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Original article

The effect of artificially reduced bilateral visual acuity on vergence adaptation

Authors:

Pooja S. Bhatt ,

Academic Unit of Ophthalmology and Orthoptics, University of Sheffield, Sheffield
About Pooja S.
BMedSci (Hons)
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Alison Y. Firth

Academic Unit of Ophthalmology and Orthoptics, University of Sheffield, Sheffield
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Abstract

Aim: To investigate the effect of bilateral artificially reduced vision on vergence adaptation, in participants with normal binocular single vision.

Methods: Seventeen participants were recruited from a student population. The inclusion criteria included the ability to adapt to a 6Δ base-out prism to within ±1Δ of the baseline heterophoria  measurement in 10 minutes. The size of the prism-induced heterophoria was measured at the start and end of the adaptation period using a Maddox rod and tangent scale. Eleven participants fitted the inclusion criteria and proceeded to a second visit; involving adaptation to a 6 Δ base-out prism within 10 minutes, whilst vision was bilaterally reduced with Bangerter foils (0.3). Participants who did not demonstrate adaptation to within  ±1Δ of the baseline measure in 10 minutes were given a further 10 minutes to adapt, with the size of the residual deviation being measured at 5-minute intervals.

Results: Eight of 11 participants demonstrated vergence adaptation to within ±1 Δ of the baseline measure in 10 minutes when vision was bilaterally reduced. Three participants required an additional 5 minutes before they achieved this level of adaptation. Statistical analysis revealed the rate of vergence adaptation was affected in some participants when vision was bilaterally reduced (p = 0.0260, t = 2.6116, d.f. =10).

Conclusion: Individuals who demonstrate vergence adaptation in normal viewing conditions appear capable of doing this with an artificial bilateral reduction in vision. In some participants, a longer period of time is required to vergence-adapt.

DOI: http://doi.org/10.22599/bioj.9
How to Cite: Bhatt, P.S. & Firth, A.Y., (2009). The effect of artificially reduced bilateral visual acuity on vergence adaptation . British and Irish Orthoptic Journal . 6 , pp . 52–55 . DOI: http://doi.org/10.22599/bioj.9
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Published on 01 Aug 2009.
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