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KMID : 1159320210230040455
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Korean Journal of Vision Science
2021 Volume.23 No. 4 p.455 ~ p.462
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Comparison of Prescription Values for Fixation Disparity Alignment Prism and Phoria Prism
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Park Byung-Ho
Jeon In-Chul
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Abstract
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Purpose : This study is to find out the difference between the prescription value of the prism of the Sheard’s criteria and fixation disparity alignment prism.
Methods : It was targeted at 35 adults (average 25.43±2.23 years old, 27 men, 8 women) who had no systemic or ophthalmic disease and had never undergone tropia surgery. After measuring the fixation disparity using a Wesson fixation disparity card, the amount of prism that makes the fixation disparity 0 using a prism bar was recorded as an alignment prism.
The phoria test used the Muscle Imbalance Measure card as the modified Thorington method.
Results : The average fixation disparity was exo-fixation disparity 9.95±5.69′, and the calibration value of the alignment prism of fixation disparity using a prism bar was exo-fixation disparity 4.09±2.80 △. The phoria was exo-phoria 8.34±5.70 △, the positive fusional vergence was 23.20±6.28 △, and the prism prescription value of the Sheard criteria was Base In 0.66±1.41 △. The average of the prescription values based on Sheard criteria and fixation disparity alignment prism showed a statistically significant difference(p<0.001).
Conclusion : Even if the fixation disparity angle is the same, the amount of alignment prism that corrects the fixation disparity angle tends to be different for each person. Therefore, it is considered that both the alignment prism for fixation disparity and Sheard's criterion should be considered when prescribing a phoria.
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KEYWORD
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Alignment prism, Fixation disparity, Phoria, Sheard
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