• Journal of Korean Ophthalmic Optics Society
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• v.11 no.3
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• pp.193-200
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• 2006

We investigated the visual analysis of the far distance phoria for 83 subjects who have emmetropia or myopia eyes, using the graphic method, and determined new norms. We got the following results from these experiments. 1. The measured norm of far distance phoria is $1.12{\Delta}$, exophoria, the that of near distance phoria is $0.50{\Delta}$, exophoria, the that of negative relative convergence at far distance(N.R.C.) is ${\times}$/11/5, the that of positive relative convergence at far distance(P.R.C.) is 10/20/8, the that negative relative convergence at near distance(N.R.C.) is 11/21/5, the that of positive relative convergence at near(P.R.C.) is 10/20/8, the that of negative relative accommodation(N.R.A.) is +2.54D, and the that of positive relative accommodation(P.R.A.) is -2.60D, respectively. We know from theses results that the measured norms of far distancet phoria is higher than Morgan's norms, while those of near distance phoria are lower than Morgan's norms. 2. We also know from these experiments that Morgan's norms are closely related to A, B, and C groups and Morgan's criterion can more usefully apply to the visual analysis. 3. In Sheard's criterion and Percival's criterion, the prism prescription is occurred when the exophoria of the far-point phoria is over $7{\sim}9{\Delta}$, and the esophoria of that is over $4{\sim}6{\Delta}$.