ORVIS
A common goal of low vision patients is to maximize their sight for reading. The Ohio Reading and Visual Impairment Study (ORVIS) examined the relationships between clinical vision measures, including reading performance, in visually impaired patients. The main goal was to evaluate predictive models for reading based on parameters collected during eye examinations. In this retrospective chart review, we evaluated examination data for 410 new patients who presented to the Low Vision Rehabilitation Service at The Ohio State University College of Optometry during a three-year period (2012 to 2015). The primary inclusion criterion was a minimum set of spatial vision data, including distance visual acuity and critical print size estimation (i.e. smallest angular print size that allows maximum reading rate). Data extracted included presenting visual acuity, contrast sensitivity, lighting preferences, estimated peak reading speed, critical print size (typically attained with the MNREAD test), and threshold print size. Descriptive statistics suggest that our patient demographics are similar to those of other large-scale low vision clinical studies. The average age of patients is 72 years, and the majority of patients are female (65%) and have age-related macular degeneration (53%). Threshold print size is on average worse (i.e. a larger angular size) than distance visual acuity by 0.077 log units, or about a factor of 1.2. In addition, both threshold print size and distance visual acuity are poor predictors of critical print size. The mean difference between critical print size and distance visual acuity is 0.273 log units, or approximately three lines, while the mean difference between critical print size and threshold print size is smaller at 0.197 log units, or approximately two lines. Regression analysis reveals that these differences diminish with poorer acuities. Furthermore, there is substantial variability in the magnitude of these differences, even for individuals with the same distance acuity or threshold print size. Calculation of 95% confidence intervals suggests that those critical print size estimates based on distance visual acuity can be approximated only within ±0.478 log units, while those based on threshold print size can be approximated only within ±0.288 log units. These results support direct measurement of critical print size with a dedicated reading assessment, rather than calculation of critical print size from a distance visual acuity or threshold acuity measurement.