Change in over-refraction after scleral lens settling on average corneas

PurposeThe purpose of this study was to determine the change in over-refraction, if any, after a scleral lens settled on the eye for 6-8h. MethodsSixteen patients of varying refractive errors and normal corneal curvatures (measured with Pentacam Oculus) were fitted with trial Mini-Scleral Design (MSD) scleral lenses (15.8mm diameter) in one eye. The sagittal depths of the scleral lenses were selected by adding 350m to the corneal sagittal heights measured at a chord length of 15mm with the Visante optical coherence tomographer (OCT) anterior segment scans and picking the closest available trial lens in the set. Initial measurements were taken 30min after lens insertion and included an auto-refraction, subjective refraction, and best sphere refraction over the contact lens. Visual acuities and Visante OCT anterior segment scans were also taken. These measurements were repeated after 6-8h of lens wear. ResultsOver the trial wearing period, the average change in the spherical component of the over-refraction was +0.06 D (S.D. 0.17) (p=0.16). The average change in cylinder was +0.04 D (S.D. 0.19) (p=0.33). The average absolute change in axis was 1.06 degrees (S.D. 12.11) (p=0.74). The average change in best sphere was +0.130.30 D (p=0.12). There was no significant change in visual acuity with the best sphere over-refraction over the 6-8h wearing period. There was a significant change in central corneal clearance over the wearing period of 83m (S.D. 22) (p<0.0001). ConclusionDespite a significant change in the central corneal clearance due to thinning of the fluid reservoir as the scleral lens settled (an average decrease of 83m after wearing the lenses for 6-8h), there was not a statistically significant change in the subjective over-refraction (sphere, cylinder, and axis) or best sphere or visual acuity. This study has confirmed that there is no link between reduction in central corneal clearance and change in over-refraction for average corneas.