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SV Subramaniam; Effect of Oblique Astigmatism on Cyclodeviations . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2006.
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Purpose: The aim of the study is to determine the degree of cyclophoria elicited by inducing oblique astigmatism. The study also compares the difference in cyclodeviations between low and high astigmatism, monocular and binocular astigmatism and between distance and near fixation. Methods: Plus cylinders, ranging from +1 to +6 D were introduced in steps of 1D at an axis of 45. in front of the right eye. Binocular astigmatism was induced by placing the cylinders at an axis of 45. in front of the right eye and 135. in front of the left eye. The type and degree of cyclodeviations was estimated by double Maddox rod test in 30 orthophoric subjects with induced astigmatism for distance and near. Results: For distance fixation, the average cyclodeviation resulting from the introduction of low cylinders (+1 to +3D) monocularly and binocularly was 0.33. and 0.67. respectively; with high cylinders (+4 to +6D), it was 1.54. and 2.4. respectively. At near (33cm), the cyclodeviation due to low astigmatism induced monocularly and binocularly averaged 1.31. and 1.7. respectively while higher astigmatism produced greater deviations of 2.69. and 3.5. respectively. The differences were significant by paired t-test ( P=0.001). There was a significant correlation between the degree of cyclodeviation and amount of induced astigmatism(r = 0.98) . Conclusion: From the results of this study, cyclodeviations were greater at near than at distance; and also greater with astigmatism induced binocularly than monocularly. The effect of oblique astigmatism on cyclodeviations is therefore an important consideration in the correction of refractive error and in evaluating asthenopic symptoms at near.
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