• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.8
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• pp.599-606
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• 2007

An experimental study was performed to measure a ice concentration of ice slurry flowing in a pipe in a real time. In the present paper, we suggested a measuring method by a refractive index and compared it to other methods by a freezing point and a density. To measure the refractive index of the solution, ice particles in the ice slurry should be completely removed and a hydro-cyclone was introduced instead of a mesh. The measuring method through the refractive index coincided with the density method using the real-time solution density within ${\pm}5%$ error range, having the error range less than the other two methods. In the other hand, the measuring method through the density has a good resolution, but the result using the initial density of the solution was different more than 10% error from that using the real-time density. And it has an error range 1.5 times greater than the method through the refractive index.

• Journal of Korean Ophthalmic Optics Society
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• v.14 no.4
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• pp.53-57
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• 2009

Purpose: To study the relationship of N.P.C, heterophoria and near convergence and divergence by amount of the refractive error. Methods: All subjects have no ocular disease and their mean age is 22.7. All 39 subjects examined about refractive error, near point of convergence (NPC), heterophoria, near convergence and divergence. Results: Classified by low refractive state, middle refractive state, and high refractive state compared with the expected value of Morgan. NPC had been measured within low and middle refractive state eight all the 8cm. However, high refractive state measured 9.64 cm. Low and middle refractive state for the classification by near phoria. Near esophoria groups was smallest by near divergence and exophoria groups was smallest by near convergence. Conclusions: Near convergence were largest with esophoria while near divergence were largest with exophoria.

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.4
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• pp.403-410
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• 2012

Purpose: The purposes of this study are to investigate accommodative response among emmetropes, spectacle wearer and contact lens wearer, and correlation between refractive error and accommodative respons for each group. Methods: The 72 subjects(144 eyes) who do not have any ocular diseases were participate in this study. Subjects were categorized into emmetropes, spectacle wearer and contact lens wearer by refractive error using closed-field auto-refractometer. We measured dominant eye, naked/habitual visual acuity and refractive error of monocular/binocular vision of refractive error for far/near distance with open-field auto-refractometer and calculated accommodative lag. Results: There were no significant difference of accommodative lag between right and left eye dominant and non-dominant eye, monocular and binocular vision, and spectacle lens wearer and contact lens wearer, However the accommodative lag of binocular vision was severe than monocular vision at near. The lag of myopia was larger than emmetropes, and male was larger than female. Significant correlation was found between refractive error and accommodative lag in total subjects and the same result was found in emmetropes and contact lens wearer. However there were no significant correlation in the spectacle wearer. Conclusions: There were significant difference between emmetrops and myopes in terms of accommodative lag, however accommodative lag of spectacle wearer was not different with contact lens wearer in myopes. There were also significant correlation between refractive error and accommodative lag in emmetropes and contact lens wearer, but the accommodative lag of spectacle wearer was not significantly correlated with refractive error.

• Journal of Korean Ophthalmic Optics Society
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• v.2 no.1
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• pp.61-76
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• 1997

In this paper, we found out the objective refractive errors, the full corrective refractive powers, and the prescriptions for 64 males and 36 females aged 18 to 26 years. To increase the unaided visual acuity 0.1 to the aided visual acuity 1.0 with the glasses, we needed the spherical equivalent refractive power of -3.00D for male and -2.91D for female respectively. To increase the unaided visual acuity 0.5 to the aided visual acuity 1.0 with the glasses, we needed the spherical equivalent refractive power of -0.5D for male and -1.38D for female respectively. Comparing unaided visual acuity and corrective refractive power, the more one has refractive error the less one has unaided visual acuity but these are not linear relationships. Comparing objective refractive error figures, full corrective refractive power figures and prescriptions, objective refractive error figures are the hightest, followed by full corrective refractive power figures. Prescriptions compared with the other two are lower. The cylindrical refractive powers are less than -2.50D. In this study, with the rule astigmatism is dominant over against the rule astigmatism and oblique astigmatism. The accommodation measured by push up method is 6.75D~10.04D for male and 7.50D~9.60D for female respectively.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.3
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• pp.293-297
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• 2011

Purpose: This study was to know the correlation among refractive error and the dimensions of ocular components on older adults. Methods: The subjects were 95 older age who had no eye diseases. The refractive error, corneal radius, corneal diopter, axial length, anterior chamber depth and lens thickness were measured and analysed. Results: The axial length(AL)/corneal radius(CR) ratio was positively correlated with the corneal diopter, axial length, the anterior chamber depth. Then it was negatively correlated with corneal radius. It was shown that the highest correlation was between the corneal diopter and axial length (r = -0.545, p = 0.000). The spherical equivalent of the refractive error was negatively correlated with the AL/CR ratio. Conclusions: It was shown that the AL/CR ratio was a very important indicator for diagnosing the refractive error of the old age.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.3
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• pp.313-317
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• 2011

Purpose: This study was to assess prevalence of refractive errors and uncorrected refractive errors in elementary school children in Mokpo and uncorrected refractive errors were to be used as the basic data. Methods: Vision tests were conducted on 400 subjects of 1st~6th grades at 3 elementary schools in Mokpo city, and subjective, objective refraction test were also performed to survey uncorrected refractive errors. Results: The prevalence of myopia was 256, 64% of total subjects, Hyperopia was 21, 5.3%, astigmatism was 19, 4.8%. The prevalence of uncorrected refractive errors were increased as higher grade and more oculus dexter higher than oculus sinister. Conclusions: Vision impairment which need an accurate vision correction for elementary school students requires the regular examination and actively correction in order to protect the elementary school students for basic welfare.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.3
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• pp.271-277
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• 2013

Purpose: The purpose was to study the corneal refractive power changes associated with the wearing of everted silicone hydrogel soft lenses. Methods: The corneal refractive power and corneal astigmatism were measured using corneal topographer (CT-1000, Shin-nippon Co., Japan) for checking change of corneal refractive power and objective refractive error was measured by auto-refractometer (Natural vision-K 5001, Shin-nippon Co., Japan). We measured at baseline and 1 week after lens wearing. Results: The correcting of corneal refractive power could be effective in low myopia. It's more effective to the higher power of greatest meridian of cornea and the more corneal astigmatism. 73% of subjects' refractive error was decrease less than 1 D and 17% of the subjects had an reverse effect (increase) occurs. The reduction of objective refractive error was more effective when cornea refractive power was great or corneal astigmatism was much. Conclusions: Pressure which the everted silicone hydrogel lens to the cornea could be caused. It occurred as the degrees of corneal power, corneal astigmatism and objective refractive error differences. Selection of an appropriate subject is important considering difficulty of changing the parameters of the lens.

• The Korean Journal of Vision Science
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• v.20 no.4
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• pp.543-551
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• 2018

Purpose : The purposes of this study were to evaluate the changes of intraocular pressure according to corneal ablation amount after corneal refractive surgery and the changes of intraocular pressure according to refractive errors before corneal refractive surgery. Methods : The mean age of adults who underwent LASIK corneal refractive surgery were $37.34{\pm}7.42years$, and 108 adults(48 males, 60 females) were participated in this study. Refractive errors, intraocular pressure, and corneal ablation amount were measured using an autorefractor, a noncontact tonometer, and an excimer laser. All test values were considered statistically significant when p<0.05. Results : The mean intraocular pressure before corneal refractive surgery was $15.08{\pm}2.60mmHg$ in males and $14.16{\pm}2.67mmHg$ in females. The decrease of intraocular pressure after corneal refractive surgery were 4.22mmHg in males and 3.61mmHg in females. Spherical equivalent power were $-3.89{\pm}2.17D$ in males and $-4.45{\pm}2.92D$ in females before corneal refractive surgery, and $-0.10{\pm}0.46D$ in males and $-0.04{\pm}0.46D$ in females after corneal refractive surgery. The corneal ablation amount after corneal refractive surgery were statistically significant, with $53.95{\mu}m$ in males and $61.26{\mu}m$ in females. There was significant correlation between corneal ablation amount and decrease of intaocluar pressure(r=0.2299, p<0.001). As the growth of corneal ablation amount in males, the decrease of intraocular pressure was significantly increased. As the growth of refractive error, the amount of decrease in intraocular pressure was also significant. The decrease of intraocualr pressure were $3.04{\pm}2.18mmHg$ in low refractive error, $4.10{\pm}2.16mmHg$ in middle refractive error, and $4.65{\pm}3.29mmHg$ in high refractive error. Conclusion : We found that intraocular pressure decreased after corneal refractive surgery by noncontact tonometer and the change of intraocular pressure which is an important index for glaucoma diagnosis, may affect the judgment of eye disease. We think that a preliminary questionnaire whether corneal refractive surgery is necessary for the measurement of intraocular pressure.

• Journal of Korean Ophthalmic Optics Society
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• v.5 no.1
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• pp.139-146
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• 2000

Once refractive error of the eye was fully corrected, Maddox rod was used to investigate binocular vision function. When the deviations of subjects' eyes were measured, orthophoria. without any horizontal deviations, was found in 10%, esophoria in 55% and exophoria in 34% of the patients. Esodeviation of the eye was found to be greater than exo-deviation by 11%. This is also refracted in deviations found to be greater than $4{\Delta}$ diopter magnitude where esophoria was 23% and exophoria was 9%. Thus for the patients to achieve comfortable binocular vision function, binocular vision anomalies need to be considered in spectacle prescription. In examining ocular anomalies of corrected refractive error, the deviation of the eye differed from under corrected refractive power to over corrected refractive power. There was a decrease in exophoria and an increase in esophoria, with over correction. This was thought to be due to accommodation. Furthermore, calculated AC/A ratio was found to vary from 1.25 to 6.61 and its relationship to refractive error could not be determined.

• Journal of Korean Clinical Health Science
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• v.10 no.2
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• pp.1587-1593
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• 2022

Purpose. This study was to investigate the degree of refractive error that occurs depending on the measurement location of the subject when performing a refraction test using the automatic refractor. Methods. When performing the auto-refraction test, measurements were taken while increasing the distance between the forehead and the forehead rest, and the measurements were made by tilting the head clockwise and counterclockwise. Results. During the auto-refraction test, significant refractive error occurred when the forehead was not attached to the forehead support or the subject's head was turned clockwise or counterclockwise. Conclusions. When performing a refraction test using an automatic refractor, the examiner will have to pay attention to whether the subject's forehead is in close contact with the forehead rest, and whether the head is tilted.