Visual fatigue effects on vergence dynamics in asymptomatic individuals. (22nd August 2013)

• Record Type: Journal Article
• Authors: Thiagarajan, Preethi; Ciuffreda, Kenneth J
• Is Part Of: Ophthalmic and physiological optics. Volume 33:Number 6(2013:Nov.)
• Page Start: 642
• Page End: 651
• Publication Date: 2013-08-22
• Subjects: Ophthalmology -- Periodicals; Physiological optics -- Periodicals; Optometry -- Periodicals; Optics -- Periodicals; Vision -- Periodicals; 617.75
• DOI: 10.1111/opo.12083
• Languages: English
• ISSNs: 0275-5408

Abstract

<abstract abstract-type="main" id="opo12083-abs-0001"> <title>Abstract</title> <sec id="opo12083-sec-0001" sec-type="section"> <title>Purpose</title> <p>To evaluate objectively changes in vergence dynamics following intentional visual fatiguing tasks using congruent (C) and non‐congruent (NC) vergence stimulus demands.</p> </sec> <sec id="opo12083-sec-0002" sec-type="section"> <title>Methods</title> <p>Pre‐ and post‐task vergence dynamics to a 10.3° disparity stimulus were recorded objectively in 12 adult, asymptomatic individuals for both convergence and divergence. There were two fatigue‐inducing tasks: Congruent or C‐task: Subjects altered bifixation (50 cycles) between reduced Snellen charts at 2 m and at 20 cm every 3 s. Non‐congruent or NC task: Subjects performed 50 cycles of vergence flipper (7Δ BO/BI), while bifixating a reduced Snellen chart at 40 cm. Pre‐ and post‐task mean amplitude, time constant, peak velocity, and steady‐state response variability were compared.</p> </sec> <sec id="opo12083-sec-0003" sec-type="section"> <title>Results</title> <p>There was a significant increase in mean post‐task, steady‐state response variability for both the C and NC tasks. However, there were no significant group differences for either convergence or divergence between the pre‐ and post‐mean amplitude, time constant, and peak velocity parameters for both the C and NC tasks, although post‐task peak velocity was consistently reduced.</p> </sec> <sec id="opo12083-sec-0004" sec-type="section"> <title>Conclusions</title> <p>Steady‐state vergence response variability was found to be the critical objective parameter to demonstrate significant fatigue effects in the group. Peak velocity was also consistently reduced to a small extent in the NC task. We speculate that these fatigue effects are of a central, and not of peripheral, origin.</p> </sec> </abstract>