• Journal of Korean Ophthalmic Optics Society
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• v.21 no.2
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• pp.91-98
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• 2016

Purpose: This study investigated the masking effect of the hydrogel lens and silicone hydrogel lens on the cornea with refractive surgery and without surgery. Methods: 24 university students (means age: $23.48{\pm}2.89years$) without refractive surgery (12, control group) and with refractive surgery (LASIK: 8, LASEK: 4, experimental group) participated in the study. Mean refractive errors of right eyes were -2.73 D for control group and -0.24 D for experimental group. The differences in the refractive power and corneal topography map between pre- and post-wearing the -3.00 D lenses were compared, and 2 kinds of hydrogel contact lenses (0.89 Mpa, 0.49 Mpa) and 2 kinds of silicone hydrogel lenses (1.5 Mpa, 0.8 Mpa) were used for -3.00 D lenses. NVision-K5001 (Shin nippon, Japan) was used to measure the refractive power and Keratograph 5M (Oculus, Germany) to measure the corneal topography map change. Results: Variations in the refractive power increased to the plus direction in the experimental group after wearing soft contact lenses. The corneal topography map showed significant changes on the both groups after wearing soft contact lenses (p<0.05). However there were no significant differences in the refractive power and corneal topography map variations by lens materials. Conclusions: Wearing soft contact lenses showed corneal topography map changes. Especially wearing soft contact lenses on the flat cornea after corneal refractive surgery showed greater corneal power changes. Therefore, it should pay attention to refractive change in case of prescribing soft contact lenses to patients with corneal refractive surgery.

• Journal of Korean Ophthalmic Optics Society
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• v.21 no.2
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• pp.99-108
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• 2016

Purpose: The present study was aimed to compare the tear volume and distribution by corneal eccentricity when fitted with spherical and aspherical RGP lenses. Methods: Spherical and aspherical RGP lenses were fitted in best alignment on a total of 77 subjects (136 eyes) in their twenties and thirties without any ocular disease or ocular surgery experience. The tear volume was analyzed by estimating the concentration of tear stained with fluorescein in the center of RGP lens as well as at the mid-peripheral and peripheral areas, and the difference of tear distributions was analyzed according to corneal eccentricity. Results: Tear distribution from the center to the peripheral area was not significantly different when spherical RGP lenses were fitted on the corneal eccentricities of e < 0.38 and $0.68{\leq}e$, indicating the relatively even tear distribution compared with other corneal eccentricity. In the case of aspherical RGP lenses, the difference of tear distribution between the central and peripheral areas was smaller than spherical RGP lenses. The significant difference of tear distribution according to RGP lens design was observed in the corneal eccentricity of 0.48 < e < 0.68. In other words, more even tear distribution was shown when aspherical RGP lenses were fitted on the cornea with eccentricity of $0.48{\leq}e<0.68$ and spherical RGP lenses were fitted on the cornea with eccentricity $0.68{\leq}e$. Furthermore, tear volume in the mid-peripheral area increased with higher corneal eccentricity. Conclusions: The results suggest that the appropriate selection of RGP lens design according to corneal eccentricity is necessary since tear volume and distribution by the regions of spherical and aspherical lenses are affected by corneal eccentricity.

• Journal of Korean Ophthalmic Optics Society
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• v.21 no.2
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• pp.109-117
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• 2016

Purpose: The study was aimed to figure out the effect of materials and pigmentation of soft contact lens on the adherence of Staphylococcus aureus upon soft contact lenses deposited with tear components. Methods: The number of adherent S. aureus on clear and circle soft contact lenses made of etafilcon A, hilafilcon B, nelfilcon A was measured before and after incubation in artificial tear. Furthermore, the denaturalization level of tear protein with time after incubation in artificial tear was estimated by electrophoresis. Results: The adherence of S. aureus was significantly different according to the lens materials. The pattern of bacterial adherence on clear and circle contact lenses was different. That is, the adherent amount of S. aureus was somewhat larger on circle lens made of etafilcon A however, amount on circle lenses made of hilafilcon B and nelfilcon A was 89.3% and 71.3% of the number on clear lenses. When the tear protein was deposited on contact lenses, the number of adherent bacteria decreased and its degree was varied according to the lens material. The degree of decrease was the biggest in clear soft lens made of etafilcon A. Anti-bacterial effect of tear protein decreased with time after deposition of tear protein on soft contact lens and the amount of lysozyme also decreased. The reduction of anti-bacterial effect and quantity of lysozyme was different according to contact lens materials and pigmentation. Conclusions: It was revealed that the adherence of S. aureus depends on contact lens materials and pigmentation, and the specification of lens material affects more on adherence of S.aureus than pigmentation. It was further figured out the denaturalization level of anti-bacterial protein on soft contact lens varies according to lens materials and pigmentation, which produces an effect on the quantity of bacterial adherence.

• Journal of Korean Ophthalmic Optics Society
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• v.21 no.2
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• pp.127-135
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• 2016

Purpose: The present study was aimed to investigate the effect of excessive near work by using a smartphone on subjective symptoms and accommodative and convergent function in their 40s. Methods: A total of 40 subjects(male, 10; female, 30; age, $43{\pm}7.2year$) in their 40s who have monocular and binocular visual acuities of 0.8 and 1.0, respectively, were divided into presbyopia group and non-presbyopia group. The subjects were asked to watch a movie on the screen of smartphone for 30 minutes. Their accommodative amplitude and facility, and relative accommodation were measured and compared before and after the use of smartphone. Changes in fusional vergence and near heterophoria by using smartphone were also evaluated. Furthermore, the change of subjective symptoms was surveyed using a questionnaire. Results: The presbyopia in mid-40s reported discomfort in an order of asthenopia, blur and dryness after the use of smartphone. Accommodative function and non-strabismic binocular function were generally decreased. Accommodative functions such as monocular accommodative amplitude, and relative accommodation were significantly decreased after smartphone use, and the change of phoria was observed as a result of decreased convergence and divergence. Negative fusional vergence was also significantly reduced. On the other hand, non-presbyopia in mid-40s reported discomfort in an order of asthenopia, dryness and blur, and only accommodative amplitude among the accommodative functions was significantly reduced. Significant reduction of negative fusional vergence was also observed. Conclusion: From the results, it was confirmed that the subjective discomfort of mid-40s after smarphone use might be related to whether presbyopia or not. It was due to not only the reduction of accommodative function but also the overall deterioration of visual function including heterophoria and fusional vergence. Therefore, it suggests that the accurate determination of the cause based on the overall visual functional tests such as heterophoria, fusional vergence as well as the decrease of accommodation due to the aging may be necessary when the mid-40s feels discomfortable symptoms by near work.

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.1
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• pp.67-74
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• 2012

Purpose: The purpose of this study to evaluate visual acuity and refractive state and measure and analyze the components of eye's optical system in children and teenagers. Methods: With subjects of 124 (230 eyes) children and teenagers who had no eye diseases, correlation between the correlation between refractive errors and component's of eye's optical system was investigated. The spherical equivalent power of cycloplegic clinical refraction or manifest clinical refraction(SE), corneal power(CP), corneal radius(CR), axial length(AL), anterior chamber depth(ACD) and axial length to corneal radius (AL/CR) ratio were measured and analysed. Results: the SE was negatively correlated with the AL(r = -0.80, p = 0.00), the ACD(r = -0.35, p = 0.00) and the CR(r = -0.11, p=0.00) and positively correlated with the CP(r = +0.11, p=0.00). The AL was positively correlated with the AL/CR ratio (r = +0.84, p = 0.00), the ACD(r = +0.47, p=0.00) and the CR(r = +0.38, p = 0.00) and negatively correlated with the CP(r = -0.38, p=0.00). The CR was negatively correlated with CP(r = -1.00, p = 0.00), the AL/CR ratio(r = -0.19, p = 0.00) and the ACD(r = -0.06, p = 0.39). The CP was positively correlated with the AL/CR ratio(r = +0.19, p = 0.00) and the ACD(r = +0.06, p = 0.39). The ACD was positively correlated with the AL/CR ratio(r = 0.53, p = 0.00). Conclusions: the highest change of refractive errors was shown that the AL/CR ratio was a very important indicator for diagnosing the refractive errors of the children and teenagers.

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.1
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• pp.37-45
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• 2012

Purpose: The change of alignment between RGP lens and cornea according to the lens design was investigated by comparing the areas of fluorescein pattern in central and peripheral regions analyzed by astigmatic degree and corneal type when spherical and aspherical RGP lenses fitted in alignment. Methods: The fluorescein patterns of 90 eyes (19-30 years, $25.12{\pm}3.52$) having with-the-rule astigmatism were analyzed after spherical and aspherical RGP lenses fitted in alignment. Then, their fluorescent areas in central and peripheral regions were calculated and compared for the quantitative evaluation. Results: The case showing concordant base curve between spherical and aspherical RGP lenses in alignment fitting was 72% however, the possibility to have same base curves between spherical and aspherical RGP lenses in alignment fitting was to be less in the case of symmetric bowtietyped cornea and high astigmatism. The fluorescent area in peripheral region of aspherical RGP lens in alignment fitting was smaller than it of spherical RGP lens. Peripheral fluorescent areas in both RGP lenses decreased according to the increase of astigmatic degree and peripheral area in symmetric bowtie-typed corea was smaller than round-typed cornea's peripheral area. In the case of same astigmatic degree, peripheral fluorescent area of aspherical RGP lens was smaller in both corneal types. Conclusions: The results above suggest the changing degree in the alignment between RGP lens and cornea can be varied according to lens design, corneal astigmatism and corneal type. Thus, the results obtained from the quantitative analysis of the alignment between lens design and cornea may be used as the basic information about the establishment of guidelines for RGP lens fitting, the development of proper lens design, and different tear volume in partial regions.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.3
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• pp.305-313
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• 2014

Purpose: A correlation between the rotating direction and rotation amount according to the eccentricity was analyzed in the present study when fitting the toric soft contact lens. Methods: One hundred fourteen eyes of with-the-rule astigmatism in 20s and 30s were appropriately applied toric soft contact lens by the guideline of manufacturer and fitting evaluations and analyzed the rotating direction and rotation amount when fixating at primary position and 8 different directions of gaze. The speed of reorientation and the correlation between the rotation amount and cornea eccentricity were also analyzed when rotating $45^{\circ}$ each toward the temporal and nasal direction. Results: The cornea eccentricity and rotation amount was shown positive correlation. For the gaze of direction, it was identified that the gaze of directions other than the gaze of direction towards the nasal and temporal had correlation, and among them, the gaze of directions to superior and the superior-temporal showed the tendency of decreasing rotation amount as the cornea eccentricity increased. On the contrary, the gaze of direction towards the inferior, inferior-temporal, superior-nasal, and inferior-nasal showed tendency of increasing rotation amount as the cornea eccentricity increased thus, it was identified that the cornea eccentricity showed different correlation according to the gaze of direction. For the case of re-orientational speed, the speed of lens reorientation in the group having the smallest corneal eccentricity was fastest in both direction but was not significantly different. Conclusions: Considering cornea eccentricity to current method of prescribing toric soft contact lens which is based on total astigmatism, it will be helpful to establish the optimal axis stabilization.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.3
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• pp.323-329
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• 2014

Purpose: To understand the pattern of prescribing contact lenses in Korea from 2010 to 2013. Methods: Four hundred survey questionnaires were randomly posted to Korean Optometric clinics for 4 years. The questionnaire was the same form as a form used for International Contact Lens Prescribing Trend. It was also designed to collect information about the contact lenses prescribed to the first 10 patients after its receipt. Results: 1937 fits were used for the analysis among the four hundred survey questionnaires. The average patient age was $26.2{\pm}7.0$ in 2010, $26.1{\pm}7.6$ in 2011, $24.7{\pm}6.6$ in 2012 and $24.8{\pm}7.2$ in 2013. The patients were mainly women (75%). Of all the soft contact lenses, silicon hydrogel lenses were 18% of fits (17% in 2010, 10% in 2011, 20% in 2012, 24% in 2013). By degine, the percentage of toric design lenses accounted for 17% of soft lenses fits and had increased during 4 years (10% in 2010, 18% in 2011, 16% in 2012, 22% in 2013), and cosmetic contact lens made up for 29% (15% in 2010, 20% in 2011, 40% in 2012, 41% in 2013). Conclusions: The contact lenses wearers were mostly women and the average patient age becomes slightly younger. In relation to the increase in the mumber of younger female contact lens wearers,the percentage of cosmetic lenses prescription was much higher (29%) than the global average (7%), and it has gradually increased for last 4 years. This trend could be related to the growth of beauty market in Korea. By emphasizing on toric lens marketing in manufactures, the prescription rate has been gradually increased.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.3
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• pp.363-369
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• 2014

Purpose: Three-dimensional (3D) displays are very useful in many fields, but induce physical discomforts in some people. This study is to assess symptom type and severity of asthenopia with their habitual distance corrective spectacle (HDCS) and their binocular vision corrective spectacle lenses (BVCSL) in people who feel physical discomforts. Methods: 35 adult subjects (ages $32.2{\pm}4.4$ yrs) were pre-screened out of 98 individuals to have the highest symptom/asthenopia scores following 65 minutes of 3D television viewing with HDCS. These 35 individuals were then retested symptom/asthenopia scores during they watched 3D television for 65 minutes at a distance of 2.7 m with wearing BVCSL of horizontal, vertical or base down yoked prisms. A 4-point symptom-rating scale questionnaire (0=no symptom and 3=severe) was used to assess 11 symptoms (e.g., blur, diplopia, etc.) related to visual fatigue/visual discomfort. Distance and near lateral phoria were measured using Howell phoria card and vertical phoria were measured using Maddox rod. Symptoms induced by watching 3D TV were compared between wearing HDCS and BVCSL. Results: Asthenopia in watching 3D TV with wearing BVCS was significantly lower than wearing HDCS at 5, 25, 45, and 65 minutes (all p < 0.001, paired t-tests). In only refractive error power correction power group, all asthenopia was not significantly different between HDCS and BVCSL (all $p{\geq}0.05$, paired t-tests). In prism correction groups for binocular imbalance, symptoms of asthenopia, however, was significantly lower for when wearing BVCSL than when wearing HDCS (all p < 0.05). Conclusions: Correction of phoria/vergence-based binocular vision imbalance can reduce asthenopia during 3D television viewing. An individual with binocular vision imbalance need corrected/compensated glasses with appropriate prisms prior to prolonged viewing of 3D television displays to reduce asthenopia/visual fatigue.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.3
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• pp.345-351
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• 2014

Purpose: The accommodative response and the near horizontal phoria were examined with additional spherical power to analyze the stimulus and response AC/A ratios that suggest reference data for the binocular vision. Methods: The open-field autorefractometer (Nvision-K 5001, Shin nippon) and modified thorington method (MIM card; Muscle Imbalance Measure card, Bernell) at 40 cm were utilized to measure the accommodative response and the near horizontal phoria for 81 persons ($20.89{\pm}1.92$ years old) with additional spherical power. The stimulus and the response AC/A ratios were calculated by gradient AC/A method. Results: The exophoria group showed the highest accommodative response ($1.92{\pm}0.26D$) at 40 cm, followed by orthophoria group and esophoria group($1.72{\pm}0.26D$ and $1.62{\pm}0.42D$, respectively) Meanwhile, the esophoria group showed the biggest ocular deviation for the near ($23.24{\Delta}$) followed by the orthophoria group and exophoria group ($19.76{\Delta}$ and $15.14{\Delta}$, respectively). The biggest difference of the stimulus and the response AC/A ratios was $1.72{\Delta}$ for the exophoria group with -2.00 D, while the one was $3.43{\Delta}$ for the esophoria group with +1.00 D. There was a significant difference between AC/A ratios for the exophoria group with -2.00 D, -1.00 D and the esophoria group with +3.00 D, +2.00D, +1.00D and -1.00D. Conclusions: The difference between stimulus and response AC/A was greater when increased minus spherical power for the exophoria group, while it was greater when increased plus spherical power for the esophoria group. Furthermore, the difference for the esophoria group was a greater than the one for the exophoria group.