• Current Optics and Photonics
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• v.3 no.1
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• pp.72-77
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• 2019

This study was performed to analyze the optical aberrations of the cornea induced by myopic refractive surgery. Corneal total higher-order aberrations, spherical aberration and coma for 4-mm and 6-mm pupils were measured using a wave-front analyzer. The amount of aberrations of the oblate corneal optics by the achieved correction was found to be larger than for the prolate corneal shape with complete eye, in an emmetropia control group. The change in corneal shape acts as an optical factor that degrades the quality of the retinal image; it seems to be one of the important factors related to quality of vision.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.2
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• pp.179-186
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• 2013

Purpose: To compare corneal asphericity, visual acuity (VA), and ocular and corneal higher-order aberrations (HOAs) between myopic refractive surgery and emmetropia groups. Methods: Twenty three subjects ($23.0{\pm}2.5$ years) who underwent myopic refractive surgery and twenty emmetropia ($21.0{\pm}206$ years) were enrolled. The subjects'criteria were best unaided monocular VA of 20/20 or better in both two groups. High and low contrast log MAR visual acuities were measured under photopic and mesopic conditions. Corneal and ocular HOAs were measured using Wavefront Analyzer (KR-1W, Topcon) for 4 mm and 6 mm pupils. Corneal asphericity was taken by topography in KR-1W. Results: There was no significant difference in VA between two groups under either photopic or mesopic conditions. In ocular aberrations, there were significant differences in total HOAs, fourthorder and spherical aberration (SA) for a 6 mm between two groups (p=0.045, p<0.001, and p<0.001, respectively). In corneal aberrations, there was a significant difference in SA for 4 mm (p=0.001) and 6 mm (p<0.001) pupils between two groups and there were statistically significant differences in total HOAs (p<0.001) and fourth-order aberrations (p<0.001) between two groups for a 6 mm pupil. There was a significant correlation in emmetropia between Q-value and SA in ocular aberrations for 4 mm and 6 mm pupils (r=0.442, p=0.004, and r=0.519, p<0.001) and in corneal aberrations for 4 mm and 6 mm pupils (r=0.358, p=0.023, and r=0.646, p<0.001). No significant correlations were found between Q-value and SA in refractive surgery group. Conclusions: VA in myopic refractive surgery is better than or similar to emmetropia. Nevertheless, the more increasing pupil size is, the more increasing aberrations are. Thus, it could have an influence on the quality of vision at night.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.2
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• pp.157-165
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• 2015

Purpose: To evaluate changes in central and peripheral refraction along the horizontal visual fields in myopic corneal refractive surgery group compared with emmetropes. Methods: One hundred twenty eyes of 60 subjects ($23.56{\pm}2.54$ years, range: 20 to 29) who underwent myopic refractive surgery and 40 eyes of 20 emmetropes ($22.50{\pm}1.74$ years, range: 20 to 25) were enrolled. The central and peripheral refractions were measured along the horizontal meridianat $5^{\circ}$, $10^{\circ}$, $15^{\circ}$, $20^{\circ}$, $25^{\circ}$ in the nasal and temporal areas using an open-field autorefractor. For analysis of post-op group, the group was classified by pre-op spherical equivalents of < -6.00 D and ${\geq}-6.00D$ as two post-op groups. Results: Pre-op spherical equivalent was $-4.56{\pm}0.92D$ (rang: -2.50 to -5.58 D) in post-op group 1, and $-7.09{\pm}0.96D$ (rang: -6.00 to -9.00 D) in post-op group 2. Spherical equivalent (M) in the emmetropes ranged from $-0.20{\pm}0.22D$ at center to $-0.64{\pm}0.83D$ at $25^{\circ}$ in the temporal visual field and to $-0.20{\pm}0.67D$ at $25^{\circ}$ in the nasal visual field; M in post-op group 1 ranged from $-0.16{\pm}0.29D$ at center to $-5.29{\pm}1.82D$ at $25^{\circ}$ in the temporal visual field and to $-4.48{\pm}1.88D$ at $25^{\circ}$ in the nasal visual field; M in post-op group 2 ranged from $-0.20{\pm}0.32D$ at center to $-7.98{\pm}2.08D$ at $25^{\circ}$ in the temporal visual field and to $-7.90{\pm}2.26D$ at $25^{\circ}$ in the nasal visual field. Among the three groups, there was no significant difference in M at central visual field (p=0.600) and at $5^{\circ}$ in the temporal visual field (p=0.647), whereas, there was significant difference in M at paracentral and peripheral visual field (p=0.000). Conclusions: Emmetropes had relatively constant refractive errors throughout the central and peripheral visual field and showed myopic peripheral defocus along the horizontal visual field. On the other hand, in myopic corneal refractive surgery group, there were significant differences in refractive errors between the central and peripheral visual field compared with differences in the central and peripheral refraction patterns of emmetropes.

• Korean Journal of Ophthalmology
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• v.32 no.6
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• pp.497-505
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• 2018

Purpose: To evaluate and compare published methods of calculating intraocular lens (IOL) power following myopic laser refractive surgery. Methods: We performed a retrospective review of the medical records of 69 patients (69 eyes) who had undergone myopic laser refractive surgery previously and subsequently underwent cataract surgery at Samsung Medical Center in Seoul, South Korea from January 2010 to June 2016. None of the patients had pre-refractive surgery biometric data available. The Haigis-L, Shammas, Barrett True-K (no history), Wang-Koch-Maloney, Scheimpflug total corneal refractive power (TCRP) 3 and 4 mm (SRK-T and Haigis), Scheimpflug true net power, and Scheimpflug true refractive power (TRP) 3 mm, 4 mm, and 5 mm (SRK-T and Haigis) methods were employed. IOL power required for target refraction was back-calculated using stable post-cataract surgery manifest refraction, and implanted IOL power and formula accuracy were subsequently compared among calculation methods. Results: Haigis-L, Shammas, Barrett True-K (no history), Wang-Koch-Maloney, Scheimpflug TCRP 4 mm (Haigis), Scheimpflug true net power 4 mm (Haigis), and Scheimpflug TRP 4 mm (Haigis) formulae showed high predictability, with mean arithmetic prediction errors and standard deviations of $-0.25{\pm}0.59$, $-0.05{\pm}1.19$, $0.00{\pm}0.88$, $-0.26{\pm}1.17$, $0.00{\pm}1.09$, $-0.71{\pm}1.20$, and $0.03{\pm}1.25$ diopters, respectively. Conclusions: Visual outcomes within 1.0 diopter of target refraction were achieved in 85% of eyes using the calculation methods listed above. Haigis-L, Barrett True-K (no history), and Scheimpflug TCRP 4 mm (Haigis) and TRP 4 mm (Haigis) methods showed comparably low prediction errors, despite the absence of historical patient information.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.2
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• pp.197-202
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• 2013

Purpose: This research was performed to measure and analyze scotopic pupil size in myopes and to figure out the factors that influence it. Methods: The pupil size of 191 healthy myopic subjects were measured with the pupillometer (Colvard pupillometer, OASIS medical, USA) in scotopic and analyzed with the age, corneal size, spherical equivalent refractive error, corneal curvature. In addition, it was compared with the measurements of intra-examiner and inter-examiner to verify reproducibility of pupillometer. Results: The mean (${\pm}$SD) scotopic pupil size was $6.64{\pm}0.68$ mm (range, 5.00~8.00 mm), the lower age and the larger corneal size, The bigger the pupil size. The lower spherical equivalent refractive error and steepper corneal curvature tends to be smaller. The reproducibility of intra-examiner and inter-examiner in pupillometer showed the reliability highly (Guttman splithalf point > 0.91). Conclusions: The pupil size associated with age, corneal size, spherical equivalent refractive error and corneal curvature in scotopic condition. It can refer to prevent inconvenience that may occur RGP contact lenses, cataract surgery and refractive surgery.

• The Korean Journal of Vision Science
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• v.20 no.4
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• pp.443-451
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• 2018

Purpose : To find out the reliability of autorefractometer after laser refractive surgery Methods : We measured and compared spherical and cylinder powers of those undergone LASEK surgery with 1.0 of naked vision after at least 3 months of the surgery with an autorefractometer(CANON Full Auto Ref-Keratometer RK-F1, Japan) and a retinoscope(Streak Retinoscope 18200, WelchAllyn, USA), and also applied spherical equivalent powers. The refractive status before surgery was divided into high, medium, and low myopia according to the results measured using an autorefractometer, and then analyzed again the reliability of the autorefractometer after surgery according to the preoperative refractive status. The agreement of two methods was identified using Bland-Altman(Bland-Altman limits of agreement(LoA)). Results : After the surgery, when comparing spherical, cylinder and equivalent powers in the whole data measured by autorefractometry and retinoscopy significant differences were found(p<0.01). According to the degree of refractive errors, all sort of refractive errors was shown significantly different(p<0.01) except for cylinder power of the medium myopia. In general, the refractive errors especially spherical and spherical equivalent powers by autorefractometry were shown a myopic trend from -0.38 D to -0.53 D. On the other hand, it was shown a hyperopic trend of approximately +0.30 D using retinoscopy. In comparison of two objective refractions, it was shown a myopic trend as $-0.51{\pm}0.45D$(LoA +0.36 D ~ -1.39 D) and compatible. Conclusion : Even though it would be positive in terms of compatibility of the methods, it is necessary that the glasses should be prescribed by subjective refraction since autorefractometry is shown myopic in those undergone the surgery and suffering from myopic regression.