• Journal of Korean Ophthalmic Optics Society
• /
• v.4 no.1
• /
• pp.27-35
• /
• 1999

The corneal power and eye refraction error were studed in 472 unaccommodated right eyes of Korean adult human aged above 20 years. The mean corneal refractive power is 44.08D (female : 44.28D, male : 43.76D). It is 1.1D higher than that of the medel eye by Gullstrand (about 43.0D). The mean corneal power of myopia(44.11D) is similar that of emmetropia(43.97D) and hyperopia(44.24D), but mean corneal power of myopia between the ages of 20 and 29 is 1.42D higher than that of emmetropia. The corneal powers as a function of ages are enlarged with increasing rate of 0.2D~0.3D/10years.

• Journal of Korean Ophthalmic Optics Society
• /
• v.4 no.2
• /
• pp.17-22
• /
• 1999

In this study, corneal power and eye refraction error were studied on myopic of unaccommodated koreans. The mean of refraction error power is -2.39D(male : -2.75D, female : -2.02D). The mean of corneal refraction error power is +43.90D(male : +44.07D, female : +43.71D). It is +0.90D higher than that of the model eye by Gullstrand(about + 43.00D).

• Journal of Korean Ophthalmic Optics Society
• /
• v.18 no.3
• /
• pp.271-277
• /
• 2013

Purpose: The purpose was to study the corneal refractive power changes associated with the wearing of everted silicone hydrogel soft lenses. Methods: The corneal refractive power and corneal astigmatism were measured using corneal topographer (CT-1000, Shin-nippon Co., Japan) for checking change of corneal refractive power and objective refractive error was measured by auto-refractometer (Natural vision-K 5001, Shin-nippon Co., Japan). We measured at baseline and 1 week after lens wearing. Results: The correcting of corneal refractive power could be effective in low myopia. It's more effective to the higher power of greatest meridian of cornea and the more corneal astigmatism. 73% of subjects' refractive error was decrease less than 1 D and 17% of the subjects had an reverse effect (increase) occurs. The reduction of objective refractive error was more effective when cornea refractive power was great or corneal astigmatism was much. Conclusions: Pressure which the everted silicone hydrogel lens to the cornea could be caused. It occurred as the degrees of corneal power, corneal astigmatism and objective refractive error differences. Selection of an appropriate subject is important considering difficulty of changing the parameters of the lens.

• Journal of Digital Convergence
• /
• v.12 no.12
• /
• pp.485-490
• /
• 2014

The purpose of this Study investigated corneal power, corneal astigmatism and corneal axis according to spherical equivalent of refractive error. We measured spherical equivalent, corneal power and corneal astigmatism in 100 subjects from January 2014 to July 2014. Measured spherical equivalent of refractive error were $-3.01{\pm}3.79D$, corneal power of $43.79{\pm}1.60D$ and corneal astigmatism of $-1.17{\pm}0.79D$ respectively. Prevalence of spherical equivalent of refractive error were as follows : myopes (61%), emmetropes (22%), hyperopes(17%). Corneal astigmatism of refractive error greater than +0.75D was 63% and prevalence of corneal astigmatism were as follows : with-the-rlue astigmatism (84.13%), against-the-rule astigmatism(9.52%) respectively. Corneal power by spherical equivalent increased from hyperopia to myopia. Between spherical equivalent of refractive error and the mean corneal power was significant correlation(r=-0.25, p=0.01). A correlation were found between corneal power and spherical equivalent of refractive error in adults. They have the highest distribution of prevalence myopia among the refractive error. When the refractive error was increased, we found that corneal power was steeper. It is recognized that this can be refractive error factor and correct visual function is considered.

• Journal of Korean Ophthalmic Optics Society
• /
• v.5 no.2
• /
• pp.27-31
• /
• 2000

As the functional test of cornea. The clinical value of keratometric information was important for assessment the curvature of the cornea, the quality of the corneal surface, the stability of the corneal curvature, and the direction of the corneal astigmatism. This study was performed the comparative analysis of male and female of adult on the base curve, power and astigmatism of the Cornea. On the corneal base curve, the male right eye was 7.656 mm in vertical and 7.966 mm in horizontal. But, the male left cornea was 7.714 mm in vertical base curve and 8.026 mm in horizontal base curve. On the other hand, the female right eye cornea was 7.559 mm in vertical base curve and 7.695 mm in horizontal base curve. But, the female left eye cornea was 7.444 mm in vertical base curve and 7.742 mm in horizontal base curve. On the corneal diopter power, the male right eye was 44.063 diopter in vertical and 43.738 diopter in horizontal. But the male left eye was 44.046 diopter in vertical and 42.304 diopter in horizontal. On the other hand, the female right eye was 44.082 diopter in vertical and 43.77 diopter in horizontal. But, the female left eye was 44.347 diopter in vertical and 43.495 diopter in horizontal. According to the corneal astigmatism axis. The male right eye have 89.9% positive for with the - rule astigmatism, and 8.1 % positive for against - the - rule astigmatism. But, he male left eye have 91.89% positive for with - the - rule astigmatism, and 8.11 % positive for against - the - rule astigmatism. On the other hand, The female right eye have 76.92% positive for with - the - rule astigmatism, and 23.08 % positive for against - the - rule astigmatism. But, the female left have 80.76 % positive for with - the - rule astigmatism, and 17.31 % positive for against - the - rule as tigmatism. The diopter power of corneal astigmatism have 25.57% positive for behind 1 diopter, 44.89% positive for 1 diopter, 18.18% positive for 2 diopter, 5.11% positive for 3 diopter and 6.25% positive for over 4 diopter.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2002.11a
• /
• pp.691-694
• /
• 2002

본 논문은 자동 시각 굴절력 곡률계의 전자 부문에 연동될 곡률 측정 알고리즘을 소개한다. 만약 자동화된 시스템이 광학계로부터 나오는 영상을 이용하여 내부 처리를 거친 후 정확한 시각 측정치를 검사자에게 알려줄 수 있다면 잘못 측정되는 측정 횟수를 크게 줄일 수 있을 것이다. 본 연구는 형태학적 필터링(morphological filtering)과 그레이-레벨의 신호 강조(signal enhance) 기술들을 이용하여 자동 시각 굴절력 곡률계에 연동될 각막 곡률과 굴절력 측정 알고리즘을 개발하였다. 알고리즘에서는 광학계로부터 도출된 링 모양 광원의 화상을 처리하기 위해서 새로운 방법을 사용하는 대신에 구면 굴절력 측정을 위해서 6 개의 점으로 구성된 화상을 처리하는 방식으로 변형 적용시킨다. 이 때 링의 띠를 6 개의 덩어리 점으로 변형하는 과정만을 제외하면 구면 굴절력 영상을 처리하는 방식과 같게 된다. 이는 알고리즘의 간결화와 측정 시간을 줄이는 효과를 얻게 된다. 그리하여 본 각막 측정 알고리즘은 정확한 측정값 도출이 어려운 시각 영상에 적용되어 효과적으로 오차를 줄임으로써 보다 효율적인 각막 측정을 가능하게 하였다.

• Proceedings of the Korean Information Science Society Conference
• /
• 2002.10d
• /
• pp.517-519
• /
• 2002

본 논문은 자동 시각 굴절력 곡률계의 전자 부문에 연동될 곡률 측정 알고리즘을 소개한다. 만약 자동화된 시스템이 광학계로부터 나오는 영상을 이용하여 내부 처리를 거친 후 정확 시각 측정치를 검사자에게 알려줄 수 있다면 잘못 측정되는 측정 횟수를 크게 줄일 수 있을 것이다. 본 연구는 형태학적 필터링(morphological filtering)과 그레이-레벨의 신호 강조(signal enhance) 기술들을 이용하여 자동시각 굴절력 곡률계에 연동될 각막 곡률 측정 알고리즘을 개발하였다. 알고리즘에서는 광학계로부터 도출된 링 모양 광원의 화상을 처리하기 위해서 새로운 방법을 사용하는 대신에 굴절력 측정을 위해서 6개의 점으로 구성된 화상을 처리하는 방식으로 변형 적용시킨다. 이 때 링의 띠를 6개의 덩어리점으로 변형하는 과정만을 제외하면 굴절력 화상을 처리하는 방식과 같게 된다. 이는 알고리즘의 간결화와 측정 시간을 줄이는 효과를 얻게 된다. 그리하여 본 각막 곡률 측정 알고리즘은 정한 측정 값 도출이 어려운 시각 영상에 적용되어 효과적으로 오차를 줄임으로써 보다 효율적인 시각 측정을 가능하게 하였다.

• Journal of Korean Ophthalmic Optics Society
• /
• v.21 no.2
• /
• pp.91-98
• /
• 2016

Purpose: This study investigated the masking effect of the hydrogel lens and silicone hydrogel lens on the cornea with refractive surgery and without surgery. Methods: 24 university students (means age: $23.48{\pm}2.89years$) without refractive surgery (12, control group) and with refractive surgery (LASIK: 8, LASEK: 4, experimental group) participated in the study. Mean refractive errors of right eyes were -2.73 D for control group and -0.24 D for experimental group. The differences in the refractive power and corneal topography map between pre- and post-wearing the -3.00 D lenses were compared, and 2 kinds of hydrogel contact lenses (0.89 Mpa, 0.49 Mpa) and 2 kinds of silicone hydrogel lenses (1.5 Mpa, 0.8 Mpa) were used for -3.00 D lenses. NVision-K5001 (Shin nippon, Japan) was used to measure the refractive power and Keratograph 5M (Oculus, Germany) to measure the corneal topography map change. Results: Variations in the refractive power increased to the plus direction in the experimental group after wearing soft contact lenses. The corneal topography map showed significant changes on the both groups after wearing soft contact lenses (p<0.05). However there were no significant differences in the refractive power and corneal topography map variations by lens materials. Conclusions: Wearing soft contact lenses showed corneal topography map changes. Especially wearing soft contact lenses on the flat cornea after corneal refractive surgery showed greater corneal power changes. Therefore, it should pay attention to refractive change in case of prescribing soft contact lenses to patients with corneal refractive surgery.

• Journal of Korean Ophthalmic Optics Society
• /
• v.14 no.3
• /
• pp.7-15
• /
• 2009

Purpose: To investigate the corneal recovery after discontinuing orthokeratology (OK) lenses wear in children for long-term period. Methods: Among the OK lens wearers who wear over 8 months and showed successful refractive correction, 25 subjects were selected who want to discontinue the OK lenses. Uncorrected visual acuity, refractive correction, corneal curvature (Sim K), central corneal thickness and corneal eccentricity were measured during the OK lens wearing period and after discontinuation for 1 month. Results: Uncorrected visual acuity and corneal shape had remodeled significantly during the OK lens wear and recovered significantly during the first week of discontinuation. Uncorrected visual acuity and refractive correction had achieved full recovery 2 weeks after discontinuation of lens wear and were highly correlated with the changes in corneal thickness. But corneal shape recovered slowly, eccentricity had recovered fully after 1 month and corneal curvature and central thickness had not been achieved full recovery until 1 month after discontinuation. Conclusions: Recovery of after longterm use of OK lens is rapid for refractive change, but slow for corneal curvature and central thickness that to refit the contact lenses, practitioners need patience.

• Journal of Korean Ophthalmic Optics Society
• /
• v.16 no.3
• /
• pp.293-297
• /
• 2011

Purpose: This study was to know the correlation among refractive error and the dimensions of ocular components on older adults. Methods: The subjects were 95 older age who had no eye diseases. The refractive error, corneal radius, corneal diopter, axial length, anterior chamber depth and lens thickness were measured and analysed. Results: The axial length(AL)/corneal radius(CR) ratio was positively correlated with the corneal diopter, axial length, the anterior chamber depth. Then it was negatively correlated with corneal radius. It was shown that the highest correlation was between the corneal diopter and axial length (r = -0.545, p = 0.000). The spherical equivalent of the refractive error was negatively correlated with the AL/CR ratio. Conclusions: It was shown that the AL/CR ratio was a very important indicator for diagnosing the refractive error of the old age.