Abstract
Purpose :
Visual acuity exams are the primary subjective exam to detect or track progression of ophthalmic disease. However, the ability to distinguish certain features to correctly identify objects is labeled “recognition” acuity and may interfere with accurate visual acuity measurements. Therefore, we sought to characterize the recognition of optotypes seen on common visual acuity exams.
Methods :
Optotypes were displayed on a high-definition digital monitor and images were captured using cell phone placed behind a phoropter with various spherical, cylindrical and axis lenses. Using a custom in-house application, images with differing amounts of distortion were displayed to human subjects with normal best-corrected visual acuity in a “forced-choice” style multiple-choice exam. Subjects were forced to determine what optotype character was displayed. Test results were presented as heatmaps to optotype recognition accuracy for a range of optical distortions.
Results :
36 healthy human subjects completed the exam. Heatmaps of each optotype show accuracy of the 4 subjects evaluated for their recognition of each optotype. No optical distortion (0 sphere/cylinder with no axis of rotation) is displayed in top left corner. Allen and Wright (pediatric) optotypes had the highest recognition accuracy, whereas letter-based optotypes scored the lowest.
Conclusions :
Optotypes have differing levels of recognition and could potentially result in a variation in performance on visual acuity exams. These results support findings that ETDRS and Snellen optotypes are not interchangeable, and this non-interchangeability applies to all optotypes. Additionally, visual acuity results may not be interchangeable unless the optotype used is fixed.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.