Lens Water Content Research Articles

Regulation of water flow in the ocular lens: new roles for aquaporins.

The ocular lens is an important determinant of overall vision quality whose refractive and transparent properties change throughout life. The lens operates an internal microcirculation system that generates circulating fluxes of ions, water and nutrients that maintain the transparency and refractive properties of the lens. This flow of water generates a substantial hydrostatic pressure gradient which is regulated by a dual feedback system that uses the mechanosensitive channels TRPV1 and TRPV4 to sense decreases and increases, respectively, in the pressure gradient. This regulation of water flow (pressure) and hence overall lens water content, sets the two key parameters, lens geometry and the gradient of refractive index, which determine the refractive properties of the lens. Here we focus on the roles played by the aquaporin family of water channels in mediating lens water fluxes, with a specific focus on AQP5 as a regulated water channel in the lens. We show that in addition to regulating the activity of ion transporters, which generate local osmotic gradients that drive lens water flow, the TRPV1/4-mediated dual feedback system also modulates the membrane trafficking of AQP5 in the anterior influx pathway and equatorial efflux zone of the lens. Since both lens pressure and AQP5-mediated water permeability ( ) can be altered by changes in the tension applied to the lens surface via modulating ciliary muscle contraction we propose extrinsic modulation of lens water flow as a potential mechanism to alter the refractive properties of the lens to ensure light remains focused on the retina throughout life.

Nutrient Supplementation Improves Contact Lens-Induced Corneal Cell Damage Based on a SIRC Cellular Model.

The long-term use of contact lenses may damage the structure of the ocular surface and cause metabolic disorders in corneal cells. Vitamins and amino acids help maintain the physiological function of the eye. In the present study, the effects of nutrient (vitamin and amino acid) supplementation on corneal cell repair after contact lens-induced damage was investigated. High-performance liquid chromatography was used to quantify the nutrient contents of minimum essential medium, and the MTT assay was used to measure the viability of corneal cells. A Statens Seruminstitut rabbit cornea cellular model was established to simulate contact lens-induced keratopathy and investigate the effects of vitamin and amino acid supplementations on corneal cell repair. The high water content lens group (78%) has a cell viability as high as 83.3%, whereas the cell viability of the low water content lens group (38%) is only 51.6%. The 32.0% difference between the two groups confirms the correlation between water content of lens and corneal viability. Vitamin B2, vitamin B12, asparagine, and taurine supplementation may help improve contact lens-induced damage.

ATR-FTIR, SAXS and UV-Vis Studies of Silicone Hydrogel and Bio-Hydrogel Soft Contact Lenses

Aims: This study aimed to evaluate the effect of contact lens materials on the structural properties and to examine ultraviolet (UVA part) and visible (Vis) transmittance with and without UV filters of the commercially available silicone hydrogel (SiHy) and bio-hydrogel (bio-Hy) soft contact lenses (CLs) in vitro.
 Place and Duration of Study: Hacettepe University, Department of Physics, Ankara, Turkey, between May 2018 and May 2021.
 Methodology:Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectra of CLs were recorded (at removing from its package, after 10 min, 1 h and 1 day at room temperature) in the 4000-650 cm-1region to estimate water contents of CLs. Hierarchical Cluster Analysis (HCA) was performed to differentiate chemical structure of CLs based on the spectral differences. Ultraviolet (UVA) and visible light transmittance of (CLs) was measured in the 315 -800 nm region. Small Angle X-ray Scattering (SAXS) analyses were performed to obtain further structural information on nano-scale. 
 Results: One of the key observations in this study is the large influence of lens water content. The HCA analysis grouped all the CLs of same brand in same cluster based on their chemical similarity. The UVA transmittance results showed that CLs with UV blockers almost met ClassI and ClassII standards. The size (11.8-39.9 nm) and differences in morphologies of the nano globules were determined and correlated with equilibrium water content (EWC).
 Conclusion: This work was designed to explain important characteristics of commercial CLs and results will have implications for future experimental and clinical research regarding hydration/ dehydration experiments with CL polymers.

Characteristics of Silicone Hydrogel Contact Lenses Commercially Available in Korea

Soft contact lenses are made of soft and flexible materials that are comfortable to wear and adapt quickly. According to the material, soft contact lenses can be divided into hydrogel contact lenses and silicone hydrogel contact lenses. Silicone hydrogel contact lenses have enhanced oxygen permeability compared to conventional hydrogel contact lenses, so side effects from long-term wear can be reduced. Representative factors that explain the characteristics of soft contact lenses are oxygen permeability, water content, and modulus. To increase the oxygen permeability of silicone hydrogel contact lenses, it is necessary to increase the silicone content, and the increase in the silicone content is accompanied by a decrease in the water content. As the water content decreases, the modulus of the contact lens increases, making the material harder and uncomfortable to wear. In this paper, the oxygen permeability, water content, and modulus of silicone hydrogel contact lenses that can be commercially available in the domestic market are investigated.

Physiological Mechanisms Regulating Lens Transport.

The transparency and refractive properties of the lens are maintained by the cellular physiology provided by an internal microcirculation system that utilizes spatial differences in ion channels, transporters and gap junctions to establish standing electrochemical and hydrostatic pressure gradients that drive the transport of ions, water and nutrients through this avascular tissue. Aging has negative effects on lens transport, degrading ion and water homeostasis, and producing changes in lens water content. This alters the properties of the lens, causing changes in optical quality and accommodative amplitude that initially result in presbyopia in middle age and ultimately manifest as cataract in the elderly. Recent advances have highlighted that the lens hydrostatic pressure gradient responds to tension transmitted to the lens through the Zonules of Zinn through a mechanism utilizing mechanosensitive channels, multiple sodium transporters respond to changes in hydrostatic pressure to restore equilibrium, and that connexin hemichannels and diverse intracellular signaling cascades play a critical role in these responses. The mechanistic insight gained from these studies has advanced our understanding of lens transport and how it responds and adapts to different inputs both from within the lens, and from surrounding ocular structures.

Novel Contact Lenses Embedded with Drug-Loaded Zwitterionic Nanogels for Extended Ophthalmic Drug Delivery.

Therapeutic ophthalmic contact lenses with prolonged drug release and improved bioavailability have been developed to circumvent tedious eye drop instillation. In this work, zwitterionic nanogels based on poly(sulfobetaine methacrylate) (PSBMA) were easily fabricated by one-step reflux-precipitation polymerization, with the advantages of being surfactant-free and morphology controlled. Then, the ophthalmic drug levofloxacin (LEV) was encapsulated into the nanogels. A set of contact lenses with varied nanogel-loading content was fabricated by the cast molding method, with the drug-loaded nanogels dispersed in pre-monomer solutions composed of 2-hydroxyethyl methacrylate (HEMA) and N-vinyl-2-pyrrolidone (NVP). The structure, surface morphology, water contact angle (WCA), equilibrium water content (EWC), transmittance, and mechanical properties of the contact lenses were subsequently investigated, and in vitro drug release and biocompatibility were further evaluated. As a result, the optimized contact lens with nanogel-loading content of 8 wt% could sustainably deliver LEV for ten days, with critical lens properties within the range of recommended values for commercial contact lenses. Moreover, cell viability assays revealed that the prepared contact lenses were cytocompatible, suggesting their significant potential as an alternative to traditional eye drops or ointment formulations for long-term oculopathy treatment.

Binding affinity of benzalkonium chloride on contact lens surfaces and the effects on their physical properties

Benzalkonium chloride (BKC) is a cationic surfactant used as a component in ophthalmic eye drops. The effects of BKC on the eye and the simple binding of BKC on the contact lens surface have been reported in other studies. However, the exact value of the BKC binding affinity on the contact lens surfaces and its effects on the physical properties of contact lenses have not been studied. Here, the binding affinity of BKC toward two types of contact lenses, those with the wetting agent polyvinylpyrrolidone (PVP) and those without, was calculated. In addition, the refractive power, UV–vis transmittance, contact angle, water content, base curve, and diameter of the contact lenses after treatment with BKC were examined to evaluate the effects of its adsorption on the contact lens. We found that the maximum amount of adsorbed BKC was 2.88 mM for the contact lens without PVP whereas it was 2.32 mM for that with PVP. In contrast, the BKC binding affinities were similar. Crucially, the physical properties of the contact lens changed significantly because of the adsorption of BKC. Although BKC is a widely used preservative, our results suggest that use of PVP-containing contact lenses reduces BKC adsorption and discomfort.

Active prevention of snow accumulation on cameras of autonomous vehicles

Accumulation of atmospheric icing, particularly wet snow, on the visual sensors/navigators of autonomous vehicles (AVs) increases the possibility of accidents by obstructing the lenses of the sensors. Here, two navigator designs were suggested that use airflow across the lens surfaces of the AVs to prevent snow accumulation on them. The impact of airflow intensity across the lens, wind velocity (relative velocity of wind with respect to vehicle), and liquid water content of snow on prevention of snow accumulation on the lenses of the AVs was explored experimentally. Here, artificial snow grains were formed using a novel snow gun and their average sizes at low liquid water content (LWC of ≈ 8%) and high liquid water content (LWC of ≈ 28%) were measured to study the impact of grain sizes on snow accumulation on camera lenses. The effects of wind velocity, snow density, and diameter of the snow grains on their trajectory in the testing section were also studied numerically. The results indicated that the snow grains with higher velocity, density, or diameter possessed higher inertia forces and were more prone to collide with the navigator, increasing collision efficiency of snow grains. We realized that the airflow across the lens effectively prevented snow accumulation on the lens at vehicle/wind velocities of up to 20 mph. The proposed designs actively reduced the snow accumulation on the camera lens, promising to be applied in future AVs.Graphic abstract

Reduction of Physical Strength and Enhancement of Anti-Protein and Anti-Lipid Adsorption Abilities of Contact Lenses by Adding 2-Methacryloyloxyethyl Phosphorylcholine

Biocompatible 2-methacryloyloxyethyl phosphorylcholine (MPC) can enhance the adsorption of water molecules and is therefore used for manufacturing contact lenses. This study investigated the mechanical strength, anti-protein deposition, and anti-lipid adsorption effects of MPC addition to contact lenses. Experimental contact lenses produced by copolymerizing multiple ratios of MPC to 2-hydroxyethyl methacrylate (HEMA) were analyzed. Atomic force microscopy revealed that MPC addition increased surface roughness. The anti-protein deposition and anti-lipid adsorption effects on poly(HEMA-MPC) polymers of various phosphorylcholine quantities were experimentally confirmed. The water content of the contact lenses was proportional to the MPC content in the polymer. The hydrated PC moiety of MPC drastically altered the network of the poly-HEMA polymer by inserting water molecules, which were trapped in the concave region of the surface. MPC addition had negative effects on all examined strength factors because of structural destabilization of the copolymer through water insertion. The anti-deposition effects of MPC were verified by examining the lysozyme and lipid adsorption abilities of the prepared contact lenses. Our results revealed that MPC enhanced interactions of the poly(HEMA-MPC) copolymer with water molecules; these interactions weakened the mechanical strength of the copolymer but markedly improved the anti-adsorption property of the biomolecules. The optimal proportion of HEMA-MPC for contact lenses is in the range 14.9%–28.5%.

THE RELATION BETWEEN WATER CONTENT IN CONTACT LENS AND DRY EYE SYNDROME (DES) IN STUDENTS OF ATMA JAYA CATHOLIC UNIVERSITY OF INDONESIA SCHOOL OF MEDICINE AND HEALTH SCIENCES

Introduction: Dry Eye Syndrome (DES) is a multifactorial disease of the eye characterized by loss of homeostasis from the tear film and is accompanied by ocular symptoms. One of many factors that can cause DES is the use of contact lenses. This research was conducted to determine the relationship of water content in contact lenses with the occurrence of DES.
 Methods: This research was conducted in 2019 with a cross-sectional study design with the Tear Break Up Time (TBUT) test, Schirmer test and questionnaire. The research respondents were students of Atma Jaya School of Medicine and Health Sciences (FKIK UAJ) whose eyes were examined as samples (n = 84). The water content of the respondent's contact lenses was obtained using a questionnaire. The inspection methods used to determine DES are TBUT test and Schirmer test. Data analysis using chi-square test with significance level of p <0.05.
 Results: The prevalence of DES obtained in students with a water content <50% is 25.9%, while the DES in students with a water content >50% is 25.5% .
 Conclusion: There is no significant relationship between water content in contact lenses with the occurrence of DES in FKIK UAJ students (p=0.963).

Effect of a Cationic Surfactant on Microemulsion Globules and Drug Release from Hydrogel Contact Lenses.

The present study evaluates the in vitro release of diclofenac sodium (DFNa) from contact lenses based on poly-2-hydroxyethyl methacrylate (pHEMA) hydrogels containing an embedded microemulsion to extend release duration. The oil (ethyl butyrate)-in-water microemulsion systems are prepared with two non-ionic surfactants, Brij 97 or Tween 80, together with a long-alkyl chain cationic surfactant, cetalkonium chloride (CKC). Without CKC, Brij 97 or Tween 80-based microemulsions showed average droplet sizes of 12 nm and 18 nm, respectively. The addition of CKC decreased the average droplet sizes to 2–5 nm for both non-ionic surfactants. Such significant reduction in the average droplet size corresponds to an increase in the DFNa release duration as revealed by the in vitro experiments. Contact lens characterization showed that important properties such as optical transparency and water content of Brij 97-based contact lenses with cationic microemulsions was excellent. However, the optical transparency of the corresponding Tween 80 based contact lenses was unsatisfactory. The results indicate that cationic microemulsion-laden contact lenses can benefit from combinatory effects of microemulsions and cationic surfactant at low CKC weight percentage, e.g., with the release of 70% of the drug in 45, 10, and 7 h for B97-CKC-0.45%, CKC-0.45%, and control lenses, respectively. However, the microemulsion effect on extending DFNa release became negligible at the highest CKC weight percentage (1.8%).

Reliability of Blotting Techniques to Assess Contact Lens Water Content.

To determine the reliability of wet and modified dry blotting techniques used in the gravimetric method to assess contact lens (CL) water content (WC), the accuracy of both techniques in comparison with the nominal WC, and also their agreement. We evaluated hydrated and dry CL mass values and WC using the gravimetric method in 440 daily disposable CLs. Samples assessed corresponded to Dailies Total 1, Dailies AquaComfort Plus, 1-Day Acuvue TruEye, and Biotrue ONEday. Back vertex power ranged from +3.00 diopters (D) to -6.00 D. Within-subject coefficient of variation (CVw) and intraclass correlation coefficients were calculated. Bland-Altman analysis was also performed. The modified dry blotting technique yielded significantly (P≤0.0001) higher hydrated CL mass values. The wet blotting technique provided significantly (P≤0.04) better consistency than the modified dry one. Values of CVw for wet and modified dry blotting techniques ranged from 1.2% to 2.1% and from 3.7% to 5.4%, respectively. As for dry CL mass values, CVw values were not significantly different (P≥0.05) between wet (range: 1.1%-1.9%) and dry (range: 1.0%-5.1%) blotting techniques, except for Dailies AquaComfort Plus (P=0.03). Bland-Altman analysis showed poor agreement between the techniques. The wet blotting technique yielded WC values close (around 1%) to nominal ones, in contrast to modified dry blotting technique (≥2.5%). The wet blotting technique is not only more reliable than the modified dry one when obtaining hydrated CL mass but also provides more accurate nominal WC measurements. Agreement between the techniques was poor.

Antibacterial and physical properties of a novel sonochemical-assisted Zn-CuO contact lens nanocoating.

This work examined the antibacterial and physical effects of a novel Zn-CuO nanocoating applied on a silicone hydrogel contact lens. Zn-CuO coating of PureVision balafilcon-A soft contact lenses (Bausch&Lomb, Rochester, NY) was performed by sonochemical deposition using a high-intensity ultrasonic horn. Non-coated PureVision lenses served as a control in all experiments. Adhesion assays for P. aerueginosa and S. epidermidis to the coated lenses were performed to identify the minimal coating concentration which still possessed antibacterial activity. Lens water content, oxygen transfer light transfer, leaching, and electron microscopy studies were performed using this concentration. Coated lenses showed 3-5 log reductions in adhesion of both species. The lowest tested coating concentration of 0.02wt% led to a log reduction of 3.25 ± 1.25 of P. aeruginosa CFU/lens (P = 0.007) and a log reduction of 4.37 ± 0.75 of S. epidermidis (p = 0.0007). Using this coating concentration, water content (36%, 33.6%), oxygen transfer (87.22 ± 10.96, 92.18 ± 2.38, × 10-11(cm2/s)(mlO2)/(ml × mmHg)), p = 0.12), and light transfer properties did not differ significantly between the coated and the control contact lenses. In the range of 380-780nm wavelength, the coated lenses transmitted 96.47 ± 1.52% while the control lenses transmitted 97.36 ± 1.35%. The corresponding values for the range of 300-380nm wavelength were 79.343 ± 8.754 and 80.169 ± 1.35. Leaching studies for 0.5mM coated lenses have demonstrated the excellent stability of the coating with the release of only 0.005% of the coating after 1week of exposure to the test solution. Sonochemical-assisted nanocoating of contact lenses showed significant and consistent antibacterial activity while preserving the basic properties of a silicone hydrogel contact lens.

Enhanced drug loading efficiency of contact lenses via salt-induced modulation

Low drug loading efficiency is one of the main obstacles hindering the application of contact lenses (CLs) as the carrier for extended ocular drug delivery. Here in this study, a simple and effective drug loading method based on salt induced modulation was proposed and demonstrated with mechanism elucidation. First of all, using poly (2-hydroxyethyl methacrylate) (p-HEMA) as the contact lens material, betaxolol hydrochloride, Diclofenac Sodium and Betaxolol Base as the model drugs with different solubility, influence of salt concentration, salt type (sodium salts of sulfate, chloride, and sulfocyanate) and drug properties in the loading solution on drug loading efficiency was investigated. Mechanism of enhanced drug loading in contact lens was further explored via studying the influence of salt on the absorption isotherm, drug solubility and water content of CLs. Applicability of this method to other CLs materials was also investigated. It was demonstrated that adjusting the ionic strength of loading solutions resulted in significant increase of drug loading in CLs. Type and concentration of the salts and solubility of the drug were the main factors influencing enhancement ratio of drug loading. The mechanism for improved drug loading was related to the reduced drug solubility in loading solutions and the reduced bound water content in contact lenses. Modulation of drug loading by adjusting ionic strength was also applicable to other CLs and the light transmittance was not affected. This method was more suitable for salt-form drugs with high solubility. In summary, adjusting ionic strength of loading solution is an economical and effective way to improve drug loading in CLs, and this simple method may also find application in other hydrogel based drug delivery systems.

Surface versus bulk activity of lysozyme deposited on hydrogel contact lens materials in vitro

To determine and compare the levels of surface versus bulk active lysozyme deposited on several commercially available hydrogel contact lens materials. Hydrogel contact lens materials [polymacon, omafilcon A, nelfilcon A, nesofilcon A, ocufilcon and etafilcon A with polyvinylpyrrolidone (PVP)] were incubated in an artificial tear solution for 16 h. Total activity was determined using a standard turbidity assay. The surface activity of the deposited lysozyme was determined using a modified turbidity assay. The amount of active lysozyme present within the bulk of the lens material was calculated by determining the difference between the total and surface active lysozyme. The etafilcon A materials showed the highest amount of total lysozyme activity (519 ± 8 μg/lens, average of Moist and Define), followed by the ocufilcon material (200 ± 5 μg/lens) and these two were significantly different from each other (p < 0.05). The amount of surface active lysozyme on etafilcon and ocufilcon lens materials was significantly higher than that found on all other lenses (p < 0.05). There was no active lysozyme quantified in the bulk of the nelfilcon material, as all of the active lysozyme was found on the surface (1.7 ± 0.3 μg/lens). In contrast, no active lysozyme was quantified on the surface of polymacon, with all of the active lysozyme found in the bulk of the lens material (0.6 ± 0.6 μg/lens). The surface and bulk activity of lysozyme deposited on contact lenses is material dependent. Lysozyme deposited on ionic, high water content lens materials such as etafilcon A show significantly higher surface and bulk activity than many other hydrogel lens materials.

Hydrogel Contact Lens Water Content is Dependent on Tearfilm pH

Based on clinical inferences, investigators theorized in situ soft lens hydration was linked to the precorneal tearfilm pH. Forty-one myopic subjects at Fort Rucker, AL, USA were fitted with one of two types of extended-wear soft contact lenses, and were followed quarterly for a period of 33 mo. The anterior soft contact lens surface pH was measured in situ, while the in vitro lens water content was measured immediately after lens removal, using a hand-held refractometer on one lens, and a gravimetric means of hydration measurement on the other lens. The in situ pH increased logarithmically across extended wearing time, reaching an asymptote at approximately 5 d' wearing time at a pH of 7.45 ± 0.03. Lens water content was shown to similarly decrease at an inversely logarithmic rate, leveling off at 4-5 d' extended wearing time. Both means of hydration assessment correlated well with each other across days' extended wearing time (R = 0.98; p < 0.0001). A log-log dual conversion yielded significantly different linear slopes (p < 0.001), based on a multifactorial analysis of both lens types, by the pH, and by their water content. The differing ionic status of each material accentuated their varied polar attraction characteristics. Two soft lenses, identical in all patient-based parameters, could provide differing oxygen availability, as well as differing physical fits in patients of identical physical characteristics, as a result of their unique tearfilm pH differences. The in situ hydrogel lens water content is directly dependent on the precorneal tearfilm pH.

Trends in Contact Lens Prescribing in Japan (2003-2016).

To review contact lens prescribing trends in Japan between 2003 and 2016. An annual survey of contact lens prescribing trends was conducted each year between 2003 and 2016. Japanese ophthalmologists were asked to provide information relating to ten consecutive contact lens fittings between January and March every year. Over the 14 years of the annual survey, data from a total of 64,122 contact lens fits were returned by ophthalmologists. The mean age (±SD) of lens wearers was 30 ± 13 years, and 68% were female. The proportion of rigid lens fits decreased over time, from 35.4% in 2003 to 14.7% in 2016. Across this period, daily disposable lens fits increased, representing 46% in 2016. The proportion of toric lenses and multifocal lenses gradually increased, from 6.6% and 1.9% to 12.3% and 5.8%, respectively. Silicone hydrogel material use grew from 0% to 43.2%, while mid and low water content lens materials declined from 54.1% and 28.2% to 36.1% and 8.3%, respectively. Multi-purpose lens care solutions dominated the market over the 14 year survey period. This survey has revealed prescribing trends and preferences in Japan over the past 14 years, with the main changes observed being a decrease in rigid lens use and an increase in the use of silicone hydrogel materials and daily disposable lenses.

Extended Ciprofloxacin Release Using Vitamin E Diffusion Barrier From Commercial Silicone-Based Soft Contact Lenses.

Ciprofloxacin (Cipro) is an antibiotic, widely used in form of ophthalmic drops (0.3%) for the treatment of eye infections. In this study, vitamin E was used as a hydrophobic barrier to improve and prolong the amount and time of Cipro release from silicone-based soft contact lenses. Three different commercial contact lenses (Air Optix, Biofinity, and Acuvue Oasys) were soaked in vitamin E solutions (0.1 and 0.2 g/mL). The effect of vitamin E on Cipro loading amount and drug releasing profile was evaluated in artificial tear. Swelling properties and diameter changes of the lenses were also investigated in aqueous media in presence and absence of vitamin E. The data indicated that vitamin E, as a hydrophobic barrier, significantly decreased the water content of silicone-based soft contact lenses. After vitamin E loading, a 5% to 18% increase was observed in lens diameter in the hydrated state, whereas the lens diameter increased by 11% to 23% in the dry state. In all commercial lenses, vitamin E loading in a 0.2-g/mL solution caused a 27.94% to 37.08% increase in Cipro binding. The results indicated that applying vitamin E loading solutions, with 0.1 and 0.2 g/mL concentrations, could effectively enhance Cipro release time from 2 hr (in a pure non-vitamin E-loaded lens) to 14 to 17 and 30 to 33 days, respectively. These values showed an increase by a factor of 168 to 204 and 360 to 396 in Cipro release time after using vitamin E loading solutions with 0.1 and 0.2 g/mL concentrations, respectively, compared with pure non-vitamin E-loaded soft contact lenses. This study indicated that vitamin E acts as an effective hydrophobic barrier, in increasing the Cipro loading capacity of silicone-based contact lenses and prolonging the drug release into the artificial tear.

Active Maintenance of the Gradient of Refractive Index Is Required to Sustain the Optical Properties of the Lens.

To determine whether the cellular physiology of the lens actively maintains the optical properties of the lens and whether inhibition of lens transport affects overall visual quality. One lens from a pair of bovine lenses was cultured in artificial aqueous humor (AAH), while the other was cultured in either AAH-High-K+ or AAH + 0.1 mM ouabain for 4 hours. Lens pairs or whole enucleated eyes were then imaged in 4.7 Tesla (T) high-field small animal magnet. Lens surface curvatures, T1 measurements of water content, and T2 measurements of water/protein ratios were extracted from cultured lenses, while the geometrical parameters that define the optical pathway were obtained from whole eyes. Gradients of refractive index (GRIN), calculated from T2 measurements, and the extracted geometric parameters were inputted into optical models of the isolated lens and the whole bovine eye. Inhibiting circulating fluxes by inhibiting the Na/K-ATPase with ouabain or depolarization of the lens potential by High K+ caused changes to lens water content, the water/protein ratio (GRIN) and surface geometry that manifested as an increase in optical power and a decrease in negative spherical aberration in cultured lenses. Changes to optical properties of the lens resulted in a myopic shift that impaired vision quality in the optical model of the bovine eye. The cellular physiology of the lens actively maintains its optical properties and inhibiting the Na/K/ATPase induces a myopic shift in vision similar to that observed clinically in patients who go on to develop cataract.

Hyaluronic acid의 첨가방법에 따른 하이드로겔 콘택트렌즈의 물리적 특성과 lysozyme 흡착량 비교

목적: 하이드로겔 콘택트렌즈에 HA(hyaluronic acid)를 IPN(interpenetrating polymer network)방법과 화학적 공유결합 방법(CCB; Chemical covalent bonding)으로 첨가하였을 때 광투과율과 함수율의 물리적 특성과 lysozyme 흡착량을 비교하여 하이드로겔 콘택트렌즈의 기능성 부여를 위한 효과적인 HA의 첨가방법을 살펴보고자 한다. 방법: 실험실에서 제조한 하이드로겔 콘택트렌즈에 IPN과 CCB의 두 가지 방법으로 HA를 첨가하였다. 광투과율은 300~800 nm 범위에서 측정하였으며, 함수율은 0.9% NaCl 생리 식염수를 사용하여 중량측정법으로 측정하였다. Lysozyme 흡착량은 lysozyme이 포함된 인공눈물을 제조하여 12시간동안 흡착시킨 후 HPLC로 정량하였다. 결과: HA가 첨가된 하이드로겔 콘택트렌즈의 함수율은 HA가 첨가되지 않은 렌즈에 비해 증가하였으며, CCB 방법에 비해 IPN 결합에서 함수율이 더 높게 나타났다. 광투과율은 HA 첨가 전과 후 모두 90% 이상으로 나타났다. Lysozyme 흡착 감소율은 IPN 방법으로 제조한 콘택트렌즈는 60.0%이며, CCB 방법으로 제조한 콘택트렌즈에서는 40.4%로 나타났다. 결론: CCB 방법은 기능성 물질을 렌즈 내부와 표면 전체에 화학적으로 균일하게 분포시키기에 적절한 방법이며, IPN 방법은 상분리 없이 렌즈 표면에 기능성을 부여하기에 적절한 방법으로 여겨진다. Purpose: The hydrogel lenses have been functionalized with HA(Hyaluronic Acid) using two different methods: construction of an IPN(Interpenetrating Polymer Networks) and formation of CCB(Chemical Covalent Bonding). The lysozyme adsorption and physical properties such as optical transmittance and water content of the hydrogel lenses have been investigated in order to determine whether method is suitable for the application potentials in contact lens industry. Methods: HA have been added to the hydrogel lenses prepared in the Lab using the two different method, e.g. IPN and CCB. The optical transmittance was measured in the wavelength range of 300~800 nm. The water content was measured by the gravimetric method using 0.9% NaCl saline solution. The amounts of adsorbed lysozyme on the contact lenses was analyzed by HPLC after incubation for 12h in artificial tears. Results: The water content of the HA added hydrogel contact lenses was increased, and the lens made by IPN method showed higher water content than the lens made by CCB method. The optical transmittance was over 90% both before and after addition of HA. Comparing the lysozyme adsorption reduction ratio, contact lens manufactured by IPN method was 60.0%, and the lens made by CCB method was 40.4%. Conclusions: CCB method is appropriate to distribute the functional material evenly throughout the lens, whereas IPN method is effective for the case of giving the functionality on the lens surface without phase separation.