Fonn,D., Sweeney,D., Holden,B. A., Cavanagh,D. Corneal oxygen deficiency Eye and Contact Lens 2005;31(1):23-27 [ Show Abstract ]

Objectives. To compare the ocular effects of low Dk hydrogel and high Dk silicone hydrogel contact lenses. Methods. A review of recent literature was conducted to determine the effects of wearing low and high Dk soft lenses on corneal swelling, vascular response, refractive error and the corneal epithelium. Results. High Dk silicone hydrogel contact lenses became available for research and clinical practice almost 10 and 5 years ago respectively. During that time many studies have been conducted and it has been demonstrated repeatedly how much improvement there has been to the physiological response of the eye particularly when wearing the lenses on an overnight basis. Conclusions. Although silicone hydrogels only constitute about 2% of current wearers, their positive effects on the eye compared with low Dk hydrogel lenses should make them the most dominant lenses in the near future. © 2005 Contact Lens Association of Ophthalmologists, Inc.

Ganguly,S., Wulff,D., Phan,C-M., Jones,L., Tang,X. Injectable and 3D Extrusion Printable Hydrophilic Silicone-Based Hydrogels for Controlled Ocular Delivery of Ophthalmic Drugs Applied Bio Materials 2024;7(9):6286-6296 [ Show Abstract ]

While silicone elastomers have found widespread use in the biomedical industry, 3D printing them has proven to be difficult due to the material’s slow drying time, low viscosity, and hydrophobicity. Herein, we arrested the hydrophilic silicone (HS) macrochains into a semi-interpenetrating polymer network (semi-IPN) via an in situ photogelation-assisted 3D microextrusion printing technique. The flow behavior of the pregel solutions and the mechanical properties of the printed HS hydrogels were tested, showing a high elastic modulus (approximately 15 kPa), a low tan δ, high elasticity, and delayed network rupturing. The uniaxial compression tests
demonstrated a nearly negligible permanent deformation, suggesting that the printed hybrid hydrogel maintained its elastic properties. Drug loading and diffusion in the microporous hydrogel are shown via the non-Fickian anomalous transport mechanism, leading to highly tunable loading/releasing profiles (approximately 20% cumulative release) depending on the HS concentration. The drug encapsulation exhibits exceptional stability, remaining intact without any degradation even after a storage period of 1 month. As far as we know, this is the first soft biomaterial based on HS that functions as an exceptional controlled drug delivery device.

Garg,P., Shokrollahi,P., Darge,H., Phan,C-M., Jones,L. Controlled PVA Release from Chemical-Physical Interpenetrating Networks to Treat Dry Eyes ACS Omega 2025;10(1):1249-1260

Glasier,M. -A, Keech,A., Sheardown,H., Subbaraman,L. N., Jones,L. Conformational and quantitative characterization of lysozyme extracted from galyfilcon and senofilcon silicone hydrogel contact lenses Current eye research 2008;33(1):1-11 [ Show Abstract ]

PURPOSE: To compare two solvents for retrieval of lysozyme deposited on a silicone hydrogel (SH) contact lens material galyfilcon A (GA; Acuvue Advance). METHODS: Two buffers used were 50:50 acetonitrile/0.02% trifluoroacetic acid (buffer 1) and 50:50 acetonitrile/50 mM NaOH (buffer 2). RESULTS: Extraction efficiency from GA lenses was 74% (buffer 1) and 83% (buffer 2). Buffer 2 decreased lysozyme activity > buffer 1. Ex vivo GA lenses showed total protein deposition of 2-16 microg/lens with total lysozyme deposition of 0.3-3.9 microg/lens. CONCLUSIONS: We have developed a low acid strength extraction buffer that can be used to efficiently extract active lysozyme protein from novel siloxane-based contact lens materials.

Glasier,M. -A, Subbaraman,L. N., Senchyna,M., Jones,L. A solid-phase assay for the quantitation of total protein eluted from balafilcon, lotrafilcon, and etafilcon contact lenses Current eye research 2008;33(8):631-640 [ Show Abstract ]

PURPOSE: To compare two variations of a membrane-based protein assay utilizing Amido black (AB) detection with a commercially available 3-(4-carboxybenzoyl) quinoline-2-carboxaldehyde (CBQCA) assay for use in the quantitation of individual tear proteins, pooled human tear proteins, and protein extracted from ex vivo lotrafilcon A, balafilcon A, and etafilcon A contact lens materials. METHODS: Ex vivo contact lens extracts, pooled human tears, and individual tear proteins (human serum albumin (HSA), bovine lactoferrin, human secretory immunoglobulin A (sIgA), human lysozyme) were subjected to three solid-phase assays: AB on polyvinylidene difluoride (AB on PVDF) and AB on nitrocellulose (AB on NC) and the CBQCA assay. Micro-bicinchonic acid (micro-BCA) assay was also employed with lens extracts to determine total protein concentration. Individual and pooled tear proteins were referenced to a micro version of the quantitative ninhydrin protein assay. RESULTS: The CBQCA demonstrated the greatest overall sensitivity and lowest intra- and inter-assay variability. AB on NC demonstrated the most accurate ability to quantify total protein in pooled human tear samples, although it also displayed the greatest protein-to-protein variation using individual tear proteins. The CBQCA assay displayed the greatest cross-reactivity with unworn balafilcon and lotrafilcon lens extracts, whereas AB on NC demonstrated the least. AB on NC measured similar amounts of total protein in extracted ex vivo lenses as the CBQCA assay if background interference was subtracted from CBQCA values. AB on PVDF measured the lowest amount of deposited protein from ex vivo lenses. CONCLUSION: Both the AB on NC and CBQCA assays can be used to measure protein in extracts of lotrafilcon, balafilcon, and etafilcon lens materials.

Gorbet,M. B., Tanti,N. C., Crockett,B., Mansour,L., Jones,L. Effect of contact lens material on cytotoxicity potential of multipurpose solutions using human corneal epithelial cells Molecular Vision 2011;173458-3467 [ Show Abstract ]

Purpose: Multipurpose solutions (MPS) are used daily to clean and disinfect silicone hydrogel (SiHy) contact lenses. This in vitro study was undertaken to identify the potential for interaction between MPS, SiHy surface treatments, and lens materials, which may lead to changes in the response of human corneal epithelial cells (HCEC) to MPS-soaked lenses. Methods: The MPS tested were renu fresh (formerly known as ReNu MultiPlus; ReNu), OptiFree Express (OFX), OptiFree RepleniSH, SoloCare Aqua, and Complete Moisture Plus. The SiHy materials evaluated were lotrafilcon A, lotrafilcon B, comfilcon A, galyfilcon A, and balafilcon A (BA). MPS-soaked lenses were placed on top of adherent HCEC. The effect of MPS dilutions (0.1 to 10% final concentration in medium) was also characterized. Cell viability, adhesion phenotype and caspase activation were studied after 24-h cell exposure. OFX released from lenses was determined using UV absorbance. Results: A significant reduction in viability (between 30 to 50%) was observed with cells exposed to lenses soaked in ReNu and OFX. A significant downregulation of α3 and β1 integrins, with integrin expression ranging from 60% to 75% of control (cells with no lens), was also observed with OFX and ReNu-soaked lenses. With the exception of BA, all other lenses soaked in OFX resulted in significant caspase activation, whereby over 18% of cells stained positive for caspases. Minimal caspase activation was observed in cells exposed to ReNu and Solo soaked lenses. For both OFX and ReNu, exposing cells to at least a 5% dilution had a significant effect on viability and integrin expression. While Complete and Solo did not lead to reduction in viability, cells exposed to a 10% dilution showed reduced integrin expression down to less than 70% of control value. Comparing cell response to diluted MPS solutions and various MPS-soaked lenses showed that it is not possible to reliably use cell response to MPS dilution alone to assess MPS biocompatibility. Conclusions: Our results demonstrate that the reaction of HCEC to MPS are affected by the type of lenses the MPS is released from and may potentially be influenced by the surface treatment (or lack of it) of SiHy materials. © 2011 Molecular Vision.

Gorbet,M. B., Tanti,N. C., Jones,L., Sheardown,H. Corneal epithelial cell biocompatibility to silicone hydrogel and conventional hydrogel contact lens packaging solutions Molecular Vision 2010;16272-282 [ Show Abstract ]

Purpose: Although all contact lenses (CLs) are applied initially to the eye directly from a packaging solution, little is known about the effects of these solutions on human corneal epithelial cells (HCECs). Due to the porous nature of CL materials, they have the potential to sorb components of the packaging solution during storage, which could then be subsequently released upon insertion of the CL on the eye. The purpose of this study was to investigate the effect of various packaging solutions on HCECs, using an in vitro model. Methods: An in vitro assay was developed whereby various silicone hydrogels and conventional, poly-2-hydroxyethylmethacrylate (polyHEMA)-based lens materials were removed directly from their packaging and then incubated for up to 24 h with HCECs. The effect of the retained and released packaging solution components on HCECs was assessed by measuring cell viability, adhesion phenotype, and apoptosis. Results: Incubation of HCECs with CLs stored in borate-buffered packaging solutions resulted in a significant reduction in cell viability. Adherent cells incubated with these CLs also exhibited reduced levels of β1 and α3 integrin. Soaking borate-buffered packaged CLs in PBS before cell incubation resolved viability and integrin expression in all cases, with the exception of galyfilcon A and balafilcon A, from which a 20% reduction in cell viability was still observed. In comparison, CLs stored in phosphate-buffered packaging solutions had cellular viability and expression of integrins similar to control cells (cells incubated in the absence of a lens). When incubated with cells at a 10% concentration in serum-free medium, borate-buffered packaging solutions and borate-containing saline (Unisol 4) significantly reduced cell viability and integrin expression. Neither caspase activation nor annexin V binding was observed on cells following exposure to borate buffer solution. However, a significant decrease in reactive oxygen species was observed at 24 h. These latter results suggest that in vitro exposure to low concentration of borate/boric acid results in cell dysfunction, leading to necrosis rather than apoptosis. Conclusions: Borate-buffered packaging solutions were shown to adversely affect the viability and integrin expression of HCECs in vitro. When used in ophthalmic packaging solutions, the antimicrobial properties of borate buffer may be outweighed by its relatively cytotoxic effects on cells. © 2010 Molecular Vision.

Gorbet,M., Peterson,R., McCanna,D., Woods,C., Jones,L., Fonn,D. Human corneal epithelial cell shedding and fluorescein staining in response to silicone hydrogel lenses and contact lens disinfecting solutions Current eye research 2014;39(3):245-256 [ Show Abstract ]

Purpose: A pilot study was conducted to evaluate human corneal epithelial cell shedding in response to wearing a silicone hydrogel contact lens/solution combination inducing corneal staining. The nature of ex vivo collected cells staining with fluorescein was also examined. Methods: A contralateral eye study was conducted in which up to eight participants were unilaterally exposed to a multipurpose contact lens solution/silicone hydrogel lens combination previously shown to induce corneal staining (renu® fresh™ and balafilcon A; test eye), with the other eye using a combination of balafilcon A soaked in a hydrogen peroxide care system (Clear Care®; control eye). Lenses were worn for 2, 4 or 6 hours. Corneal staining was graded after lens removal. The Ocular Surface Cell Collection Apparatus was used to collect cells from the cornea and the contact lens. Results: In the test eye, maximum solution-induced corneal staining (SICS) was observed after 2 hours of lens wear (reducing significantly by 4 hours; p < 0.001). There were significantly more cells collected from the test eye after 4 hours of lens wear when compared to the control eye and the collection from the test eye after 2 hours (for both; n = 5; p < 0.001). The total cell yield at 4 hours was 813 ± 333 and 455 ± 218 for the test and control eyes, respectively (N = 5, triplicate, p = 0.003). A number of cells were observed to have taken up the fluorescein dye from the initial fluorescein instillation. Confocal microscopy of fluorescein-stained cells revealed that fluorescein was present throughout the cell cytoplasm and was retained in the cells for many hours after recovery from the corneal surface. Conclusion: This pilot study indicates that increased epithelial cell shedding was associated with a lens-solution combination which induces SICS. Our data provides insight into the transient nature of the SICS reaction and the nature of fluorescein staining observed in SICS. © 2014 Informa Healthcare USA, Inc.

Guthrie,S. E., Jones,L., Blackie,C. A., Korb,D. R. A Comparative Study Between an Oil-in-Water Emulsion and Nonlipid Eye Drops Used for Rewetting Contact Lenses Eye and Contact Lens 2015;41(6):373-377 [ Show Abstract ]

OBJECTIVES: The purpose of this study was to determine the clinical impact of using SYSTANE BALANCE Lubricant Eye Drops (Alcon, Fort Worth, TX), an oil-in-water emulsion, as a rewetting eye drop in symptomatic contact lens wearers.
METHODS: Subjects who had previously experienced contact lens discomfort (CLD), with a mean lens wearing history of 18.6±12.8 years, were randomly assigned to use a Test (SYSTANE BALANCE Lubricant Eye Drops; n=76) or control (habitual nonlipid contact lens rewetting eye drop; n=30) drop over their contact lenses within 5 min of lens insertion and then subsequently at 2 hr intervals up to a maximum of 4 drops per eye daily for a 1-month period. Assessments of subjective comfort, comfortable wearing time, lid wiper epitheliopathy (LWE), and corneal staining were conducted at baseline and after 1 month, after 6 hr of lens wear.
RESULTS: Comfort, wearing time, LWE, and corneal staining all showed statistically significant improvements in the test group using SYSTANE BALANCE Lubricant Eye Drops at the 1-month visit compared with baseline data (all P<0.01) and compared with the control group at the 1-month visit (P<0.01, P=0.01, P<0.01, and P=0.03, respectively).
CONCLUSIONS: The use of SYSTANE BALANCE Lubricant Eye Drops as a rewetting drop in a group of wearers who experienced symptoms of CLD improved subjective comfort scores, increased comfortable wearing time, and reduced signs of LWE and corneal staining, when compared with the use of non–lipid-containing contact lens rewetting eye drops.

Guthrie,S. E., Luensmann,D., Woods,J., Vega,J., Orsborn,G. Relationships Between Success Factors in Daily Disposable Multifocal Contact Lenses Clinical Optometry 2024;16157-167 [ Show Abstract ]

Purpose: To explore links between subjective comfort and vision in habitual multifocal soft contact lens (MFCL) wearers when refit with daily disposable MFCLs, to determine which factors are relevant for success with MFCLs and evaluate consistency between MFCLs of different designs.

Patients and Methods: This work examined subjective measures in a randomised, participant masked, bilateral wear crossover study at five optometry practices. Fifty-eight habitual MFCL wearers wore stenfilcon A multifocal (stenA-MF; CooperVision Inc) and delefilcon A multifocal (delA-MF; Alcon) for two-weeks. Subjective ratings included satisfaction with comfort and vision and agreement questions.

Results: Agreement with “I would like to wear this MFCL in the future” was taken to indicate success with each MFCL; agreement was significantly higher with stenA-MF. There was strong correlation between agreement responses for “I would like to wear this MFCL in the future” and “MFCL met my needs for vision” with both lenses (p< 0.01). However, it was only with stenA-MF, which had higher agreement responses to both statements (p< 0.05), that responses to these two statements correlated with satisfaction with end-of-day (EOD) comfort (p< 0.01). These differences in correlations between the two lenses are seemingly driven by greater satisfaction with stenA-MF for near and intermediate vision (p< 0.05).

Conclusion: Subjective vision and comfort were only correlated when vision met the needs of most participants. Meeting participants’ needs for vision correlated strongly with wanting to wear a MFCL. Results indicate that meeting vision needs is more important than meeting comfort needs when influencing whether presbyopic patients continue wearing MFCLs.

Guthrie,S., Luensmann,D., Schulze,M., Woods,J., Jones,L. Investigation of Delefilcon A Contact Lenses for Symptomatic Daily Disposable Contact Lens Wearers with Dry Eye Disease: A Prospective Comparative Study Clinical Ophthalmology 2024;18(October):2999-3008 [ Show Abstract ]

Purpose: This prospective comparative study aimed to assess the effects on contact lens comfort, dryness, and wear time when symptomatic daily disposable (DD) contact lens (CL) wearers were refit with delefilcon A (DT1) lenses.

Patients and methods: Thirty five symptomatic DD CL wearers with dry eye disease as determined according to the TFOS DEWS 2 guidelines, were enrolled and completed the study. Participants wore their habitual DD CLs during an initial assessment and were subsequently refit with DT1 for one month. Participants were masked to the study lens type. Subjective ratings of end-of-day comfort and dryness, average wear time, and comfortable wear time were evaluated as primary endpoints.

Results: Of the 35 participants, two participants were classified as aqueous deficient dry eye, while the remaining participants exhibited symptoms primarily due to evaporative causes. The median CLDEQ-8 score for dryness significantly improved from 17 (fair) with habitual lenses to 13 (good) with DT1 lenses (p<0.01). Participants reported significantly better end-of-day comfort (p=0.01) and less end of day dryness (p=0.01) with DT1 compared to their habitual DD lenses. The comfortable wear time was significantly longer with DT1 (8.5 ± 4.1 hours) compared to habitual DD lenses (6.7 ± 3.2 hours) (p=0.04). No significant differences were observed in vision ratings (p=0.07).

Conclusion: Refitting symptomatic DD CL wearers with DT1 resulted in improved end-of-day comfort, reduced end-of-day dryness, and extended comfortable wear time compared to their habitual lenses. These findings suggest that DT1 may offer benefits for symptomatic DD wearers with dry eye disease.

Guthrie,S., Ng,A. Y., Woods,J., Vega,J., Orsborn,G., Jones,L. Exploring the factors which impact overall satisfaction with single vision contact lenses Contact Lens Anterior Eye 2022;45(5):101579 [ Show Abstract ]

Purpose
To explore the impact of subjective factors (lens handling, comfort and vision) on overall single vision contact lens satisfaction.

Methods
Correlation analysis of a prospective, randomised, double-masked, bilateral crossover study involving 55 adapted lens wearers fitted with somofilcon A (SiHy) (clariti® 1 day, CooperVision) and etafilcon A (Hy) (1 DAY ACUVUE® MOIST, Johnson & Johnson Vision) was conducted. Subjective ratings of lens handling, comfort and vision collected after 1 week of lens wear for each lens type were correlated with overall satisfaction. Data were analysed by combining data for both lens types and also for each lens separately.

Results
For the combined analysis, significant correlations (p < 0.01) were found between subjective ratings of overall satisfaction and ratings of handing for application (r = 0.64), handling for removal (r = 0.50), comfort upon application (r = 0.59), comfort at end of day (r = 0.61), overall satisfaction with comfort (r = 0.88) and overall satisfaction with vision (r = 0.64).

Correlation analysis of the per lens data showed that lens specific correlations of overall satisfaction with handling for lens application varied greatly with lens material (SiHy: r = 0.26, p = 0.05 vs Hy: r = 0.72, p < 0.01). Correlation strength of comfort upon application/at end of day with overall satisfaction also varied with lens material (Application: SiHy: r = 0.40 vs Hy: r = 0.61; End of day: SiHy: r = 0.76 vs Hy: r = 0.58; all p ≤ 0.01).

Conclusion
Overall satisfaction was significantly correlated with the specific subjective evaluations of handling, vision and comfort. Correlations of overall satisfaction and ease of handling for each lens type suggest that, for habitual contact lens wearers, dissatisfaction with handling at the time of lens application can play a major role in overall dissatisfaction with a lens. Handling for application had a similar correlation (r) value as vision, suggesting that handling for application should not be underestimated when considering overall patient satisfaction.

Hagedorn,S., Drolle,E., Lorentz,H., Srinivasan,S., Leonenko,Z., Jones,L. Atomic force microscopy and Langmuir-Blodgett monolayer technique to assess contact lens deposits and human meibum extracts Journal of Optometry 2015;8(3):187-199 [ Show Abstract ]

Purpose The purpose of this exploratory study was to investigate the differences in meibomian gland secretions, contact lens (CL) lipid extracts, and CL surface topography between participants with and without meibomian gland dysfunction (MGD). Methods Meibum study: Meibum was collected from all participants and studied via Langmuir-Blodgett (LB) deposition with subsequent Atomic Force Microscopy (AFM) visualization and surface roughness analysis. CL Study: Participants with and without MGD wore both etafilcon A and balafilcon A CLs in two different phases. CL lipid deposits were extracted and analyzed using pressure-area isotherms with the LB trough and CL surface topographies and roughness values were visualized using AFM. Results Meibum study: Non-MGD participant meibum samples showed larger, circular aggregates with lower surface roughness, whereas meibum samples from participants with MGD showed more lipid aggregates, greater size variability and higher surface roughness. CL Study: Worn CLs from participants with MGD had a few large tear film deposits with lower surface roughness, whereas non-MGD participant-worn lenses had many small lens deposits with higher surface roughness. Balafilcon A pore depths were shallower in MGD participant worn lenses when compared to non-MGD participant lenses. Isotherms of CL lipid extracts from MGD and non-MGD participants showed a seamless rise in surface pressure as area decreased; however, extracts from the two different lens materials produced different isotherms. Conclusions MGD and non-MGD participant-worn CL deposition were found to differ in type, amount, and pattern of lens deposits. Lipids from MGD participants deposited irregularly whereas lipids from non-MGD participants showed more uniformity. © 2014 Spanish General Council of Optometry. Published by Elsevier España, S.L.U. All rights reserved.

Hall,B. J., Jones,L. Contact lens cases: The missing link in contact lens safety? Eye and Contact Lens 2010;36(2):101-105 [ Show Abstract ]

Purpose: To summarize a variety of issues associated with contact lens case contamination and discuss appropriate methods that can limit this. Methods: A literature review was undertaken investigating the major factors associated with case contamination, with specific reference to the major pathogens associated with contamination, the role of bacterial biofilms, and methods that can limit contamination. Results: The use of antimicrobial cases, regular case cleaning and case replacement, avoidance of topping up solutions, and not using tap water to rinse cases all appear to be important in avoidance of significant case contamination. Conclusions: Contact lens case contamination is a significant public health concern and may contribute significantly to the development of microbial keratitis in contact lens wearers. Patients should be reminded that they must clean and disinfect their lens cases daily, should avoid the use of tap water for rinsing them, must not top up their solutions, must take into careful consideration where and how the cases are stored during the time that lenses are being worn and that they must be replaced regularly. The adoption of these methods will substantially reduce the levels of contamination of cases with pathogenic microbes. © 2010 Lippincott Williams & Wilkins.

Hall,B. J., Jones,L. W., Dixon,B. Silicone allergies and the eye: Fact or fiction? Eye and Contact Lens 2014;40(1):51-57 [ Show Abstract ]

OBJECTIVE: The purpose of this manuscript was to review the evidence concerning the role of an allergic reaction to silicone as the basis for the reported increase in contact lens-associated infiltrates in wearers of silicone hydrogel contact lenses. METHODS: A literature review was undertaken to investigate the antigenic properties of silicone and the causes of contact lens-associated inflammatory reactions. RESULTS: Immune cells cannot interact with silicone directly but can interact with antigens on these lenses. These antigens could be due to tear film deposits, microbial contamination, or components of care systems used with these lenses. CONCLUSIONS: Inflammatory reactions associated with silicone hydrogel contact lens wear are not caused by an allergic reaction to silicone alone. © 2013 Contact Lens Association of Ophthalmologists.

Hall,B., Forrest,J. A., Jones,L. A Review of Techniques to Measure Protein Sorption to Soft Contact Lenses Eye and Contact Lens 2017;43(5):276-286 [ Show Abstract ]

Purpose: To compare and critically evaluate a variety of techniques to measure the quantity and biological activity of protein sorption to contact lenses over short time periods. Methods: A literature review was undertaken investigating the major techniques to measure protein sorption to soft contact lens materials, with specific reference to measuring protein directly on lenses using in situ, ex situ, protein structural, and biological activity techniques. Results: The use of in situ techniques to measure protein quantity provides excellent sensitivity, but many are not directly applicable to contact lenses. Many ex situ techniques struggle to measure all sorbed proteins, and these measurements can have significant signal interference from the lens materials themselves. Techniques measuring the secondary and tertiary structures of sorbed proteins have exhibited only limited success. Conclusions: There are a wide variety of techniques to measure both the amount of protein and the biological activity of protein sorbed to soft contact lens materials. To measure the mass of protein sorbed to soft contact lenses (not just thin films) over short time periods, the method of choice should be I 125 radiolabeling. This technique is sensitive enough to measure small amounts of deposited protein, provided steps are taken to limit and measure any interaction of the iodine tracer with the materials. To measure the protein activity over short time periods, the method of choice should be to measure the biological function of sorbed proteins. This may require new methods or adaptations of existing ones. © 2017 Contact Lens Association of Ophthalmologists.

Hall,B., Heynen,M., Jones,L. W., Forrest,J. A. Analysis of Using I125 Radiolabeling for Quantifying Protein on Contact Lenses Current eye research 2016;41(4):456-465 [ Show Abstract ]

Purpose: To investigate the accuracy of I125 radiolabeling to quantitatively determine the deposition of protein onto various commercially available contact lens (CL) materials. Methods: Commercially available silicone hydrogel and conventional hydrogel CL materials were examined for times ranging from 10 s to 1 week. Adsorption of free I125 was measured directly for the CL. The use of dialyzing labeled proteins and/or using NaI to compete with free I125 uptake was investigated as ways to minimize effects due to free I125. Results: At all time points and with all lens materials, there was 0.3 µg/lens or greater of apparent mass attributable to free I125 uptake. Dialyzing labeled proteins significantly reduced free I125 uptake for all materials investigated. The benefit of using dialyzed protein was most prominent at shorter times, as free I125 is continuously generated over time. Using NaI can reduce free I125 uptake for some lens materials, but this is shown to directly affect protein deposition on some materials. Conclusions: Periodic replenishment of incubation solutions with freshly dialyzed labeled protein to limit free I125 generation is recommended, but the incorporation of NaI onto the buffer solution is not. Irrespective of the exact procedure to limit free I125 uptake, extra steps must be performed to quantify the amount of I125 adsorbed onto contact lens materials, to determine thresholds of confidence with respect to the actual protein deposition that occurs.

Hall,B., Jones,L. W., Forrest,J. A. Competitive effects from an artificial tear solution to protein adsorption Optometry and Vision Science 2015;92(7):781-789 [ Show Abstract ]

Purpose To compare the adsorption of lysozyme, lactoferrin, and albumin to various contact lens materials, between single-protein solutions and a multicomponent artificial tear solution (ATS). Additionally, extra steps were taken to distinguish loosely and tightly bound protein, the latter of which may be fully or partially denatured. Methods Using a previously described ATS, we measured the time-dependent adsorption of lys, lac, and alb onto one conventional hydrogel and four silicone hydrogel contact lens materials between the first minute and up to 1 week of protein interaction with the material surface. Proteins were quantified using I125 radiolabeling of each protein individually in ATS and buffered saline. Extra steps were taken to limit the amount of unbound I125 and to quantify the amount of reversibly bound protein. Results Comfilcon A, balafilcon A, and etafilcon A did not show any relevant competitive adsorption between the ATS components and lys, lac, or alb until after 1 week. Competitive adsorption effects for lys, lac, and alb were observed in as little as 1 minute on lotrafilcon B. Lotrafilcon B had no reversibly bound protein at any time points. The ionic materials balafilcon A and etafilcon A deposited significant amounts of reversibly bound lysozyme and lactoferrin in just 10 minutes. Senofilcon A apparent deposition was below our thresholds of confidence for this protein quantification method. Conclusions Both the competition between lys, lac, and alb and ATS components and the reversibility of these bound proteins is material specific. Coadsorption of lys, lac, and alb with ATS components can increase the reversibility of their adsorption. © 2015 American Academy of Optometry.

Hall,B., Jones,L., Forrest,J. A. Measuring the kinetics and activity of adsorbed proteins: In vitro lysozyme deposited onto hydrogel contact lenses over short time periods Journal of Biomedical Materials Research - Part A 2013;101 A(3):755-764 [ Show Abstract ]

A new process has been developed to determine the biological activity of an intact layer of lysozyme deposited onto a biomaterial surface. This process is applied to a number of common hydrogel contact lenses. The activity of the surface-adsorbed protein is measured using a standard micrococcal activity assay, with extra steps to distinguish between protein on the surface and protein in solution. This is in contrast to protein extraction work in which the activity of all adsorbed protein is measured. For ionic materials, which are known to deposit large amounts of protein, particularly positively charged proteins such as lysozyme, there is evidence for loosely bound protein re-entering the solution, thus making it impossible to truly separate out the surface-adsorbed protein. This optimized process provides the first quantification of the biological activity of an intact layer of surface-adsorbed protein at a hydrogel interface. © 2012 Wiley Periodicals, Inc.

Hall,B., Jones,L., Forrest,J. A. Kinetics of competitive adsorption between lysozyme and lactoferrin on silicone hydrogel contact lenses and the effect on lysozyme activity Current eye research 2015;40(6):622-631 [ Show Abstract ]

To determine the effect of competitive adsorption between lysozyme and lactoferrin on silicone hydrogel contact lenses and the effect on lysozyme activity. Methods: Three commercially available silicone hydrogel contact lens materials (senofilcon A, lotrafilcon B and balafilcon A) were examined, for time points ranging from 10s to 2h. Total protein deposition was determined by I125 radiolabeling of lysozyme and lactoferrin, while the activity of lysozyme was determined by a micrococcal activity assay. Results: Senofilcon A and balafilcon A did not show any relevant competitive adsorption between lysozyme and lactoferrin. Lotrafilcon B showed reduced protein deposition due to competitive adsorption for lactoferrin at all time points and lysozyme after 7.5min. Co-adsorption of lactoferrin and lysozyme decreased the activity of lysozyme in solution for senofilcon A and lotrafilcon B, but co-adsorption had no effect on the surface activity of lysozyme for all lens types investigated. Conclusions: Competition between lysozyme and lactoferrin is material specific. Co-adsorption of lysozyme and lactoferrin does not affect the activity of surface-bound lysozyme but can reduce the activity of subsequently desorbed lysozyme. © 2015 Informa Healthcare USA, Inc.

Hall,B., McCanna,D., Jones,L. Identification of coagulase-negative staphylococci in daily disposable contact lens wearers Letters in applied microbiology 2014;59(3):313-319 [ Show Abstract ]

This study aimed to identify and quantify the number of contaminating organisms on daily disposable (DD) soft contact lenses, which may be responsible for mild cases of keratitis that occur with this lens wear modality. Ten participants wore DD lenses, and 10 participants wore planned replacement (PR) lenses. Lenses were collected aseptically and analysed for microbial contamination. Colony-forming units (CFU) were recorded, and representative colonies were used for identification using the API identification system. The DD lenses evaluated in this study were contaminated with coagulase-negative staphylococcus (CNS), ranging from 1 to 653 CFU. PR lenses showed more diversity in the types of contaminating micro-organisms and consisted of CNS, Gram-negative bacteria (Pseudomonas), a yeast (Candida) and a mould (Aspergillus), ranging from 1 to 230 CFU. CNS was the only type of micro-organism found on DD contact lenses and therefore may be the cause of any form of keratitis observed in DD lens wearers. © 2014 The Society for Applied Microbiology.

Hall,B., Phan,C. -M, Subbaraman,L., Jones,L. W., Forrest,J. Extraction versus in Situ techniques for measuring surface-adsorbed lysozyme Optometry and Vision Science 2014;91(9):1062-1070 [ Show Abstract ]

PURPOSE: To compare two techniques for measuring the activity of lysozyme deposited onto hydrogel contact lens and to image the binding of Micrococcus lysodeikticus to contact lenses. METHODS: Using a previously described protein extraction technique and a recently developed in situ technique, we measured the time-dependent activity of adsorbed lysozyme on six different contact lens materials during the first minute and up to 1 week of interaction with the material surface. Total activity of extracted lysozyme, total in situ activity, and the activity of the outer surface layer of sorbed lysozyme were determined using the two different techniques. Micrococcal cellular interaction with surface-adsorbed lysozyme was imaged using confocal microscopy. RESULTS: The differences between total extracted activities, total in situ activities, and surface activities were both measurable and material specific. In most cases, total extracted activity is greater than total in situ activity, which, in turn, is greater than surface activity. After 1 week, etafilcon A had the highest extracted activity at 137 µg/lens, followed by omafilcon A, balafilcon A, comfilcon A, senofilcon A, and lotrafilcon B at 27.4, 2.85, 2.02, 0.46, and 0.27 µg/lens, respectively. Micrococcal cell adhesion was greatest on contact lenses with high contact angles, such as balafilcon A, omafilcon A, and senofilcon A and lowest on contact lenses with low contact angles, such as etafilcon A, comfilcon A, and lotrafilcon B. Subsequent removal/prevention of adhered micrococcal cells was greatest on balafilcon A, which had the highest surface activity, and lowest on lotrafilcon B, which had the lowest surface activity. CONCLUSIONS: This study has measured and made direct comparisons between two established techniques for measuring the activity of adsorbed lysozyme. The extraction technique determines the activity of underlying layers of lysozyme or lysozyme within the matrix of the material. Conversely, the in situ technique allows conclusions to be drawn about only the biologically relevant lysozyme including the activity of just the outer surface of adsorbed lysozyme. © American Academy of Optometry.

Haque,S., Fonn,D., Simpson,T., Jones,L. Corneal and epithelial thickness changes after 4 weeks of overnight corneal refractive therapy lens wear, measured with optical coherence tomography Eye and Contact Lens 2004;30(4):189-193 [ Show Abstract ]

Purpose. To investigate thickness changes of the total cornea and epithelium across the horizontal corneal meridian after 4 weeks of overnight corneal refractive therapy (CRT) rigid contact lens (Paragon Vision Sciences, Mesa, AZ) wear. Methods. Thirty subjects were fitted with CRT contact lenses (Dk/t = 67), which were worn overnight for 4 weeks. Corneal thickness was measured at nine locations along the horizontal meridian by using optical coherence tomography (OCT) before lens insertion in the evening. Corneal thickness was measured the next morning immediately after lens removal and 1, 3, 7, and 14 hours later. This was repeated on days 4, 10, and 28 of the study and then 3 days after discontinuing lens wear. Results. Twenty-three subjects completed the study. At lens removal on day 1, the central and paracentral cornea swelled by 4.9% and 6.2%, respectively (both P = 0.000). The central epithelium thinned by 7.3%, and the mid peripheral epithelium thickened by 13% (both P = 0.000). Corneal swelling recovered throughout the day, with most of the deswelling taking place within the first 3 hours after lens removal. Maximal central epithelial thinning reached 13.5% by day 4. Three days after the study completion, corneal and epithelial thickness had recovered to baseline values. Conclusions. This study shows that CRT lenses induce differential overnight swelling across the cornea, with rapid deswelling during the day. Central epithelial thinning and paracentral thickening occurs, with recovery 3 days after discontinuation of lens wear. © 2004 Contact Lens Association of Ophthalmologists, Inc.

Haque,S., Fonn,D., Simpson,T., Jones,L. Corneal refractive therapy with different lens materials, Part 1: Corneal, stromal, and epithelial thickness changes Optometry and Vision Science 2007;84(4):343-348 [ Show Abstract ]

PURPOSE. To assess the corneal swelling response to two myopic correction corneal refractive therapy (CRT) lenses of varying Dk/t values, worn for a single night. Change in thickness of the total cornea, stroma, and epithelium was measured across the horizontal meridian using optical coherence tomography (OCT). METHODS. In this double-masked, randomized study, twenty subjects wore a CRT design lens in each eye, manufactured from Menicon Z (MenZ; Dk/t = 91) and Equalens II (EqII; Dk/t = 47) materials. Baseline corneal thickness was measured centrally and at four points either side of the central cornea using OCT, the night before sleeping at the Centre for Contact Lens Research. The next morning, lenses were removed, and thickness measurements were repeated 1, 3, 6, and 12 h after removal. RESULTS. On lens removal, the MenZ eye had central and paracentral corneal swelling (mean ± SD) of 4.1 ± 2.0% and 5.6 ± 2.4%, and the EqII eye had 5.8 ± 2.6% and 7.0 ± 2.6%. These values were significantly different from baseline (ReANOVA; p 0.05). Stromal swelling values on lens removal were 5.7 ± 2.2% centrally and 5.5 ± 3.0% mid-peripherally (MenZ) and 7.7 ± 3.1% centrally and 6.6 ± 2.9% mid-peripherally (EqII) (all p < 0.001 from baseline). Central stromal swelling was different between eyes at lens removal (p < 0.001). Stromal thickness in both eyes returned to baseline values within 3 h. CONCLUSION. The higher-Dk/t MenZ material caused significantly less overnight corneal and stromal swelling than the Eqll material, which reinforces the need to prescribe lenses with high Dk/t for overnight wear. Neither central epithelial thinning nor paracentral thickening are significantly affected by Dk/t. © 2007 American Academy of Optometry.

Haque,S., Fonn,D., Simpson,T., Jones,L. Epithelial thickness changes from the induction of myopia with CRTH RGP contact lenses Investigative Ophthalmology and Visual Science 2008;49(8):3345-3350 [ Show Abstract ]

PURPOSE. To investigate changes in epithelial thickness after overnight wear of CRTH rigid gas-permeable (RGP) lenses (Paragon Vision Sciences, Mesa, AZ) for the correction of hyperopia. METHODS. Twenty subjects wore a +3.50 D hyperopia-correcting CRTH lens on one eye for a single night in an attempt to induce myopia (first study). The untreated eye served as the control. Corneal and epithelial thickness was measured at nine points across the horizontal meridian by OCT. Measurements were obtained the night before lens wear, immediately after lens removal the next morning, and 1, 3, 6, and 12 hours after removal. Measurements were obtained 28 hours later, to observe recovery. Then, the attempted hyperopic corrections of +1.50 and +3.50 D were evaluated, using CRTH lenses in both eyes of 20 subjects for a single night (second study). RESULTS. All values were compared to baseline unless otherwise stated. In the first study, the treated eye's central and midperipheral epithelial thickness increased by 21.5% ± 8.6% and 13.3% ± 7.6%, respectively, after lens removal (P < 0.001). The control eye's central epithelial thickness (CET) increased by 7.1% ± 6.0% (P < 0.05). In the second study, CET increased by 17.6% ± 8.5% (P < 0.001) in the +3.50 D-treated eye and by 13.3% ± 4.8% (P < 0.001) in the +1.50 D-treated eye. Midperipheral epithelial thickening was 5.9% ± 4.7% (P < 0.05) in the +3.50 D-treated eye and 6.0% ± 6.3% (P < 0.05) in the +1.50 D-treated eye. CONCLUSIONS. CRTH lenses, designed to correct hyperopia, when worn overnight, caused an increase in CET. The amount of epithelial change seemed to differ with modified lens design. Copyright © Association for Research in Vision and Ophthalmology.