• Journal of Korean Ophthalmic Optics Society
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• v.17 no.3
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• pp.311-319
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• 2012

Purpose: One of the critical aspects on dispensing glasses is to match the center of pupils to the optical center of lenses as the mismatched glasses are able to induce uncomfortable effects called prism which has been known to induce phoria, a main cause for asthenopia in many cases. Therefore, we investigated the induced prism occurred by mismatching centers between the center of pupils and the optical center of lenses. Methods: In this study, total 103 subjects were examined whether the center of pupils and the optical center of lenses are matched in horizontal and vertical directions, and then, the data was categorized into 4 groups based on the structural components of glasses. Total amount of prism was compared to show the effect of the glasses frame on the prism induction, and the value of measured prism was compared with the German RAL-RG 915 regulations. Results: The results in respect to the horizontal component showed that the induced prism was not found in 10.7% of total subjects. 73.8% of total subjects were influenced by induced prism, the range of prism was in a tolerance level. However, the 15.5% of total subjects seemed to be influenced by prism which is out of the criterion of tolerance. In case of vertical component, 23.3% of total subjects showed no effects of prism while early adopting glasses, 54.4% of total subjects showed a little prism effect within the criterion of tolerance, and 22.3% of total subjects showed the prism effect out of the tolerance range. This data indicates that group A and B that are less likely adjustable by fitting induce more prism than group C and D in horizontal and vertical components. Conclusions: In higher refractive error condition, it was found that aligning the optical center of lenses with the center of pupils by pre-fitting of glasses frame minimized prism induction in horizontal and vertical components, which ameliorates ocular fatigue. Therefore, appropriate optometric dispensing through fitting by opticians and precise design about monocular PD and monocular Oh are necessary to improve visual perception.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.1
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• pp.1-5
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• 2011

Purpose: Measurement of the horizontal and vertical prism diopter was investigated which was occurred due to distance differences between the optical inter-centeral distance (OC) and the interpupillary distance (PD) of the prescribed glasses. Methods: We surveyed 96 subjects (192 eyes) at the average age of 21.56 years old. The PD was measured by using the PD measurement system (DONGYANG PD-85, Korea), and the OC of the glasses was measured by using the projective peak refractive power measurement system (TOPCON CL-200, Japan). The OH value was measured by using Penlight and the PD ruler. Results: The PD which had been measured by the PD system and the OC of the glasses revealed 78.1% of differences. 62.5% of the objects were base-in value prescribed glasses; 58.3% were out of permissible error. Only 8 subject showed concurrence between the prescribed glasses and the OH value, and 82.3% of the objects were induced vertical prism of over 1 (prism diopter). Conclusions: In order to improve the vision function of people who wear glasses, it is necessary to advance the accuracy of PD, OH measurement and making glasses as well.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.4
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• pp.527-532
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• 2014

Purpose: The matching of the optical center and the pupil center was measured by photographs in wearing glasses. In this study, the influences of the induced prism by the mismatching are studied. Methods: 74 subjects (148 eyes) who were spectacles wearer were participated in this study. The mean age was $29.19{\pm}12.22$ years (range 19-55 years). The facial photographs of subjects were taken while wearing spectacles. The matching of the corneal reflected image and optical center of the spectacle lens in the horizontal deviations, and the vertical deviations were measured by the observation of the photo image. The prisms induced in accordance with various frame type were calculated from the mismatching deviations. Results: The binocular horizontal deviations were $1.55{\pm}1.70mm$ for the metal frame, $1.71{\pm}2.21mm$ for the clings type plastic frame, and $1.15{\pm}1.38mm$ for the plastic frame. In the horizontal direction induced prism, the ratio over the tolerance was 23%. The ratio were the 17.6% at the BI prism, and 5.4% at the BO prism. The binocular vertical deviation comparisons were $3.93{\pm}1.91mm$ for the metal frame, $5.79{\pm}1.93mm$ for the clings type plastic frame, and 1$6.01{\pm}2.94mm$ for the plastic frame. In the vertical direction induced prism, the ratio over the tolerance was 44.6%. Based on the refraction power, the ratio were 12.2% at -0.25${\leq}-3.00$, and 32.4% at -3.00${\leq}-12.00D$. Conclusions: The induced prisms in the horizontal direction were much in the BI prism. The binocular vertical deviations of the glasses.

• Journal of Korean Ophthalmic Optics Society
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• v.1 no.2
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• pp.85-91
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• 1996

Among the 110 glasses wearers, the hyperopic glasses wearers were 18(16.36%) persons and myopic glasses wearers were 92(83.64%) persons. The distance for optical centers was coincided to the pupillary distance in 9(8.18%) persons and discrepant in 101(91.82%) persons. Ophthalmic dispensing Pupillary Distance resulted from testing by the trouble error range(Germany RAL-915), unadopt spectacles had been wearers 52(51.49%) persons. The 65(64.56%) persons and 36(35.64%) persons showed the induced esophoria and the induced exophria, respectively. The maximal induced esophoria was 3.69 prism diopters and maximal induced exophoria was 3.68 prism diopters.

• Journal of Korean Ophthalmic Optics Society
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• v.14 no.2
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• pp.1-8
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• 2009

Purpose: The purpose of this study is to compare degrees of asthenopia in after wearing of dispensed reading glasses with different criterion of P.D. Methods: The person who has minus near correction power (distance correction value (-)) is compared to the degree of asthenopia by wearing of dispensed reading glasses with near P.D(-B) and distance P.D. The person who has plus near correction power is compared to degree of asthenopia by wearing of dispensed reading glasses with near P.D-B, distance P.D, near P.D-A. The "Near-P.D-A" means reduced optical centre distance of reading glasses of positive correction value at which the same effect of prism B.O through near visual point in distance glasses exist at near visual point in reading glasses. Results: When near correction value is (-), dispensed reading glasses with distance P.D have caused less asthenopia than dispensed glasses with near P.D-B. When the near correction value is (+), we cannot confirm that which P.D is more useful for reading glasses. As a result of this study, dispensed reading glasses with near P.D-A have caused less asthenopia than another criterion of P.D. Conclusion: The effect of prism B.I through a near visual point in distance glasses ((-) correction value) reduce convergence demand. Therefore (-) correction value-reading glasses support convergence in near vision, because the effect of prism B.I of reading glasses is smaller than that of distance glasses. When the near correction value is (+), centration points can be determined by one of near P.D-A, near P.D-B, distance P.D.