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Comparing the Single Maddox Rod Test to the Alternate Cover Test in Normal Individuals
Victoria Erickson1, Kimberly Merrill1, Collin M McClelland1
1Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota.
Purpose:
The single Maddox rod test (SMRT) is a rapid subjective method for detecting ocular misalignment. In this study, we compared the prism single Maddox rod test (PSMRT) to the prism alternate cover test (PACT) in normal individuals to see if there was any disagreement.
Methods:
Ocular alignment was measured at distance and near with the PSMRT and PACT in 52 normal participants. Secondary measurements included visual acuity, near point of convergence, and stereoacuity.
Results:
The difference between each participants' measurements at near (ΔX') was 4.44 ± 3.87 Δ (p < .001) meaning each participant was an average of 4.44 Δ more exophoric at near with the PSMRT compared to their measurement at near with the PACT. There was no significant difference between PSMRT and PACT at distance (-0.09 ± 1.33 Δ (p > .5)).
Discussion:
Among visually normal participants, the PSMRT measures more exophoria at near than the PACT. This difference may affect the interpretation of near alignment in various clinical settings, especially when evaluating patients with symptoms suggestive of convergence insufficiency. The PSMRT should be used with caution and be confirmed with the PACT when clinically indicated.
