AUTHOR=Alvarez Tara L. 

TITLE=A pilot study of disparity vergence and near dissociated phoria in convergence insufficiency patients before vs. after vergence therapy

JOURNAL=Frontiers in Human Neuroscience

VOLUME=9

YEAR=2015

URL=https://www.frontiersin.org/journals/human-neuroscience/articles/10.3389/fnhum.2015.00419

DOI=10.3389/fnhum.2015.00419

ISSN=1662-5161

ABSTRACT=<p><bold>Purpose:</bold> This study examined the relationship between the near dissociated phoria and disparity vergence eye movements. Convergence insufficiency (CI) patients before vergence therapy were compared to: (1) the same patients after vergence therapy; and (2) binocularly normal controls (BNC).</p><p><bold>Methods:</bold> Sixteen subjects were studied—twelve BNC and four with CI. Measurements from the CI subjects were obtained before and after 18 h of vergence eye movement therapy. The near dissociated phoria was measured using the flashed Maddox rod technique. Vergence responses were stimulated from 4° symmetrical disparity vergence step stimuli. The peak velocity of the vergence response and the magnitude of the fusion initiating component (FIC) from an independent component analysis (ICA) were calculated. A linear regression analysis was conducted studying the vergence peak velocity as a function of the near dissociated phoria where the Pearson correlation coefficient was computed.</p><p><bold>Results:</bold> Before vergence therapy, the average with one standard deviation FIC magnitude of convergence responses from CI subjects was 0.29° ± 0.82 and significantly less than the FIC magnitude of 1.85° ± 0.84 for BNC (<italic>p</italic> &lt; 0.02). A paired <italic>t</italic>-test reported that the FIC and near dissociated phoria before vergence therapy for CI subjects significantly increased to 1.49° ± 0.57 (<italic>p</italic> &lt; 0.04) and became less exophoric to 3.5Δ ± 1.9 exo (<italic>p</italic> &lt; 0.02) after vergence therapy. A significant correlation (<italic>r</italic> = 0.87;<italic> p</italic> &lt; 0.01) was observed between the near dissociated phoria and the vergence ratio of convergence peak velocity divided by divergence peak velocity.</p><p><bold>Conclusion:</bold> The results have clinical translational impact in understanding the mechanism by which vergence therapy may be changing the vergence system leading to a sustained reduction in visual symptoms.</p>