Changes in High and Low Contrast logMAR Visual Acuity with Overnight Orthokeratology

Abstract

Abstract: : Purpose:The difference between unaided logMAR high and low contrast visual acuity was evaluated to determine whether low contrast visual acuity changes at a different rate than high contrast visual acuity over time in a sample of overnight orthokeratology patients. In previous reports in the literature, traditional soft contact lenses, PRK, and LASIK have all been shown to reduce contrast sensitivity and/or low contrast visual acuity. Methods:Two lens designs were used: the Fargo lens from G.P. Specialists and the CRT lens from Paragon Vision Sciences. Subjects were examined at the time of lens removal (morning) and a minimum of 6 hours later (afternoon) at visits one, three and six months following a baseline examination. Standardized protocols to measure high and low contrast visual acuity using Bailey-Lovie charts were used for study outcome measures. Unaided visual acuity was recorded as the number of letters read correctly. This number was converted to logMAR for analysis Results:  

No significant changes were found for any of the above comparisons. Conclusion:Low contrast visual acuity does not improve at a different rate than high contrast visual acuity with overnight orthokeratology.

Keywords: 367 contact lens • 620 visual acuity