Short-term changes in corneal curvature and thickness after scleral lens wear

Scleral lenses are often used in patients with keratoconus to optimize vision. This small study sought to measure changes in corneal curvature and thickness after 6 hours of wearing scleral lenses. Measurements included Kflat, Ksteep, and Kmax.

Study design

This single-center, prospective study included 17 eyes of 12 patients with keratoconus. All had endothelial cell counts of more than 2000 cells/mm² and all were new to contact lens wear except 1 patient who had previously used rigid gas permeable lenses for a few days 3 months before the study visit. Patients were fitted with a 16.0 mm-diameter scleral lens. Corneal thickness and anterior flat, steep, and maximal keratometry values were obtained at baseline, after 6 hours of lens wear, and the next morning using a Scheimpflug rotating camera.

Outcomes

All 3 keratometry readings had minimal flattening that was not statistically significant after 6 hours of lens wear and all returned to baseline the next morning. After 6 hours of wear, the mean Kflat was 0.28 ± 0.31 D flatter, Ksteep was 0.37 ± 0.09 D flatter, and Kmax was 0.19 ± 0.24 D flatter. Central corneal thickness increased by 7.76 ± 3.00 μm but returned to baseline the next morning.

Limitations

One of the limitations of this study is the small sample size. Also, there was no control group so it is unclear what degree of change (if any) would be seen in a similar population not wearing scleral lenses. The study only looked at patients new to wearing scleral lenses and only evaluated for changes after 6 hours of wear; patients with keratoconus who have been wearing scleral lenses every day for months or years and/or wear their lenses for 12–14 hours each day may have different results. It would be interesting to perform the same study in keratoconic eyes that have already undergone corneal crosslinking to see if that procedure would affect results.

Clinical significance

Short-term scleral lens wear in keratoconic eyes new to contact lenses causes minimal flattening of keratometry readings and minimal increase in central corneal thickness measurements, all of which return to baseline the next morning. These results can be helpful to keep in mind when assessing these patients for progression.