Consistency between visual acuity scores obtained at different test distances: Theory vs observations in multiple studies

Li Ming Dong, Barbara S. Hawkins, Marta J. Marsh

Research output: Contribution to journalArticlepeer-review

Abstract

Objective: To investigate the consistency of visual acuity (VA) scores measured at 2 different distances in patients with or at risk for choroidal neovascularization. Methods: Best-corrected VA scores measured at 2 distances for the same eyes at the same examinations were collected from 4 sets of randomized clinical trials among patients with or at risk of choroidal neovascularization. Within each trial, the pairs of VA scores were compared and their relationship was explored. Results: After adjustment for test distance, VA scores obtained at the closer distance were found to be systematically lower than those obtained at the farther distance in all data sets. In the Submacular Surgery Trials pilot study, the average discrepancy between 2- and 0.5-m VA scores was 7.5 letters. In an ancillary study of the Macular Photocoagulation Study, the discrepancy between 10-ft and 5-ft VA scores was 3.1 letters. In the Laer to Drusen Trial pilot study, the discrepancy between 3.2- and 1-m VA scores was 7.3 letters. In the Treatment of Age-Related Macular Degeneration With Photodynamic Therapy Study, in which the VA scores at the closer test distance were censored, the estimated discrepancy between 2- and 1-m VA scores was 8.2 letters. Reduction in visual angle at closer test distance did not explain the discrepancy completely. Features of the macular lesion, poor accommodation of the elderly population with age-related macular degeneration, or the test charts did not account for the discrepancies. Conclusion: The VA scores at distances less than 2 m were lower than expected in all 4 studies. The observed discrepancy was consistent with findings from a study among healthy young subjects, suggesting that the phenomenon is real and common.

Original languageEnglish (US)
Pages (from-to)1523-1533
Number of pages11
JournalArchives of ophthalmology
Volume120
Issue number11
DOIs
StatePublished - Nov 1 2002

ASJC Scopus subject areas

  • Ophthalmology

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