• 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 the Korean Chemical Society
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• v.53 no.6
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• pp.749-754
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• 2009

HEMA (2-hydroxyethyl methacrylate) is a hydrophilic material which is broadly used for ophthalmologic purposes and especially in the manufacture of soft contact lenses. Also, the oxygen transmissibility (Dk/t) is a very important physical characteristic in the evaluation of a material’s adequacy to be used to produce contact lenses. This study used HEMA (2-hydroxyethyl methacrylate), MMA (methylmethacrylate), NVP (Nvinyl-pyrrolidone), the cross-linker EGDMA (ethylene glycol dimethacrylate) for copolymerization, and measured the oxygen transmissibility of the central and peripheral areas of the manufactured general and color contact lenses using the polarographic method. The measurement showed that the decreased amount of oxygen transmissibility of the central and peripheral areas of the contact lenses measured using the polarographic method range between 40.77% and 49.13%, and the oxygen transmissibility of the color contact lens showed a larger decrease due to the effects of the coloring materials.

• Journal of Korean Ophthalmic Optics Society
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• v.9 no.1
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• pp.53-68
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• 2004

Protein deposit buildup on soft contact lenses(SCLs) is responsible for discomfort, optical defects and is even damaging to the eye. To better understand protein deposit formation on SCL, we investigated the pattern of protein attachment on patient-worn SCLs and the effect of the protein on the contact angle of SCLs and the transmission of visible light. This study used data from a clinical trial where subjects wore either daily-wear SCL(etafilcon A, N=40) for various period up to 14 days, or extended-wear SCL(balafilcon A, N=40) for 8 h day or night. The adsorption of protein in daily-wear SCLs was significantly increased in patient-worn time-dependent manner although the lenses were cleaned everyday by using the multi-purpose SCL solution. After 2 weeks wearing, the protein on the SCL influenced the contact angle of the lenses. Furthermore, the transmission of visible light of the lenses decreased up to almost 7%. Extended-wear SCLs worn during the closed eye condition were found to deposit significantly more protein than SCLs worn during the open eye condition. The amounts of protein adsorbed both after daily SCL wear and after overnight SCL wear were not affected the contact angle and the transmission of visible light of the lenses. The protein deposit buildup on SCL related to the corneal temperature and pH of tear fluid.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.4
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• pp.391-401
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• 2011

Purpose: In the present study, the actual management state of trial contact lenses and lens care products in local optical shops was surveyed and analyzed to reduce the risk of lens complication possibly induced by neglecting lens care. Methods: The feeling of contact lens wearers during the wear of trial contact lenses was surveyed. Futhermore, the actual management state of trial contact lenses such as cosmetic lens and RGP lens and lens care products was also investigated by surveying opticians who trade contact lenses in local optical shops. Results: It was found that consumers trusted the sanitary conditions of the lens since trial cosmetic contact lens and RGP lens were cleaned before and after trails by over 98% of opticians in local optical shops. For trial cosmetic lens, cleaning with normal saline, multipurpose solution for soft lens and combination of saline and multipurpose solution were 38.5%, 40.5% and 21%, respectively, before trials. After trials, cosmetic lenses were cleaned with normal saline, multipurpose solution for soft lens and a combination of saline and multipurpose solution were 13%, 75%, and 12%, respectively. On the other hand, cleaning with normal saline, multipurpose solution for RGP lens and combination of saline and multipurpose solution were 28.5%, 38.5% and 33%, respectively, before trying trial RGP lens. After trials, RGP lenses were cleaned with normal saline, multipurpose solution for RGP lens and a combination of saline and multipurpose solution were 2.5%, 70%, and 27.5%, respectively, indicating that relatively many opticians followed the lens cleaning regimen. In local optical shops, the cleaning trial cosmetic lens was mainly conducted at every 10 days or a month and the washing cycle of cosmetic lens case was in a month or 2~3 months. The cleaning interval of trial RGP lens was primarily in a month or 2~3 months. For those lens cases, more than 75% of opticians washed them with a surfactant and then rinsed with cold water. The storing periods of lens care products were primarily in a week for saline and in a month and 2~3 months indicating that storing period of lens care products was relatively well-kept in local optical shops. Conclusions: It is thought that the concern about any microbial infection is not that high since trial contact lenses and lens care products were generally well-managed by opticians in local optical shops from the results above. However, better public eye health and better public confidence in opticians may be possible if further strengthen in avoidance of lens cleaning with saline, keep of cleaning cycles within 2 weeks and rinsing of lens cases with hot water happens.

• Journal of Korean Ophthalmic Optics Society
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• v.8 no.2
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• pp.1-11
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• 2003

A mathematical model was proposed to analyze the oxygen diffusion reaching the cornea through the tear layers and contact lens based on Fick's law and the principle of continuity of the diffusion flux through the each layers. The model predicts how the parameters such as the thickness of tear layer on the cornea, both the Dk and thickness of contact lenses etc., affect the oxygen tension at cornea and oxygen flux entering the cornea. It is found that either too flat or too tightly fitted contact lenses can cause the oxygen deficiency inside the periphery of the cornea because of the reduction of oxygen flux resulted from too thickened tear layer.

• 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.19 no.2
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• pp.145-151
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• 2014

Purpose: The material properties of contact lenses were measured by varying the amounts of an initiator and a cross-linking agent that are the basis for the manufacture of contact lenses, and the drug delivery effects depending on the material properties of contact lenses were compared. Methods: Contact lens samples were manufactured using HEMA by varying the concentration of the cross-linking agent and the initiator. To investigate the changes in physical characteristics depending on the material properties, the results of the experiments on the amount of drug elution, water content, refractive index, and the amount of protein adsorption were compared. Results: For the contact lenses manufactured by varying the amount of the initiator, the water content hardly changed, and the refractive index also hardly changed. The amount of drug elution was not much affected by the changes in the initiator, but the amount of elution increased as the water content increased. The amount of protein adsorption was hardly affected by the changes in the initiator, but the amount of adsorption increased as the water content decreased. Conclusions: The changes in the properties were hardly affected by the changes in the amount of the initiator, but were significantly affected by the changes in the amount of the cross-linking agent. As the amount of the cross-linking agent increased, the water content decreased, while the refractive index increased. Also, when the water content increased, the amount of drug elution increased, while the amount of protein adsorption decreased.

• 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.20 no.2
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• pp.117-124
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• 2015

Purpose: The purpose of this study was to compare the accommodative function of young adult in their 20s wearing monovision, modified monovision, and aspheric multifocal contact lenses at near task. Methods: Thirty young adults ($23.53{\pm}2.37years$) were fitted with monovision, modified monovision (the application of single vision contact lenses and center-near low addition aspheric multifocal contact lenses), and aspheric center-near multifocal contact lenses. After wearing these modalities during a week for adaption, and after watching visual display at computer for inducing accommodative pressure for 1 hour. The following assessments of accommodative function were made: contrast visual acuity (VA) at distance and near; accommodative response; near accommodative facility; and negative relative accommodation (NRA)/positive relative accommodation (PRA). All measurements were carried out binocularly. Results: In binocular distance VA with contrast of 10%, monovision was the worst among the four modalities (p=0.005). In accommodative response at 1 m (1.00 D), monovision was the lowest (p<0.05) and accommodative response at 40 cm (2.50 D) with monovision was lower than that of modified monovision and multifocal contact lens (p<0.05). We also found that there were no significant differences in accommodative facility and NRA/PRA among the four modalities. Conclusions: In young adult (20s), monovision with low add reduced the accommodative response at near task, however, modified monovision and multifocal lens with center-near type did not affect accommodative relaxation.

• 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.