Abstract
Purpose :
In many low-vision patients, visual function is measured by visual acuity, which measures the patient’s ability to resolve fine detail. Contrast sensitivity, which measures the ability to discern an object from its surroundings based on differences in luminance, is also an important marker for functional vision loss. Loss of contrast sensitivity is linked with difficulty doing everyday tasks and many ophthalmic diseases.
The Pelli-Robson (“PR”) chart is the standard for contrast sensitivity measurement and uses a letter-identification task. The Ohio Contrast Cards© (“OCC”), which uses a 0.15 cy/deg square-wave grating target, and the Mayer-Kran Double-Happy Cards™ (“DH”), which uses letter-like diagram of a face, are based on detection of their respective targets.
Previously, the OCC revealed higher contrast sensitivity compared to the PR chart. Was this due to the bold stripes of the OCC, or was it due to the detection task for the OCC compared to the letter-identification task of the PR? If the higher OCC performance was due to the stripes, then contrast sensitivity for the DH cards should be similar to that for the PR chart. If the higher OCC performance was due to the detection task, then DH performance should be similar to the OCC.
Methods :
50 adult participants with diverse vision disorders were patients in the OSU College of Optometry Low Vision Rehabilitation/Bioptic Driving Clinics. They participated after informed consent and were paid $10. Two examiners tested each participant: tester 1 used the PR and either DH or OCC; tester 2 used either the OCC or the DH. The card tests were used under a protocol similar to the Teller Acuity Cards. The order of testers and card tests varied across participants in a random-blocks design. The study was designed (power=0.90) to reveal differences >=0.15 Log10 units between the tests. Performance was examined by bootstrapped analysis of median performance.
Results :
Compared to the PR chart, both card tests revealed higher contrast sensitivity by ~.2 log units (95% ranges: OCC,.035—.340; DH,.033—.393). However, there was no significant difference between the card tests (difference=.002 Log units, 95% range: -.054—+.059).
Conclusions :
The superior contrast sensitivity revealed by the Ohio Contrast cards, compared to the Pelli-Robson chart, is due to the task (detection vs letter identification), rather than to the target stimulus (bold stripes vs letters).
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.