Contact Lens Industry Research Articles

A Microfluidic Contact Lens to Address Contact Lens-Induced Dry Eye.

The contact lens (CL) industry has made great strides in improving CL-wearing experiences. However, a large amount of CL wearers continue to experience ocular dryness, known as contact lens-induced dry eye (CLIDE), stemming from the reduction in tear volume, tear film instability, increased tear osmolarity followed by inflammation and resulting in ocular discomfort and visual disturbances. In this article, to address tear film thinning between the CL and the ocular surface, the concept of using a CL with microchannels to deliver the tears from the pre-lens tear film (PrLTF) to the post-lens ocular surface using in vitro eye-blink motion is investigated. This study reports an eye-blink mimicking system with microfluidic poly(2-hydroxyethyl methacrylate) (poly(HEMA)) hydrogel with integrated microchannels to demonstrate eye-blink assisted flow through microchannels. This in vitro experimental study provides a proof-of-concept result that tear transport from PrLTF to post-lens tear film can be enhanced by an artificial eyelid motion in a pressure range of 0.1-5kPa (similar to human eyelid pressure) through poly(HEMA) microchannels. Simulation is conducted to support the hypothesis. This work demonstrates the feasibility of developing microfluidic CLs with the potential to help prevent or minimize CLIDE and discomfort by the enhanced transport of pre-lens tears to the post-lens ocular surface.

Affluence and Contact Lens Prescribing.

To assess the impact of national affluence on the extent of prescribing of various types of soft contact lenses. Using information derived from a large bank of contact lens prescribing data, the relationship between the percentage prescribing of daily disposable, toric, silicone hydrogel, and multifocal contact lenses versus the gross domestic product at purchasing parity per capita (GDP [PPP]) was determined for all countries in which contact lens prescribers returned survey forms relating to greater than 100 contact lens fits between 2017 and 2021, inclusive. Data from 39 countries were analyzed, comprising 94,181 contact lens fits. The relationship between percentage contact lens prescribing versus GDP (PPP) was highly statistically significant for daily disposable lenses (r 2 =0.35, P <0.0001), marginally significant for toric lenses (r 2 =0.08, P =0.06), and not significant for silicone hydrogel lenses (r 2 =0.01, P =0.42) or multifocal lenses (r 2 =0.02, P =0.35). The rate of prescribing daily disposable contact lenses, and to a lesser extent toric lenses, is related to national affluence. The contact lens industry, practitioners, and governments/regulatory bodies should remain cognizant of this association and, where possible, reduce cost barriers to the purchase of such contact lens products so that they can be prescribed based on important clinical, refraction, and lifestyle considerations.

Global contact lens prescribing 2000-2020

ABSTRACT Clinical relevance Contact lens prescribing data serve as a benchmark for eye care clinicians in assessing their own prescribing patterns and provide useful contextual information for researchers and the contact lens industry. Purpose To document global trends in contact lens prescribing during the first two decades of this century. Methods A longitudinal survey of contact lens prescribing was conducted by asking contact lens practitioners to provide 11 items of information from 10 consecutive contact lens fits between January and March each year from 1996 to 2020, inclusive. Results Data relating to 406,859 contact lens fits were collected from 71 countries between 1996 and 2020, generating 4.5 million data points. Demographic analysis for 61 nations returning ≥100 fits demonstrated that a majority of lenses (65–70%) were fitted to females. The average age of lens wearers was 30.8 ± 13.9 years for males and 32.5 ± 14.3 years for females. Trend analysis of 20 countries returning prescribing data for ≥13 years between 2000 and 2020 revealed the following: increase in the age of lens wearers; dramatic rise in the extent of fitting silicone hydrogel and daily disposable lenses; increased fitting of soft toric and multifocal lenses; increasing proportion of rigid lens fits in specialist (non-spherical) designs; incomplete provision of near contact lens corrections for contact lens wearing presbyopes; ongoing low levels of extended wear fits; and almost exclusive use of multi-purpose care systems. Daily disposable lenses were used for both full-time and part-time wear, whereas rigid and soft reusable lenses were primarily worn full time. Conclusions The evolution of international contact lens fitting over the first two decades of this century is documented. The data presented here may assist all stakeholders in advancing contact lens clinical practice, informing contact lens research, and guiding contact lens manufacturers.

An integrated operating mechanism for lot sentencing based on process yield

ABSTRACT A flexible sampling policy integrated with the consideration of past records is discussed in this paper for the quality evaluation of submission based on process yield. Lot sentencing plays the main role in buyer-seller business contracts for deliveries. A continuous partnership between the vendor and buyer can help in maintaining historically traceable results whereby the recording information is considered valuable. Hence, we propose a new sampling strategy with an integrated operating mechanism that considers the preceding inspection results to lessen the required average sample number based on process yield. Compared with the conventional methods, the proposed modified sampling strategy has the advantage of having a small number of samples for inspection while providing desirable protection under the same quality requirements and tolerable sampling risks. An application taken from the contact lens industry is presented to demonstrate the practicability of this research.

Analysis of diamond nanomachining of contact lens polymers using molecular dynamics

Contact lens polymer-based materials are extensively used in optical industry due to excellent corrosion resistance, possibility of mass production, and the ability to be processed without external lubrication. The demand for high accuracy and least surface roughness in contact lens industry drives the development of ultra-high precision machining technology of single-point diamond turning. Ultra-high precision machining of contact lens polymer involves material removal at a nanometric level that results in high surface finish. Due to the fast growth in optical industries, contact lens manufacture requires high accuracy and high surface quality. In this study, the nanometric machining of roflufocon E contact lens polymer with precise tool specifications and parameter choices have been investigated by a comparative analysis of molecular dynamics (MD) model with experimental study. Simulated MD acting cutting force, machine stresses, and temperature at the cutting region were used as bases of evaluation to observe the similarities of the model with the experimental surface roughness (Ra) nanomachining results. From the analysis, it can be inferred that the observed MD results commemorates with the different Ra as noted in the experiment.

A Study on the Manufacturing of Photochromic Contact Lenses using Spiropyran Derivatives

Purpose: The purposes of this study are to synthesize spiropyran derivatives for the development of photochromic contact lens using both casting-mould and sandwich processes and to investigate their photochromic and physical properties. Methods: The casting-mould method was performed by a manufacturing process in which monomers including spiropyran, HEMA, EGDMA, NVP and MMA were introduced into a solid mold and polymerized to solidify. The sandwich process producing triple-layered structures started with the 1st-copolymerization of HEMA, EGDMA, NVP and MMA. The resulting substrate was coated with a mixture of binder and spiropyran derivative, followed by 2nd-copolymerization with the same monomer ratio as the 1st-copolymerization process. The water content, contact angle, and optical properties of the manufactured lenses were investigated. The photochromic properties of the lenses such as color change behavior and absorbance were investigated under UV-light exposure for 1 min or in dark-room for 10 min. Results: The contact lenses prepared by casting-mould method showed water content of 35.21% and contact angle of 70.80° with a non-photochromic property. For the sandwich process, the lenses exhibited water content of 35.21% and contact angle of 70.80° with a good photochromic property. The lenses showed deep purple in color after exposure of UV light while they became colorless in dark-room. Conclusions: The contact lenses prepared by casting-mould method showed a non-photochromic property. The application of sandwich process exhibited a photochromic behavior without changes in the water content and contact angle of the lenses, suggesting that this method has practical and potential applications in contact lens industry.

Hyaluronic acid의 첨가방법에 따른 하이드로겔 콘택트렌즈의 물리적 특성과 lysozyme 흡착량 비교

목적: 하이드로겔 콘택트렌즈에 HA(hyaluronic acid)를 IPN(interpenetrating polymer network)방법과 화학적 공유결합 방법(CCB; Chemical covalent bonding)으로 첨가하였을 때 광투과율과 함수율의 물리적 특성과 lysozyme 흡착량을 비교하여 하이드로겔 콘택트렌즈의 기능성 부여를 위한 효과적인 HA의 첨가방법을 살펴보고자 한다. 방법: 실험실에서 제조한 하이드로겔 콘택트렌즈에 IPN과 CCB의 두 가지 방법으로 HA를 첨가하였다. 광투과율은 300~800 nm 범위에서 측정하였으며, 함수율은 0.9% NaCl 생리 식염수를 사용하여 중량측정법으로 측정하였다. Lysozyme 흡착량은 lysozyme이 포함된 인공눈물을 제조하여 12시간동안 흡착시킨 후 HPLC로 정량하였다. 결과: HA가 첨가된 하이드로겔 콘택트렌즈의 함수율은 HA가 첨가되지 않은 렌즈에 비해 증가하였으며, CCB 방법에 비해 IPN 결합에서 함수율이 더 높게 나타났다. 광투과율은 HA 첨가 전과 후 모두 90% 이상으로 나타났다. Lysozyme 흡착 감소율은 IPN 방법으로 제조한 콘택트렌즈는 60.0%이며, CCB 방법으로 제조한 콘택트렌즈에서는 40.4%로 나타났다. 결론: CCB 방법은 기능성 물질을 렌즈 내부와 표면 전체에 화학적으로 균일하게 분포시키기에 적절한 방법이며, IPN 방법은 상분리 없이 렌즈 표면에 기능성을 부여하기에 적절한 방법으로 여겨진다. Purpose: The hydrogel lenses have been functionalized with HA(Hyaluronic Acid) using two different methods: construction of an IPN(Interpenetrating Polymer Networks) and formation of CCB(Chemical Covalent Bonding). The lysozyme adsorption and physical properties such as optical transmittance and water content of the hydrogel lenses have been investigated in order to determine whether method is suitable for the application potentials in contact lens industry. Methods: HA have been added to the hydrogel lenses prepared in the Lab using the two different method, e.g. IPN and CCB. The optical transmittance was measured in the wavelength range of 300~800 nm. The water content was measured by the gravimetric method using 0.9% NaCl saline solution. The amounts of adsorbed lysozyme on the contact lenses was analyzed by HPLC after incubation for 12h in artificial tears. Results: The water content of the HA added hydrogel contact lenses was increased, and the lens made by IPN method showed higher water content than the lens made by CCB method. The optical transmittance was over 90% both before and after addition of HA. Comparing the lysozyme adsorption reduction ratio, contact lens manufactured by IPN method was 60.0%, and the lens made by CCB method was 40.4%. Conclusions: CCB method is appropriate to distribute the functional material evenly throughout the lens, whereas IPN method is effective for the case of giving the functionality on the lens surface without phase separation.

CLAE to move to online format

CLAE to move to online format

Electronic liquid crystal contact lenses for the correction of presbyopia

Presbyopia, the age-related reduction in near vision acuity, is one of the leading issues facing the contact lens industry due to an increasingly ageing population and limitations associated with existing designs. A plastic-based liquid crystal contact lens is described which is designed to allow switchable vision correction. The device is characterized by low operating voltages (<5V(rms)) and has curvatures suitable for placement upon the cornea. Imaging and Point Spread Function analysis confirm that the lens provides an increase in optical power of + 2.00 ± 0.25 D when activated, ideal for presbyopia correction.

Cytotoxic Effect on Corneal Surface of Multipurpose Soft Contact Lens Solution Which Contains Aloe Vera

Multipurpose solutions (MPSs) used for soft contact lens care contain agents, which can produce alterations in the tear film and ocular surface, such as keratitis, dry eye or conjunctivitis [1,2] Currently, the objective in the contact lens industry is to create novel formulations of MPSs with new agents in order to improve the ocular heath, comfort and to avoid discontinuing contact lens wear [3-5].

Characterization of materials for commercial and new nanophotonic soft contact lenses by optomagnetic spectroscopy

The contact lens industry and market have displayed a high level of dynamism in the past few decades, and have evolved into a rapidly changing field in which science and everyday practice constantly interact. This work presents the comparative research of characteristics of the basic (commercial) material and nanophotonic materials which were obtained by incorporation of fullerene nanoparticles and its derivate in basic material for soft contact lenses. Basic contact lens material was sintetized of monomer 2-hydroxyethyl methacrylate (HEMA), and fullerene and its derivates were used due to their good transmission characteristics in ultraviolet, visible and near infra-red spectrum. For the purposes of characterization of materials for soft contact lenses Optomagnetic Spectroscopy (OMS) was used. OMS is based on difference between diffusely reflected white light and reflected polarized white light. This research contributes to applied optical science and biomedical application industry.

Editorial

You will be forgiven if you have not heard of EUROMCONTACT. It is a non-profit organization and represents the European Federation of National Associations and International Companies of Contact Lens (and Lens Care) Manufacturers. It has three types of members: 1.National Associations of Manufacturers, such as SYFFOC (France), SPECTARIS (Germany), NAC (The Netherlands), ASSOTTICA (Italy), AEO (Spain), OPTICS Swiss Suppliers Association (Switzerland) and the ACLM (United Kingdom). 2.International Companies, such as Alcon, AMO Ltd., Bausch & Lomb, CooperVision, Johnson & Johnson Vision Care, Mark Ennovy and Menicon. 3.European Federation for the Contact Lens Industry, with about 100 members in 30 countries.

Exploring Compliance

Using both quantitative and qualitative research methods, this article explores in detail the lens wear and care habits of adapted contact lens wearers and seeks a better understanding of what enables and constrains patient compliance with appropriate lens wear and lens care. The study was conducted in two phases: a preliminary online questionnaire (quantitative phase), identifying types of noncompliance, and a series of sequentially conducted focus groups (qualitative phase), exploring constraints to, and enablers of, compliance. One hundred participants completed the online questionnaire; 12 of them also participated in one of four focus groups. The most frequently reported aspects of noncompliance revealed were failure to replace lenses when scheduled, inappropriate lens purchase and supply, sleeping while wearing lenses, use of tap water with lenses and failure to wash hands, failure to clean and replace cases regularly, and inappropriate use of care systems. Using an iterative process, a number of "themes" associated with noncompliance were identified in the focus group discussions. The most frequently occurring themes related to the consequences that may occur if patients were noncompliant with one or more aspects of their contact lens wear and the importance of receiving instructions regarding the most appropriate way to wear and care for their lenses. Most of the themes that emerged during the analysis were both constraints to, and enablers of, compliance. This study confirms the frequent types of noncompliance with contact lens wear and care while offering a greater understanding of what may constrain and enables contact lens wear and care compliance. Future qualitative studies may help eye care practitioners and the contact lens industry to develop strategies and tools to aid compliance and success in contact lens wear.

Biocompatibility in the Development of Silicone-Hydrogel Lenses

In response to patient demands for extended contact lens wearing times, the contact lens industry has developed novel silicone-hydrogel (SiHy) lens materials that combine the enhanced oxygen permeability of silicone polymers with the water-based comfort of conventional hydrogels. In the past 12 years since the successful launch of these SiHy lenses, much has been learned about their ability to provide the biocompatibility necessary to sustain ocular health and comfort. A review of the unique physiologic requirements for a successful extended wear lens and how the first and current SiHy lenses address them is provided.

The future of refractive surgery

Drug delivery by contact lenses has been a goal since Wichterle ndLimfirstmadementionof thepossibility in their originalhydroel lens patent. Many ophthalmic drugs could be better delivered hrough a contact lensmodality to achieve a therapeutic dosewithut toxic overload. The ophthalmic pharmaceutical market globally is more than ouble the size of the contact lens market, so there is a financial ncentive for the contact lens industry to develop this concept. hy then have we yet to see mass commercialisation of such roducts? One of the key reasons is the regulatory environment. he FDA classifies products that combine a medical device (such s a contact lens) and drugs as combination products, and the edicines and Healthcare products Regulatory Authority (MHRA) n the UK classifies them as Class III combination medical devices, hich are then subject to review by both the Notified Body and HRA for the medicinal component. Combination products comrise components that are regulated by different centres, so they aise challenging approval, policy, and review management chalenges. Differences in regulatory pathways for each component can mpact the regulatory processes for all aspects of product develpment, including preclinical testing, manufacturing and quality ontrol, adverse event reporting, promotion and advertising. This reaof contact lens research is sonewthatdepartments todealwith hese combinationproducts haveonly recently beenestablished, so he guidelines for obtaining approval are still in their infancy. Diferences in requirements between different countries across the lobe as well as differences in education levels between eye practiioners add to the complexity. Other barriers to the development of ombination products include the difficulties in achieving desired lution rates from lenses. Soaking lenses in a solution containing a rug does not necessarily provide prolonged consistent dosing.

Effect of Prophylactic Antibiotic Drops on Ocular Microbiota and Physiology during Silicone Hydrogel Lens Wear

Bacterial contamination of the contact lens surface has been demonstrated to cause corneal infiltrative events. A reduction in the rate of bacterially driven corneal infiltrative events associated with lens wear is one of the major goals of the contact lens industry. There is a concern over the potential of any antimicrobial strategy that there will be unwanted changes to the ocular microbiota or the development of resistance to the antimicrobial. The aim of this study was to investigate the effect of prophylactic topical antibiotic instillation during continuous wear of silicone hydrogel lenses on the normal ocular microbiota, the throat microbiota, and the ocular physiology. Forty-two male subjects were dispensed with lotrafilcon A silicone hydrogel contact lenses for a 3-month, 30 night continuous wear, monthly replacement trial. Subjects were randomized into either tobramycin 0.3% (test) or saline (control) drop group. Two drops were instilled into each eye on waking and before sleep. At monthly visits, lenses were collected aseptically, and ocular and throat swabs were performed, followed by standard microbial recovery and identifications. Any corneal infiltrative event at scheduled or unscheduled visits was recorded. Numbers of microbes recovered from eye swabs from the tobramycin (test) group were significantly lower than the control (p = 0.01). Gram-positive cocci were recovered less frequently from the test group (p = 0.001). There were no significant differences in the numbers and types of microbes recovered from lens samples, or the contamination rate of the lenses between the two groups. There were no changes in the numbers of fungi or bacteria from throat swabs. There was no evidence of changes to resistance profile of microbes in the throat. More eye swabs from the test group (68.5%) were culture-negative than swabs from control (46.5%; p = 0.002). The test group had less corneal staining superiorly (0.0 ± 0.0 vs. 0.3 ± 0.4; p = 0.025) but increased bulbar redness (2.2 ± 0.5 vs. 1.5 ± 0.4; p < 0.001) at the 3-month visit only, compared with control group. Overall, there appeared to be a minimal safety risk with 3-month's prophylactic antibiotic drop use during continuous wear of silicone hydrogel lenses. Clinically, antibiotic drop use induced a mild to moderate increase in bulbar redness by the 3-month time-point. Antibiotic use reduced microbiota on lids but did not affect the microbiota of the throat or change resistance to tobramycin.

Wettability conundrum: Discrepancies of soft contact lens performance in vitro and in vivo

The recognition and appreciation of soft contact lenses as simple, efficient and aesthetically gratifying vision-correction devices is ever growing, especially among younger population. Stable thin tear film uniformly spread over corrective lens surface is essential for acute vision, and also for comfortable and safe contact lens wear. The significant efforts have been invested by the contact lens industry to develop soft lens surface that is completely wet by tear aqueous in the ocular environment. Number of the publications dedicated to the wettability properties of the soft hydrogel lenses is on the steady rise. However, the clinical results show that no unambiguous correlation emerges when lens surface wettability in vitro is judged against tear film stability evaluated in vivo. This paper assesses and compares the modern techniques used for evaluation of soft contact lens surface wettability and reports some findings regarding relations between lens surface wettability in vitro and in vivo.

Pathogenesis of Contact Lens-Associated Microbial Keratitis

Sight-threatening microbial keratitis associated with contact lens wear remains a serious concern for patients, eye-care practitioners, and the contact lens industry. Several decades of research and some major advances in lens and solution technology have not resulted in a decline in disease incidence. Here, we offer a perspective on the complex pathogenesis of microbial keratitis, the factors that have prevented a better understanding of this disease, and new approaches being used to tackle this important clinical problem.

Demographics of international contact lens prescribing

Knowledge of differences in the demographics of contact lens prescribing between nations, and changes over time, can assist (a) the contact lens industry in developing and promoting various product types in different world regions, and (b) practitioners in understanding their prescribing habits in an international context. Data that we have gathered from annual contact lens fitting surveys conducted in Australia, Canada, Japan, the Netherlands, Norway, the UK and the USA between 2000 and 2008 reveal an ageing demographic, with Japan being the most youthful. The majority of fits are to females, with statistically significant differences between nations, ranging from 62 per cent of fits in Norway to 68 per cent in Japan. The small overall decline in the proportion of new fits, and commensurate increase in refits, over the survey period may indicate a growing rate of conversion of lens wearers to more advanced lens types, such as silicone hydrogels.

Patterns of fitting cosmetically tinted contact lenses

Cosmetically tinted soft contact lenses are an attractive option for contact lens wearers. Data that we have gathered from annual contact lens fitting surveys demonstrate that those wearing tinted lenses are more likely to be female (4.6% of all soft lenses fitted vs. 1.6% for males; p<0.0001) and younger (27+/-11 years vs. 33+/-13 years for those wearing non-tinted lenses; p<0.0001). Tinted lenses tend to be worn more on a part-time basis and are replaced less frequently than non-tinted lenses. The decline in fitting tinted lenses over the past 12 years may be due to (a) the current limited availability of tinted lenses in silicone hydrogel materials and daily disposable replacement frequencies, which together represent a significant majority (78%) of new soft lenses fits today, (b) growing concerns among lens wearers and practitioners relating to the risks of complications associated with the wearing of tinted lenses, and (c) reduced promotion of such lenses by the contact lens industry.