• Journal of Korean Ophthalmic Optics Society
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• v.20 no.3
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• pp.349-354
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• 2015

Purpose: To investigate the changes of corrective values of astigmatism caused by the position of circle of least confusion on retina in refining astigmatic test using cross cylinder. Methods: 62 subjects (115 eyes) aged $22.24{\pm}2.48$ years participated for this study. After astigmatic test using a radial chart, refining test was performed using a cross cylinder in a condition of maximum plus to maximum visual acuity (MPMVA). Astigmatic refining test was repeatedly performed in each condition of which S+0.75 D, S+0.50 D, S+0.25 D, S-0.25 D, S-0.50 D, and S-0.75 D are added to spherical lenses of MPMVA. The measured values were compared with the values in MPMVA condition. Results: As compared with values in condition of MPMVA, change of astigmatic axis was increased with add the power of (+) spherical lenses and (-) spherical lenses. In same spherical condition, change of astigmatic axis was decreased with increment of astigmatic power (p<0.05). The corrective power of astigmatism was reduced with increment of (+) spherical lenses (p<0.05), and was raised with increment of (-) spherical lenses compared with the power in MPMVA condition. In case of adding (+) spherical lenses, difference of astigmatic power increased with increment of corrective astigmatism power in same test condition. Conclusions: In order to obtain a proper values for corrective astigmatism, position of circle of least confusion should be accurately adjusted before the performing an astigmatism's refining test.

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.2
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• pp.209-213
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• 2012

Purpose: To assess the repeatability of the monocular spherical endpoints, a test was performed with four methods which are the retinoscopy, the MPMVA (maximum plus maximum visual acuity) method, the R/G duochrome method, and the crossed cylinder method. Methods: The monocular spherical endpoints was measured by four kinds of method (Retinoscopy, MPMVA method, R/G duochrome method, Crossed cylinder method) on 20 subjects (40 eyes) of average age 23.0 year-old men and women. After a week, retest was performed by same procedure and the test-retest repeatability was assessed by using the Bland-Altman plot analysis. Results: The test-retest mean difference of retinoscopy was the smallest diopters of -0.03 and that of R/G duochrome method was the largest diopters of -0.19. The upper/lower 95% limits of agreement for repeatability was the narrowest in retinoscopy and was the widest in crossed cylinder method. When compared the spherical endpoints of each eye between by retinoscopy and by other three methods, the error rate of ${\pm}0.25D$ in total eyes was 85% in MPMVA method, 80% in R/G duochrome method, and 24% in crossed cylinder method. Conclusions: Test-retest repeatability is the highest in the retinoscopy, and the retinoscopy, the MPMVA method, and R/G duochrome method are suitable for monocular spherical endpoints test.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.2
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• pp.177-186
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• 2015

Purpose: The Purpose of this study is to investigate if the relative legibility of optotypes affects the corrected visual acuity in visual acuity test. Methods: After measuring the relative legibility of 'Landolt ring target', 'arabic number target', 'alphabet target' by showing as a single-letter-target in 24 subjects without specific ocular diseases and ocular surgery experience, the relative legibility of 0.8, 1.0, 1.25 row of vision according to type of target in 7 types of chart were compared. After then we compared by measuring the corrected visual acuity according to type of target by using binocular MPMVA test (#7A) in 60 myopic subjects. Results: In 3 types of target the worst relative legibility target was 'Landolt ring target' with legible distance of $98.97{\pm}4.57cm$ and the best relative legibility target was 'alphabet target' with legible distance of $108.42{\pm}3.46cm$. There was no difference of the relative legibility according to type of chart or visual acuity level in the row of vision if other conditions are the same. In 1.0 and 1.25 row of vision the difference of relative legibility according to type of target was shown the statistically significant difference between 'Landolt ring target' and 'alphabet target' as $-0.07{\pm}0.06$ (p=0.02) and $-0.06{\pm}0.06$ (p=0.04) respectively. In myopia the difference of corrected visual acuity according to type of target was statistically significant difference between 'Landolt ring target' and 'arabic number target' as $-0.04{\pm}0.02$ (p=0.02) and it was especially remarkable in the low myopia. Conclusions: Measuring visual acuity with different optotypes could cause the errors in best vision measurement value because there was difference of the relative legibility according to type of target even though visual acuity level is same in the row of vision.