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KMID : 1159320090110040293
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Korean Journal of Vision Science
2009 Volume.11 No. 4 p.293 ~ p.306
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The Analysis of Prism Adaptation by Prism-induced Deviation Changes
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Kwon Mi-Jung
Mah Ki-Choong
Buyn Jang-Won
Jeon In-Chul
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Abstract
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Purpose : To investigate the prism adaptation by measuring induced deviation with introduction of horizontal or vertical prism during the time course.
Methods : 42 subjects (23 males, 19 females) aged 25.31±3.23 yrs who have normal binocular vision participated for this study. 16Δ base-out, 8Δ base-in, 3Δ base-up and 3Δ base-down prism were randomly assigned to induce deviation on four different days. The magnitudes of horizontal and vertical heterophoria responsed at distance(3 m) and near(40 cm) with binocular viewing were measured 6 times for 30 minutes after insertion prism using Modified Thorington phoria test.
Results : Immediately after insertion of 16Δ base-out, 8Δ base-in, 3Δ base-up and 3Δ base-down prism, exo-deviation, eso-deviation, hyper-deviation and hypodeviation at distance and near were significantly induced. At this time, there was the first adaptation approximately 36∼60% of introduced prism by the fast fusional vergence system. Prism-induced deviation returned baseline with the exponential decay curve regressionn by the slow vergence system during 30 minutes. In the corse of prism insertion, the second adaptation was occurred until 12-minute with a large amount of recovery and then the third adaptation was occurred until 30-minute with a small amount. In the result the total prism adaptation was about 90%. Also prism adaptation was different from base direction of introduced prisms or viewing
distances.
Conclusion : As the prism was introduced, the fast fusional vergence took place and gradually got slower to recover toward the baseline of heterophoria in the time course by the first, second and third adaptation. When horizontal and/or vertical prism is prescribed to a patients, practicals should consider the prism adaptation. And the pre-prescribing prism adaptation test should be taken to minimize the effect of prism adaptation.
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KEYWORD
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Heterophoria, Prism adaptation, Prism-induced deviation, Prism prescribing
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