• Journal of Korean Ophthalmic Optics Society
• /
• v.19 no.2
• /
• pp.145-151
• /
• 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
• /
• v.21 no.1
• /
• pp.11-21
• /
• 2016

Purpose: The aim of this study was to analyze the difference in tear film stability according to the wearing time when wearing clear and circle soft contact lens(circle lens) made of same material. Methods: The clear and circle contact lenses of hilafilcon B and nelfilcon A materials were respectively applied on the subjects classified as normal and dry eyes depending on their tear volume, and their tear film stability was investigated by measuring the non-invasive tear film break-up times, lens centration and the first appearing area of tear breakup after 30 mins and 6 hrs of lens wearing. Results: Non-invasive tear film breakup time significantly reduced with increase of the wearing time for normal and dry eyes when wearing clear and circle contact lenses. The starting ratio of tear film break-up was higher at the peripheral area of clear and circle lenses in all two different materials, and higher at the peripheral area of dry eyes than normal eyes. Starting ratio of tear film break-up was higher at the peripheral area of nelfilcon A lenses compared with hilafilcon B lenses, however, its change with the increase of wearing time showed a different aspect. The number of tear film break-up per unit area when wearing circle lenses of nelfilcon A increased at the central area with the wearing time while its number was higher at the peripheral area when wearing circle lenses of hilafilcon B. The centration of clear lenses made of two materials was closer to pupil compared to circle lenses with the increase of wearing time, however, a larger decentration was shown in dry eyes compared with normal eyes. Conclusions: The research revealed that an effect on tear film stability may be changed by clear lenses as well as circle lenses with coloring process according to the increase of wearing time, and the factors affecting on tear film stability may also vary depending on lens materials. Thus, the appropriate lenses should be selected by the consideration of lens material as well as coloring method/dyes according to the wearers' habit such as daily wearing time and wearing period when trying to wear clear and circle lenses.

• Journal of Korean Ophthalmic Optics Society
• /
• v.13 no.2
• /
• pp.1-7
• /
• 2008

Purpose: This study was performed to evaluate the changes of lens morphology and tear stability during wearing soft contact lenses (SCLs) which were kept in drying condition like dry eye or became to be dried due to heedless care. Method: SCLs having different water content, thickness or material were rehydrated after being dehydrated artificially 2 or 4 times, and estimated their diameter and radius. Furthermore, the changes of tear film break-up time (TBUT) during SCL wearing were also measured. Result: Due to the dryness, the diameter of both 70% water content SCL and 59% water content SCL decreased, but the decrement was larger in 59% water content SCL. The more 59% water content SCL was dehydrated, the more its radius changed. However, the radius of 70% water content SCL did not change by 2 times dehydration and increased greatly by 4 times dehydration. The reduction of diameter of -1.00 D SCL was greater than that of -9.00 D SCL. Moreover, the radius of -1.00 D SCL increased depending on the frequency of dehydration but that of -9.00 D SCL did not changed. The diameter and radius changes of lotrafilcon B, silicone hydrogel lens, were less than those of hilafilcon B, copolymer of HEMA and N-vinyl pyrrolidone. TBUT during wearing SCLs decreased by wearing dehydrated SCLs. Conclusion: The diameter and radius of dehydrated SCLs as well as TBUT during wearing them were changed in spite of rehydration, which would be the important cause of uncomfortable feeling when people wore dehydrated SCL. The changes of SCL morphology and TBUT differed according to the water content, lens thickness and material.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.11a
• /
• pp.488-491
• /
• 2006

In this paper, a slim type actuator is proposed rising a bimorph PZT and a circular rotor link. The bimorph contacts the circular rotor, and its displacement generates the rotational motion of the rotor. The rotor causes the linear motion of AF and zoom lens through gear and a motion guide. The proposed model enables the actuations of many lens groups for zoom module by extending the single lens model. The important design parameter is the contact force determined by the frictional coefficient and preload between the rotor and PZT bimorph. A prototype of the single actuator model is manufactured and experiments results using LDV and tachometer are compared to the theoretical and numerical predictions. Experiments show the linear bimorph actuator model meets the performance criteria of the lens actuation, and it can be applicable to various slim type actuators for AF and zoom motions in mobile cameras.

• Journal of Korean Ophthalmic Optics Society
• /
• v.19 no.1
• /
• pp.1-8
• /
• 2014

Purpose: To observe changes of coatings and lens materials with varying temperature to understand effect of temperature on plastic lens. Methods: In this study, three lenses of different refractive indices (2 of thiourethane oriented lenses, an allyl diglycol carbonate oriented lens) were exposed to high temperature (50, 80, and 100 degree) for 5 hours and changes of individual coating (anti-refractive coating, hard coating, and water repellent coating) were measured. Results: As a result, high-refractive index lenses did not exhibit significant variation of hardness. However, hardness of mid-refractive index lens were decreased when exposed to high temperature and destructions of hard coating layer was inferred. Surface contact angles of lens were decreased with increasing temperature and water repellent coating layer were damaged at higher than 80 degree. Conclusions: Multi including water repellent coatings on all three lenses with different refractive indices were damaged when exposed to at or higher than 80 degree. The degree of changes in mechanical and physical properties were depended on polymer material type.

• Journal of Korean Ophthalmic Optics Society
• /
• v.14 no.2
• /
• pp.27-30
• /
• 2009

Purpose: Transmittance at UV-visible spectra range was measured to confirm the effect of wet/dry state of commercially available SCL on human eyes. Method: Commercially available five SCLs fabricated by different materials were selected to measure optical properties according to humidity. Results: A relatively high transmittance above about 80% in the visible spectra range of the SCLs were observed. In the UV spectra range, the wet samples showed higher transmittance than those dried except an unusual case. Conclusions: All the samples having a high optical properties in the visible spectra range exhibit a high transmittance in the UV region. Further research will be needed to develop new materials having a sharp absorption edge in the UV spectra range.

• Journal of the Korean Chemical Society
• /
• v.53 no.3
• /
• pp.340-344
• /
• 2009

HEMA/vinyl-substituted polyphosphazene was prepared by the ring-opening polymerization of phosphonitrillic chroride trimer at $200{\sim}300\;{^{\circ}C}$, followed by Grignard reaction with vinyl magnesium bromide and then by the reaction with HEMA(2-hydroxyethyl methacrylate). HEMA/vinyl-substituted polyphosphazene was copolymerized with EGDMA(ethylene glycol dimethacrylate; used as a cross-linker for the free-radical copolymerization), NVP (N-vinyl-pyrrolidone) in the presence of AIBN (azobisisobutyronitrile) as a radical initiator. The oxygen transmissibility, water content and visible-ray transmissibility of the resulting copolymer were measured to be Dk/t 88, 30.89% and 87%, respectively, indicating that the copolymer can be used as a good contact lens material.

• Journal of the Korean Chemical Society
• /
• v.40 no.6
• /
• pp.385-393
• /
• 1996

The interaction between poly(HEMA) which is material of contact lens containing about 45% water and amino acids (alanine, arginine, methionine, proline, glycine, serine, lysine) have been studied by using the thermal analysis methods through DSC and TGA. The experimental results of DSC and TGA were shown that lysine, arginine and alanine have the most stable interaction between poly(HEMA) and amino acids.

• Journal of the Korean Chemical Society
• /
• v.53 no.6
• /
• pp.749-754
• /
• 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.

• Design & Manufacturing
• /
• v.17 no.2
• /
• pp.15-21
• /
• 2023

In this study, a diamond turning machine and a laser-assisted machining module were utilized for the complex combined cutting of aspheric shapes and fine patterns on the surface of high-hardness brittle material, silicon. The analysis of material's form accuracy and corrective machining was conducted based on key factors such as laser output, rotational speed, feed rate, and cutting depth to achieve form accuracy below 1 ㎛ and surface roughness below 0.1 ㎛. The cutting condition and corrective machining methods were investigated to achieve the desired form accuracy and surface roughness. The rotational speed of the spindle and the linear feed rate of the diamond turning machine were varied in five stages for the cutting condition test. Surface roughness and form accuracy were measured using both a contact surface profilometer and a non-contact surface profilometer. The experimental results revealed a tendency of improved surface roughness with increased rotational speed of the workpiece, and the best surface roughness and form accuracy were observed at a feed rate of 5 mm/min. Furthermore, based on the cutting condition experiments, corrective machining was performed. The experimental results demonstrated an improvement in form accuracy from 0.94 ㎛ to 0.31 ㎛ and a significant reduction in the average value of the surface roughness curve from 0.234 ㎛ to 0.061 ㎛. This research serves as a foundation for future studies focusing on the machinability in relation to laser output parameters.