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KMID : 1011420180230040415
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Journal of Korean Ophthalmic Optics Society
2018 Volume.23 No. 4 p.415 ~ p.422
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Effect of Undercorrected Astigmatism on Visual Acuity According to Essential Astigmatism Power
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Jeong Hyung-Ryul
Jung Su-A
Kim Hyun-Jung
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Abstract
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Purpose: This study was conducted to investigate the effect of undercorrected astigmatism on visual acuity according to the essential astigmatism power.
Methods: Thirty-four patients (mean age: 22.18±2.37 years) presenting with ‘withthe- rule’ myopic astigmatism were selected and classified into four groups based on the essential astigmatism power (Group I: ?0.50 ≤ DC ≤ ?0.75, Group II: ?1.00 ≤ DC ≤ ?1.75, Group III: ?2.00 ≤ DC ≤ ?2.75, and Group IV: ?3.00 ≤ DC). Visual acuity was measured for full correction (undercorrected 0.00 DC), undercorrected astigmatism (?0.50 DC, ?1.00 DC), and spherical equivalent correction, after it was converted to relative visual acuity based on visual acuity of full correction of the condition, visual acuity changes according to undercorrected astigmatism among groups, and visual acuity among groups with same degree of undercorrected astigmatism according to essential astigmatism power were compared.
Results: Visual acuity was lower in undercorrected astigmatism and spherical equivalent correction, as compared to full correction, in all essential astigmatism power groups and decreased as undercorrected astigmatism increased. There was no statistically significant difference in the visual acuity in patients with the same degree of undercorrected astigmatism according to the essential astigmatism power, but visual acuity of the group with high astigmatism was significantly lower than that with spherical equivalent correction. Additionally, there was a statistically significant positive correlation (r > 0.04) between visual acuity and undercorrected astigmatism in all astigmatism groups, especially those with high astigmatism.
Conclusions: A higher essential astigmatism power would have a greater influence on visual acuity change even with the same degree of undercorrected astigmatism. Spherical equivalent correction should especially be prescribed with caution as visual acuity loss may be greater with a certain degree of undercorrected astigmatism depending on the essential astigmatism power (especially over ?2.00 DC).
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KEYWORD
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Astigmatism, Essential astigmatism power, Undercorrected astigmatism, Visual acuity
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