Lewis N Reich | PubMed Health

PubMed2003

Accommodative response to PRIO Computer Vision Tester versus printed text.

BACKGROUND: Video display terminals (VDTs) have Gaussian display characteristics. Research suggests that patients accommodate differently to Gaussian images. In the present study, we asked if the accommodative response to the PRIO Computer Vision Tester (a Gaussian image) is different than the accommodative response to a Monocular Estimation Method (MEM) printed text target. METHOD: A normally sighted prepresbyopic group of subjects (N = 60) was recruited from the student body of Nova Southeastern University. Low neutral retinoscopy was performed on each subject at a distance of 50 cm. using both the PRIO vision tester and an MEM target. RESULTS: The PRIO vision tester and the printed text provided essentially the same measures of accommodative response. In addition, the luminance of the PRIO dropped by nearly 40% over the course of 1 hour of intermittent use. CONCLUSION: The PRIO vision tester and traditional nearpoint retinoscopy provided essentially the same measures of accommodative response in prepresbyopic subjects. Further studies should be considered to evaluate whether the change in luminance of the PRIO system has any effect on the measurement of accommodative response.

Accommodation, Ocular↗

PubMed2002

The effects of optical defocus on the legibility of the Tumbling-E and Landolt-C.

BACKGROUND: The Tumbling-E and Landolt-C are both used to test visual acuity in young, illiterate, or non-English-speaking patients. In this study, we sought to determine how optical blur affects visual acuity thresholds measured with both of these optotypes. METHODS: Ten subjects were tested with 4-position Tumbling-E and Landolt-Cs using the method of constant stimuli. The subjects were tested wearing their habitual corrections and with +1.50 D spherical and cylindrical lenses to simulate myopic refractive errors in the optical blur test conditions. RESULTS: Visual acuity thresholds for the Tumbling-E were slightly better for all test conditions, while the largest threshold difference between the test letters was found for the simulated against-the-rule astigmatism. For both test letters, vertical orientations were more difficult to resolve than horizontal. Also, the slopes of the psychometric functions were steeper for the Tumbling-E than for the Landolt-C. CONCLUSIONS: The Tumbling-E can be considered comparable with the Landolt-C except for the simulated against-the-rule-astigmatism test condition. Although the ranges are quite large, the average psychometric functions of the Landolt-Cs are flatter, which gives rise to the possibility that more confidence can be placed in the visual acuity thresholds obtained with the Tumbling-E.

Astigmatism↗