• Journal of Korean Ophthalmic Optics Society
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• v.14 no.2
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• pp.35-39
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• 2009

Purpose: In this study a program was developed to determine corneal aberrations using corneal shape of topographer and represented a wavefront and corneal aberrations using zernike polynomial. Methods: When the pupil size was 6 mm, we calculated new corneal shape data with zernike polynomials using corneal shape data of ORBSCAN topographer. We programmed the wavefront construction using ray tracing for corneal shape, then represented corneal aberrations having zernike polynomial with 6th order and 28 terms. Conclusions: We developed programs to determine a wavefront and corneal aberrations using corneal shape of ORBSCAN topographer. Theses results will be applied to a development of new topographer and prescription of contact lens and OK lens.

• 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.16 no.1
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• pp.97-106
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• 2011

Purpose: This review article was written to theoretically compare the depressing force (pressure, adhesion) to the cornea between when the spherical lenses were being tightly and flat fitted. Methods: Mathematical equations and their numerical solution programs (model) were formulated to calculate the depressing (adhesion) force to the cornea by both the tightly and flat fitted contact lenses. Based on this proposed model the effects of parameters characterizing a contact lens such as BCs, diameters, edge shape and corneal shape (ratio of long and short corneal axis, p) on the depressing force to the cornea were predicted/analyzed in both tightly and flat fitting regimes. Results: Corneal adhesion increased as the corneal p-value increased. Adhesion increase caused by the increased p-value was much larger in flat fitted case than in tight fitted one. Corneal adhesion reduced abruptly as the BC increased in flat fitting regimes while the adhesion rise was insignificant in tight fitting ones. Reduction in corneal adhesion due to lens-size increase was predicted to be insignificant in both tight and flat fitting regimes. Both the lens edge shape (edge angle) and thickness were relevant only in tight fitting regime. Corneal adhesion increased as the increased with tight-fitted lenses. As the thickness of tight fitted lenses increased, corneal adhesion inversely decreased. Conclusions: The two most significantly affecting the depressing force to cornea were found to be the degree of corneal bending toward the periphery and the BCs of lenses.

• Journal of Korean Ophthalmic Optics Society
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• v.14 no.3
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• pp.7-15
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• 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
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• v.17 no.4
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• pp.389-394
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• 2012

Purpose: The purpose of this study was to examine the corneal topographical changes associated with the wearing of everted silicone hydrogel soft lenses. Methods: The shape and fluorescein pattern of everted silicone hydrogel lenses were investigated. The subject wore the silicone hydrogel everted lenses overnight for 8 hours. Objective refractive error and corneal shape were evaluated at baseline, 1, 2, 3, 5, and 7 days after lens wearing and 1,2,3, and 4 days after discontinuation of lens wear. Results: The Fluorescein pattern of everted silicone hydrogel lenses was similar to the reverse geometry lenses with pressure profile. Objective refractive error(sphere power) and corneal refractive power were decreased and corneal shape had changed during the everted silicone hydrogel lenses wear and recovered during the 4 days of discontinuation. Subject experienced no discomfort associated with the everted silicone hydrogel lenses. Conclusions: It appears that everted silicone hydrogel lenses are capable of inducing significant changes in corneal topography, with overnight wear. Further study must be done to help understand these changes to develop a predictable and effective way of using soft contact lenses for corneal reshaping.

• Proceedings of the KOSOMBE Conference
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• v.1992 no.11
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• pp.58-62
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• 1992

Hybrid optical-electronic procedures are introduced for the automated estimation of cell parameters (e.g., size, size variation, and shape). Two different optical Fourier analysis procedures are applied to high contrast cell boundary patterns obtained from specular micrographs of the endothelial layer. In one case, a large number of cell patterns are illuminated to extract average cell size information. Once the average cell size information has been obtained, individual cells are illuminated to extract shape information.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.3
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• pp.383-387
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• 2014

Purpose: To investigate the effect of corneal unique shape to changes of refractive full corrections when pupil size changes. Methods: Subjective refraction for monocular full correction was performed to 30 subjects ($23.33{\pm}1.78$ of age, 60 eyes) in two room conditions, 760 lx and 2 lx, respectively. Pupillary diameter was measured in two conditions and the change pattern was analyzed using a peak data of corneal topography. Results: Pupillary diameter was 3.74~4.00 mm in 760 lx and 5.52~5.90 mm in 2 lx. By comparison with refractive data in 760 lx, those data in 2 lx was changed as follows: more (-) spherical power of 17 eyes (28.3%), more (+) spherical power of 10 eyes (17.7%), more (-) cylinderical power of 17 eyes (28.8%), less (-) cylinderical power of 9 eyes (15.3%), and astigmatic axis rotation of 36 eyes (62.1%). From peak data of corneal topography, the changing pattern of two principal meridians was classified into 4 types. Conclusions: Expansion of the corneal refractive surface accompanied with pupillary dilation may be a main factor that effects the changing a values of subjective refraction because of unique corneal shape. Therefore, subjective refraction should be performed under the nearest lighting condition to a main living environment.

• Applied Microscopy
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• v.24 no.4
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• pp.98-106
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• 1994

The corneal formation of compound eye of Pieris rapae L., which was mostly made during pupal stage, was morphologically investigated with light microscope, scanning electron microscope and transmission electron microscope. The regeneration of the microvilli were found on the surface membranes of corneagen cells and retinular pigment cells of preommatidium after apolysis pupal cuticle. The microvilli were finally differentiated to corneal nipples of the ommatidium. The corneal cuticle was generated on the superficial layer of the preommatidium from corneagen cells and retinular pigment cells. The corneal process was also formed under the cuticular layer from the corneagen cells. The pore canal was appeared within the cuticular layer and connected with the retinular pigment cell as if the root of interommatidial hair was connected. The interommatidial hair was projected randomly among the ommatidial facets and cornal nipple was arrayed regular on the ommatidial facets. The cornea was convex lens and the refracting power by its convex shape was 4 diopter.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.1
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• pp.111-120
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• 2014

Purpose: This study was to investigate changes in the thickness of cornea, curvature of cornea, and aberration depending on the water contents, materials, and refractive power of contact lens. Methods: The differences in the corneal thickness between pre- and post-wearing the lenses were compared using 5 kinds of lenses. The changes in the corneal thickness, the curvatures of the anterior and posterior cornea, and high order aberration (HOA) before and after wearing the lenses were investigated at the center of the cornea, and the different distance and the direction away from the center of the cornea. For the equipments of measurement, ORB ScanII (Bausch & Lomb Inc, ver 3.14) was used to measure the corneal topography and thickness, and Zywave (Bausch & Lomb Inc, ver 5.20) was used to analyze the high order aberration. Results: Five (S1, S2, S3, T1, T2) of the lens was used for this study, excluding the lens T2 lens has four lenses and the thickness of the corneal shape, but the impact is minimal. In the case of the hydrogel soft contact lenses (T2 lens) with low oxygen permeability, the corneal thickness showed distinct increasing patterns. The high order aberration and coma aberration were most changed in the silicon hydrogel toric lens, while the depth of anterior was most changed in the hydrogel toric lens. Conclusion: Among the 5 kinds of contact lenses with different water contents, materials, and refractive power used for this study, the corneal shape change was small for the lenses with an oxygen permeability (Dk) of more than 28, and the largest for the lenses with a very low oxygen permeability.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.4
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• pp.449-456
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• 2013

Purpose: The present study aimed to investigate the effects of corneal eccentricity and shape on the rotational pattern of toric soft lens by the postural change of lens wearers. Methods: The corneal eccentricity of 41 eyes (aged 20s) having -1.0 D with-the-rule corneal astigmatism (WRCA) was measured, and then toric soft lenses were fitted with the amount of total astigmatism. In lying and straight postures, the rotation of toric soft lenses was recorded by a camera attached to slitlamp and analyzed. Results: Most toric soft lens designed with accelerated stabilization rotated to the temporal direction, which was the lying position direction, regardless of corneal eccentricity, and some lenses rotated to the nasal direction for high corneal eccentricity and corneal type of asymmetric bowtie. There was no correlation between the amount of rotation and corneal eccentricity right after of contact lens wearing in straight and lying posture, however, the amount of rotation was the greater for the cornea with the higher eccentricity after the subjects laying down for some period. The speed of lens rotation started to decrease after the subjects laying down, but the speed was not different according to corneal eccentricity difference. The amount of lens rotation for symmetric and asymmetric bowtie-typed corneas increased more than it for oval-typed cornea, and it was same even with time elapsing. The speed of lens rotation in lying posture was the slowest in asymmetric bowtie-typed cornea compared with other corneal types. Conclusions: From the present study, it was revealed that the rotational pattern of toric soft lens was affected by corneal eccentricity and corneal shape when the wearer's posture changed. Thus, it should be considered for the development of the fitting guideline and the design of toric soft lens.