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Peer-reviewed articles

2022

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.

2020

Wolffsohn,J. S., Calossi,A., Cho,P., Gifford,K., Jones,L., Jones,D., Guthrie,S., Li,M., Lipener,C., Logan,N. S., Malet,F., Peixoto-de-Matos,S. C., González-Méijome,J. M., Nichols,J. J., Orr,J. B., Santodomingo-Rubido,J., Schaefer,T., Thite,N., van der Worp,E., Tarutta,E., Iomdina,E., Ali,B. M., Villa-Collar,C., Abesamis-Dichoso,C., Chen,C., Pult,H., Blaser,P., Parra Sandra Johanna,G., Iqbal,F., Ramos,R., Carrillo Orihuela,G., Boychev,N. Global trends in myopia management attitudes and strategies in clinical practice – 2019 Update Cont Lens Anterior Eye 2020;43(1):9-17 [ Show Abstract ]

Purpose: A survey in 2015 identified a high level of eye care practitioner concern about myopia with a reported moderately high level of activity, but the vast majority still prescribed single vision interventions to young myopes. This research aimed to update these findings 4 years later. Methods: A self-administrated, internet-based questionnaire was distributed in eight languages, through professional bodies to eye care practitioners globally. The questions examined: awareness of increasing myopia prevalence, perceived efficacy of available strategies and adoption levels of such strategies, and reasons for not adopting specific strategies. Results: Of the 1336 respondents, concern was highest (9.0 ± 1.6; p < 0.001) in Asia and lowest (7.6 ± 2.2; p < 0.001) in Australasia. Practitioners from Asia also considered their clinical practice of myopia control to be the most active (7.7 ± 2.3; p < 0.001), the North American practitioners being the least active (6.3 ± 2.9; p < 0.001). Orthokeratology was perceived to be the most effective method of myopia control, followed by pharmaceutical approaches and approved myopia control soft contact lenses (p < 0.001). Although significant intra-regional differences existed, overall, most practitioners did not consider single-vision distance under-correction to be an effective strategy for attenuating myopia progression (79.6 %), but prescribed single vision spectacles or contact lenses as the primary mode of correction for myopic patients (63.6 ± 21.8 %). The main justifications for their reluctance to prescribe alternatives to single vision refractive corrections were increased cost (20.6 %) and inadequate information (17.6 %). Conclusions: While practitioner concern about myopia and the reported level of activity have increased over the last 4 years, the vast majority of eye care clinicians still prescribe single vision interventions to young myopes. With recent global consensus evidence-based guidelines having been published, it is hoped that this will inform the practice of myopia management in future.

2015

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.

2013

Woods,J., Guthrie,S. E., Keir,N., Dillehay,S., Tyson,M., Griffin,R., Choh,V., Fonn,D., Jones,L., Irving,E. Inhibition of defocus-induced myopia in chickens Investigative Ophthalmology and Visual Science 2013;54(4):2662-2668 [ Show Abstract ]

PURPOSE. To determine the effect of wearing a lens with a unique peripheral optical design on the development and progression of defocus-induced myopia in newly hatched chickens.METHODS. Eighty-five newly hatched chickens underwent bilateral retinoscopy and A-scan ultrasound to determine their refractive error and axial length. They were randomly divided into Control and two Test groups, in which each chicken was fitted with a goggle-lens over the right eye, with the left eye remaining untreated. The Control group wore a lens of power - 10.00 diopters (D) of standard spherical optical design. The two Test lenses both had a central optical power -10.00 D, but used different peripheral myopia progression control (MPC) designs. For all groups, retinoscopy was repeated on days 3, 7, 10, and 14; ultrasound was repeated on day 14.RESULTS. On day 0 there was no statistical difference in refractive error (mean +6.92 D) or axial length (mean 8.06 mm) between Test and Control groups or treated and untreated eyes (all P > 0.05). At day 14, 37 (43.5%) of 85 chickens had not experienced goggle detachment and were included in the final analyses. In this cohort there was a significant refractive difference between the treated eyes of the Control group (n = 17) and those of Test 1 (n = 14) and Test 2 (n = 6) groups (both P < 0.01): Control -4.65 ± 2.11 D, Test 1 +4.57 ± 3.11 D, Test 2 +1.08 ± 1.24 D (mean ± SEM). There was also a significant axial length difference (both P < 0.01): Control 10.55 ± 0.36 mm, Test 1 9.99 ± 0.14 mm, Test 2 10.17 ± 0.18 mm.CONCLUSIONS. Use of these unique MPC lens designs over 14 days caused a significant reduction in the development of defocus-induced myopia in chickens; the degree of reduction appeared to be design specific. © 2013 The Association for Research in Vision and Ophthalmology, Inc.

Scientific Presentations

2023

Luensmann D, Tucker AW, Voltz K, Guthrie S, Woods J, Vega J. Orthokeratology Lens Fit Success Using a New Software Global Specialty Lens Symposium, Las Vegas, Jan 20, 2023 [ Show Abstract ][ PDF ]

Purpose: To determine orthokeratology (Ortho-K) lens parameters in as few steps possible is beneficial for the eye care professionals (ECPs) and patient and this study investigated how the new Visavy software can help to inform the initial lens parameters.

Methods: This prospective study recruited participants aged 6-35 years and fit them with Paragon CRT or Paragon CRT Dual Axis Ortho-K lenses (CooperVision Specialty EyeCare), worn every night for 1 month. Topography images (Oculus Keratograph 5) were uploaded in the software and together with additional entries for subjective refraction and white-to-white corneal diameter, the software populated the initial lens parameters. Lens modifications for fit and/or vision were permitted at any of the following three timepoints: the dispense visit, after the first night or after one week of wear. Visual acuity (LogMAR) was determined with subjective refraction at baseline and unaided after one month of Ortho-K wear. Subjective comfort was collected after the first lens application and after one month (0-10 scale, 10=very comfortable). Subjective vision clarity was collected via home ratings just after lens application on the first night and after one month (0-10 scale, 10=Sharp, clear/ very good vision).

Rresults: Sixteen participants (12F:4M), mean age 11.3±3.2 years [7 to 18 years] were included in the analysis. The mean refraction of all 32 eyes was Sph -2.80±1.38DS [-1.00 to -5.75DS] and Cyl -0.56±0.46DC [0.00 to -1.25DC]. Best-corrected visual acuity prior to lens insertion was 0.00±0.01 logMAR and unaided vision after 1 month was +0.09±0.11 logMAR. Remaining correction after 1 month was Sph -0.12±0.46DS [+0.75 to -1.25DS]. Almost all lens designs predicted by the software were considered acceptable (fit and vision) by the investigator with just one lens requiring a modification after the first night due to corneal staining. Comfort ratings were significantly better after 1 month (7.8 ± 1.4) compared to the dispense visit (5.2 ± 2.2)(p<0.01). Vision clarity ratings were also better after 1 month (8.4 ± 1.5) compared to after the first night (7.0 ± 3.2)(p=0.02).

Conclusions: The Visavy software could help determine acceptable lens parameters for the Paragon CRT or Paragon CRT dual axis Ortho-K lenses in 97% of eyes (31 of 32 eyes). This high initial success rate has the potential to reduce chair time and assist ECPs to confidentially fit these lenses to their patients.

2022

Guthrie S, Luensmann D, Woods J, Vega J, Orsborn G. Acceptability of different lens materials in habitual wearers of frequent replacement lenses American Academy of Optometry, San Diego, 2022 [ Show Abstract ]

Purpose: New soft lens materials frequently enter the market for different lens wear modalities and the question remains as to how these compare to established products. The purpose of this study was to compare the subjective performance of two silicone hydrogel (SiHy) lenses that employ different technologies to improve wearer comfort: the recently introduced lehfilcon A (leh-A)(Alcon) lens employs ‘Water Gradient Technology’ and the established comfilcon A (com-A)(CooperVision) lens employs ‘Aquaform Technology’.

Methods: This study was a prospective, bilateral, double-masked, randomized, cross-over, daily-wear design involving two different monthly replacement SiHy lens types (leh-A and com-A). Young adults who habitually wore frequent replacement spherical lenses were recruited at four clinical sites in the US. Each of the two lens types was worn for one month and participants used their habitual care products. Throughout each month, participants recorded their lens wear comfort on several days at home and during study visits (0-10 scale, 10=can’t feel the lenses) and answered agreement (5-point strongly/slightly agree, neither agree or disagree, strongly/slightly disagree) and preference (5-point strong/slight prefer first/second lens pair, no preference) questions. Statistical differences were determined by Wilcoxon matched pairs and binomial testing.

Results: Sixty-three participants (44F:19M), mean age 27.5 ± 4.8 years [18 to 35 years] were included in the analysis. The mean spherical refraction was -3.12 ± 1.6D [-6.50D to +1.25D]. Overall comfort ratings on Days 1, 14, 27 were 8.5, 8.0, 7.7 for com-A and 8.8, 8.2, 8.1 for leh-A. For both lens types, comfort ratings were higher at the beginning of the month (p<0.01), with no statistically significant difference between lenses for any time point (all p>0.05). The mean drop in overall comfort after one month of wear was the same for both lens types (com-A: 0.7, leh-A: 0.7, p>0.05). At 1-month, participants rated overall satisfaction with comfort similarly (com-A: 8.0, leh-A: 7.8, p>0.05) and there was no difference in the number of participants preferring each lens when considering comfort on application (26:24), removal (27:24) and overall (29:27)(com-A:leh-A, all p>0.05). For each lens type, a similar number of participants agreed compared to disagreed with the statement “These lenses feel like nothing even after one month of wear” (each lens type p>0.05) and no statistically significant differences were found between the lens types (p>0.05).

Conclusion: Despite significant differences in material composition and surface technologies between com-A and leh-A, the subjective contact lens comfort experience over 1 month was similar. The preference ratings further highlight the importance of providing patients with different options and deciding together which lens type is best for them to help ensure long-term success with lens wear.

Luensmann D, Guthrie S, Woods J, Vega J, Orsborn G. Performance evaluation of two toric multifocal contact lenses available in different parameter increments Nederlands Contactlens Congres, Veldhoven, Netherlands, Jun 27, 2022 [ Show Abstract ]

Purpose:
Toric multifocal contact lenses (TMFCLs) offer vision correction to the astigmatic presbyopic population. The vision outcome was determined in existing soft lens wearers when fit with two TMFCLs, available in different parameter steps; 5 vs 10 degree axis increments and 6 vs 2 near adds.

Methods:
In a multisite, prospective, randomised, participant-masked, 1-month crossover, bilateral dispensing study, habitual soft lens wearers ≥42years old with minimum 0.75DC astigmatism were fit with two monthly replacement, silicone hydrogel TMFCLs (comfilcon A (com-A); CooperVision, samfilcon A (sam-A); Bausch & Lomb). The manufacturer’s fitting guides were followed, and lens prescriptions were optimised after 3-7 days of wear, before the 1-month wear period. Vision outcomes included visual acuity (LogMAR), 3-point ratings (met/exceeded or did not meet my needs), and 5-point preference ratings (strongly/slightly prefer lens 1 or 2, no preference).

Results:
Fifty-six participants age 53.6±8.6 years were included in the analysis (OD mean(±SD): sph -2.47D(±2.38), cyl -1.27D(±0.47), add 1.88D(±0.48)). For com-A axes ending in 5 degrees were chosen for 47% of eyes and each add power was prescribed. After one month, LogMAR acuity was similar for both lens types for distance, intermediate and near (p>0.05 for all). On days 7, 14 and 28 participants rated that com-A met their needs better for ‘Overall speed and ability to change focus between distances’, ‘Vision stability throughout the day’ and ‘Overall vision clarity’ (p<0.05 for all); other ratings showed no difference between lenses. A preference was found for com-A for vision clarity for ‘intermediate tasks’ (p=0.03), ‘near tasks’ (p=0.01), ‘during digital device use' (p<0.01) and for ‘overall vision clarity’ (p=0.01). No preference was indicated for distance tasks (p>0.05).

Conclusion:
The higher accuracy of prescribing for com-A due to the 5-degree axis steps and the 6 near adds may have contributed to the better vision outcomes reported with com-A.

Schulze M, Luensmann D, Ng A, Guthrie S, Woods J, Jones L. Performance of verofilcon A daily disposable contact lenses in digital device users American Academy of Optometry, San Diego, 2022 [ Show Abstract ][ PDF ]

Purpose: To evaluate the performance of Precision1 (verofilcon A) daily disposable (DD) contact lenses (CLs) in habitual CL wearers who undertake substantial digital device use.

Methods: CL wearers between 18-40 years of age who reported a daily digital device use of ≥6 hours while wearing their habitual CLs participated in the study. Eligible participants were dispensed with verofilcon A DD CLs for a period of 12-16 days and were asked to wear these for at least 5 days/week and at least 10 hours/day, while continuing their normal routine of ≥6 hours digital device use. At the 2-week follow-up visit, participants rated their experience with the study lenses on a 0 to 100 scale, with 100 being best, and reported their lens wear times and digital device use. Comfort, dryness and clarity of vision ratings with verofilcon A lenses were collected directly after lens insertion, after 6 hours of digital device use, just before removal, and for overall lens performance. Participants also completed a 4-point (strongly agree, slightly agree, slightly disagree, strongly disagree) Likert scale-based questionnaire. Subjective ratings were not normally distributed, therefore non-parametric analysis was conducted and data are reported as median (range). The Likert scale responses were analyzed using binomial testing.

Results: Thirty-two participants completed the study (27F:5M), mean age of 25.8 ± 6.0 years (range 19-40). Participants reported total and comfortable CL wear time of 14 hours (10-17) and 11.6 hours (2.8-16), respectively, and digital device use of 8.5 hours (6-18) on a typical day. Subjective ratings for overall lens performance after 2 weeks of CL wear were high, with median ratings of 90 (68 – 100) for comfort, 90 (52-100) for dryness and 95 (70-100) for clarity of vision. There were no differences in comfort, dryness and clarity of vision ratings over the course of a typical day, with similar ratings at insertion, after 6 hours of digital device use and just before removal (all p≥0.05). The majority of participants agreed that the study lenses provided good comfort (28/32 subjects; p<0.01) and good vision (29/32; p<0.01) all day long. Considering CL performance when using digital devices for 6 hours, the majority of participants were satisfied with CL comfort (27/32; p<0.01) and vision (29/32; p<0.01) and most agreed that the verofilcon A lenses provided good performance (26/32; p<0.01). Most study participants (24/32; p<0.01) agreed that they did not experience any eye strain during digital device use while wearing verofilcon A lenses. No significant lens-related ocular health findings were observed after 2 weeks of wear.

Conclusions: After 2 weeks of wear, most participants rated the performance of verofilcon A DD CLs highly, with median overall performance ratings for comfort, dryness and vision all 90 on a 0 to 100 scale.

2021

Guthrie S, Luensmann D, Woods J, Vega J, Orsborn G. Relationships between success factors in daily disposable multifocal lenses American Academy of Optometry, Boston, 2021 [ Show Abstract ]

PURPOSE:
To evaluate relationships between subjective responses to two daily disposable multifocal contact lenses (MFCLs), stenfilcon A (stenA-MF) and delefilcon A (delA-MF).

METHODS:
Habitual MFCL wearers participated in a prospective, randomized, subject-masked, bilateral crossover study at five optometry offices. Subjects wore each study contact lens (SCL) for 2 weeks and answered lens handling (0-10), satisfaction (1-fell short of needs; 2-met needs; 3-exceeded needs) and agreement (4-strongly agree; 3-slightly agree; 2-slightly disagree; 1-strongly disagree) questions. Responses were analyzed using Wilcoxon Matched-Pairs testing for differences between lens types. Spearman correlations were done for each lens type separately.

RESULTS:
Fifty-eight subjects (50F:8M; mean 54.4 ± 7.3 years) were included in the analysis; mean spherical-equivalent refraction OD: -1.10 ± 2.7D [-6.50D to +3.75D], add +2.00 ± 0.4D [+1.00D to +2.50D]. Subjects had greater agreement for stenA-MF compared to delA-MF for “SCL met my needs for vision” (stenA-MF: 3.3; delA-MF: 2.9; p=0.02) and for “I would like to wear SCL in the future” (stenA-MF: 2.9; delA-MF: 2.6; p=0.03). For each SCL there was a significant correlation between responses to these two questions (stenA-MF: rs=0.81; delA-MF: rs=0.84; p<0.05). For stenA-MF, “SCL met my needs for vision” was significantly correlated (p<0.05) with Day 13 (D13) end-of-day (EOD) satisfaction with comfort (rs=0.36) and dryness (rs=0.39). There were no significant correlations for delA-MF (comfort: rs=-0.06; dryness: rs=0.11; both p>0.05). Similarly, for stenA-MF, “I would like to wear SCL in the future” was significantly correlated (p<0.05) with D13 EOD satisfaction with comfort (rs=0.46) and dryness (rs=0.41). Again, there were no significant correlations for delA-MF (comfort: rs=0.03; dryness: rs=0.10; both p>0.05). There were no statistically significant differences between stenA-MF and delA-MF for D13 EOD satisfaction with comfort (stenA-MF: 2.0; delA-MF: 2.0; p=0.72) or dryness (stenA-MF: 1.9; delA-MF: 1.9; p=0.88). For both SCLs, EOD satisfaction with comfort was significantly correlated (all p<0.05) with EOD satisfaction with dryness (stenA-MF: rs=0.71; delA-MF: rs=0.67), ease of handling for removal (stenA-MF: rs=0.35; delA-MF: rs=0.51) and comfortable wear time (CWT) (stenA-MF: rs=0.30; delA-MF: rs=0.37). CWT was similar for both SCLs (stenA-MF: 11.6 hours; delA-MF: 11.0; p=0.08), but stenA-MF was rated significantly better for ease of handling for removal (stenA-MF: 8.4 vs delA-MF: 7.6, p=0.02).

CONCLUSIONS:
While end-of-day comfort and dryness are important factors in contact lens success, these results suggest that satisfaction with vision for these multifocal lens wearers was a better indicator (both rs>0.80) of their desire to continue wearing the multifocal lenses in the future.

Guthrie S, Luensmann D, Woods J, Vega J, Orsborn G. Comfort and vision correlations in daily disposable multifocal lenses BCLA Virtual Clinical Conference & Exhibition, 2021 [ Show Abstract ][ PDF ]

Purpose: To evaluate the subjective responses to two daily disposable multifocal contact lenses (MFCLs), stenfilcon A (stenA-MF) and delefilcon A (delA-MF), and to see if there is a correlation between preferences based on vision and comfort.
Method: Habitual MFCL wearers participated in a prospective, randomized, subject-masked, bilateral crossover study at five sites. Subjects wore the study MFCLs for 2-weeks each and then responded to preference questions comparing the study lenses for comfort and vision for near, intermediate, distance, digital device use and overall at all distances. A 5-point Likert scale (Strong/slight preference for each lens or no preference) was used.
Results: For the 58 eligible subjects (50F:8M; mean 54.4±7.3 years), preferences were as follows (#stenA-MF:#delA-MF, p-value): subjects favoured stenA-MF for overall comfort (26:9, p=0.03), intermediate vision (25:8, p=0.03), overall vision (34:10, p=0.04) and vision for digital device use (27:10, p=0.03). Preferences were equivocal for near vision (29:14, p=0.06) and distance vision (13:19, p=0.51). Correlation analysis found that the lens preference based on overall comfort was significantly correlated (all p<0.05) with lens preference based on vision at near (rs=0.61), intermediate (rs=0.48), overall (rs=0.65) and for digital device use (rs=0.66). Lens preference based on overall vision was also correlated with lens preference based on vision at near (rs=0.85), intermediate (rs=0.71), and for digital device use (rs=0.87). Lens preference based on vision with digital device use correlated with lens preference based on vision at near (rs=0.85), and intermediate distance (rs=0.69).
Conclusions: Subjects preferred stenA-MF for a range of comfort and distance measures. Preferences for overall comfort and overall vision were both significantly correlated to the same three preferences of near, intermediate and digital device vision, illustrating how comfort and vision are intricately related when evaluating MFCLs and supporting how poor vision could potentially impact comfort.

2020

Guthrie S, Woods J, Vega J, Orsborn G, Ng AY, Jones L. Exploring the factors which impact overall satisfaction with contact lenses Academy at Home, 2020 [ Show Abstract ]

Purpose: To evaluate the performance of two spherical lenses, one silicone hydrogel (SiHy) (somofilcon A) and one hydrogel (Hy) (etafilcon A), using subjective evaluations after 1-week and to correlate the relationships between specific subjective evaluations of lens performance and subjective overall satisfaction.
Methods: Fifty-five subjects participated in a prospective, double-masked, bilateral crossover dispensing study, wearing each lens for 1 week in a randomized order. Subjective ratings (0-10 scale) were completed after 1 week based on a typical day experience and a 4-point Likert scale (Strong/slight preference for each lens) was used to determine lens preference.
Results: Data for both lenses were combined and correlation analyses were conducted. Overall satisfaction was found to be significantly correlated (p<0.01) with handling for insertion (r=0.64), overall satisfaction with vision (r=0.64), handling for removal (r=0.50), comfort at insertion (r=0.59), comfort at end of day (r=0.61) and overall satisfaction with comfort (r=0.88). In addition, insertion comfort was significantly correlated with overall satisfaction with comfort (r=0.66). Considering the lenses separately, SiHy was rated significantly higher for handling for lens insertion compared to Hy (9.4 vs 8.1, p<0.01) and correlation strength with overall satisfaction varied greatly with lens material (SiHy: r=0.26, p=0.05 vs Hy: r=0.72, p<0.01). Overall lens preference based on lens handing for insertion also strongly favoured SiHy (37 subjects vs 18, p<0.01). Comfort at insertion was rated significantly higher at insertion with SiHy (9.0 vs 8.1, p<0.01) and similarly at end of day (8.1 vs 7.9, p=0.80). Correlation strength of comfort at insertion/end of day with overall satisfaction again varied with lens material (Insertion: 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). There were no other statistically significant differences in subjective results for SiHy and Hy.
Conclusions: Significant correlations were found between overall satisfaction and the specific subjective evaluations of handling, vision and comfort. Interestingly, handling for insertion had a similar correlation (r) value as vision, suggesting that handling for insertion should not be underestimated when considering overall patient satisfaction. And while insertion and end of day comfort correlated moderately with overall satisfaction, overall satisfaction with comfort highly correlated with overall satisfaction. Separate analysis of SiHy and Hy also indicate that lower handling and comfort scores for Hy at insertion drove a higher correlation, suggesting that dissatisfaction with both handling for lens insertion and comfort upon lens insertion can play major roles in overall dissatisfaction with a lens.

Schulze M, Ng AY, Luensmann D, Guthrie S, Woods J, Jones L. The subjective response to verofilcon A daily disposable contact lenses during extensive digital device use Academy at Home, 2020 [ Show Abstract ]

Purpose: To evaluate the subjective response of habitual lens wearers during extensive digital device use when switched to Precision1 (verofilcon A) daily disposable (DD) contact lenses (CLs).
Methods: Volunteers between 18-40 years of age who used digital devices for at least 6 hours/day while wearing their habitual CLs were recruited for the study. Eligible participants were dispensed with verofilcon A DD CLs for a period of 2 weeks, during which they were required to wear the study CLs for at least 5 days/week and at least 10 hours/day. Participants returned after 142 days for their final visit, where they reported their CL wear time and time spent using digital devices, and rated their typical experience on a 0 to 100 scale, with 100 being best. Comfort, dryness and clarity of vision with verofilcon A were rated directly after insertion, after 6 hours of digital device use, and just before removal, as well as by rating their overall performance. Participants also completed a 4-point (strongly agree, slightly agree, slightly disagree, strongly disagree) Likert scale-based questionnaire. Subjective ratings were not normally distributed, therefore non-parametric analysis was conducted and data are reported as median (range). The Likert scale responses were analyzed using binomial testing.
Results: Twenty participants completed the study (18F:2M), mean age of 25.1 ± 6.0 years (range 19-40). They reported their typical day to include median CL wear time of 13.8 hours (10.5-17), comfortable CL wear time of 12.1 hours (8-16.5) and digital device use of 9 hours (6-12). After 2 weeks of verofilcon A DD CL wear, subjective ratings after 6 hours of digital device use were high, with ratings for a typical day of 93 (68-100) for comfort, 93 (52-100) for dryness and 96 (70-100) for clarity of vision. After 2 weeks of wear, the majority of participants agreed that the study lenses provided good comfort (16/20 subjects; p=0.01) and good vision (18/20; p<0.01) all day long. Similarly, the majority of participants were satisfied with the comfort (16/20; p=0.01), vision (18/20; p<0.01) and overall performance (16/20; p=0.01) they experienced with the study lenses while using digital devices for 6 hours. Additionally, most reported they did not experience any eye strain while using verofilcon A lenses (n=16/20; p=0.01). No significant lens-related ocular findings were observed after 2 weeks of wear.
Conclusions: After 2 weeks of wear, participants rated the performance of verofilcon A DD CLs very highly, with median overall performance ratings for comfort, dryness and vision all 93 on the 0 to 100 scale (with 100 being best). Verofilcon A DD CLs may be a viable alternative for those struggling with their habitual lens performance when spending long hours using digital devices.

Woods J, Guthrie S, Varikooty J, Jones L. Satisfaction of habitual wearers of reusable multifocal lenses when refitted with a daily disposable, silicone hydrogel multifocal lens Contact Lens Anterior Eye 2020 [ Show Abstract ][ PDF ]

Purpose: Visual performance with multifocal contact lenses (MFCL) can vary with lens design. This study simulated a real-world refit of habitual wearers of reusable MFCL with a silicone hydrogel (somofilcon A), daily disposable multifocal (DDMF) lens to assess visual and overall experience with the new design and modality.

Method: Subjects rated the DDMF and compared it with their habitual reusable MFCL. The habitual MFCL prescription was not reviewed or confirmed as optimal, though all reported having an eye-examination within 2-years. Subjects were masked to the DDMF brand. After 2 weeks of daily wear with the new lens, subjects reported their experience using 0-10 ratings and Likert scales.

Results: Twenty-eight subjects, spanning 14 habitual lens brands, completed the study. Visual acuity with DDMF was statistically better than with habitual MFCL for all four distances measured (all p<0.05); distance (≥6m): -0.04±0.09, long intermediate (1.5m): -0.11±0.11, short intermediate (0.75m): -0.10±0.09, and near (0.4m): 0.02±0.09. Subjective vision clarity was statistically better with the DDMF for distance tasks in the dark, long intermediate tasks, and when considering all visual needs (all p<0.05). There were no statistical differences (all p>0.05) for vision clarity performing tasks at distance, short intermediate and near. When asked for a preference, the DDMF was significantly preferred over habitual for long intermediate tasks (p=0.03), but not different for tasks at other distances. Ease of insertion was statistically better with the DDMF (p=0.03); ease of removal was not different. End of day comfort was not different from the habitual lenses (p=0.10), however the DDMF was rated better for end-of-day dryness (p=0.01) and overall satisfaction with lenses (p=0.04).

Conclusions: This daily disposable, silicone hydrogel (somofilcon A), multifocal lens provided good vision and overall performance. Many ratings showed it to provide statistically better performance than their habitual reusable MFCL, supporting the benefits of a trial wear period.

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 ]

Purpose: To evaluate the subjective acceptance of two different types of prism ballast toric lens geometries, when worn on a daily wear modality over 1 month.
Methods: The study was a prospective, double-masked, bilateral, randomized, cross-over, 1-month wear, dispensing study where 45 astigmats wore two different soft toric lenses: comfilcon A toric which utilises a uniform horizontal iso-thickness design and samfilcon A toric which utilises a thin-edge design. Assessments were completed at 1-month. Ratings (0-10 scale) were competed at 2-weeks and 1-month.
Results: At 1-month, investigator-rated lens fit acceptance was high for both lens designs (3.65 vs 3.58, p=0.29), as was logMAR visual acuity for high contrast, high illumination (-0.12 vs -0.12, p=0.63) and low illumination (-0.10 vs -0.09, p=0.71). Subjective ratings for ‘overall visual quality’ were significantly higher for comfilcon A at 1-month (8.1 vs 7.4, p=0.04), but not different at 2-weeks (8.2 vs 7,6, p=0.05). ‘Vision stability’ ratings were significantly higher for comfilcon A at 2-weeks (8.2 vs 7.3, p=0.01) and 1-month (8.0 vs 7.2, p=0.03). ‘Overall comfort’ was rated significantly better with comfilcon A at 2-weeks (8.1 vs 7.4, p=0.04) and 1-month (8.1 vs 7.4, p=0.03). ‘End of day comfort’ ratings were similar after 1-month but significantly better with comfilcon A at 2-weeks (7.2 vs 6.5, p=0.03). ‘Overall satisfaction’ was statistically higher for comfilcon A after 2-weeks (8.0 vs 7.0, p<0.01) and 1-month (7.8 versus 7.0, p=0.02). Comfortable wearing time was not different at 2-weeks (9.2 vs 8.8, p=0.12), but was significantly longer with comfilcon A at 1-month (8.9h vs 8.0h, p=0.03).
Conclusions: Although both comfilcon A and samfilcon A use a prism ballast stabilisation principle and both provide excellent acuity and lens fit results, comfilcon A provided better subjective results for vision, vision stability, comfort, comfortable wear time and overall satisfaction.

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.

2018

Woods J, Ng AY, Luensmann D, Guthrie S, Jones L. Short-term comfort comparison of two daily disposable contact lenses of different material and modulus Invest Ophthalmol Vis Sci 2018;E-Abstract 1753 [ Show Abstract ][ PDF ]

Purpose: Daily disposable contact lenses (DDs) are now widely available in both silicone hydrogel (SH) and hydrogel (H) materials. The higher oxygen transmissibility of SH materials provides many benefits, but their higher modulus has been linked with reduced lens comfort compared to H lenses. This randomized, double-masked clinical trial assessed the short-term comfort of two DDs of differing modulus, yet similar water content (WC): a SH-DD (somofilcon A; clariti® 1 day; CooperVision; 0.50MPa modulus, 56% WC) and a H-DD (etafilcon A; 1-Day Acuvue® Moist®; Johnson & Johnson; 0.29MPa modulus, 57% WC).

Methods: 120 subjects wore the lenses contralaterally, over one day. Targeted recruitment meant that 60 subjects were habitual H-DD wearers (all adapted wearers of 1-Day Acuvue Moist), 60 were non-DD habitual wearers (adapted to various SH and H re-usable lenses). Subjects rated lens comfort on a 0-100 integer scale (100= cannot be felt) at insertion and then hourly until 8hrs. Of particular interest was the comfort at the beginning and end of the 8hr wear period and these data points were tested for equivalence. At the final visit subjects were asked for their lens preference, based on comfort.

Results: Mean subjective comfort was not different between SH-DD and H-DD across the wear period (p>0.05), on insertion (87±14 SH-DD vs 89±14 H-DD; p>0.05) or after 8hrs (82±18 SH-DD vs 83±17 H-DD; p>0.05). Based on equivalency margins of ±5-points, the study lenses showed equivalent comfort at insertion (p=0.03) and at 8hrs (p=0.001). Both lenses exhibited a significant reduction in comfort over the 8hr period (both p<0.001). When subjects’ data was divided according to their habitual lens modality groups (60 H-DD wearers and 60 re-useable wearers), there were also no comfort differences between the study lenses, either across time, or at insertion and 8hrs (all p>0.05). Lens preference was not different between lenses at dispensing or at the final visit (both p>0.05).

Conclusions: Initial and 8hr comfort were not compromised with the SH-DD compared to the H-DD, despite its higher modulus, and there was no difference in the lens preference distribution. The results suggest that lower comfort should not be anticipated when fitting SH-DDs of an appropriate design, thus allowing other material properties such as high oxygen permeability to be considered.

2016

Jones L, Guthrie S, Dumbleton K. Is there a relationship between care system and compliance? Asian Cornea and Contact lens Conference, Hong Kong, 2016 [ PDF ]

Stahl U, Keir N, Guthrie S, Jones L. Effect of monocular lens wear on ocular comfort TFOS conference, Montpelier, France, 2016

2015

Guthrie S, Dumbleton K, Jones L. Is there a relationship between care system and compliance? BCLA Clinical Conference and Exhibition, 2015 [ PDF ]

Guthrie S, Woods J, Dumbleton K, Fonn D, Jones L. Contact lens discomfort management strategies of ECPs Optom Vis Sci 2015;92: E-abstract 155050 [ PDF ]

2014

Dillehay S, Woods J, Situ P, Guthrie S, Paynor R, Griffin R, Tyson M, Jones L. Comparison of Three Power Levels of A Novel Soft Contact Lens Optical Design to Reduce Suspected Risk Factors for the Progression of Juvenile Onset Myopia Invest Ophthalmol Vis Sci 2014;55: E-abstract 3637

2011

Guthrie S, Woods J, Keir N, Dillehay S, Tyson M, Griffin R, Fonn D, Jones L, Irving E. Controlling lens induced myopia in chickens with peripheral lens design Optom Vis Sci 2011;88:E-Abstract 110421

Woods J, Guthrie S, Keir N, Choh V, Fonn D, Jones L, Irving E. Myopia development – what can the chicken tell us? Contact Lens & Anterior Eye 2011;34, Supplement 1:s13

Woods J, Guthrie S, Keir N, Dillehay S, Tyson M, Griffin R, Jones L, Irving E. The effect of a unique lens designed for myopia progression control (MPC) on the level of induced myopia in chicks Invest Ophthalmol Vis Sci 2011;51:E-Abstract 6651

2009

Brodland G, Jones L, Horst C, McDonald M, Guthrie S. A novel method for measuring contact lens tensile properties Optom Vis Sci 2009;86:E-abstract 095818

Dumbleton K, Richter D, Guthrie S, Woods C, Jones L, Fonn D. Patient and practitioner compliance with silicone hydrogel and daily disposable lens replacement CAO (Charlottetown, PEI), 2009

Dumbleton K, Woods C, Jones L, Guthrie S, Fonn D. Patient and practitioner compliance with silicone hydrogel and daily disposable lens replacement Contact Lens & Anterior Eye 2009;32, 5:213

Jones L, Brodland G, Horst C, McDonald M, Guthrie S. A novel method for measuring contact lens tensile properties Contact Lens & Anterior Eye 2009;32, 5:254

2008

Dalton K, Jones L, Guthrie S. pH, Osmolality and viscosity of artificial tears Optom Vis Sci 2008;85: E-abstract 85310

Dalton K, Jones L, Guthrie S. Physical properties of artificial tears Contact Lens & Anterior Eye 2008;31, 5:272

2006

Guthrie S, Simpson T, Varikooty J, Fonn D. Background subtraction and contrast enhancement for interferometric images of the human corneal tear film Invest Ophthalmol Vis Sci 2006;47:E-abstract 2399

Professional Publications

2022

Guthrie S. Relationships between success factors in daily disposable multifocal lenses https://contactlensupdate.com/2022/12/21/relationships-between-success-factors-in-daily-disposable-multifocal-lenses/ 2022;69

2021

Guthrie S. Comfort and vision correlations in daily disposable multifocal lenses https://contactlensupdate.com/2021/06/15/comfort-and-vision-correlations-in-daily-disposable-multifocal-lenses/ 2021;60

2019

Guthrie S. Summary: IMI Report on Experimental Models of Emmetropization and Myopia ContactLensUpdate.com 2019

Guthrie S. Report on Experimental Models of Emmetropization and Myopia - An article review ContactLensUpdate.com 2019

2016

Guthrie S, Dumbleton K, Jones L. Is there a Relationship Between Care System and Compliance? Contact Lens Spectrum 2016;31, April: 40-43

2014

Guthrie S, Dumbleton K, Jones L. Financial Implications of Patient Compliance Contact Lens Spectrum 2014;29, December: 42-45

2011

Guthrie S. Effect of dual-focus soft contact lens wear on axial myopia progression in children - An article review ContactLensUpdate.com 2011

2010

Richter D, Dumbleton K, Guthrie S, Woods C, Jones L, Fonn D. Patient and practitioner compliance with silicone hydrogel and daily disposable lens replacement in Canada Canadian Journal of Optometry 2010;72, 1: 10-19

Books

2021

Jones L, Stahl U, Guthrie S, Yang M, Moezzi A, Thom M. Contact Lens Compendium: Contact Lenses & Solutions Available in America. Vol 2 2021.

Jones L, Stahl U, Guthrie S, Yang M, Moezzi A, Thom M. Contact Lens Compendium: Contact Lenses and Solutions Available in Canada. Vol 47 2021.

2020

Jones L, Stahl U, Guthrie S, Yang M, Yee A, Thom M. Contact Lens Compendium: Contact Lenses and Solutions Available in Canada. Vol 46 2020.

Jones L, Stahl U, Guthrie S, Yang M, Yee A, Thom M. Contact Lens Compendium: Contact Lenses & Solutions Available in America. Vol 1 2020.

2019

Jones L, Stahl U, Guthrie S, Luensmann D, Yang M, Thom M. Contact Lens Compendium: Contact Lenses and Solutions Available in Canada. Vol 45 2019.

2018

Jones L, Sorbara L, Stahl U, Yang M, Thom M, Guthrie S. Contact Lens Compendium: Contact Lenses and Solutions Available in Canada. Vol 44 2018.

2017

Jones L, Sorbara L, Stahl U, Thom M, Guthrie S. Contact Lens Compendium: Contact Lenses and Solutions Available in Canada. Vol 43 2017.

2016

Jones L, Sorbara L, Stahl U, Thom M, Guthrie S. Contact Lens Compendium: Contact Lenses and Solutions Available in Canada. Vol 42 2016.

2015

Jones L, Sorbara L, Stahl U, Thom M, Guthrie S. Contact Lens Compendium: Contact Lenses and Solutions Available in Canada. Vol 41 2015.

2014

Jones L, Sorbara L, Stahl U, Thom M, Guthrie S. Contact Lens Compendium: Contact Lenses and Solutions Available in Canada. Vol 40 2014.

2013

Jones L, Sorbara L, Stahl U, Guthrie S, Menzies K, Rossy J, Thom M. Contact Lens Compendium: Contact Lenses and Solutions Available in Canada. Vol 39 2013.