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T. R. Hussoin, D. S. Jacobs, P. Rosenthal; The Effect of Scleral Lens Eccentricity on Vision in Patients for Corneal Ectasia. Invest. Ophthalmol. Vis. Sci. 2009;50(13):6349.
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© ARVO (1962-2015); The Authors (2016-present)
To report on the effects of scleral lens front surface eccentricity on best corrected visual acuity (BCVA), contrast sensitivity (CS) and higher-order aberrations (HOA) in patients with corneal ectasia.
Subjects already fitted with the Boston Ocular Surface Prosthesis (BOSP), a fluid-ventilated gas-permeable scleral lens, were recruited at the time of routine visit. Inclusion criteria include age 18 or greater, diagnosis of ectasia (keratoconus, pellucid marginal degeneration, post-Lasik ectasia), BCVA in BOSP of 20/30 or greater, and empiric inclusion of eccentricity in prior lens design based on patient subjective preference in at least one eye. If both eyes met inclusion criteria, the eye with better BCVA was selected for further study. Steepest SimK values were extracted from medical records. Through the habitual BOSP, BCVA and over-refraction (OR) were recorded, CS was measured using a Vector Vision CSV- l000CVA20/30 chart, and HOAs were measured using a COAS Wavefront Analyzer. Identical BOSPs, identical in except for amount of eccentricity, were manufactured in whichever values of 0, 0.3, 0.6, 0.8 eccentricity were not present in the habitual lens. BCVA, OR, CS, HOA with incremental amounts of eccentricity were recorded.
Results in our first three subjects are reported (M:F=3:0; Age:31-49). Steepest Sim K in the study eye was between 55.1-72.0D. Standard Snellen testing revealed that each patient achieved 20/20 in all lenses, regardless of eccentricity. In these patients, low contrast visual acuity does not appear to correlate with amount of eccentricity. Total HOAs and eccentricity had a strong negative correlation (Pearson correlation coefficient r = -0.861, P = 0.097). There was a significant correlation between total HOAs and coma along the x-axis (Pearson correlation coefficient r = 0.963, P<0.05).
Our results demonstrate that scleral lens front surface eccentricity modulates HOAs. Understanding the impact of front surface eccentricity on BCVA, low contrast visual acuity, and specific HOA may allow improved optical correction of vision in patients treated with scleral lens for corneal ectasia.
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