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Peer-reviewed articles


Kao,E. C. Y., Seo,J., McCanna,D. J., Subbaraman,L. N., Jones,L. In vitro assessment of the biocompatibility of chemically treated silicone materials with human lens epithelial cells Nature - Scientific Reports 2022;12(1):Article 4649 [ Show Abstract ]

Cytotoxicity testing is a regulatory requirement for safety testing of new ocular implants. In vitro toxicity tests determine whether toxic chemicals are present on a material surface or leach out of the material matrix. A method of evaluating the cytotoxicity of ocular implants was developed using fluorescent viability dyes. To assess the assay’s sensitivity in detecting toxic substances on biomaterials, zinc diethydithiocarbamate (ZDEC) and benzalkonium chloride (BAK) were deposited on silicone surfaces at different concentrations. Human lens epithelial cells (HLEC) were added to the surface of these treated silicone surfaces and were assessed for viability. The viability of both the adherent and non-adherent cells was determined using confocal microscopy with, annexin V, ethidium homodimer, and calcein. Cell metabolism was also evaluated using resazurin and the release of inflammatory cytokines was quantified using a multiplex Mesoscale Discovery platform. Confocal microscopy was shown to be a sensitive assay for evaluating material toxicity, as significant toxicity (p < 0.05) from ZDEC and BAK-treated surfaces compared to the untreated silicone control was detected. Patterns of cytokine release from cells varied depending on the toxin evaluated and the toxin concentration and did not directly correlate with the reduction in cell metabolic activity measured by alamarBlue.


Chang,J. M. L., Seo,J., Kwan,M. M. Y., Oh,S., McCanna,D. J., Subbaraman,L., Jones,L. Determining the Toxicity of UV Radiation and Chemicals on Primary and Immortalized Human Corneal Epithelial Cells Journal of Visualized Experiments 2021;173(July):e62675 [ Show Abstract ]

This article describes the methods of measuring the toxicity of ultraviolet (UV) radiation and ocular toxins on primary (pHCEC) and immortalized (iHCEC) human corneal epithelial cell cultures. Cells were exposed to UV radiation and toxic doses of benzalkonium chloride (BAK), hydrogen peroxide (H2O2), and sodium dodecyl sulfate (SDS). Metabolic activity was measured using a metabolic assay. The release of inflammatory cytokines was measured using a multi-plex interleukin (IL)-1β, IL-6, IL-8, and tumor necrosis factor-alpha (TNF-α) assay, and cells were evaluated for viability using fluorescent dyes.

The damaging effects of UV on cell metabolic activity and cytokine release occurred at 5 min of UV exposure for iHCEC and 20 min for pHCEC. Similar percent drops in metabolic activity of the iHCEC and pHCEC occurred after exposure to BAK, H2O2, or SDS, and the most significant changes in cytokine release occurred for IL-6 and IL-8. Microscopy of fluorescently stained iHCEC and pHCEC BAK-exposed cells showed cell death at 0.005% BAK exposure, although the degree of ethidium staining was greater in the iHCECs than pHCECs. Utilizing multiple methods of assessing toxic effects using microscopy, assessments of metabolic activity, and cytokine production, the toxicity of UV radiation and chemical toxins could be determined for both primary and immortalized cell lines.

Mirzapour,P., McCanna,D. J., Jones,L. In vitro analysis of the interaction of tear film inflammatory markers with contemporary contact lens materials Contact Lens Anterior Eye 2021;44(5):101430 [ Show Abstract ]

Several clinical studies have suggested that reusable silicone hydrogel contact lens materials exhibit a two-times increased rate of corneal infiltrative events compared to reusable hydrogels. One potential factor contributing to this complication relates to the differential uptake of tear film-based pro-inflammatory cytokines. The purpose of this study was to use an in vitro assay to investigate whether four pro-inflammatory cytokines differed in their uptake onto six contemporary contact lens materials.

Conventional hydrogel (etafilcon A, omafilcon A) and silicone hydrogel (balafilcon A, comfilcon A, senofilcon A, somofilcon A) contact lens materials were soaked in solutions containing pro-inflammatory cytokines IL-1β, IL-6, IL-8 and TNF-α. Samples of the soaking solutions were collected over various time points and analyzed using the Meso Scale Discovery system, which served as a measurement of cytokine uptake onto the contact lens materials.

Both conventional hydrogels (etafilcon A, omafilcon A) and two of the four silicone hydrogels tested (balafilcon A, comfilcon A), exhibited some uptake of IL-1β, IL-8 or TNF-α (p < 0.05). Senofilcon A and somofilcon A did not exhibit uptake of any of these cytokines (p > 0.05). There was no uptake of IL-6 onto any of the contact lens materials investigated (p > 0.05).

The contact lens materials tested did not exhibit any uptake of IL-6 and furthermore, did not exhibit more than 10 ± 3 % to 25 ± 12 % uptake of IL-1β, IL-8 or TNF-α. Numerous factors could contribute to the reported increase in corneal infiltrative events with reusable silicone hydrogel materials, however, based on these results, it appears that uptake of these four cytokines are unlikely to contribute to this finding.

Ulkuseven,E., McCanna,D. J., Subbaraman,L. N., Jones,L. W. The Effect of Antimicrobial Peptides on the Viability of Human Corneal Epithelial Cells Probiotics and Antimicrobial Proteins 2021;13(2):518-526 [ Show Abstract ]

Antimicrobial peptides are polypeptides composed of less than 100 amino acids and are a class of antibiotics with strong activity against some infectious bacteria. This study examined the safety of four chosen antimicrobial peptides using primary human corneal epithelial cells (HCEC) and explored their potential therapeutic use. The efficacy of the peptides was also studied by evaluating the minimum inhibitory concentrations (MIC) against Gram-negative and Gram-positive bacteria. One of the peptides (polymyxin E) was found to have antibacterial efficacy against a common Gram-negative bacterium (MIC 1.56 μg/mL for Pseudomonas aeruginosa), and another one (nisin) was found to have antibacterial efficacy against a common Gram-positive bacterium (MIC 125 μg/mL for Staphylococcus aureus). Metabolic activity and live/dead/apoptotic effects were measured with fluorescent dyes after HCEC were exposed to the peptides for 30 min. Three of the peptides exhibited lower toxicity against HCEC than a currently marketed eye drop product. Regarding both efficacy and safety, two of the peptides (polymyxin E and nisin) were found to have potential use for treating ocular infections.

Xu,M., Sivak,J. G., McCanna,D. J. Neutralization of the eye and skin irritant benzalkonium chloride using UVC radiation Cutaneous and Ocular Toxicology 2021;40(2):78-84 [ Show Abstract ]

Benzalkonium chloride (BAK) is a widely used disinfectant and preservative which is effective against a wide range of viruses (e.g. SARS-CoV and SARS-CoV-2), bacteria and fungi. However, it is toxic to the eye and skin. This study investigated the neutralization of BAK using ultraviolet C (UVC) radiation as an effort to reduce BAK toxicity potential.

BAK solutions were irradiated with a germicidal UVC lamp at various doses. Human corneal epithelial cells (HCEC) were then exposed to the UVC-irradiated BAK solutions for 5 minutes. After exposure, the cultures were assessed for metabolic activity using PrestoBlue; for cell viability using confocal microscopy with viability dyes; and for tight junction proteins using immunofluorescence staining for zonula occludens (ZO)-1.

UVC radiation reduced BAK toxicity on cell metabolic activity in a dose-dependent manner. When the solution depth of BAK was 1.7 mm, the UVC doses needed to completely neutralize the toxicity of BAK 0.005% and 0.01% were 2.093 J/cm2 and 8.374 J/cm2, respectively. The cultures treated with UVC-neutralized BAK showed similar cell metabolic activity and cell viability to those treated with phosphate buffered saline (PBS) (p = 0.806 ∼ 1.000). The expression of ZO-1 was greatly disturbed by untreated BAK; in contrast, ZO-1 proteins were well maintained after exposure to UVC-neutralized BAK.

Our study demonstrates that the cell toxicity of BAK can be neutralized by UVC radiation, which provides a unique way of detoxifying BAK residues. This finding may be of great value in utilizing the antimicrobial efficacy of BAK (e.g. fighting against SARS-CoV-2) while minimizing its potential hazards to human health and the environment.

Yamasaki,K., Mizuno,Y., Kitamura,Y., McCanna,D. J., Ngo,W., Jones,L. W. The efficacy of povidone-iodine, hydrogen peroxide and a chemical multipurpose contact lens care system against Pseudomonas aeruginosa on various lens case surfaces Cont Lens Anterior Eye 2021;44(1):18-23 [ Show Abstract ]

To determine the antimicrobial efficacy of a povidone-iodine system (PVP-I; cleadew, OPHTECS Corporation, Kobe, Japan), a peroxide system (AOSEPT Plus with HydraGlyde, Alcon, Fort Worth, TX), and a chemical multipurpose system (renu fresh, Bausch & Lomb, Rochester, NY) on contact lens case surfaces that are both in contact and not in contact with the solutions during lens disinfection.

The surfaces of the inner walls, underside of the lid, and lens holder (if applicable) of the cases were inoculated with P. aeruginosa ATCC 27853. The cases were disinfected with the solutions as per their manufacturer instructions. After disinfection, the inoculated surfaces were swabbed and the amount of surviving P. aeruginosa was determined. Following this experiment, separate cases were inoculated and disinfected as before. This time the cases were agitated after recommended disinfection time and the amount of P. aeruginosa in the disinfecting solution was quantified immediately, and again after resting for 7 days. Experiments were conducted in triplicate (n = 3).

Units are expressed in log CFU. All three solutions significantly reduced P. aeruginosa on direct-contact surfaces (all p < 0.039). On non-contact surfaces, the reduction of P. aeruginosa in the PVP-I system (pre-disinfection: 6.8 ± 0.5, post-disinfection: 1.0 ± 0.0; p < 0.001) was significant, but not for the hydrogen peroxide system (pre-disinfection: 6.3 ± 0.6, post: 5.5 ± 0.5; p = 0.194) and the chemical multipurpose system (pre-disinfection: 6.6 ± 0.1, post-disinfection: 5.6 ± 0.8; p = 0.336). After 7 days post-disinfection, no P. aeruginosa regrowth was observed in the PVP-I system (Day 1: 1.0 ± 0.0, Day 7: 1.0 ± 0.0; p = 1) and the chemical multipurpose system (Day 1: 4.2 ± 0.2, Day 7: 1.8 ± 0.9; p = 0.012), however regrowth was observed in the hydrogen peroxide system (Day 1: 3.4 ± 0.6, Day 7: 6.1 ± 0.4; p = 0.003).

The PVP-I system was more effective against P. aeruginosa on non-contact surfaces than the hydrogen peroxide system or the chemical multipurpose system and is capable of inhibiting regrowth of P. aeruginosa for at least 7 days post-disinfection.


Rangarajan,R., Ketelson,H. A., Do,R., McCanna,D. J., Suko,A., Enstone,D., Subbaraman,L., Dantam,J., Jones,L. W. Effect of Artificial Tear Formulations on the Metabolic Activity of Human Corneal Epithelial Cells after Exposure to Desiccation Journal of Visualized Experiments 2020 (159):e60812 [ Show Abstract ]

Artificial lipid-containing tear formulations are developed to reduce tear evaporation by the restoration of a deficient tear lipid layer. Artificial tear formulations that prevent cell desiccation will result in ocular surface protection and the maintenance of cell metabolic activity. During dehydration, cells undergo the process of loss of metabolic activity and subsequently cell death. This work describes a method for assessing the efficacy of artificial tear formulations. The metabolic dye (i.e., alamarBlue) changes from a low fluorescent molecule resazurin to a fluorescent molecule resorufin in viable cells. The biological performance of an artificial tear formulation is measured as the ability of the formulation to (a) maintain cell viability and (b) provide cell protection from desiccation. Growth media and saline are used as controls for the cell viability/desiccation tests. Cells are incubated with test solutions for 30 min and then desiccated for 0 or 5 min at 37 °C and 45% relative humidity. Cell metabolic activity after initial exposure and after cell desiccation is then determined. The results show the comparative effects of eye drop formulations on cell metabolic activity and desiccation protection. This method can be used to test dry eye formulations that are designed to treat individuals with evaporative dry eye.

Xu,M., Sivak,J. G., McCanna,D. J. Ocular toxicology: synergism of UV radiation and benzalkonium chloride
Cutaneous and Ocular Toxicology 2020;39(4):370-379 [ Show Abstract ]

Purpose: To investigate the combined toxic effect of ultraviolet (UV) radiation and benzalkonium chloride (BAK), a common preservative in ophthalmic eye drops, on human corneal epithelial cells (HCEC).

Methods: Cultured HCEC were exposed to different combined and separate UV (280-400 nm) and BAK solutions at relevant human exposure levels. Human exposure to UV can occur before, during, or after eye drop installation, therefore, three different orders of ocular exposures were investigated: UV and BAK at the same time, UV first followed by BAK, and BAK first followed by UV. Control treatments included testing HCEC exposed to BAK alone and also HCEC exposed to UV alone. In addition, phosphate-buffered saline (PBS) was used as a negative control. After exposure, cell metabolic activity of the cultures was measured with PrestoBlue, and cell viability was determined using confocal microscopy with viability dyes.

Results: BAK alone reduced the metabolic activity and cell viability of HCEC in a dose- and time-dependent manner. UV alone at a low dose (0.17 J/cm2) had little toxicity on HCEC and was not significantly different from PBS control. However, UV plus BAK showed combined effects that were either greater than (synergistic) or equal to (additive) the sum of their individual effects. The synergistic effects occurred between low dose UV radiation (0.17 J/cm2) and low concentrations of BAK (0.001%, 0.002%, 0.003%, and 0.004%).

Conclusions: This investigation determined that at relevant human exposure levels, the combination of UV radiation (280-400 nm) and BAK can cause synergistic and additive toxic effects on human corneal epithelial cells. This finding highlights the importance of considering the combined ocular toxicity of BAK and solar radiation in the risk assessment of BAK-preserved ophthalmic solutions.


McCanna,D. J., Oh,S., Seo,J., Coles-Brennan,C., Fadli,Z., Subbaraman,L. N., Jones,L. W. The effect of denatured lysozyme on human corneal epithelial cells Investigative Ophthalmology and Visual Science 2018;59(5):2006-2014 [ Show Abstract ]

PURPOSE. During contact lens wear, the amount of lysozyme deposited on contact lenses varies depending on the lens material. The binding of lysozyme to some contact lens materials may result in a conformational change that denatures the protein to an inactive form. This investigation evaluated the effect that denatured lysozyme has on human corneal epithelial cells (HCECs) by measuring cell viability and the release of inflammatory cytokines. METHODS. HCECs were exposed to lysozyme that was denatured to various activity levels. After 24-hour exposure to the lysozyme (1.9 mg/mL) in growth media, the cells were evaluated for cell viability using confocal microscopy. The metabolic activity of the cells was determined using an alamarBlue assay. Cell supernatants were analyzed for inflammatory cytokines. RESULTS. Using confocal microscopy, there was no detectable change in the viability of the HCECs after exposure to the denatured lysozyme. However, using alamarBlue, a decrease in the metabolic activity of the HCECs exposed to denatured lysozyme was detected. HCECs exposed to lysozyme that was 67%, 47%, and 22% active showed a reduction in metabolic activity when compared with native (100% active) lysozyme and the media controls (P < 0.05). Exposure to the denatured lysozyme also caused an increase in the release of inflammatory cytokines (P < 0.05) from the HCECs. CONCLUSIONS. The results of this study show that denatured lysozyme can have a detrimental effect on HCECs. Both a reduction in metabolic activity and an increase in the release of inflammatory cytokines occurred after HCEC exposure to denatured lysozyme. © 2018 The Authors.

Oh,S., McCanna,D., Subbaraman,L.N., Jones,L. Cytotoxic and inflammatory effects of contact lens solutions on human corneal epithelial cells in vitro Contact Lens and Anterior Eye 2018;41(3):282-289 [ Show Abstract ]

Purpose: To ascertain the effect that four contact lens (CL) multipurpose solutions (MPS) have on the viability and release of pro-inflammatory cytokines from human corneal epithelial cells (HCEC). Methods: HCEC were exposed to four different MPS at various concentrations for 18 hours. The cells were also exposed to phosphate buffer, borate buffer, and PHMB. The cell viability was evaluated using the alamarBlue assay. The release of pro-inflammatory cytokines was measured using a Multiplex electrochemiluminescent assay. Results: MPS-A, MPS-B and MPS-C all reduced cell metabolic activity p < 0.05 from control with MPS-A showing the greatest cytotoxic effect (maximum reduction, 90.6%). In contrast, MPS-D showed no significant reductions in cytotoxicity except at the highest concentration tested (19% reduction at 20% MPS concentration). Of the four cytokines evaluated MPS-C showed a substantial increase in the release of IL-1β, IL-6, IL-8, and TNF-α at higher concentrations when compared to control p < 0.05. At the 20% concentration of MPS-A and MPS-B the release of IL-1 β increased p < 0.05 but the release of IL-6, IL-8, and TNF-α decreased. MPS-D did not cause a change in the release of cytokines IL-1β, IL-6, IL-8 and TNF-α p > 0.05. Exposing the cells to borate buffer and PHMB caused an increase in the release of TNF-α p < 0.05. Conclusions: This investigation demonstrates that at different concentration levels, several of the MPS tested showed a decrease in viability and an increase in the release of inflammatory cytokines from HCEC. The borate buffer component as well as PHMB appears to contribute to this pro-inflammatory reaction.


Dantam,J., McCanna,D. J., Subbaraman,L. N., Papinski,D., Lakkis,C., Mirza,A., Berntsen,D. A., Morgan,P., Nichols,J. J., Jones,L. W. Microbial contamination of contact lens storage cases during daily wear use Optometry and Vision Science 2016;93(8):925-932 [ Show Abstract ]

Purpose. To evaluate contact lens (CL) storage case contamination when used with four different CL care solutions during daily wear of three different CL materials. Methods. A parallel, prospective, bilateral, randomized clinical trial (n = 38) was conducted. Subjects were randomly assigned to use one of three CL materials (etafilcon A, senofilcon A, or galyfilcon A) on a daily wear basis. Subsequently, each subject randomly used one of four different CL care solutions (Biotrue, OPTI-FREE PureMoist, RevitaLens OcuTec, and CLEAR CARE) for 2 weeks, along with their respective storage cases. After every 2-week period, their storage cases were collected and the right and left wells of each storage case were randomized for two procedures: (1) microbial enumeration by swabbing the storage case surface and (2) evaluation of biofilm formation (multipurpose solution cases only) using a crystal violet staining assay. Results. More than 80% of storage cases were contaminated when used in conjunction with the four CL care solutions, irrespective of the CL material worn. Storage cases maintained with CLEAR CARE (mean Log colony forming units (CFU)/ well ± SD, 2.0 ± 1.0) revealed significantly (p < 0.001) greater levels of contamination, compared to those maintained with Biotrue (1.3 ± 0.8) and RevitaLens OcuTec (1.2 ± 0.8). Predominantly, storage cases were contaminated with Gram-positive bacteria (= 80%). There were significant differences (p = 0.013) for the levels of Gram-negative bacteria recovered from the storage cases maintained with different CL care solutions. Storage cases maintained withOPTI-FREE PureMoist (0.526 ± 0.629) showed significantly higher biofilm formation (p = 0.028) compared to those maintained with Biotrue (0.263 ± 0.197). Conclusions. Levels of contamination ranged from 0 to 6.4 Log CFU/storage case well, which varied significantly (p < 0.001) between different CL care solutions, and storage case contamination was not modulated by CL materials. © Copyright 2016 American Academy of Optometry.

Liu,L. Y., Seo,J., McCanna,D. J., Subbaraman,L. N., Jones,L. W. Assessment of biofilm formation of E. meningoseptica, D. acidovorans, and S. maltophilia in lens cases and their growth on recovery media Contact Lens and Anterior Eye 2016;39(2):117-123 [ Show Abstract ]

Purpose: Bacterial biofilm formation in contact lens cases is a risk factor in the development of both microbial and infiltrative keratitis. This investigation evaluated three emerging pathogens: Stenotrophomonas maltophilia, Elizabethkingia meningoseptica, and Delftia acidovorans for biofilm formation and metabolic activity in lens cases. Also, growth of these bacteria on different media was assessed to optimize recovery conditions. Methods: The three bacteria were incubated in lens cases with different concentrations of tryptic soy broth. Biofilm formation was evaluated by measuring metabolic activity using MTT and enumerating the number of viable bacteria. To determine the optimal recovery media, dilutions of these microorganisms were plated on six different media. The number of colony forming units (CFU) was recorded after 48, 72, and 96 h of incubation at 32 °C and 37 °C for S. maltophilia, and at 37 °C for E. meningoseptica and D. acidovorans. Results: All three microorganisms established biofilms in the lens cases, with significant numbers of CFU recovered. Biofilms of S. maltophilia and E. meningoseptica were metabolically active. Significant reduction in metabolic activity and number of viable S. maltophilia occurred when the incubation temperature was raised from 32 °C to 37 °C (p < 0.05). The metabolic activity of the biofilms increased with greater organic load present. The highest percent recovery for all three organisms was given by Columbia blood agar, followed by chocolate. Conclusion: Based on the results, the presence of the three emerging pathogens present in lens cases and from corneal isolates can be accurately determined if proper growth media and incubation temperatures are utilized.

Phan,C. -M, Bajgrowicz,M., McCanna,D. J., Subbaraman,L. N., Jones,L. Effects of Antifungal Soaked Silicone Hydrogel Contact Lenses on Candida albicans in an Agar Eye Model Eye and Contact Lens 2016;42(5):313-317 [ Show Abstract ]

Purpose: To evaluate the effects of two commercial silicone hydrogel contact lenses (CLs) soaked with natamycin (NA) or fluconazole (FL) on the growth of Candida albicans in an in vitro eye model. Methods: Three-D printed molds were used as a cast for making eye-shaped models comprising potato dextrose agar. Senofilcon A (SA) and lotrafilcon B (LB) CLs were incubated with either 2 mL of NA or FL at a concentration of 1 mg/mL for 24 hr. To simulate a fungal infection, the eye models were coated with C. albicans. The drug-soaked lenses were placed on top of the eye models. Seven experimental conditions were examined: (1) NA-SA, (2) NA-LB, (3) FL-SA, (4) FL-LB, (5) SA, (6) LB, and (7) control - no lens. At specified time points (t1, 8, 16, 24, 48 hr), the agar eyes from each experimental condition were removed from the incubator and photographed. The yeast cells from the 24 and 48 hr time point were also analyzed using light microscopy. Results: At 24 and 48 hr, there was considerable growth observed for all conditions except for the NA-SA and NA-LB conditions. When observed under the microscope at 24 and 48 hr, the morphology of the yeast cells in the FL-SA and SA condition were similar to that of the control (oval shaped). There was limited hyphae growth observed for LB and significant visible hyphae growth for the NA-LB group. For NA-SA, NA-LB, and FL-LB groups, the cells were significantly smaller compared with the control. Conclusions: For NA-SA and NA-LB, there was limited growth of C. albicans observed on the eye models even after 48 hr. Under the microscope, the cell morphology differ noticeably between each testing condition, and is dependent on drug-lens combinations. © 2015 Contact Lens Association of Ophthalmologists.


Chang,J. M. L., McCanna,D. J., Subbaraman,L. N., Jones,L. W. Efficacy of antimicrobials against biofilms of achromobacter and pseudomonas Optometry and Vision Science 2015;92(4):506-513 [ Show Abstract ]

Purpose. Achromobacter xylosoxidans and Pseudomonas aeruginosa biofilms can develop in ophthalmic products and accessories such as contact lens cases, leading to the development of ocular infections. This study evaluated the efficacy of the antimicrobials polyaminopropyl biguanide (PAPB) and benzalkonium chloride (BAK) against A. xylosoxidans and P. aeruginosa biofilms. Methods. Biofilms of A. xylosoxidans and P. aeruginosa used as a comparative control were formed by incubating the bacteria on contact lens cases and on coverslips in phosphate-buffered saline. The biofilms were then exposed to PAPB and BAK for 5 minutes and 4 hours. After exposure, alginate swabs were used to remove the biofilms from the lens cases and the bacteria were plated on tryptic soy agar for determination of survivors. Also, after exposure to these disinfectants, the A. xylosoxidans and P. aeruginosa biofilms were stained with SYTO 9 and propidium iodide. Using a confocal microscope with a 488-nm laser, the number of cells with damaged cell membranes was determined. Results. After 5 minutes of exposure to BAK or PAPB, A. xylosoxidans biofilms were more resistant to the antimicrobial effects of these disinfectants than P. aeruginosa biofilms. After 4 hours, both organisms were reduced by more than 3 logs after exposure to either BAK or PAPB. Confocal microscopy studies revealed that BAK was more effective at damaging A. xylosoxidans and P. aeruginosa cell membranes than PAPB at the concentrations used in ophthalmic products. Conclusions. Biofilms of the emerging pathogen A. xylosoxidans were more resistant to the disinfectants PAPB and BAK than biofilms of P. aeruginosa. Because of the emergence of A. xylosoxidans and the demonstrated greater resistance to the common ophthalmic preservatives BAK and PAPB than the standard Gram-negative organism P. aeruginosa, A. xylosoxidans biofilms should be assessed in antimicrobial challenge tests to assure the safety of multiuse ophthalmic products. Copyright © 2015 American Academy of Optometry.


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.

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.


Kao,E. C. Y., McCanna,D. J., Jones,L. W. Utilization of in vitro methods to determine the biocompatibility of intraocular lens materials Toxicology in Vitro 2011;25(8):1906-1911

Youn,H. -Y, McCanna,D. J., Sivak,J. G., Jones,L. W. In vitro ultraviolet-induced damage in human corneal, lens, and retinal pigment epithelial cells Molecular Vision 2011;17237-246

Scientific Presentations


Nagaarudkumaran N, McCanna D, Ngo W, Jones L. In vitro quantification of cytokines adhered to contemporary contact lens materials The Association for Research in Vision and Ophthalmology, 2020 [ Show Abstract ][ PDF ]

Purpose : Contact lenses (CL) may induce a low-level inflammatory response on the ocular surface. Previous studies have quantified the concentration of inflammatory mediators present in the tear film during CL wear. Analyzing the inflammatory mediators loosely adhered to CL materials may provide another perspective on the role that contact lenses play in inflammation. The purpose of this in vitro study was to quantify a variety of cytokines found in the tear film that adhered to various CL materials and to develop a method that could extract them.

Methods : Cytokines IL-1β, IL-6, IL-8, and TNF-α (Meso Scale Diagnostics, Rockville, MD) were combined with 5 mL of Diluent 2 to prepare a cytokine solution with a final concentration of 119.41, 166.05, 101.48 and 40.73 pg/mL, respectively. Contact lenses (etafilcon A, somofilcon A, omafilcon A, delefilcon A) (n=4 each) were each placed into a polypropylene tube containing a volume of 200 μL of the prepared cytokine solution and were incubated at 23°C for 6 hours. The lenses were removed from the tubes using tweezers and placed into a 0.6 mL microcentrifuge tube containing 200 μL of Diluent 2 and were incubated at 23°C for 1 hour. The microcentrifuge tube was then vortexed for 5 seconds and pin sized holes were made at the base of the tube. The tube was then placed into a larger 2.0 mL microcentrifuge tube acting as a carrier and were centrifuged at 604 RCF. The eluent in the 2.0 mL microcentrifuge was then collected and stored at -80°C for cytokine quantification at a later date, using the MESO QuickPlex SQ 120 (Meso Scale Diagnostics, Rockville, MD). Statistical analysis was performed using a one-way ANOVA.

Results : There was no significant difference between cytokine concentrations for all CL materials (p>0.05).

Conclusions : While there were no significant differences between the concentrations of cytokines found loosely adhered to the soft CL materials investigated, the results support this method as a means to quantify such cytokines on soft lens materials. This method may be used to examine human-worn lenses in future studies.

This is a 2020 ARVO Annual Meeting abstract.


Jones L, Yee A, Jabeen A, Subbaraman L, McCanna D, Phan CM. Novel in-vitro method to study bacterial interaction with contact lenses Global Specialty Lens Symposium, Las Vegas, Nevada, 2019 [ PDF ]

Rangarajan R, Ketelson H, Do R, McCanna D, Suko A, Enstone D, Subbaraman L, Jones L, Meyer A. Characterization of a New Phospholipid Containing Nanoemulsion Lubricant Eye Drop for Dry Eye Invest Ophthalmol Vis Sci 2019;E-abstract 303


Subbaraman L, Dare E, Fung CK, McCanna D, Jones L. Establishment of optimal culture media in human corneal epithelial wound healing models Invest Ophthalmol Vis Sci 2018;E-Abstract 4337 [ Show Abstract ]

Purpose: Damage to the human corneal epithelium can potentially result in severe vision loss. Corneal epithelial cell damage should be quickly repaired to prevent infection and adequate wound healing is required for corneal transplants and recovery from LASIK surgery. To study corneal epithelial wound healing, an in vitro scratch model and an in vitro exclusion zone model are often used. The purpose of this study was to establish the optimum media to use as a control solution in wound healing models.

Methods: Immortalized human corneal epithelial cells were cultured in different growth media. A scratch wound was made on the epithelial cell monolayers and cell recovery was followed for up to 48 hours by measuring the area of the wound. The effect of normoxic and hypoxic conditions on tight junctional integrity and metabolic activity of cells grown in different growth media were also investigated. Using an exclusion zone model, the degree of cell proliferation into the exclusion zone was determined after seven and nine days of growth in cell culture media.

Results: Wound healing with Dulbecco’s Modified Eagle Medium: Nutrient mixture F-12 (DMEM/F-12) was significantly faster than both the keratinocyte serum-free medium (KSFM) (p<0.05) and EpiLife (p<0.05) 10 hours after wounding using the scratch model and nine days after wounding using the exclusion zone technique (p<0.05). In addition, hypoxic culture significantly delayed wound healing by an average of 32.4%. In the culture media DMEM/F-12, human corneal epithelial cells stained for abundant zona occludens-1 (ZO-1), connexion 43 (Cx43) and had a high metabolic activity indicating significant epithelial barrier formation, gap junction formation and high cell viability.

Conclusions: DMEM/F-12 led to superior wound healing under hypoxic and normoxic conditions and in two different wound healing models. DMEM/F-12 appears to be the optimum wound healing control for corneal wound healing models due to superior metabolic activity, wound healing and formation of a greater number of tight junctional proteins in cells grown in this medium over the other media tested.

Yee A, Jabeen A, Subbaraman L, McCanna D, Phan C-M, Jones L. Novel In-Vitro Method to Study Bacterial Interaction with Contact Lenses American Academy of Optometry, San Antonio, USA, 2018 [ Show Abstract ][ PDF ]

Purpose: Previous in-vitro studies have used a “soak” or closed vial method to assess bacterial binding to contact lenses (CL). The purpose of this study was to develop a novel in-vitro drip model to determine if bacterial adhesion to a CL material was possible. The novel in-vitro drip model would more closely resemble an accurate eye model in comparison to current methods undertaken.

Methods: The novel in-vitro drip method consists of a 5.5 mL syringe with saline solution and a flow rate controller dispensing 5 µl of saline solution containing the bacteria. The consistent drip volume is adjustable and mimics the normal human tear volume and flow. The solution flows through a silicone tube and onto a CL. The CL was placed on a sterile glass eyeball in an enclosed container to maintain the environment’s humidity. In the soak method, the CL was placed on top of a sterile glass eyeball and placed in the enclosed container with a 5 mL saline solution of 1.0 x 107 colony forming units (CFU)/mL. For both methods, lenses were incubated in the solution for 16 hours. After removal, the viable cells were diluted in serial dilutions. Aliquots of each dilution were plated on a trypticase soy agar plate and incubated for 24 hours at 37°C. After 24 hours, the CFU per lens were calculated manually under magnification.

Results: Using the in-vitro drip method, adhesion of Staphyloccocus aureus onto senofilcon A was successfully demonstrated. Preliminary analysis showed no significant difference (p = 0.34) between the drip and soak method when compared at high CFU/mL.

Conclusion: The novel drip method is a promising alternative to the conventional soak method, as this model is closer to the contamination that would occur in a human eye. The drip method may be an acceptable method of testing once the method can be further developed and tested in future studies, using a variety of lenses and bacteria.


Dantam J, McCanna D, Subbaraman L, Jones L. Pro-inflammatory cytokine expression in human corneal epithelial cells after exposure to LPS derived from Pseudomonas aeruginosa Optom Vis Sci 2017;94: E-Abstract 174082

Khalid S, McCanna D, Jones L. Efficacy of a peroxide-based contact lens care solution against Pseudomonas aeruginosa and Staphylococcus aureus biofilms formed under four different nutrient conditions Optom Vis Sci 2017;94: E-Abstract 174072

McCanna D, Bidar M, Subbaraman L, Jones L. The effect of artificial tear solution and organic load on the efficacy of contact lens disinfectant solutions Invest Ophthalmol Vis Sci 2017;E-Abstract 3075

Subbaraman L, Hwang Y, Liu L, McCanna D, Jones L. Metabolic activity of human corneal epithelial cells after exposure to artificial tear-like formulations with varying pH and osmolalities Invest Ophthalmol Vis Sci 2017


Bajgrowicz M, Phan C, McCanna D, Subbaraman L, Jones L. Effects of antifungal soaked silicone hydrogel contact lenses on Candida albicans in an agar eye model ISCLR Budapest, Hungary, 2015

McCanna D, Oh S, Seo J, Coles_brennan C, Fadli Z, Subbaraman L. In vitro evaluation of the effect of lysozyme coated contact lenses on cell viability and inflammatory response BCLA Clinical Conference and Exhibition, 2015 [ PDF ]

McCanna D, Oh S, Seo J, Subbaraman L, Coles-Brennan C, Fadli Z, Jones L. Effect of Denatured Lysozyme on Human Corneal Epithelial Cells Invest Ophthalmol Vis Sci 2015;56: E-abstract 3511 [ PDF ]

Subbaraman L, Heynen M, McCanna D, Omali N, Jansen M, Fadli Z, Toubouti Y, Coles-Brennan C, Jones L . Impact of pigment presence in etafilcon A on in vitro interaction of lysozyme and impact on inflammatory biomarker release Optom Vis Sci 2015;92: E-abstract 150097

Subbaraman L, McCanna D, Oh S, Ng A, Coles-Brennan C, Fadli Z, Jones L. Lysozyme activity on contact lenses and the impact of denatured lysozyme on human corneal epithelial cells BCLA Clinical Conference and Exhibition, 2015 [ PDF ]


Dantam, McCanna D, Subbaraman L, Lakkis C, Morgan P, Nichols J, Jones L. Microbial contamination of contact lens storage cases with the use of different contact lens care solutions and lens materials Invest Ophthalmol Vis Sci 2014;55: E-abstract 4675 [ PDF ]

Jones L, Dantam J, McCanna D, Subbaraman L, Morgan P, Nichols J, Lakkis C. Impact of different contact lens care solutions and lens materials on contact lens storage case contamination BCLA Clinical Conference and Exhibition, 2014 [ PDF ]

Lorentz H, McCanna D, Subbaraman L, Jones L, Salapatek A, Soong F. Changes in cytokine expression for dry eye and non dry eye subjects exposed to a low humidity environmental exposure chamber Optom Vis Sci 2014;91: E-abstract 140106

McCanna D,Liu L, Seo J, Subbaraman L, Jones L. Assessment of the growth of Stenotrophomonas maltophilia, Elizabethkingia meningoseptica and Delftia acidovorans in contact lens cases and on recovery media Invest Ophthalmol Vis Sci 2014;55: E-abstract 6051

Subbaraman L, McCanna D, Lorentz H, Soong F, Salapatek A, Jones L. Tear Cytokines in Non-Dry Eye and Dry Eye Participants After Exposure to a Low Humidity Environmental Exposure Chamber Invest Ophthalmol Vis Sci 2014;55: E-abstract 3682


McCanna D, Chang J, Subbaraman L, Jones L. Efficacy of contact lens solutions against Achromobacter xylosoxidans biofilms using confocal microscopy Invest Ophthalmol Vis Sci 2013;54: EAbstract 523

McCanna D, Chang J, Subbaraman L, Jones L. Efficacy of contact lens solutions against Achromobacter xylosoxidans biofilms using confocal microscopy Canadian Optometry Schools Research Conference, Waterloo, Canada, 2013

McCanna D, Chang J, Subbaraman L, Jones L. Efficacy of contact lens solutions against Achromobacter xylosoxidans biofilms using confocal microscopy Tear Film & Ocular Surface International Conference, Sicily, Italy, 2013

McCanna D, Jones L. The effect of contact lens solutions on membrane permeability of Staphylococcus aureus aggregates Contact Lens & Anterior Eye 2013;36, S2:e40-e41

McCanna D, Jones L. Membrane permeability of staphylococcus aureus aggregates exposed to contact lens care solutions Canadian Optometry Schools Research Conference, Waterloo, Canada, 2013

McCanna D, Jones L. Membrane permeability of staphylococcus aureus aggregates exposed to contact lens care solutions Tear Film & Ocular Surface International Conference, Sicily, Italy, 2013

Subbaraman L, Thangavelu M, McCanna D, Jones L. Tear film cytokine analyses using a novel electrochemiluminescent array technique Invest Ophthalmol Vis Sci 2013;54: E-Abstract 4325

Subbaraman L, Thangavelu M, McCanna D, Jones L. Tear film cytokine analyses using a novel electrochemiluminescent array technique Canadian Optometry Schools Research Conference, Waterloo, Canada, 2013

Subbaraman L, Thangavelu M, McCanna D, Jones L. Quantification of lipocalin-1 in tears and contact lens deposits using a sandwich elisa technique Canadian Optometry Schools Research Conference, Waterloo, Canada, 2013

Subbaraman L, Thangavelu M, McCanna D, Jones L. Quantifying tear film inflammatory markers using a novel, multiplex electrochemiluminescent technique Tear Film & Ocular Surface International Conference, Sicily, Italy, 2013


McCanna D, Jones L. Membrane Permeability Of Staphylococcus Aureus Aggregates Exposed To Contact Lens Care Solutions Invest Ophthalmol Vis Sci 2012;53:ARVO E-Abstract 6089

Situ P, McCanna D, Gorbet M, Jones L. Confocal Imaging Of Hyper-reflective Corneal Epithelial Cells During And After Contact Lens Wear Invest Ophthalmol Vis Sci 2012;53:ARVO E-Abstract 4698


Kao E, McCanna D, Jones L. In vitro model for determining the viability and strength of adhesion of human lens epithelial cells to silicone NSERC 2020 Network Meeting (Orllia, Ontario), 2011

McCanna D, Mikkelsen S, Rahimi M, So F, Zhou Y, Sivak J, Jones L. Determining toxicity thresholds in ocular in vitro test batteries using benzalkonium chloride International Society for Contact Lens Research (Napa Valley, California), 2011

Professional Publications


McCanna D. Being “SunSmart”: Finding the right life-light balance ContactLensUpdate.com 2015


McCanna D. How safe is your lens case? ContactLensUpdate.com 2012