Ohio Contrast Cards are reliable and robust to blur under cycloplegia in visually normal children

Few clinical tests of visual performance can be performed equally well regardless of whether the patient has been dilated with a cycloplegic agent. This report shows that the Ohio Contrast Card test (OCC) is reliable across repeated measurements and robust to blur under cycloplegia.

The OCC measures clinical contrast sensitivity, including of patients who cannot read and report the letters on an eye chart. The OCC presents a 0.15 cycle per degree (20/4000, 2.3 logMAR) square-wave grating of variable contrast. We examined the test/retest reliability of the OCC, whether it can be used equally successfully to measure contrast sensitivity before versus after dilation with a cycloplegic agent, and whether it is sensitive to blur from uncorrected refractive error and cycloplegia. Participants were a group of visually normal pediatric optometric patients.

Two examiners used the OCC to measure the eyes of 38 children who were seen for full eye examinations. Two tests were performed before cycloplegic agents were administered while participants wore their habitual refractive corrections. The examiners were randomly assigned to the two tests. After the eye examination (post-cycloplegia), the measurements were repeated, with and without correction. Statistical analyses examined test/retest reliability before and after cycloplegia and the impact of blur due to cycloplegia and uncorrected refractive error.

The first two (pre-cycloplegic) tests indicated high reliability. The contrast sensitivity values from the second test were within ±0.15 log 10 units of the first in 97.4% of cases (mean difference = 0.012 log 10 units). Similar results were obtained when the first test was compared with the post-cycloplegic tests, with or without correction. Limits of agreement were the same (±0.220) when the first test was compared with each repeat test. Under cycloplegia, participants' contrast sensitivity was not associated with the absolute amount of blur for the OCC grating. Thus, the OCC results did not depend systematically on the refractive state of the eye in this pediatric population.

The OCC is a reliable test that can be used on pediatric patients irrespective of whether the patient is under cycloplegia. Its resistance to blur is due to the very low-spatial-frequency square-wave target.