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KMID : 1011420170220030253
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Journal of Korean Ophthalmic Optics Society
2017 Volume.22 No. 3 p.253 ~ p.260
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Reliability of Javal’s Rule Based on Dioptric Power Matrix
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Yu Dong-Sik
Cho Hyun-Gug
Kim Sang-Yeob
Kim Hyeong-Su
Moon Byeong-Yeon
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Abstract
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Purpose: To evaluate the reliability of several versions of Javal’s rule predicting refractive astigmatism from corneal astigmatism on the basis of dioptric power matrix.
Methods: A total of 84 subjects (168 eyes, mean age 24.67±1.59 years) participated in this study. Corneal astigmatism (Ac) was measured by auto kerato-refractometer. Refractive astigmatism (At) was predicted by dioptric power matrix using four versions of original Javal’s rule (OJR), simplified Javal’s rule (SJR), Yoo’s regression equation (YRE), and vector-based Javal’s rule (VJR) from Ac. The subjectively determined refractive astigmatism (SAt) was taken best corrected visual acuity.
Results: The relations between axes of Ac and At were represented high values (r = 0.891 to 0.971, p<0.001), the relations between axes of At and SAt were represented low values (r = 0.182 to 0.223, p = 0.004-0.018) for all four versions. The mean magnitudes of At and SAt for the VJR were 0.80±0.58 D and 0.82±0.65 D respectively. The difference between two values was not significant in paired t-test as relative reliability (p = 0.662). In Bland-Altman analysis as absolute reliability, the mean difference of At and SAt for the VJR had a small bias of ?0.02±0.51 D. In comparison of previous cylindrical power, the difference between At and SAt was decreased in order of OJR, YRE, SJR, and VJR. In those of differences, OJR showed the lowest distribution within all intervals (≤ 2.00 D), VJR showed the highest distribution at the less than 0.75 D. The anticipated constant optimization were range from 0.79 to 1.00 for corneal astigmatism as the differences between At and SAt were the boundaries between more and less.
Conclusions: Vector-based Javal’s rule is more reliable in predicting refractive astigmatism from corneal astigmatism, and the constant of 0.79 to 1.00 for corneal astigmatism in Javal’s rule except this rule may be applied in clinical prediction with simplicity by arithmetic operation.
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KEYWORD
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Javal’s rule, Dioptric power matrix, Astigmatism, Vector, Refractive astigmatism, Corneal astigmatism
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