaze image only covered 68%, 53%, 39%, 18%, and 6% of the ocular surface diameters while the stitched image covered 98%, 96%, 93%, 75%, and 32% respectively. In the case showing the most scleral coverage at 16 mm (straight-gaze), there was only 75% coverage (straight-gaze) compared to 100% (stitched image); the case with the least coverage had 7% (straight gaze) and 92% (stitched image). The 95% limits of agreement between the 50% and 100% coverage scleral toricity was between 1.4D (50% coverage value larger) and 1.2D (100% coverage larger), a 2.6D spread. The absolute difference between 50% to 100% coverage scleral toricity was 0.50D in 28% and 1.0D in 16% of cases.


It appears that a single straight-gaze image would introduce significant measurement inaccuracy in fitting scleral lenses using the sMap3D while a 3-gaze stitched image would not.