• Journal of Korean Ophthalmic Optics Society
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• v.19 no.2
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• pp.189-198
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• 2014

Purpose: The present has analyzed the correlation between the direction of lens and the amount of rotation upon soft toric contact lens fitting after classifying the corneal astigmatism. Methods: Soft toric contact lens was fitted on 114 with-the-rule astigmatic eyes with total astigmatism of at least -0.75 D in their 20s and 30s according to the fitting guideline of the manufacturer and the correlation between the astigmatic degree and the rotational direction/amount of rotation was analyzed by when keeping the eyes on the front and by changing the direction of gaze. As for re-orientation movement. The speed of lens re-orientation and total amount of lens rotation was compared and analyzed by corneal astigmatism after mis-location of lens of $45^{\circ}$ to temporal and nasal direction, respectively. Results: The positive correlations were shown between corneal astigmatism and the direction of lens rotation and between corneal astigmatism and the amount of lens rotation. Meanwhile, the amount of lens rotation was different by the direction of gaze however, there was no correlation with corneal astigmatism. The speed of lens re-orientation was fastest in the group of high astigmatic degree when the lens was mis-located to both temporal and nasal directions. Conclusions: For optimal axis stabilization of toric soft lens, it is proposed that the adjustment of fitting guideline considering corneal astigmatism is necessary since the current fitting guideline is only based on total astigmatism.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.4
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• pp.441-447
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• 2013

Purpose: The present study was conducted to investigate the axial rotations of toric soft lens during the change of lens wearer's posture, and the relationship between its rotation and corneal astigmatism. Methods: The amount, direction, and speed of toric soft contact lens rotation were measured for 42 eyes (aged 20s) with the rule astigmatism in the straight and lying postures, and it compared between their changes according to corneal astigmatism. Results: There was no significant difference in the axial rotation of lens for the astigmatism prescription between the straight and lying postures. However, the rotation angle was significantly different according to the posture of lens wearer. Rotating directions in straight posture were nasal direction for 20 eyes and temporal direction for 22 eyes. In lying posture, lenses of most wearers were rotated to a direction of lying posture, and the initial rotating speed was very fast in initial wearing for -0.75 D toric lenses, but consistency for -1.25 D toric lenses. The rotation angle in lying posture showed significantly different according to the amount of corneal astigmatism, the lens speed was also significantly different according to the wearing time but not the amount of corneal astigmatism. Conclusions: The axial rotation of toric soft lens was different by the lens wearer's posture and its amount was the greater with the higher degree of corneal astigmatism. Thus, these factors should be considered for the development of toric lens design.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.4
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• pp.445-454
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• 2015

Purpose: The present study was aimed to investigate the effect of tear volume on a change of axial rotation according to wearing time of toric soft contact lens and gaze directions. Method: Toric soft contact lenses with double thin zone design applied on 62 eyes. Then, changes in non invasive tear film break-up time and the rotational direction/amount of lens when changing gaze direction were respectively measured after 15 minutes and 6 hours of lens wear. Results: Lens rotation to temporal direction was more found when changing gaze direction after lens wear. However, its rotation was varied according to wearing time and the subjects' tear volume. Furthermore, the frequency of lens rotation to temporal direction was higher in dry eyes compared with normal eyes at nearly all gaze directions after 15 minutes and 6 hour of lens wear. The rotational amount of lens was generally greater in dry eyes after 15 minutes of lens wear. However, its difference between normal eyes and dry eyes was not great after 6 hours of lens wear. Conclusion: The present study revealed that axial rotation of toric soft contact lens was varied according to the wearer's tear volume and lens rotational patterns at the initial, and extending periods of lens wear were different. The change in rotational pattern of toric soft contact lens from these results means the possibility of visual change after extending lens wear, and the identification of its correlation with tear volume suggests the necessity of considering factors for choosing appropriate toric soft contact lens.

• Journal of Korean Ophthalmic Optics Society
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• v.11 no.2
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• pp.77-83
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• 2006

We have studied the astigmatism according to the bevel position and the tilting(pantoscopic) angle of decentered spectacle lens for prism prescription. For prism prescription, generally we make a general spectacle lens into decentered spectacle lens. At this time the bevel position of decentered lens is a important matter, because the difference between optic axis and visual axis occur aberrations. Using the calculation we find that the case that the axis of bevel rotation band passes the front curvature center of (+) lens has a smaller astigmatism than the case that the axis of bevel rotation band passes the rear curvature center of (+) lens and that the case that the axis of bevel rotation band passes the rear curvature center of (-) lens has a smaller astigmatism than the case that the axis of bevel rotation band passes the front curvature center of (-) lens. We find the lens with higher refraction index has a smaller astigmatism.

• Journal of Sensor Science and Technology
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• v.22 no.6
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• pp.393-399
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• 2013

We propose a method of sensing the rotation and distance of a camera by using a fisheye lens system as a vision sensor. We estimate the rotation angle of a camera with a modified correlation method by clipping similar regions to avoid symmetry problems and suppressing highlight areas. In order to eliminate the rectification process of the distorted points of a fisheye lens image, we introduce an offline process using the normalized focal length, which does not require the image sensor size. We also formulate an equation for calculating the distance of a camera movement by matching the feature points of the test image with those of the reference image.

• Journal of Korean Ophthalmic Optics Society
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• v.21 no.1
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• pp.35-45
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• 2016

Purpose: The present study was aimed to investigate the effect of corneal eccentricity on the axial rotation when wearing toric soft contact lenses were worn for certain time and changing the gaze directions. Methods: Toric soft contact lenses with double thin zone design applied on 85 of with-the-rule astigmatic eyes. Then, rotational direction and amount of contact lenses were measured after 15 minutes and 6 hours of lens wear. The difference was further compared and analyzed according to corneal eccentricity. Results: The rotation of toric lens showed a tendency to rotate to temporal direction in all gaze directions except temporal-upper direction in all groups of corneal eccentricity. The amount of lens rotation in the frontal gaze direction exhibited a negative correlation since the amount was decreased with increasing corneal eccentricity after both 15 minutes and 6 hours of lens wearing. In many cases, the cornea with small eccentricity also showed the lens rotation larger than $10^{\circ}$. The difference in rotational amount after 15 minutes of toric lens wear was small according to the corneal eccentricity however, the change of rotational amount of contact lens according to corneal eccentricity was shown after 6 hours of lens wear. Conclusions: The present study revealed that the amount of axial rotation was largely varied according to the wearer's corneal eccentricity when wearing toric lens and the rotational amount after certain time of lens was also affected by corneal eccentricity. Thus, it is suggested that the selection of toric soft contact lenses based on corneal eccentricity is necessary.

• 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.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.1
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• pp.21-30
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• 2011

Purpose: The study was performed to compare the differences in lens rotation, lens movement by blinking and lens centration with alignment or steep fitting of soft contact lens in normal and dry eyes. Methods: Total 40 eyes (aged 20~30 years) were classified into the normal (n=20) or dry eye group (n=20) by the diagnosis methods for dry eyes and worn soft contact lens (polymacon material) with alignment fitting or steep fitting. Lens rotation, lens movement by blinking and lens centration were separately measured immediately after lens wearing and after stabilization of tear film and compared by fitting states of soft contact lenses. Results: With steep fitting of soft contact lens in dry eyes, averaged lens rotation immediately after lens wearing was not significantly different from that of the normal eye group with alignment fitting however, lens rotation after stabilization in dry eyes was significantly larger than that in normal eyes. Any significant difference in lens movement by blinking was not shown in normal eyes. However, lens movement by blinking in dry eyes was increased with steep fitting. The range of lens centration on cornea in normal eyes with alignment fitting was more vertically distributed. On the other hand, the range of lens centration on cornea in dry eyes with alignment fitting was more horizontally distributed. Lens centration was shown to be changed by stabilization of tear film. That is, lens centrations were somewhat vertically widespread immediately after lens wearing and restrictively distributed in horizontal direction, respectively, with steep fitting in dry eyes. Conclusions: These results suggested that lens movements and centration in dry eyes were different from those of normal eyes. Especially, those differences between normal and dry eyes were much bigger with steep fitting of soft contact lenses. Thus, those differences should be considered for the comfortable and safe fitting of soft contact lens in dry eyes.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.2
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• pp.133-140
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• 2015

Purpose: It was investigated whether two different stabilization designs of toric contact lenses changed the rotational axis and degree of toric lenses according to body posture and gaze direction in the present study. Methods: Toric soft contact lenses with Lo-Torque$^{TM}$ design and ASD design (accelerated stabilized design) were fitted on 52 eyes aged in 20s-30s. Then, rotational degree was measured at the five gaze directions including front gaze and the lying position. Results: When gazing the front and vertical directions in the upright posture, lens was much rotated to nasal side for the Lo-Torque$^{TM}$ design and temporal side for the ASD design. When gazing horizontal direction, both design lenses were rotated against to the gaze direction. Rotation degree was the smallest at superior direction gaze and the largest at nasal gaze. In case of the rotation degree less than $5^{\circ}$, Lo-Torque$^{TM}$ design was more frequent when gazing front and vertical directions, and ASD design was more frequent when gazing horizontal direction. In addition, the lens with Lo-Torque$^{TM}$ design was lesser rotation degree than with ASD design immediately after lying. On the other hand, the lens with ASD design was lesser rotation degree than with Lo-Torque$^{TM}$ design 1 minute later after lying. Conclusions: This study confirmed that axis rotation of the lens induced by gaze direction and posture was different according to axis stabilization design during wearing toric soft contact lens.

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.1
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• pp.27-35
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• 2012

Purpose: The present study was conducted to compare any difference caused by pigmentation in the centrations and movement patterns on the cornea between circle and soft contact lens with identical material and parameters during lens wearing. Methods: Soft and circle contact lenses with identical material and parameters were applied to twenty eyes with normal tear volume for 3 hrs a day during a total of 5 days and then their lens centrations, the moving distances and rotations by repeat blinking were compared. Results: The lens centration beyond the fitting criteria was shown in initial wears of both soft contact lens and circle contact lens. However, the centration of soft contact lens was changed to the pupil center for being suitable to the fitting criteria with longer wearing time. On the other hand, the decentration of circle contact lens in the horizontal direction was still presented even with longer wearing time. The moving distances of soft contact lens and circle contact lens decreased with the expand of lens wearing but were not significantly different between total wearing period and daily wearing time. The rotation of circle contact lens by repeat blinking was significantly different from that of soft contact lens even when the wearing period was extended. Conclusions: We revealed that the lens centration and movement of circle contact lens on cornea were different from those of regular soft contact lens resulting in bigger difference with the expand of wearing period in the study.