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KMID : 1159320150170020123
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Korean Journal of Vision Science
2015 Volume.17 No. 2 p.123 ~ p.130
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Variation of Horizontal Phoria of Myopic Refraction Error According to Gaze Direction and Gaze Angle
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Kim Ha-Na
Cho Hyun-Gug
Moon Byeong-Yeon
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Abstract
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Purpose: To investigate the variations of phoria and NPC(near point of convergence) in accordance with the gaze direction and the gaze angle at distance.
Method: 61 subjects (male 29, female 32) who had no ocular diseases and manifest heterotropia were participated and their corrected visual acuity were more than 0.9. After full correction of sybject's refractive error, The horizontal phoria at distance (5m) was measured using subjective alternate cover test with prism bar in accordance with gaze angles of 10?, 20?, 30? in the right and left directions as well as the primary position. Also NPC was measured in primary position and 10?, 20?, 30? in the right and left direction.
Result: The exophoria tended to decrease with increase of gaze angle as compared with phoria measured from primary position. There were more subjects who showed different variations of phoria according to the gaze direction. The decrement of exophoria was larger when subjects gazed to the left direction rather than the right direction. As the gaze angle increased, near point of convergence was receded significantly.
Conclusion: Phoria and NPC are dependent on gaze direction and angle, therefore it is necessary to consider gaze direction and angle in evaluation of visual function.
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KEYWORD
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Gaze direction, Gaze angle, Horizontal phoria
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