2010 – Centre for Ocular Research & Education

Scientific Presentations

2019

Bitton E, Srinivasan S, Elder M, Luensmann D, Jones L. Dry Eye Disease (DED) in Canada: A retrospective chart review American Academy of Optometry, Orlando, 2019 [ Show Abstract ]

Bose S, Phan CM, Rizwan M, Tse J, Yim E, Jones L. Release of FitC-Dextran from a MMP9-triggered material for corneal wound healing ISCLR, Singapore, 2019

Guthrie S, Moezzi A, Varikooty J, Woods J, Jones L. A bilateral dispensing evaluation of two different toric lens geometries
BCLA Conference, Manchester, UK, 2019 [ Show Abstract ][ PDF ]

Guthrie S., Woods J., Moezzi A., Varikooty J., Jones L. Comparing in-office evaluations to subjective evaluations for two toric lenses American Academy of Optometry, Orlando, 2019 [ Show Abstract ][ PDF ]

Purpose: To evaluate the performance of two monthly replacement silicone hydrogel toric lenses, comfilcon A toric and samfilcon A toric, using in-office assessments and subjective evaluations after 1 month.

Methods: A prospective, double-masked, bilateral, cross-over, dispensing study was conducted, where 45 subjects wore each lens type in a reusable, daily wear modality for 1 month, in a randomised order. Both in-office and subjective evaluations (0 [worst]-10 [best] scale) were completed at 1-month.

Results: Comfilcon A and samfilcon A toric lenses both performed well and similarly in all aspects of investigator lens evaluation. At 1-month, there was no significant difference for ‘fit acceptance’ grades (3.65 vs 3.58, p=0.29), ‘overall lens stability’ (3.56 vs 3.42, p=0.09) or for measures of logMAR high contrast acuity under ‘high illumination’ (-0.12 vs -0.12, p=0.63) or ‘low illumination’ (-0.10 vs -0.09, p=0.71). However, subject evaluations did show some significant differences related to comfort and vision. At 1-month comfilcon A toric lenses were rated significantly better for ‘overall comfort’ (8.1 vs 7.4, p=0.03). The difference in the 1-month ratings for ‘end of day comfort’ was not statistically significant (7.1 vs 6.7, p=0.15), however the ‘comfortable wear time’ was significantly longer for comfilcon A toric (8.9h vs 8.0h, p=0.03). For vision, comfilcon A toric was rated significantly better for ‘overall vision quality’ (8.1 vs 7.4, p=0.04) and ‘vision stability’ (8.0 vs 7.2, p=0.03). Subjects were asked to rate their ‘overall satisfaction’ and comfilcon A toric was rated significantly higher (7.8 versus 7.0, p=0.02). Subjects were also asked if they had a lens preference. Of those with a preference, significantly more subjects preferred the comfilcon A toric lens in terms of comfort (32 vs 10, p<0.01), dryness (28 vs 10, p=0.01) and overall (31 vs 13, p=0.01).

Conclusions: Although both comfilcon A and samfilcon A toric lenses both provided similar, high-level results for lens fit, stability and acuity, comfilcon A toric was rated statistically significantly higher in the subjective evaluations, specifically for comfort, vision, vision stability, overall satisfaction and comfortable wear time. These results illustrate that the patient experience cannot always be predicted from in-office evaluations.

Jones L, Jabeen A, Subbaraman L, Heynen M, Keir N, Srinivasan S. Method optimization to quantify four different neuropeptides in the human tear film Global Specialty Lens Symposium, Las Vegas, Nevada, 2019 [ PDF ]

Jones L, Pucker A, Jones-Jordan LA, Marx S, Powell D, Kwan JT, Srinivasan S, Sickenberger W. Clinical factors associated with contact lens dropout ISCLR, Singapore, 2019

Jones L, Pucker A, Jones-Jordan LA, Marx S, Powell D, Kwan JT, Srinivasan S, Sickenberger W. Impact of soft contact lens factors and compliance on contact lens dropout ISCLR, Singapore, 2019

Jones L, Subbaraman L, Dare E, Fung CK. Establishment of optimal culture media in human corneal epithelial wound healing models Global Specialty Lens Symposium, Las Vegas, Nevada, 2019 [ PDF ]

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 ]

Luensmann D, Woods J, Patel S. Validation of an online lens fitting app for two daily disposable toric lenses BCLA Conference, Manchester, UK, 2019 [ Show Abstract ][ PDF ]

Muntz A, Subbaraman L, Jones L. Comparison of LWE grades with histological measures of the lid wiper region in contact lens wearers ISCLR, Singapore, 2019

Muntz A, Subbaraman L, Jones L. LWE grades compared with histological measures of the lid wiper region in contact lens wearers American Academy of Optometry, Orlando, 2019 [ Show Abstract ]

Purpose: The clinical assessment of lid wiper epitheliopathy (LWE) is often considered inconsistent. The number of publications reporting an association between contact lens (CL) wear and LWE is approximately equal to those that report a lack of association. To date, the extent of LWE has not been evaluated using histological techniques. The aim of this study was to histologically evaluate the extent of LWE staining in a diverse CL wearing population.

Methods: Seventy-seven participants were enrolled into four study groups: asymptomatic soft, symptomatic soft, rigid CL, and non-CL wearers. Subjective symptoms and CL wear habits were recorded, and an ocular surface assessment conducted. LWE at both lid margins of both eyes was graded using lissamine green according to the Korb scale. Impression cytology samples were collected from all lid margins, according to a previously optimized technique. Samples underwent histological staining with Papanicolaou dyes for keratinization and up to 100 high-resolution images were captured per sample and stitched into large-scale, panoramic images. The extent of the muco-cutaneous junction and lid wiper conjunctival areas were dimensioned using ImageJ.

Results: The histologically measured width (mean ± SD) of the keratinized lid wiper conjunctiva for samples clinically graded 0, 1, 2 and 3 for sagittal width of LWE staining was 279 ± 169, 406 ± 241, 513 ± 260 and 694 ± 292 µm, respectively. Average clinical grades for LWE sagittal width for asymptomatic, symptomatic, rigid and non-CL wearers were 0.4 ± 0.7, 0.5 ± 0.7, 1.2 ± 1.0 and 0.07 ± 0.2, whereas the histologically measured width of the keratinized lid wiper conjunctiva was 339 ± 218; 314 ± 185; 532 ± 278 and 243 ± 112 µm, respectively. Only 43% of all histologically measured widths (n=159) corresponded to the clinical grading range for LWE staining width proposed by Korb. Clinical LWE grades were overestimated in 25% and underestimated in 32% of cases, compared to objective histological measures.
Both clinical and histological measures of LWE were similar between symptomatic and asymptomatic soft CL wearers (all p>0.05). However, LWE was significantly higher in the rigid lens and significantly lower in the non-lens wear group, both clinically and histologically, versus all other groups. Clinical grades were underestimated by up to three times relative to the histological width in all cases, and particularly in the non-CL group.

Conclusion: We provide a first account of a histologically dimensioned equivalent of clinically observed LWE. The ranges proposed by Korb for grading LWE may not correspond with histological dimensions of the lid wiper width. Knowledge of patients’ habits (such as the lens type worn) may bias clinicians’ clinical appraisal of LWE. These findings lend support to the development and implementation of objective, computerized dimensioning methods for use in clinical settings.

Ng A, Woods J, Jahn T, Jones L, Ritter J. The effect of a novel oral supplement containing omega-3 and omega-6 fatty acids on the signs and symptoms of dry eye disease American Academy of Optometry, Orlando, 2019 [ Show Abstract ][ PDF ]

Purpose: To determine the effect of daily intake of an essential fatty acid supplement on the signs and symptoms of dry eye disease (DED) in patients with moderate to severe symptoms. The supplement contains omega-3 fatty acids (1200mg eicosapentaenoic acid [EPA] and 300mg docosahexaenoic acid [DHA]) and the novel addition of an omega-6 fatty acid (150mg gamma-linoleic acid [GLA]).

Methods: This was a prospective, double-masked, randomized, parallel group pilot study. Participants were eligible if they had an Ocular Surface Disease Index (OSDI) score ≥ 23 and had not taken omega-3 or -6 supplements in the previous 3 months. Participants were randomized to use one of two liquid supplements: the treatment supplement (EPA, DHA and GLA combination), or the placebo supplement (coconut and olive oil). Participants were instructed to take one teaspoon, once daily for three months. In addition to keeping a diary, an omega-3 index blood test was conducted at baseline and 3 months to confirm compliance of supplement use. At baseline, 1 and 3 months the following assessments were conducted: OSDI questionnaire, non-invasive tear break-up time (NITBUT), tear meniscus height (TMH), tear osmolarity, ocular redness and surface staining, Schirmer test and meibography to assess meibomian gland (MG) dropout.

Results: Fifty participants completed the study: 24 randomized to the treatment group, 26 randomized to placebo. Participants were 95% compliant with daily dosing over the study period. After 3 months of supplement use, a 34% increase in omega-3 index blood values was observed in the treatment group (baseline: 5.3±0.8, 3 months: 8.0 ± 2.1, p< 0.001) whereas there were no changes in the placebo group (baseline: 4.8 ± 0.8, 3 months: 4.8 ± 0.6, p=0.948). At baseline, the mean OSDI score of all participants was 52.2±16.5, with no significant difference between groups. There was a statistically significant improvement in OSDI score at 3 months for both groups (treatment 13.4 point reduction, p=0.003; placebo 7.8 point reduction, p=0.022). Those participants with the most severe OSDI scores (>50) at baseline demonstrated a clinically significant improvement with the treatment supplement (n=13, 20.8 point reduction, p=0.002) at 3 months compared to the placebo group (n=12, 8.4 point reduction, p=0.066). There were no clinically significant changes in NITBUT, TMH, tear osmolarity, ocular redness and surface staining, Schirmer test or MG dropout, (all p>0.05).

Conclusions: Omega-3 supplementation is an established therapeutic option for DED. This cohort of participants who were predominantly in the severe DED category by OSDI classification, experienced clinically meaningful improvements in their dry eye symptoms associated with supplementation with EPA, DHA and GLA. The addition of the omega-6 GLA in this formulation may have contributed to the significant improvement in dry eye symptoms.

Phan C, Walther H, Jones L.. Development of a blink model for testing contact lenses American Academy of Optometry, Orlando, 2019 [ Show Abstract ][ PDF ]

Phan CM, Qiao H, Jones L. A simple method to synthesize PVA hydrogels Canadian Biomaterials Society, Quebec, 2019 [ PDF ]

Phan CM, Qiao H, Shinde R, Jones L. Development of an in vitro eye model with polyvinyl alcohol The Association for Research in Vision and Ophthalmology. Vancouver, British Columbia, 2019 [ Show Abstract ][ PDF ]

Purpose: The purpose of this study was to develop a simple method to synthesize an in vitro eye model using polyvinyl alcohol with similar wettability and water content as the cornea, sclera, and lens.

Methods: Bovine eyes, donated by an abattoir, were used as the ex vivo eye model for comparison. The eyes were dissected fresh, and the wettability and water content for the cornea, sclera, lens, and vitreous humour were measured. Four molecular weights of polyvinyl alcohol, 89-98 kDa, 85-124 kDa, 130 kDa, and 146-186 kDa, were tested. The monomer was added to a mixed solvent of dimethyl sulfoxide and Milli-Q water to achieve a range of concentrations between 5 – 30 % w/v. The mixture was heated at 120oC for 3 hours, and polymerized at -30o C for 3 hours. The gels were then equilibrated with Milli-Q water for 3 days before characterization. A model eyeball from polyvinyl alcohol was also synthesized using a custom mould.

Results: The bovine cornea had the highest wettability, with the lowest advancing contact angle (28.0 ± 7.2°), followed by the lens (64.0 ± 4.6°) and sclera (56.73 ± 6.5°). The contact angles for the polyvinyl alcohol gels ranged between 40.4 ± 2.5° and 61.6 ± 4.7° for various gels. The vitreous humour had the highest water content (98.7 ± 0.2 %), followed by the cornea (80.9 ± 1.2%), sclera (64.8 ± 0.7%), and lens (59.7 ± 7.5%). The water content for the gels decreased with increasing concentrations of the polyvinyl alcohol (p<0.001), and ranged between 66.1 ± 0.1 % to 91.4 ± 0.2 %. The eye models made from polyvinyl alcohol were translucent, smooth, wettable, lubricous, and pliable.

Conclusion: This study presents a simple method to synthesize hydrogels from polyvinyl alcohol, which can be formulated to closely match the wettability and water content of a bovine cornea, sclera, and lens. The method can be easily modified in future studies to incorporate other reagents. The eye model synthesized from this study could be used as a potential model to study in vitro tear-break up or drug absorption.

Phan CM, Walther H, Jones L. Mass spectrometry detection of phosphatidyl choline from delefilcon A Canadian Biomaterials Society, Quebec, 2019 [ PDF ]

Phan CM, Walther H, Jones L. Development of a polymeric eye model for foreign body removal Canadian Biomaterials Society, Quebec, 2019

Phan CM, Walther H, Qiao H, Jones L. Development of a novel in vitro blink model Canadian Biomaterials Society, Quebec, 2019 [ PDF ]

Phan CM, Walther H, Qiao H, Jones L. The development of an eye model that truly blinks ISCLR, Singapore, 2019

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

Rappon J, Woods J, Jones D, Jones L. Tolerability of novel myopia control spectacle designs Invest Ophthalmol Vis Sci 2019;E-abstract 5845

Rappon JM, Chalberg TW, Neitz M, Woods J, Jones D, Jones L Neitz J. Clinical Development of a Novel Myopia Treatment for Myopia Management The 17th International Myopia Conference, Tokyo, Japan, 2019

Tichenor A, Cofield S, Gann D, Elder M, Ng A, Walsh K, Jones L, Nichols J. Frequency of contact lens complications between contact lens wearers using multipurpose solutions versus hydrogen peroxide in the United States and Canada American Academy of Optometry, Orlando, 2019 [ Show Abstract ]

Purpose: To retrospectively compare frequency and likelihood of contact lens complications in long-term soft contact lens (CL) users of hydrogen peroxide (PXD) and multipurpose solutions (MPS).

Methods: This was a multicenter, retrospective chart review study of soft CL patient records. The study was conducted at two academic clinic sites, the University of Alabama at Birmingham School of Optometry and CORE, School of Optometry & Vision Science, University of Waterloo, and across five private practice clinical sites (three in the US and two in Canada). Records of established, adult soft CL wearers were reviewed from the three most recent full examination visits. Patients must have used the same CL solution technology (either MPS or PXD) documented at the first and last visit for at least three years. Data collected included demographics, CL solution, and any complications for either eye. Univariate analyses were conducted using Chi-Square or Fisher’s Exact test for categorical measures, as applicable. Covariate adjusted logistic regression models were used for categorical outcomes using Likelihood Ratio Chi-Square Test.

Results: In total, there were 1137 subjects included across the seven clinical locations, with 670 (59%) MPS users and 467 (41%) PXD users. The MPS users were 57% female with a mean (±SD) age of 42.9 (±14.7) years. The PXD users were 43% female with a mean age of 43.2
(±14.2) years. At the academic clinic sites, 428 records (38%) were reviewed of which 244 (57%) were MPS users. At the private practice sites, 709 records (62%) were reviewed and 426 (60%) were MPS users. Of all subjects, 706 (62%) experienced at least one complication over three visits; 409 were MPS users and 297 were PXD users. The most common complication was papillae (n=311, 27%) followed by hyperemia (n=242, 21%) and discomfort (n=240, 21%).There was no difference in the proportion of subjects experiencing at least one complication over the three visits between MPS (61%) and PXD (64%) users (p=0.38). Nonetheless, MPS users were more likely to report discomfort at least one time over the three visits compared to PXD users (p=0.04). Infectious keratitis was experienced by 25 subjects (2%); 19 were MPS users and 9 were PXD users (p=0.60).

Conclusion: While no differences were found in the frequency of contact lens complications between MPS and PXD users, the ocular surface health benefits of PXD should be considered when determining the best lens care option for patients. In addition, MPS users were more likely to report low levels of discomfort at least once over the time period reviewed. Therefore, PXD may be a beneficial solution alternative in CL users who report discomfort.

Varikooty J, Woods J, Jones L. Visual performance with a daily disposable silicone hydrogel center-near progressive design multifocal lens with two independent intermediate zones BCLA Conference, Manchester, UK, 2019 [ Show Abstract ][ PDF ]

Walther H, Chan V, Phan CM, Jones L. Modelling non-invasive tear break-up times of soft lenses using a sophisticated in vitroblink platform Invest Ophthalmol Vis Sci 2019;60, E-abstract 6328 [ Show Abstract ][ PDF ]

Walther H, Phan CM, Jones L.. Detection of Phosphatidylcholine from Delefilcon A Contact Lenses using Mass Spectrometry American Academy of Optometry, Orlando, 2019 [ Show Abstract ][ PDF ]

Purpose: The gradual release of phospholipids from contact lenses could potentially stabilise the tear film over the front surface of the lens and increase comfort during wear. Delefilcon A (Dailies Total 1) contact lenses inherently contain phosphatidylcholine (PC), a zwitterionic phospholipid that is a potent wetting agent and lubricant found in the human tear film.Due to its molecular structure, PC is relatively difficult to detect using standard spectrophotometric techniques. However, it has been detected previously at low concentrations using ultra-high performance liquid chromatography mass spectrometry (UHPLC-MS). The aim of this study was to detect the presence of PC from contact lens extracts of delefilcon A lens materials and its blister packaging solution using UHPLC-MS.

Methods: PC was extracted from the contact lens and the blister pack using 3 mL of 2:1 chloroform: methanol and 0.5 mL of monosodium phosphate aqueous buffer. The chloroform layer containing PC was collected, dried down using nitrogen gas, and then resuspended in 100 µL sample buffer. A PC standard, L-α-Phosphatidylcholine (Sigma Aldrich, St. Louis, MO), was prepared at 8 pmol/µL. The samples were analyzed using UHPLC-MS on a Waters and Thermo/Dionex system using a multi-step, reversed-phase gradient consisting of A: 60:40 acetonitrile: water and B: 90:10 isopropanol: acetonitrile, both with 10mM ammonium formate and 0.1% formic acid. The flow was set at 250 uL/min, the column was kept at 45C, sample tray at 4C, and injection volume was 10 uL.

Results: During the electrospray process, L-α-Phosphatidylcholine, also known as 1,2-diacyl-sn-glycero-3-phosphocholine, protonates to form C42H10NO8P+, with a theoretical mass m/z = 758.57. Elution peaks from the UHPLC-MS corresponding to PC were detected in the PC standard at m/z = 758.5-758.6. Other elution peaks for PC were also detected at m/z = 760.58-760.60, 786.60-786.61, and 788.62-788.63. These same peaks, with nearly identical retention times, were detected in both the blister pack solution and contact lens extracts for delefilcon A.

Conclusion: These results indicate that PC is present within the delefilcon A material and also in its blister pack solution. Future studies will determine if PC is released over time from the contact lens using a novel in vitro blink platform.

Wong S, Bhamra T, Jones L, Tighe B. Subjective assessment of contact lens handling: what can we learn from the past? BCLA Conference, Manchester, UK, 2019 [ Show Abstract ]

Purpose: This study examines correlations between clinician-assessed subjective ease of handling of soft contact lenses, and laboratory-assessed physicochemical characteristics. High CL dropout rates caused by handling problems and difficulties in objectively measuring handling performance underline the clinical importance of such studies. The first stage involved assessment of conventional hydrogel lenses widely available in the 1980s, some currently available and some not. This is a platform for assessment of SiHy lenses in which effects of inherently lower coefficients of friction need to be assessed in parallel.

Methods: The prospective, single-masked study involved participants (no previous long-term CL wear history) each asked to rate the ease of handling of 23 different types of soft CLs on a 10-point continuous scale. Primary physicochemical data (e.g. EWC, lens thickness and mass, tensile modulus) were collected and additionally transposed into derived quantities (e.g. stiffness factor, plasticising factor).

Results: The data for the conventional hydrogels revealed:
• The early conventional hydrogels Hydrocurve II and SofLens 38 had lowest mean ± SD handling scores of 6.08 ± 1.56 and 6.08 ± 1.98, respectively.
• Excelens had the highest mean handling score of 8.67 ± 1.78.
• No significant correlation was found between handling and the equilibrium water content (Spearman’s r = -0.34, p = 0.11) or centre thickness (Spearman’s r = 0.33, p = 0.13)
• Handling of hydrogel CLs was strongly correlated with the stated modulus (Spearman’s r = 0.70, p = 0.02), the equilibrium water content (Spearman’s r = 0.64, p = 0.04) and centre thickness (Spearman’s r = 0.76, p = 0.01).

Conclusions: The poster will discuss detailed lens data including graphical presentation of “derived” factors combining thickness and modulus together
with the observations that SiHy CLs had higher mean handling scores than hydrogel CLs. All current CLs had mean handling scores of > 6.0.

Woods J, Varikooty J, Lumb E. Validation of a multifocal contact lens online fitting app BCLA Conference, Manchester, UK, 2019 [ Show Abstract ][ PDF ]

Purpose: Online tools to assist complex contact lens fittings are becoming more commonplace, replacing traditional fitting guides. Data from a daily disposable multifocal lens refit study were used to conduct a post-study comparison of the multifocal lens power recommendations of one such online tool, the OptiExpert app, with those powers determined by investigators who used the traditional fitting guide.

Methods: For 48 habitual multifocal lens wearers, subjective refraction data (sph, cyl, add, ocular-dominance) were determined by investigators who refit them with a somofilcon A lens, using the fitting guide. At an ‘optimization visit’ 3-10 days later, lens power was re-assessed and new powers dispensed if necessary. Subsequent to study completion, subjects’ refraction data was input to the online app, and the
recommended power for each eye (App-Rx) was compared to the power dispensed at the optimization visit (Optimized-Rx). Bland-Altman and correlation analyses were conducted to measure agreement between methods.

Results: The 48 presbyopes (38F:10M) had a mean (±SD) age of 55.6 (±7.3SD, range 41-67) years. Subjective refraction range across all 96 eyes was +5.25 to -6.75DS, all with cylinder ≤-1.00D. Reading add ranged between +1.25 to +2.50D. At the optimization visit, 10% of eyes (10 eyes across 10 subjects) required change in lens power, meaning 100% of eyes were successfully fit with just 1 additional lens. The App-Rx was significantly correlated with Optimized-Rx (r=0.996 and p<0.0001). Bland Altman analysis showed a mean difference (and 95% limits of agreement) between App-Rx and Optimized-Rx of 0.08D (-0.58 to +0.42). The app predicted powers were within 0.25D of the investigatoroptimized lens powers in 82% of eyes, within 0.50D in 96% eyes.

Conclusions: The OptiExpert app recommended CL powers were in close agreement with those determined by investigators. Therefore, OptiExpert multifocal app is a useful tool to aid somofilcon A multifocal fitting success.

Yee A, Chan V, Heynen M, Jones L. A radioactive labelling technique for evaluating the uptake and release of myristamidopropyl dimethylamine (MAP-D) from contact lenses Invest Ophthalmol Vis Sci 2019;E-abstract 6370 [ Show Abstract ][ PDF ]

Purpose: The uptake and subsequent release of biocides from contact lens (CL) materials is of relevance as it has been linked with outbreaks of microbial keratitis and potential cytotoxic responses. Previous uptake and release studies of myristamidopropyl dimethylamine (MAP-D; ALDOX®) have used light-scattering techniques, which are time consuming and have relatively low sensitivity. The purpose of this study was to develop a radioactive labelling technique in order to improve the accuracy and sensitivity of biocide uptake and release to CL materials.

Methods: Four soft CL materials (lotrafilcon A, balafilcon A, senofilcon A, etafilcon A) were tested (N=4). Radioactive (14C) MAP-D was purchased from Moravek Inc. (California, USA). The lenses were incubated in PBS (ISO 18369-3) solution containing radioactive MAP-D (5µg/mL) for 8 hours. After the incubation period of 8 hours, the lenses were placed into the release condition. The release of MAP-D was assessed over 24 hours in 2 mL of PBS. Aliquots were removed at 0.25, 0.5, 1, 2, 4, 8, and 24 hour time points and added to scintillation fluor (PerkinElmer, USA). The samples were counted for their radioactive signal (CPM) using the LS6500 Beckman Coulter liquid scintillation beta counter (Beckman Coulter, ON, CA). The CPM was converted to µg of MAP-D based on a standard curve.

Results: After the incubation period of 8 hours, the uptake of MAP-D by etafilcon A (2.78±0.19µg) was significantly different than lotrafilcon A (4.69±0.1µg, p<0.01), balafilcon A (4.55±0.31µg, p<0.01), and senofilcon A (4.35±0.13µg, p<0.01). The total amount of MAP-D released by etafilcon A (1.41±0.09µg) was significantly greater than lotrafilcon A (0.27±0.02µg, p<0.01), balafilcon A (0.23±0.04µg, p<0.01), and senofilcon A (0.21±0.01µg, p<0.01). The results demonstrate that the uptake of MAP-D was higher for all silicone hydrogel (SH) lenses and lower for the conventional hydrogel lens. The release profile of etafilcon A was greater than the SH lenses, with a burst release of 0.33µg at 0.25 hr.

Conclusions: Radioactive labelling of MAP-D offers a highly sensitive, accurate way of assessing the uptake and release profiles of biocides to CL materials. Future studies using this methodology will investigate the profiles for other biocides, such as polyhexamethylene biguanide (PHMB), a common biocide used in CL solutions.