Hydrogel Lenses Research Articles

Localization of full-length recombinant human proteoglycan-4 in commercial contact lenses using confocal microscopy

The aim of this study was to determine the sorption location of full-length recombinant human proteoglycan 4 (rhPRG4) tagged with fluorescein isothiocyanate (FITC) to four silicone hydrogel contact lenses [balafilcon A (PureVision, Bausch + Lomb), senofilcon A (Acuvue Oasys, Johnson & Johnson), comfilcon A (Biofinity, CooperVision), lotrafilcon B (Air Optix, Alcon)] and one conventional hydrogel lens [etafilcon A (Acuvue 2, Johnson & Johnson)], using confocal laser scanning microscopy (CLSM). Lenses (n = 3 each) were incubated under two conditions: (1) FITC-rhPRG4 solution at 300 μg/mL and (2) phosphate-buffered saline, for 1 h at 37 °C in darkness with gentle shaking. The central 4 mm of each lens was removed and viewed with the Zeiss 510 CLSM using an argon laser at 488 nm (FITC excitation 495 nm, emission 521 nm). Depth scans were taken at 1 μm intervals to a maximum depth of 100 μm. All lens materials demonstrated sorption of rhPRG4. Both senofilcon A and balafilcon A revealed FITC-rhPRG4 penetration into the bulk of the lens, generally favoring the surface. rhPRG4 was observed exclusively on the surface of lotrafilcon B, with no presence within the bulk of the lens. rhPRG4 was evenly distributed throughout the bulk of the lens, as well as on the surface, for comfilcon A and etafilcon A. The sorption profile of FITC-rhPRG4 was successfully visualized using CLSM in various contact lens materials. The polymer composition, surface treatment and pore size of the material can influence the sorption of rhPRG4.

Effect of Graphene Nanoparticles on the Physical Properties of Ophthalmic Polymer Containing Pyrrolidone Group.

In this study, the functional ophthalmic hydrogel lens containing graphen oxide nanoparticles, PVP (polyvinylpyrrolidone) were manufactured. For 2-hydroxyethyl methacrylate (HEMA), which is the main component of the ophthalmic hydrogel lens, and azobisisobutyronitrile (AIBN), an initiator for thermal polymerization. And for photopolymerization, 2-hydroxy-2-methylpropiophenone (2H2M). And used for cross linker ethylene glycol dimethacrylate (EGDMA). The prepared ophthalmic hydrogel lens samples were hydrated in a sterile physiological saline solution for 24 hours before evaluating their physical properties, such as optical transmittance, refractive index, and water content. The surface characteristics of the lenses were also evaluated by measuring the AFM and contact angle. The results of this study suggest that PVP and graphene oxide nanoparticles have high wettability as additives, and that the lens manufactured by using the photopolymerization method demonstrated an ultraviolet shielding effect, thereby prompting us to conclude its suitability as a highly functional ophthalmic lens.

Fast versus gradual adaptation of soft daily disposable contact lenses in neophyte wearers

PurposeDespite the widespread practice of gradually adapting all new soft contact lens wearers (neophytes), there is little evidence-based research underpinning such practice. This work determined if a gradual adaptation period is necessary for neophytes when fitted with modern hydrogel or silicone-hydrogel daily disposable contact lenses. MethodAt four sites, neophytes (19–32 years) were randomly assigned to an adaptation schedule: fast (10 h wear from the first day) or gradual (4 h on the first day, increasing their wear-time by 2 h on each subsequent day until they had reached 10 h) with hydrogel (n = 24 fast; n = 21 gradual) or silicone-hydrogel (n = 10 fast; n = 10 gradual) contact lenses. Masked investigators graded ocular surface physiology and non-invasive tear breakup time (NIBUT). A range of subjective scores (using 0–100 visual analogue scales) were recorded at the initial visit and after 10 h of lens wear, 4–6 days and 12–14 days after initial fitting. Subjective scores were also repeated after 7 days. ResultsThere was no difference (p > 0.05) in ocular surface physiology between the fast and gradual adaptation groups at any time point in either lens type. NIBUT was similar at all time points for both adaptation groups in both lens types with the exception that the gradual adaptation silicone-hydrogel wearers had a slightly longer NIBUT (p = 0.007) than the fast adaptation group at 12-14 days. Subjective scores were also similar across the visits and lens types with the exception of ‘lens awareness’ and ‘ease of lens removal’ which were better (p < 0.05) in the fast compared with the gradual adaptation hydrogel lens group at day 7. Additionally, ‘end-of-day discomfort’ was better (p = 0.02) in the fast compared with the gradual adaptation hydrogel lens group at 12–14 days. ConclusionThere appears to be no benefit in daily disposable soft contact lens adaptation for neophytes with modern contact lens materials.

Multi-Center Cross-Over Evaluation Of Fanfilcon A Silicone Hydrogel Contact Lens and Two Hydrogel Lenses in Daily Wear

Multi-Center Cross-Over Evaluation Of Fanfilcon A Silicone Hydrogel Contact Lens and Two Hydrogel Lenses in Daily Wear

Preparation and Characterization of Functional Ophthalmic Polymer Containing Nanoparticles Using Heat Treatment Method After Polymerization

The functional hydrogel lens containing HEMA (2-hydroxyethylmethacrylate) was manufactured by thermal polymerization and heat treatment method after room temperature polymerization, respectively. In this study, HEMA, EGDMA (ethylene glycol dimethacrylate) and the initiator AIBN (azobisisobutyronitrile) were used for thermal copolymerization and the mixture was heated at 100 °C for 1 hour. And also, HEMA, EGDMA, the initiator and distilled water were used for heat treatment method after room temperature copolymerization and the mixture was heated 80 °C for 1 hour and then treated at 100 °C for 1 hour to produce the hydrogel ophthalmic lens by cast mold method. To make the functional hydrogel lens, ZnPC and platinum octaethyl porphyrin were used as additives. The measurements of the physical characteristics of the copolymerized material showed that refractive index and contact angle of sample was in the range of 1.4010∼1.4585 and 21.46∼87.28°, respectively. In case of heat treatment method after room temperature copolymerization, the refractive index and wettability of sample was higher than that of thermal polymerization. And also, the addition of ZnPC nanoparticles allowed the hydrogel lens to block UV-light. The absorbance value of solution in which the lens prepared by the heat treatment method was immersed were much lower than that of thermal polymerization, so it can be judged that the stabilization of produced polymer maintained well. Based on the results of this study, the produced optical lens can be considered to satisfy the basic requirements of optical lens and can be used effectively as an additive for functional ophthalmic lens material with high refractive index and wettability.

Study on the High Functional Contact Lens Material with Superior Oxygen Transmissibility and Antibacterial Properties.

The silicone monomer (SiH2) used in this study contains acrylate monomer, DMA (n,n-dimethylacrylamide). For the polymerization, PtOEP (platinum octaethylporphyrin) was added to the synthesized silicone, DMA (n,n-dimethyl acrylamide), HPMA (hydroxy propyl methacrylate), PEGMEMA [poly(ethylene glycol) methyl ether methylacrylate], EGDMA (ethylene glycol dimethacrylate) and the initiator AIBN (azobisisobutyronitrile) with various concentrations. Using the polymer produced through the thermal polymerization process, the optical and physical characteristics of high performance silicone hydrogel lenses were measured. The water content of sample containing PtOEP was in the range of 65.21∼66.56%. And also, oxygen permeability (Dk) of sample containing PtOEP was in the range of 30.20∼30.85 × 10-11 cm²/sec × mlO₂/ml × mmHg. In case of the sample with nanoparticle, the oxygen permeability was higher than that of Ref. sample without nanoparticle. Silicone hydrogel monomer containing PtOEP was expected to be used usefully as a material for red tinted chromagen optical lens with high oxygen permeability for color amblyopia.

Ocular surface response and subjective symptoms associated to lens care solutions in Palestine

PurposeTo compare the biocompatibility and subjective symptoms of four multipurpose solutions marketed in Palestine with hydrogel contact lenses. Methods50 habitual soft contact lens wearers were recruited in this interventional crossover study. Subjects were asked to attend the optometry clinic five times. A new pair of hydrogel lenses (Bioxifilcon-B) were fitted each time. This pair was soaked randomly overnight in one of the following four-multipurpose solutions (NEOPLUS®, AvizorUnicaSensitive®, ReNuMultiPlus® and COMPLETERevitaLens®) which contain different disinfecting agents (PHMB, Phx, PAPB, and PQ-1+Alexidine, respectively), or non-preserved saline. At each visit, corneal staining, ocular redness and subjective symptoms were assessed. ResultsThe percentage of corneal staining increased significantly (P≤0.050) after soaking the lenses with PHMB (86%), PAPB (64%) and Phx (32%) based-solutions. However, a non-significant increase was noticed after the use of PQ-1+Alexidine based solution (30%, P=0.083). Ocular redness evaluation showed a significant increase (P≤0.050) in limbal hyperemia after the use of all solutions, while bulbar redness was significantly increased after the use of biguanide-based solutions (P≤0.050). The subjective assessment analysis showed a non-significant change in comfort, dryness, photophobia and scratchiness (P≥0.050) at 2-h intervention using all solutions, except for the PHMB based solution which showed a significant change in subjective symptoms (P≤0.050). ConclusionThe combination of Bioxifilcon-B hydrogel contact lenses and solution containing PHMB, PAPB and Phx-disinfectants induced a significant increase in corneal staining after 2h of CL-wear with a higher severity when the PHMB-based solution was used, while the PQ-1+Alexidine-based solution did not. Only the PHMB-based solution triggered a significant change in subjective symptoms which might which suggests that it might be related to the severity of staining rather than the induction of staining.

Carbon compositional analysis of hydrogel contact lenses by solid-state NMR spectroscopy

Contact lenses are worn by over 140 million people each year and tremendous research and development efforts contribute to the identification and selection of hydrogel components and production protocols to yield lenses optimized for chemical and physiological properties, eye health and comfort. The final molecular composition and extent of incorporation of different components in contact lenses is routinely estimated after lens production through the analysis of the soluble components that were not included in the lens, i.e. remaining starting materials. Examination of composition in the actual intact materials is always valued and can reveal details that are missed by only examining the non-incorporated components, for example identifying chemical changes to components in lenses during the production process. Solid-state nuclear magnetic resonance (NMR) spectroscopy is a powerful tool for the direct compositional analysis of insoluble and heterogeneous materials and is also uniquely suited to determining parameters of architecture in contact lenses. We utilized 13C cross-polarization magic angle spinning (CPMAS) NMR to examine and compare the carbon composition of soft contact lenses. 13C NMR spectra of individual polymer components enabled the determination of the approximate molecular carbon contributions of major lens components. Comparisons of the conventional etafilcon A hydrogel (1 Day Acuvue MOIST) lenses and silicone hydrogel lenses (Acuvue Oasys, Dailies Total 1, Clariti 1 Day, Biofinity, and Pure Vision) revealed major spectral differences, with considerable variation even among different silicone hydrogel lenses. The solid-state NMR approach provides a direct spectral reporting of carbon types in the hydrogel lens itself. This approach represents a valuable complementary analysis to benefit contact lens research and development and could be extended to isotopically labeled hydrogel lenses to map proximities and architecture between hydrogel components.

Analysis of Physical Properties of Hydrogel Lenses Polymer Containing Styrene and PVP

This research is carried out to analyze the effects of Styrene and PVP on the properties of silicone hydrogel lenses. Styrene group and PVP(Polyvinylpyrrolidone) are used as additives for a basic combination containing silicone monomer, TSMA(trimethylsilyl methacrylate) and DMA(n,n-dimethylacrylamide) added to the mix at ratios of 1~10 %. Silicone hydrogel lens is produced by cast-mold method. The polymerized lens sample is hydrated in a 0.9 % saline solution for 24 hours before its optical and physical characteristics are measured. Measurement of the physical characteristics of the produced material shows that the refractive index is 1.3682~1.4321, water content 77.11~45.73 %, visible light transmittance 95.14~88.20 %, and tensile strength 0.0652~0.3113 kgf. The results show a decrease of refractive index as the ratio of additives and water content decreases. The result of the stabilization test of polymerization show an increase of extractables along with increase of the ratio of additives, but the difference is not significant for all samples, so it can be judged that the stabilization of the polymer is maintained. Therefore, the additions of styrene and PVP should be taken into consideration for their effects on the physical properties of silicone hydrogel lens.

Standardization of Wettability Evaluation for Ophthalmic Hydrogel Lenses

Standardization of Wettability Evaluation for Ophthalmic Hydrogel Lenses

Effect of Base Curve on Silicone Hydrogel Contact lens Fitting Characteristics and Comfort

Purpose : To compare the fitting assessment and subjective comfort according to the base curves of silicone hydrogel lens. Methods : Thirty adults (60 eyes, mean age: 21.9 years) who had no ocular disease and no problem in wearing contact lenses were included. Contact lens fittings were performed with empirical and trial fitting methods. ln empirical fitting. base curve of contact lenses were selected based on K–reading (fitting contact lens with 8.5 mm base curve in the case of steeper than 7.8 mm. 9.0 mm base curve in the case of flatter than 7.8 mm), and in trial fitting, two base curves were fitted by a double blind method. The fitting characteristics were assessed with centration, movement, lag, push-up test and keratometer mire. The subjective comfort was evaluated through questionnaires with Likert 5-point scale. Results : It was shown that 91.67% of the subjects was acceptable to base curve determined by empirical fitting. However, 33.33% of steep curve group showed ideal fitting with 9.0 mm base curve and 25% of flat curve group showed ideal fitting with 8.5 mm base curve, and empirical and trial fitting showed 71.67%, 100% in success rate, respectively. It was appeared that 63.33% of subjects felt no difference in the comfort sensation of contact lenses with different base curves, but the comfort sensation with the 8.5 mm base curve (3.53 points) was significantly higher than 9.0 mm base curve (2.75 points), (t=4.528, p<0.001) and 27.78% of a flat cornea group felt comfortable with steeper fitting. Conclusion : In order to determine the base curve of silicone hydrogel contact lenses, it is suggested that evaluating the fitting condition is more important than subjective fitting condition of the wearer or empirical determination.

WETTABILITY – ANOTHER PARAMETER FOR GOOD FITTING OF A SILICONE-HYDROGEL DAILY DISPOSABLE CONTACT LENS

The modern world is very fast and dynamic. Consumer requirements rise to every commodity part of their everyday life - food, clothing, cosmetics, and medical devices. Eye care and eye health are also part of them. Companies producing contact lenses work daily to improve the safety and comfort of wearing, as well as on the technical characteristics of the material (type of material, wear time, module, Dk / t etc.). Silicon hydrogel contact lenses (SiHy) were introduced almost two decades ago. At that time it was estimated that there are about 70 million contact lenses all over the world. Since then, their number has doubled and a significant majority now have silicone-hydrogel contact lenses, resulting in a steady and noticeable reduction in the number of regular hydrogel lenses. When the first one-day silicon-hydrogel contact lenses were introduced in 2008, they were announced as breakthroughs in technology. When they were introduced to the market, they were presented in spherical, toric and multifocal designs, which led to a significant increase in the use / prescription of silicon-hydrogel daily disposable contact lenses. A survey conducted in 2014 by the International Consortium illustrates this point. Although, according to this study, the use of SiHy contact lenses varies widely across the world. In the United States, Canada, Australia and the United Kingdom, four to six times more patients were fitted with silicone-hydrogel CLs compared to hydrogels in 2014 and in each country, daily disposable SiHy contact lenses were prescribed with a larger frequency compared to daily disposable hydrogel lenses. It is important to make a good fit to ensure and increase the comfort of wearing contact lenses. In addition to some of the standard fitting techniques such as: keratometry and choice of base curve of the lens; size and eccentricity; an assessment of the mobility of a lens placed in the eye - look positions, mobility, push up test, can be added and the wetting of the contact lens. Even in perfect fit, if the lens does not interact well with the tear film, it would lead to complaints and discomfort in the patient. The degree of wetting is determined by the balance between adhesive and cohesive forces acting on the surface of the lens. CLs, which can support full wetting, allow a tight coating of the tear film, a smooth recovery of the tear layer after eyelid opening and good visual acuity. The interaction between CL, eye surface and tear film is vital to their successful fit. It has long been known that both the organic and inorganic components of the tear film and anterior surface of the eye can deposit deposits on the contact lenses. There are various non-invasive methods for assessing the tear film and, above all, the lipid layer. Some of these are Non invasive breakup time (NIBUT) and specular biomicroscopy. In the present work we will look at daily disposable silicone-hydrogel contact lenses that have been tested in vivo for good wetting, stability and good regeneration of the tear film.

Synthesis and Characterization of Silicone Contact Lenses Based on TRIS-DMA-NVP-HEMA Hydrogels.

In this study, silicone-based hydrogel contact lenses were prepared by the polymerization of 3-(methacryloyloxy)propyltris(trimethylsiloxy)silane (TRIS), N,N-dimethylacrylamide (DMA), 1-vinyl-2-pyrrolidinone (NVP), and 2-hydroxyethylmethacrylate (HEMA). The properties of silicone hydrogel lenses were analyzed based on the methods such as equilibrium water content, oxygen permeability, optical transparency, contact angle, mechanical test, protein adsorption, and cell toxicity. The results showed that the TRIS content in all formulations increased the oxygen permeability and decreased the equilibrium water content, while both DMA and NVP contributed the hydrophilicity of the hydrogels. The maximum value of oxygen permeability was 74.9 barrers, corresponding to an equilibrium water content of 44.5% as well as a contact angle of 82°. Moreover, L929 fibroblasts grew on all these hydrogels, suggesting non-cytotoxicity. In general, the silicone hydrogels in this work exhibited good oxygen permeability, stiffness, and optical transparency as well as anti-protein adsorption. Hence, these silicone hydrogel polymers would be feasible for making contact lens.

Optimization of intraocular lens hydrogels for dual drug release: Experimentation and modelling

Topical administration of both antibiotic and non-steroidal anti-inflammatory drugs after cataract removal surgery is usually recommended to avoid infection and inflammatory process development. In this work, a HEMA/MMA based hydrogel was developed as a platform for simultaneous release of an antibiotic (moxifloxacin) and a non-steroidal anti-inflammatory drug (diclofenac). Initially, hydrogels with different HEMA/MMA compositions and cross-linking contents were produced and loaded separately with moxifloxacin and diclofenac. The in vitro release profiles of the drugs from the hydrogels were obtained and a mathematical model was employed to estimate the concentration in vivo induced by such systems. The most promising hydrogel was then sequentially loaded with diclofenac and moxifloxacin, and the same mathematical model was applied to the in vitro release results. The results suggest that the dual-drug loaded hydrogel could potentially release effective amounts of antibiotic and anti-inflammatory for three weeks. Nonetheless, adjustment of the concentration profiles can be achieved for example by tailoring of the loading conditions.

Strong Wet Adhesion of Tough Transparent Nanocomposite Hydrogels for Fast Tunable Focus Lenses.

Tough hydrogel adhesives that can bond strongly to wet surfaces have shown great potential in various applications. However, it still remains a challenge to develop the adhered hydrogels integrated with strong wet adhesion, high transparency, exceptional mechanical properties, and fast self-recovery. Herein, tough nanocomposite hydrogels demonstrating high tensile strength, high transparency, and fast self-recovery are reported. The strong wet adhesion between two tough hydrogel films can be realized by introducing chemical bridging across the hydrogel-hydrogel interface, while the interfacial adhesion energy and shearing adhesion strength are up to 2216 J m-2 and 385 N m-1, respectively. The strong adhesion and superior toughness of our hydrogels enable their reassembly capability to produce stretchable sealed balloons that can endure high air pressure without leakage. Most interestingly, the combination of excellent sealability and high transparency also allows our hydrogel balloons to turn into hydraulically driven fast tunable focus convex lenses, which is first reported here for hydrogel lenses. The hydrogel adhesives may open up the door to develop soft sealed containers and intelligent optical devices.

Comparing Pre-Lens Non-invasive TBUT with Two Different Silicone Hydrogel Contact Lens Materials

Purpose : To compare pre-lens non-invasive tear break-up time(NITBUT) and subjective ocular symptoms with two different silicone hydrogel lens materials. Methods : Samfilcon A and Comfilcon A lenses were worn on the right and left eyes of 32 (23.5± 2.92 years, female: 24, male: 8), respectively. After Each subjects attended three visits (on day 1 after 3 hours: on days 1 and 7 after 9 hours of wear), visual acuity using high (100%) and low (10%) contrast chart and pre-lens NITBUT using Keratograph 5M were measured. The subjects were surveyed with questionnaire for subjective ocular symptoms in terms of discomfort, dryness, changeable vision, closing eyes and removing lenses. Results : High and low contrast visual acuity, and pre-lens NITBUT values were not significantly different between Samfilcon A and Comfilcon A. There was no significant difference in visual acuity and NITBUT change during 7 days of wearing each lens. The relative frequency of subjective symptoms of 5 items related to wearing contact lenses was not significantly different in all items, the responses of the wearers in terms of lens preference were not statistically different (40.6%, 37.5%, respectively). Conclusion : The study demonstrates similar clinical results for pre-lens NITBUT and subjective ocular symptoms with Samfilcon A and Comfilcon A. The two silicone hydrogel lenses could not find the difference between the two lenses in the lens wearer despite difference lens materials and manufacturers.

Assessment of Contact Lens with the High Definition (HD) Property

AbstractBackground: Contact lenses have been in use since the 1930s. During these years, many materials have been consid-ered with the aim of producing more advanced and biocom-patible devices. The 1940s was the era of the first modern contact lenses, with the debut of polymethyl methacrylate (PMMA). The lack of oxygen supply to the cornea was the main disadvantage of PMMA. This oxygen impermeability was solved with the development of different contact lens materials, new generation of contact lens use hydrogel and silicone to enhance oxygen permeability. Recently, the new contact lens material known as silicone hydrogel lenses has been used to produce a new lens with the HD property.Aim of Study: The aim of this study was to assess a new high definition silicone hydrogel contact lens.Patients and Methods: 22 subjects have been recruited from King Saud University students (male, age 21±1.5 years). The new Balafilcon A lenses (PUREVISION 2 HD); (Bausch + Lomb, Tokyo, Japan) has been assessed and compared with another (non HD) silicone hydrogel lens Balafilcon A (Pure-Vision, Bausch & Lomb Inc., Rochester, NY).The participants asked to wear each of the two lenses for one week (the lens was given randomly) and 48 hours wash out period was allowed between the lenses. Clinical tests including visual acuity (VA) and contrast sensitivity (CS) were applied to evaluate the lens performance at the end of each week. Additionally, contact lens dry eye questionnaire (CLDEQ-8) has been used to obtain the subjective feedback.Result: The mean of CLDEQ-8 with PureVision was 8.1 and with Pure Vision 2 HD was 6. For contrast sensitivity the mean with PureVision was 1.74 while with Pure Vision 2 HD was 1.77. The mean of Visual Acuity was equal with the two lenses 1.00 log. Statistical tests using Wilcoxon-signed rank test showed no significant difference exist between the HD PureVision 2 and PureVision lens. For Visual Acuity (p= 0.317), Contrast sensitivity (p=0. 150) (Fig. 2) and CLDEQ-8 (p=0.339).Conclusion: The silicone hydrogel HD lens evaluated in this study showed good performance. However, no significant difference in clinical performance was observed between the HD lens and the non HD silicone hydrogel lens.

Influence of Solution pH on Drug Release from Ionic Hydrogel Lens

Hydrogel contact lenses have shown the possibility for uses in ophthalmological treatment for the last decades. Moreover, structural changes responsive to solution pH have given further applications toward more complicated drug delivery for physiological and pathological states of a wearer. However, unpredicted variables, swelling degree, and polymer degeneration, have been hurdles for the evaluation and quantification of a designed pharmaceutic system. Many scientists believe understanding empirical/semi-empirical mechanisms behind the drug release can offer simple solutions to quantify and furthermore control the drug release. In this study, we developed silicon-copolymerized hydrogel contact lenses with various functional monomers for delivery of hydroxypropyl methylcellulose, one of the commonly used dry eye drugs. Under the physiological pH, the prepared hydrogels showed different swelling reactions in response to ionic interaction. In addition, analysis of the pH sensitivity and maximum release amounts against the artificial tear pH suggested possible molecular changes in the functional groups and swelling behaviors. Accordingly, the mathematical parameters were calculated to better understand the drug release mechanism from hydrogels. By evaluating these parameters, the primary rate-limiting factors of the silicone hydrogel contact lenses were determined at the investigated pH. These results, with the simple mechanistic study, imply the potentials of silicone hydrogel contact lens in controlled drug delivery under the physiological conditions.

Spectroscopy of Oxygen-Sensitive Material for Measuring Contact Lens Oxygen Transmissibility

ABSTRACTPurpose: Oxygen permeability or transmissibility is a crucial parameter for contact lenses to ensure that extended wear will not induce corneal hypoxia. This work tests a new method of using the oxidation of cysteamine, an oxygen-sensitive chemical, to quantify the oxygen transmissibility of current commercial contact lenses and contact lenses loaded with vitamin E.Methods: 3D printing was used to modify eye drop bottles and quartz cuvettes to create systems that allowed insertion of a contact lens in between the cysteamine solution and air. Both systems were exposed to atmospheric conditions where the only path of entry for oxygen was through the contact lens. The entering oxygen reacted with cysteamine, and the rate of cysteamine oxidation was measured using UV-vis spectrophotometry. The rate was then stoichiometrically related to oxygen transmissibility.Results: The eye drop method predicted transmissibility values within 9% of established, commercial values. The cuvette method predicted values within 10% of established values for silicone hydrogel lenses without any correction factor and within 11% for poly-hydroxyethyl-methacrylate lenses after correcting for oxygen entering the system. Incorporation of 20% (w/w) vitamin E into Acuvue® Oasys® lenses did not have a significant impact on the oxygen transmissibility.Conclusions: Both methods presented in this work can reliably measure oxygen transmissibility of contacts lenses or other materials. Further improvements in manufacturing could lead to improved accuracy and reliability, allowing wider use of this method for quantifying the oxygen transport in contact lenses.

Development and Preliminary Evaluation of a System to Rapidly Measure Coefficient of Friction on Soft Contact Lenses

This study was undertaken to 1. develop an apparatus to rapidly measure coefficient of friction (COF) on soft contact lenses; 2. determine if COFs measured on two daily-disposable lens models before and after wear are consistent with changes in lens surface morphology observed in parallel atomic force microscopy (AFM) images. Methods: A stress rheometer was adapted to measure COF on a soft contact lens by custom fabrication of a rapid-mount sample stage for increased throughput. Five subjects were randomly assigned to wear daily disposable nesofilcon A and delefilcon A contact lenses bilaterally for 4 hours, after which time lenses were removed. Static and kinetic COFs of lenses worn on left eyes was measured, while lenses worn on right eyes were imaged in parallel by AFM in tapping mode. Root mean square (RMS) surface roughness was calculated for all lenses to determine the effect of wear on surface topography. Results: Both static and kinetic COFs measured on unworn delefilcon A silicone hydrogel lenses were greater than on nesofilcon A traditional hydrogel lenses. Static COF on nesofilcon A increased significantly after wear, while kinetic COF trended higher but did not change significantly. Similarly, static COF on delefilcon A also increased significantly after wear, and kinetic COF trended higher but did not change significantly, both remaining greater than on worn nesofilcon A. Parallel AFM analysis demonstrated that nesofilcon A lenses are smoother than are delefilcon A out of the package. Both lenses attracted deposits during wear, but the nesofilcon A surface was less altered by on-eye wear than was the delefilcon A surface. Conclusion: A system to rapidly measure static and kinetic COFs was successfully developed. Static and kinetic COFs measured on delefilcon A were greater than on nesofilcon A lenses. More deposits and greater surface roughness were observed after wear on delefilcon A relative to nesofilcon A. Parallel AFM images of worn and unworn lenses were not predictive of measured COFs, but increased roughness visible by AFM was consistent with observed increases in COF, although not all increases were statistically significant.