• Journal of Korean Ophthalmic Optics Society
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• v.19 no.1
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• pp.79-85
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• 2014

Purpose: This study investigated accommodative changes by measuring accommodative response, appearing on the normal and convergence insufficiency Group, by using both eyes open-view auto-refractometer (Nvision-K5001, shin-nippon, Japan). Methods: It carried out objective and subjective refractions, targeting 74 college students (54 males and 20 females) aged between 19 and 29 ($21.59{\pm}2.53$), spherical equivalent OD $-2.28{\pm}2.03$ D, OS $-2.18{\pm}2.01$ D, by measuring accommodative responses at full correction and under correction with plus lens +0.25, +0.50, +0.75 arbitrarily added. Results: In the group of normal and convergence insufficiency, the shorter fixation distances were, the greater accommodative lags showed. The group of convergence insufficiency showed the lesser changes of accommodative response than those of normal. But we found that the convergence insufficiency group had a little larger accommodative amplitude in the total fixation distances. The full correction of convergence insufficiency group and the under correction (+0.50 D) of normal were alike in the accommodative responses. We have also investigated that the correlation between accommodative responses and fixation distances was decreased steeply at the excessive low vision correction. Conclusions: Under correction (+0.50 D) in a near distance is expected to avoid unnecessary accommodative responses, make eyes relaxed and comfortable.

• Journal of Korean Ophthalmic Optics Society
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• v.14 no.4
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• pp.45-51
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• 2009

Purpose: The purpose of this study is to compare and analyze the survey results of clinical performance and visual problem, and the survey were carried out before and after of VDT working for 4 hours by wearing functional lens designed for improving VDT syndrome and single-vision lens. Methods: We tested near & far visual acuity, change of spherical equivalent, near point of accommodation, near point of convergence, AC/A ratio, accommodative facility and survey of subjective symptoms to visual problem of before and after VDT working for 4 hours after wearing single-vision lens and functional lens subjected on 30 males and females in the age of 20 to 45. Results: When wearing functional lens comparing to single-vision lens, near visual acuity, near point of accommodation, near point of convergence, and accommodative facility are significantly improved. It is investigated that average scores of 10 items to visual problem after VDT working for 4 hours are 3.63${\pm}$0.75 at single-vision lens and 4.69 ${\pm}$ 0.83 at functional lens, and therefore functional lens is significantly improved. Conclusions: It is thought that functional lens is an excellent lens which helps to improve accommodative function and visual problem after VDT working for 4 hours than single-vision lens.

• Journal of Korean Ophthalmic Optics Society
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• v.9 no.2
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• pp.211-221
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• 2004

The purpose of this study is to evaluate the distribution and change of curvature of the anterior corneal surface with age in emmetropia. 504 subjects who have emmetroia with good naked vision of at least 0.6-1.0 (spherical equivalent: +0.75D- -0.75D) participated in this study. The 504 subjects into 8 groups with 10 year interval from 3-year to 83-year, and their corneal curvatures were analyzed using manual keratometry. The results are as follows. In individual analysis: First, regression analysis of corneal curvature radius with age has given an equation: Y = -0.003x + 7.796 (r = -0.26). The average corneal curvature radii was measured to be $7.68{\pm}0.25mm$ at 38.3-year and range was 6.98-8.54 mm. Second, frequency of corneal curvature radius were obtained in 36% between 7.61 and 7.80 mm, 78% between 7.41 and 8.00 mm, 96% between 7.21 and 8.20 mm, 100% between 6.98 and 8.54 mm. Third, as for the comparison of corneal curvature radius with respect to sex, The mean value of male (n = 304, mean: 37.6-year $7.72{\pm}0.24mm$, Range: 7.09-8.54 mm) is larger than that of female (n = 200, mean: 39.3-year $7.62{\pm}0.24mm$, Range: 6.98-8.42 mm) by 0.1mm (p<0.01). In groups analysis: First, regression analysis of corneal curvature radius with age has given an equation: $Y=-0.0066x^2+0.0227x+7.7282$ (r = -0.90). Second, vertical and horizontal curvature radius decreased with age (p < 0.01). Especially the decrease of horizontal curvature radius were more pronounced than the decrease of vertical (horizontal:10-70 age group: 0.38 mm decrease, vertical:10-70 age group: 0.20 mm decrease). Third, difference between steep and flat meridian (astigmatism) progressively decreased with age. (low age group:0.18 mm difference, high age group: 0.08 mm difference). Fourth, the corneal curvature radius of male was larger than female's in total groups(p < 0.01). Consequently, the change of corneal curvature radius with age progressively decreased in all conditions (mean, vertical, horizontal, male, and female) and this change was more outstanding in horizontal rather than in vertical.