Eye care professionals' perceptions of the benefits of daily disposable silicone hydrogel contact lenses

Application of Silicone in Ophthalmology: A Review

This paper reviews the latest trends and applications of silicone in ophthalmology, especially related to intraocular lenses (IOLs). Silicone, or siloxane elastomer, as a synthetic polymer, has excellent biocompatibility, high chemical inertness, and hydrophobicity, enabling wide biomedical applications. The physicochemical properties of silicone are reviewed. A review of methods for mechanical and in vivo characterization of IOLs is presented as a prospective research area, since there are only a few available technologies, even though these properties are vital to ensure medical safety and suitability for clinical use, especially if long-term function is considered. IOLs represent permanent implants to replace the natural lens or for correcting vision, with the first commercial foldable lens made of silicone. Biological aspects of posterior capsular opacification have been reviewed, including the effects of the implanted silicone IOL. However, certain issues with silicone IOLs are still challenging and some conditions can prevent its application in all patients. The latest trends in nanotechnology solutions have been reviewed. Surface modifications of silicone IOLs are an efficient approach to further improve biocompatibility or to enable drug-eluting function. Different surface modifications, including coatings, can provide long-term treatments for various medical conditions or medical diagnoses through the incorporation of sensory functions. It is essential that IOL optical characteristics remain unchanged in case of drug incorporation and the application of nanoparticles can enable it. However, clinical trials related to these advanced technologies are still missing, thus preventing their clinical applications at this moment.

Impact of the physical properties of contact lens materials on the discomfort: role of the coefficient of friction

Contact Lens Discomfort (CLD) is the main cause in contact lens (CLs) discontinuation, referred in literature as drop-out phenomenon. Despite such evidence was reported in several clinical studies, a relationship between physico-chemical properties of CLs and CLD is not still totally understood. In this regard, the friction of CLs surfaces seems to be related to discomfort feeling events, probably due to an alteration of the lubricate function of the tear film after the CL placement inside the ocular environment. In the last years, many studies have been finalized to the friction measurements of CLs surface, finding conflicting data due to a lack in standardized protocol. The aim of this review is primarily to show evident relationships between CLs surface properties (i.e. wettability, tear evaporation, tear film quality, etc.) and the coefficient of friction (CoF), resulting therefore the most relevant physical quantity in the CLs characterization. In addition, we reported the most recent studies in CLs tribology, which highlight that the introduction of a standard protocol in CoF measurements is necessary to obtain reproducible results, considering the aim to evaluate in a more precise way the relationship between this material surface property and comfort in CLs users.

The pH-induced physical properties of ionic contact lens material

The degree of protonation of contact lens materials is affected by the surrounding pH environment, due to the different pK_a values. The swelling of ionic contact lenses is generally controlled by these factors which determines physical properties of contact lenses. The purpose of this study was to evaluate the pH dependence of the physical properties of contact lenses. The ionic etafilcon A and non-ionic hilafilcon B contact lenses were used in this study. The diameter, refractive power, equilibrium water content (EWC), and the amounts of freezable-free water (W_ff), freezable-bound water (W_fb) and non-freezable water (W_nf) in the contact lens at each pH condition were measured. The diameter, refractive power and EWC of etafilcon A decreased with decreasing pH below 7.0 or 7.4, whereas hilafilcon B showed relatively constant values. The quantity of W_fb tended to increase with increasing pH, showing a relatively constant value above 7.0, whereas W_nf decreased. Hilafilcon B did not show changes in EWC and specific trends in W_fb and W_nf. The significant change of etafilcon A at more acidic condition is derived from the presence of methacrylic acid (MA) which makes it vulnerable to pH. Additionally, though the EWC is composed of various states of water, (i) various states of water could response to surrounding environment in different way with EWC and (ii) W_fb could be the crucial factor that determines physical properties of contact lens.

Long Day Wear Experience with Water Surface Daily Disposable Contact Lenses

OBJECTIVE

The purpose of this study was to assess the wear experience of silicone hydrogel daily disposable contact lenses with water surface technology over a long day of lens wear.

METHODS

Thirty-five soft contact lens wearers were refit with the daily disposable study lenses and participants scored their initial impressions of comfort, vision and satisfaction using a visual analog scale (VAS). Participants used their smart phones to complete surveys of comfort and vision on a scale of 1-10 at 10, 12, 14, and 16 hours of lens wear on 5 weeknights. A participant score for each time point was calculated by averaging the evening responses. End of study VAS surveys of symptoms were also completed.

RESULTS

Median (Interquartile Range) VAS initial impression scores were 99.00 (12.00) for quality of vision, 98.00 (16.00) for comfort, and 100.00 (13.00) for satisfaction. The end of study surveys found end of day median VAS scores of 87.00 (19.00) for end of day quality of vision and 75.00 (24.50) for end of day comfort. The median score for overall quality of vision was 93.00 (14.00) and for overall comfort was 93.00 (16.50). The median score for end of day dryness was 37.00 (55.00) and overall dryness was 13.00 (34.00).

CONCLUSION

The daily disposable lenses with water surface treatment used in this study maintained high median scores for comfort and quality of vision for up to 16 hours of wear.

Perceptions of potential barriers to soft contact lens wear among university students in Jordan

CLINICAL RELEVANCE

Identifying potential barriers to contact lens wear could increase awareness about contact lenses and their benefits and boost the confidence of optometrists offering contact lenses to their patients.

BACKGROUND

Contact lenses provide better visual performance according to many studies. Nevertheless, resistance to wearing them remains an issue. This study will identify barriers to contact lens wear among university students in Jordan.

METHODS

This study enrolled university students who wore spectacles for their refractive error correction and have had no history of contact lens wear. A questionnaire of potential barriers was constructed whereby participants were required to respond to a set of questions that asked how each suggested item was considered a barrier for contact lens wear; responses were recorded within a 5-points scale (1: strongly disagree to 5: strongly agree).

RESULTS

A total of 260 participants (175 females and 85 males) were enrolled in the study. All participants showed normal findings for contact lens wear candidacy. The mean score of total barriers to contact lens wear was high, at 33.8 (±5.4 SD) (out of 55 the maximum possible score). The major identified barriers were: decision of eye care practitioners that contact lenses are unsuitable for them (64.6% of the study sample); decision of the participants that contact lens were unsuitable for their work environment (63.5%); and reported symptoms of ocular dryness (61.6%) that made participants reluctant to try contact lenses.

CONCLUSION

This work identified several patient-related barriers to contact lens wear. Probing these barriers may encourage eye care providers and contact lens manufacturers to promote contact lenses as a viable option for the correction of refractive error. This in turn will increase awareness among patients about contact lenses and encourage them to try contact lenses as alternative to spectacles.

Effect of Contact Lenses on Contrast Sensitivity under Various Lighting Conditions

Purpose

To assess contrast sensitivity in clear and colored soft contact lenses under different lighting conditions.

Methods

This study was performed on 34 medical students. Visual acuity was measured using a tumbling E chart at a distance of 6 m, and contrast sensitivity was determined by Pelli Robson chart at a distance of 1 m. These tests were repeated in mesopic (3 lux) and glare (2000 lux) conditions. Then, a clear contact lens was applied to one eye and a colored contact lens was applied to the other. After 2 hr, visual acuity and contrast sensitivity were measured for each individual. The results were compared with and without contact lenses under normal, mesopic, and glare conditions.

Results

The mean refractive error was 0.44 ± 0.20 diopters. Repeated measures ANOVA showed a decline in contrast sensitivity with colored and clear contact lenses as compared to no-lens condition (P < 0.001). Additionally, lighting conditions had a significant impact on contrast sensitivity (P < 0.001); contrast sensitivity was lower in mesopic and glare conditions than under normal lighting condition.

Conclusion

In addition to the drop in contrast sensitivity under unusual lighting conditions (e.g., glare and mesopic), wearing soft contact lenses can further reduce contrast sensitivity in different lighting conditions. Therefore, people who wear contact lenses should be aware of this reduction in visual performance in conditions like driving at night or in the fog.

Opportunities and threats to contact lens practice: A global survey perspective

AIM

To understand the views of contact lens (CL) practitioners across the globe regarding what they perceive as opportunities and threats in CL practice.

METHODS

A self-administered anonymised questionnaire, constructed in English and translated in six more languages, was distributed through reputed international professional bodies and academic institutions worldwide. The questionnaire included items on demographic characteristics, type of practice, and questions designed to explore practitioners' perspective on the future of their CL practice over the next five years.

RESULTS

A total of 2408 valid responses were analysed. Multifocal CLs for presbyopia, CLs for myopia control, use of daily disposable (DD) CLs for occasional wear, and biocompatible materials to improve comfort were identified as promising areas of opportunities by practitioners (all 8/10). Respondents from North America, and Europe valued DDCLs for occasional wear moderately more favourable (Median: 9/10 for all) as compared to colleagues in Asia (Median: 8/10, p < 0.001), South America (Median: 8/10, p < 0.01), and Africa (Median: 8/10p < 0.01). Multifocal CLs for presbyopia was perceived as a better opportunity by practitioners in North America and Europe (Median: 9/10 for both), as well as in Australasia (Median: 8/10), in comparison to Asia, Africa, and Middle East (for all Median: 6/10, p < 0.001). Practitioners expressed concerns about the availability of CLs and CL prescriptions online without direct professional involvement (both 9/10).

CONCLUSIONS

Overall, the most appealing opportunities for CL practice growth were identified in occasional use of DD CLs, biocompatible materials to reduce CL discomfort, multifocal CLs for presbyopia correction and management of myopia control with CLs. Lack of regulation in CL sales, especially online, seemed to be a constant threat. The insights from this study can be used to design targeted strategies to enhance CL practice across the globe and in specific geographical areas.

Lifetime Corneal Edema Load Model

Purpose

To highlight the potential benefits for long-term use of silicone hydrogels daily disposable (DD) contact lenses, particularly with patients who are noncompliant, sleeping or napping while wearing their lenses, or those who have higher oxygen demands and wear this modality for decades.

Methods

Published data for corneal swelling with lenses and no lens wear were used to develop a nonlinear least squares model. The edema load experienced with a range of oxygen transmissibilities (Dk/t) and wear compliance (sleep and napping) was determined. A mixed-effects linear regression model was used to compare the edema load for high and average corneal swellers.

Results

The edema load generated demonstrates that a high Dk/t silicone hydrogel lens results in edema levels close to that with no lens wear. In comparison, hydrogels with a Dk/t of 27 (× 10⁻⁹ [cm mL{O₂}][s mL mm Hg]), worn on a daily wear schedule will result in 1.5 times more edema and up to two times more if the patient is noncompliant over each decade of wear. High swellers after four decades of wear will have an edema load 10 to 17 times greater than average swellers depending on Dk/t and their degree of noncompliance with the daily wear modality.

Conclusions

Prescribing silicone hydrogel DD lenses, particularly with higher DK/t, may help to maintain the long-term ocular health of patients, when they wear their lenses fulltime for many decades.

Translational Relevance

Illustrates the importance of Dk/t for any CL wear modality where patients nap or sleep in lenses or have high oxygen needs.

Influence of the COVID-19 pandemic on contact lens wear in Spain

PURPOSE

To investigate the behaviour of contact lens (CL) wearers in Spain during the COVID-19 pandemic.

METHODS

An anonymized web-based questionnaire was used to assess demographics, CL history, and activity, CL wear habits and perceived risk of infection due to CL wear during the COVID-19 pandemic.

RESULTS

A total of 737 participants with an average age of 27.4 (±9.3) years completed the online questionnaire. The vast majority of respondents were soft CL wearers and reported at least two years of CL wear. Patients concerns about the increased risk of SARS-CoV-2 infection due to CL wear (40.6 % of participants) were significantly related (χ2(1) = 11.195, p < 0.05) to CL discontinuation (46 % of participants) during the COVID-19 pandemic. This fact joins the significant changes in the frequency of CL wear during the COVID-19 pandemic (χ2(4) = 31.982, p < 0.05), with a tendency to increase occasional CL wear from 29.1 % to 61.8 %. Interestingly, the majority of respondent (87.9 %) indicated that no professional had offered them information related to CL wear and COVID-19, and that they had not sought it on their own (82.2 %).

CONCLUSION

There is a relationship between the perceived risk of infection and CL dropout during the COVID-19 pandemic, and a tendency to change the CL frequency of wear, with an increase in occasional CL wear. During the ongoing pandemic, eye care practitioners should reinforce CL patient education to minimize the risk of SARS-CoV-2 infection and CL-related complications requiring clinical care.

Quarter of a century of contact lens prescribing trends in the United Kingdom (1996 - 2020)

PURPOSE

To document contact lens prescribing trends in the United Kingdom over the past quarter of a century.

METHODS

An annual survey of contact lens prescribing was conducted each year from 1996 to 2020, inclusive, by asking a random selection of optometrists and contact lens opticians to provide information relating to 10 consecutive contact lens fits between January and March.

RESULTS

Over the 25 year survey period, 2,671 practitioners returned survey forms, reporting a total of 25,575 contact lens fits. The mean (± standard deviation) age of lens wearers was 35 ± 15 years, of which 64 % were female. Over the survey period, rigid lens new fits decreased from 22 % to 2%. The prescribing of silicone hydrogel lenses has increased steadily since their introduction towards the end of the 1990s, and now represent 80 % of soft lens fits. Soft toric lens prescribing has gradually increased to 47 % - a value at which astigmatism ≥ 0.75DC is theoretically corrected in all contact lens wearers. Daily disposable prescribing increased steadily over the survey period and now represents 63 % of lenses prescribed. Extended wear fits remain at very low levels, except for some prescribing for overnight orthokeratology. Multi-purpose lens care solutions are ubiquitous; peroxide and other systems are now seldom prescribed. Rigid lenses and monthly replacement soft lenses are predominantly worn on a full time basis, whereas daily disposable soft lenses are mainly worn part time.

CONCLUSIONS

This report documents the evolution of contact lens fitting in the United Kingdom over the past 25 years. The most likely lens fit is a spherical design silicone hydrogel daily disposable contact lens prescribed for a 35 year old female and worn on a part-time basis.

An investigation into disposal and recycling options for daily disposable and monthly replacement soft contact lens modalities

PURPOSE

To examine the annualised waste and end-of-life disposal options with two representative soft contact lens (CL) modalities.

METHODS

The component parts of two representative soft CL modalities were catalogued, separated, weighed and inspected for material identification: somofilcon A soft CLs (clariti elite, CooperVision Inc.) used with multi-purpose solution (MPS) (All in one Light, CooperVision Inc.) and somofilcon A CLs (clariti 1 day, CooperVision Inc). Using a model that assumed compliant wear and care of CLs, the mass of material solid waste generated by CL use over a year was calculated. Disposal options were explored using household and specialist recycling streams in order to develop recommendations for responsible disposal of CL waste.

RESULTS

Full-time daily disposable (DD) CL wear generates 1.06 kg of waste annually compared to 0.83 kg generated by reusable-monthly replacement daily wear ('reusable') CLs. Plastic was the dominant material in both modalities. With full-time use of DD CLs, 64% of waste by mass was plastic blister trays. For full-time use of reusable CLs, where figures from lens and MPS packaging are combined, plastics accounted for 67% of waste by mass. MPS bottles alone made up almost half the waste (45%) associated with full-time reusable CL wear.

CONCLUSION

Full-time DD wear generates 27% more waste annually than full-time reusable lens wear. Reusable CL wearers can recycle 78% of waste at home. DD lens wearers have access to recycling options that allow them to recycle 100% of CL related waste. Full-time CL lens wear represents just 0.20-0.26% of the 412 kg of household waste generated per person, per year in the United Kingdom. Worn CLs should never be disposed of down the sink or lavatory. CL wearers should be aware of responsible end-of-life recycling and disposal options for all CL waste.

Fluorescent contact lens for continuous non-invasive measurements of sodium and chloride ion concentrations in tears

Rapid and non-invasive measurement of hydration status is medically important because even mild levels of dehydration can have a significant impact on physical and cognitive performance. Despite the potential value of determining whole-body hydration based on the electrolytes found in tears, very few tests are available. An area of intense interest is the development of a contact lens which could measure ion concentrations in tears, specifically that of sodium (Na⁺) and chloride (Cl^-) ions, the dominant electrolytes in blood plasma and tears. Here, we describe a method to make fluorescent contact lenses which allow determination of Na⁺ and Cl^- ion concentrations in tears. Fluorophores known to be sensitive to Na⁺ and Cl^- were derivatized to bind non-covalently to two commercially-available silicone hydrogel (SiHG) contact lenses-the Biofinity (Comfilcon A) or MyDay (Stenfilcon A) lenses. The sodium- and chloride-sensitive fluorophores displayed spectral changes in the physiological range for Na⁺ and Cl^- ions in tears. The lenses for both Na⁺ and Cl^- ions were completely reversible. The sodium responses were not sensitive to protein interference including human lysozyme, human serum albumin and mucin type 2. The chloride sensitivity was similar with both lenses, but the sodium-sensitive range was different in the Biofinity and MyDay lenses. We also fabricated a lens with both the Na⁺ and Cl^- probes in a single MyDay lens resulting in a contact lens that independently measured Na⁺ and Cl^- concentrations without physical separation of the fluorophores. Our findings indicated that a sodium and chloride-sensitive contact lens (NaCl-lens) could be used for rapid non-invasive detection of whole-body hydration, as well as associated diseases or other infections.

Silicone hydrogel daily disposable benefits: The evidence

Daily disposable (DD) contact lenses first came to the market approximately 25 years ago and eye care professionals (ECPs) started prescribing silicone hydrogel (SiH) contact lenses, primarily for extended or continuous wear, approximately 20 years ago. It has now been over ten years since SiH DD contact lenses have been available, and while SiH materials are routinely prescribed by ECPs for reusable daily wear, hydrogel materials are still frequently selected for the DD modality of contact lens wear. This article reviews the evidence to support the benefits of both a DD modality and SiH materials and how patients' needs may be met with SiH DD contact lenses, with respect to clinical performance, health outcomes, satisfaction, compliance and convenience. Factors which may enable or constrain ECPs from prescribing SiH DD contact lenses, as opposed to hydrogel DD and reusable contact lenses, for more of their patients are discussed with the objective of providing ECPs with a greater understanding of the advantages that can be afforded by prescribing SiH DD contact lenses to both their new and existing contact lens wearers.

A Survey of Contact Lens Wearers and Eye Care Professionals on Satisfaction with a New Smart-Surface Silicone Hydrogel Daily Disposable Contact Lens

PURPOSE

To assess the patient and ECP preference of verofilcon A lenses over approximately a one-week period when worn on a daily wear, daily disposable (DD) basis by current DD contact lens wearers (CLWs) and new CLWs. ECPs assessed the lens fit, performance on eye and lens preference (to habitual DD lens) for current wearers.

METHODS

A total of 218 current DD CLWs and 129 new CLWs aged >18 years participated in the survey. Baseline demographics and one-week data were obtained by 31 ECPs after fitting up to 10 current and 10 new wearers each. The survey was conducted online for both the participants and the ECPs. The survey took place in Australia and New Zealand from April to May 2019.

RESULTS

For new wearers, the surveyed results demonstrated strong wearer preference for the verofilcon A lens with quality of life as a main driver. For current wearers, comfort was the main driver for verofilcon A preference. Post survey, 73% of ECPs stated they would most likely continue to fit verofilcon A lenses.