• Journal of Korean Ophthalmic Optics Society
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• v.19 no.3
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• pp.377-382
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• 2014

Purpose: To investigate the effect of anterior, posterior corneal astigmatism and total corneal astigmatism on posterior corneal astigmatism by analyzing correlation. Methods: Participants were 31 patients (31 eyes) without corneal disease at the age range of 22 to 28 who had visited hospital to receive corneal refractive surgery. The total corneal astigmatism and anterior and posterior corneal astigmatism were measured using a rotating scheimpflug camera before surgery. The magnitude of astigmatism was calculated with the difference between the meridian of the steep refractive power and the flat, and With-The-Rule and inverse astigmatism were divided according to the direction of the meridian that was the steepest. Results: The averages of total corneal astigmatism and anterior and posterior astigmatism were found to be $1.13{\pm}0.76D$, $1.51{\pm}0.84D$, and $-0.59{\pm}0.17D$. The magnitude of posterior corneal astigmatism was distributed between -1.0 D and -0.25 D in all the subjects, and when the magnitude of total corneal astigmatism was set as 100, the magnitude of anterior corneal astigmatism was $142.9{\pm}29.9%$. Total corneal astigmatism indicated the highest correlation with the magnitude of anterior astigmatism (y = 0.871x-0.184, $R^2=0.982$) and high negative correlation with posterior astigmatism (y = -2.974x-0.184, $R^2=0.698$). All the subjects' anterior and posterior corneal astigmatism was classified into With-The-Rule. Conclusions: Anterior and posterior corneal astigmatism in the subjects in their 20's showed the magnitude of -3.8 D in 0.2 D and -0.25 D in -1.0 D separately, and both anterior and posterior astigmatism indicated a high percentage of With-The-Rule.

• Korean Journal of Optics and Photonics
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• v.19 no.6
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• pp.439-447
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• 2008

There is a need for a finite schematic presbyopic eye that models vision and image quality under various conditions such as cataract or refractive surgery, as well as near vision corrections with an ophthalmic lens or contact lens. Using recently measured biometric data of presbyopic eyes, new model eyes were designed that are optically and anatomically close to real eyes. The parameters changing significantly with age were incorporated into models for four different age groups. The new model eyes have alpha angle, decentered pupil, aspheric GRIN lens and aspheric retinal surface. It is likely that the new finite presbyopic model eyes will be useful for designing visual instruments such as low vision aids, PALs, IOL and contact lenses, and for the clinical prediction of the retinal image quality of a presbyopic patient.

• Journal of Korean Medical Science
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• v.33 no.44
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• pp.275.1-275.15
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• 2018

Background: We compared the efficacy between trifocal and bifocal diffractive intraocular lens (IOL) implantation. Methods: Through PubMed, MEDLINE, EMBASE, and CENTRAL, we searched potentially relevant articles published from 1990 to 2018. Defocus curves, visual acuities (VAs) were measured as primary outcomes. Spectacle dependence, postoperative refraction, contrast sensitivity (CS), glare, and higher-order aberrations (HOAs) were measured as secondary outcomes. Effects were pooled using random-effects method. Results: We included 11 clinical trials, with a total of 787 eyes (395 subjects). The trifocal IOL group showed better binocular distance VA corrected with defocus levels of -0.5, -1.0, -1.5, and -2.5 diopter than the bifocal IOL group (All $P{\leq}0.004$). The trifocal IOL group showed better monocular uncorrected distance and intermediate VAs (mean difference [MD], -0.04 logarithm of the minimum angle of resolution [logMAR]; 95% confidence interval [CI], -0.07, -0.01; P = 0.006 and MD, -0.07 logMAR; 95% CI, -0.13, -0.01; P = 0.03, respectively). Postoperative refraction, glare, CS, and HOAs were not significantly different from each other. Conclusion: The overall findings indicate that trifocal diffractive IOL implantation is better than the bifocal diffractive IOL in intermediate VA, and provides similar or better in distance and near VAs without any major deterioration in the visual quality.

• Journal of the Optical Society of Korea
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• v.15 no.1
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• pp.68-73
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• 2011

This study investigated, using the Orbscan II topography system, the influence of age and sex related changes on the corneal thickness and anterior corneal curvature, more specifically the fine structure of the cornea, in a Korean young population. The Orbscan II topography system is a computer-assisted slit-beam scanning technology that can map the anterior section of the cornea. The mean central corneal thickness of all subjects was $547.532{\pm}44.529\;{\mu}m$. There was no statistical difference (p>0.5) in the mean central corneal thickness between males and females. Sex and age related changes in the mean central corneal thickness had no specific statistical difference (P>0.5). There was a negative correlation between the anterior corneal curvature and the central corneal thickness in all subjects, except for the twenty year olds. However, the thickness relationship between the mean central corneal and the eight paracentral corneal thicknesses had strong statistical differences in all subjects. Also age and sex related changes in the central corneal thickness and the anterior corneal curvature in all subjects had no statistically significant difference, except from 20-26 years old (p>0.05). This information could be a suitable reference basis for future studies in the young population of Asia and for the development of examination tools for corneal refractive surgery.

• Korea Journal of Hospital Management
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• v.7 no.1
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• pp.88-104
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• 2002

According to the change of mandatory referral system in July 1, 2000, the effect to the medical utilization of outpatient clinic and medical income in ophthalmology of tertiary care medical institute, S Hospital in Seoul was evaluated for 6 months before(1999. 12$\sim$2000. 5) and after(2000. 12$\sim$2001. 5). The results were as follows: 1. The number of outpatients was reduced by 16.6%. The number of patient with blindness low vision, retina, glaucoma increased and that of patient with accommodation refractive error, cataract decreased. 2. The number of cataract patients was reduced by 36.6%. The major location of patient's address was changed to nearer to the hospital. The number of cataract surgery reduced in 4.1%, the waiting time reduced in 42.2%, however surgery time increased in 20.2% and number of postoperative complications increased in 11.4%. 3. The income of outpatient clinic and cataract surgery reduced. Among items of outpatient clinic income, the most increased was ocular examination and the most reduced was injection and drugs. Among items of cataract surgery income, the most increased was operation fee and the most decreased was doctor's fee. In conclusion, for the patient, due to the lowered density of outpatient population more space was provided to the patients with more severe disease entity such as blindness' low vision, retina and glaucoma. For the hospital, the need for the expansion of ophthalmology was not found, however that for creation of the special clinics dealing with more severe disease entity was found. Due to reduced income and increased need of financial investment for the equipment and manpower for the more severe disease entity, the ophthalmology of tertiary care medical institute is faced with financial disaster. It is strongly suggested that the cost of medical practice of more severe disease entity be raised to achieve the success after change of mandatory referral system in ophthalmology.

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.4
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• pp.469-476
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• 2012

Purpose: The purpose of this study is to investigate the changes of asphericity according to diameter and direction of the cornea. Methods: The changes of asphericity according to diameter and direction of cornea is measured by using Pentacam(Oculus Co., Germany), as targeting 57 adults (average $27.0{\pm}4.8$, 20 men, 37 women) without any ophthalmic diseases, which may be effective in eyesight, and refractive surgery. Results: As diameter increases in every direction based on the corneal vertex, asphericity has attentively increased (p<0.05), and the size of asphericity in each direction from every measured diameter showed as superior > nasal > inferior > temporal. In group comparison by nearsightness and astigmatism level, asphericity measured high when nearsightness and astigmatism levels were higher, and this appears to be statistically attentive.(p<0.05). Conclusions: Asphericity of cornea significantly increased according to increase of diameter of cornea, and as measured figure or increased quantity appeared differently in all directions based on corneal vertex, so it helps to understand shape of cornea, and considered that is the part to be considered during manufacturing and fitting of RGP lenses.

• Current Optics and Photonics
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• v.4 no.1
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• pp.31-43
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• 2020

The feasibility of the application of terahertz electromagnetic waves in the diagnosis of prostate cancer was examined. Four samples of incomplete cancerous prostatic paraffin-embedded tissues were examined using terahertz spectral imaging (TPI) system and the results obtained by comparing the absorption coefficient and refractive index of prostate tumor, normal prostate tissue and smooth muscle from one of the paraffin tissue masses examined were reported. Three hundred and sixty cases of absorption coefficients from one of the paraffin tissues examined were used as raw data to classify these three tissues using the Principal Component Analysis (PCA) and Least Squares Support Vector Machine (LS-SVM). An excellent classification with an accuracy of 92.22% in the prediction set was achieved. Using the distribution information of THz reflection signal intensity from sample surface and absorption coefficient of the sample, an attempt was made to use the TPI system to identify the boundaries of the different tissues involved (prostate tumors, normal and smooth muscles). The location of three identified regions in the terahertz images (frequency domain slice absorption coefficient imaging, 1.2 THz) were compared with those obtained from the histopathologic examination. The tissue tumor region had a distinctively visible color and could well be distinguished from other tissue regions in terahertz images. Results indicate that a THz spectroscopy imaging system can be efficiently used in conjunction with the proposed advanced computer-based mathematical analysis method to identify tumor regions in the paraffin tissue mass of prostate cancer.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.3
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• pp.353-362
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• 2014

Purpose: The present study was aimed to investigate the change of higher-order aberrations induced by aging and the effect of myopic degree on the correlation between age and higher-order aberrations. Methods: The higher-order aberrations in 931 eyes aged from 20 to 60 were measured by using a LADARWave device employing Hartmann-Shack system to analyze the effect of myopic degree measured by manifest refraction test on higher-order aberrations. Results: Coma and vertical coma aberrations were significantly decreased by the increase of myopic degree while vertical astigmatic aberration was significantly increased. The correlations of age and coma, vertical coma, spherical, vertical trefoil, horizontal trefoil, vertical astigmatic, horizontal astigmatic and vertical tetrafoil aberrations depended on the myopic degree, except for horizontal coma and horizontal tetrafoil aberrations. Conclusions: It is suggested to consider the myopic degree for the refractive correction including the laser surgery based on the present result that higher-order aberrations are affected by the myopic degree.

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.3
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• pp.285-291
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• 2012

Purpose: This study was conducted to research any effect on visual function related to accommodation by VDT work. Methods: The refraction power, accommodative lag, accommodative facility, relative accommodation, amplitude of accommodation and blink rate were measured before and after VDT work for 2 hours on 48 university students (16 males and 32 females), without abnormal accommodative function and systemic and ocular disease, who had never undergone corrective eye surgery. All examinations were performed with distant refraction, and a survey was conducted on the items related to subjective symptoms of VDT syndrome. Results: After 2 hours of VDT work, refractive power increased by 0.23 D, the amount of change in accommodative lag were $0.17{\pm}0.42D$ in the right eye and $0.23{\pm}0.47D$ in the left eye (t=2.26, p=0.03). There were statistically significant differences. Both the accommodative facility and relative accommodation and amplitude of accommodation were decreased after work. However, blink rate were increased. After VDT work, 33.4% of the subjects showed subjective symptoms of asthenopia and 33.3% of them showed shoulder pain. Conclusions: As a result, the accommodative lag increased in response to the two hours of VDT work, and overall accommodative functions were decreased. In addition, as symptoms of providing visual strain, asthenopia showed the most prominent subjective symptoms.

• Journal of The Korean Ophthalmological Society
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• v.60 no.2
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• pp.126-134
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• 2019

Purpose: To assess the accuracy of toric intraocular lens (IOL) implantation by the location and size of the corneal incision. Methods: We retrospectively reviewed the medical records of 98 patients (98 eyes) who underwent phacoemulsification with toric IOL implantation from January 2014 to March 2017. The patients were divided into two groups: group 1 got an incision of the superior side of the cornea (n = 54) and group 2 received an incision on the temporal side of the eye (n = 44). For both groups, incisions were made at their steep corneal astigmatism axises. Each group was further divided into subgroups for whom different sized blades were employed (2.75 vs. 2.2 mm widths). We measured the refractive index and autokeratometric parameters. We postoperatively assessed residual astigmatism and any reduction thereof. Results: In both groups, uncorrected and best-corrected visual acuity, refraction cylinder astigmatism, and autokeratometric astigmatism improved statistically. Between two groups, corneal astigmatism decrease was not significant. Residual astigmatism also showed no significant differences between the two. Patients in both groups treated using 2.75 mm wide blades exhibited greater increases in corneal astigmatism. Conclusions: During cataract surgery, precise correction of astigmatism via toric IOL implantation is possible when surgically induced astigmatism is minimized by careful choice of the location and size of the corneal incision.