Contact Lens Field Research Articles

Amphiphilic ionic liquids as catalysts for efficient synthesis of novel isosorbide-based optical polymers with good biocompatibility and tunable properties

Accurate design and green synthesis of sustainable optical materials from renewable biomass has become vital in polymer science, especially in field of corneal contact lenses or intraocular lens (IOLs). Here we demonstrate the structure design of monomers and efficient synthesis of novel optical poly(isosorbide thioethers) (PITEs) with methyl, alicyclic or aromatic side-groups for high-performance biomedical optical materials. To regulate and control the polymerization process accurately, ionic liquids (ILs) were selected as catalysts and evaluated systematically. Since the presence of hydroxyl in anion improved proton-accepting ability combined with cations functionalized with dual activation sites, the IL tetraethylammonium lactate [TEA][Lac] in trace amount was discovered to show outstanding catalytic performance, better than the reported catalysts. According to experimental results, NMR analysis and DFT calculations, the anion-cation synergistic catalytic mechanism for nucleophilic hydrothiolation was proposed at molecular level. The activation barriers of transition structures decreased significantly from 211.1 to 16.7 kJ·mol−1 after using IL catalyst. The novel PITEs exhibited excellent biocompatibility for L929 cells, good optical transparency (>90 %) and higher refractive index (nD = 1.57 ∼ 1.61) than commercial IOLs (nD = 1.46 ∼ 1.55). Meanwhile, the PITEs possessed not only tunable mechanical properties (strain at break of 1.6 %∼367 %, storage modulus of 2.5 ∼ 4.3 GPa), but also suitable glass-transition temperature (Tg = 41.6 ∼ 92.9 °C) and good thermal stability for polymer melting or moulding process. This work provides a versatile approach for convenient fabrication of novel isosorbide-based polymers with adjustable properties for biomedical optical lenses, which are promising to achieve scale-up and application in future.

Evaluation of pigment distribution in contact lenses with iris patterns by multiprobe analysis methods

Iris-patterned lenses have recently become popular in the field of soft contact lenses (SCLs), and SCLs are typical examples of an industrial application of gel materials. As these patterns can be printed using oxidized-metal-containing pigments, the oxidized metals may be exposed on the lens surface depending on the printing method, potentially accounting for various health hazards. To evaluate the state of the exposed oxidized metal on the lens surface, we analyzed the colored layer, mainly consisting of pigments, on the lens surface via multiple probing methods, such as transmission electron microscopy (TEM), scanning TEM with energy-dispersive X-ray spectroscopy, hard X-ray photoelectron spectroscopy, and X-ray absorption fine structure (XAFS). Furthermore, we confirmed that the XAFS conversion electron yield (CEY) and fluorescence yield (FY) methods demonstrated high sensitivity toward revealing the existence of pigments. Thus, the use of a combination of XAFS CEY and FY methods can facilitate the effective distribution analysis of various elements in the interior of materials such as cosmetic CLs.

On the art and science of rigid contact lens fitting

ABSTRACT Clinical relevance Examination of the literature can help answer the age-old question of the extent to which rigid contact lenses can be considered an art versus a science. Background This work aims to assemble rigid contact lens-related publication metrics to identify the most impactful papers, authors, institutions, countries and journals. Methods A search was undertaken of the Scopus database to identify rigid contact lens-related articles published since this lens type was first described in 1949. The 25 most highly cited papers were determined from the total list of 1,823 papers found. Rank-order lists by count were assembled for the ‘top 25ʹ in each of four categories: authors, institutions, countries and journals. A subject-specific rigid contact lens h-index (hRL-index) was derived for each author, institution, country and journal to serve as a measure of impact in the field. A short list of the top constituents in each category were ranked by hRL-index and tabulated. Results The most highly cited paper (467 citations) is entitled ‘Risk factors and prognosis for corneal ectasia after LASIK’, by Randleman et al. Karla Zadnik (hRL = 20; 32 papers) and Richard Hill (h = 10; 50 papers) are most impactful and prolific authors, respectively. The Ohio State University (hRL = 24; 96 papers) is the most impactful and prolific institution and the United States (hRL = 51; 680 papers) is the most impactful and prolific country. Optometry and Vision Science (hRL = 30; 233 papers) is the most impactful journal. Conclusions Impactful authors, institutions, countries and journals in the field of rigid lenses are identified. Although there is perhaps an artistic element to rigid contact lens fitting, the solid literature base underpinning the field of rigid contact lenses revealed here belies the notion that rigid lenses fitting is more of an art than a science.

21st century citation analysis of the field of contact lenses

ABSTRACT Clinical relevance: The scientific foundations for clinical contact lens practice are rooted in the ophthalmic literature. This analysis of contact lens papers celebrates contemporary research achievements in the contact lens field. Background: This work aims to assemble contact lens-related publication metrics so as to identify the most impactful papers published so far this century, as well the top countries, authors, institutions and journals. Methods: A search was undertaken of the titles of papers on the Scopus database to identify contact lens-related articles published this century. The ten most highly cited papers were determined from the total list of 4,164 papers found. Rank-order lists by count were assembled for the ‘top 25ʹ in each of four categories: authors, institutions, countries and journals. A 20-year subject-specific contact lens h-index (hCL-20-index) was derived for each author, institution, country and journal to serve as a measure of impact in the field. The top 10 constituents (of the top 25) of each category were ranked by hCL-20-index and tabulated for consideration. Results: The most highly cited paper this century is entitled ‘Soft contact lens polymers: An evolution’, by Nicholson and Vogt. Lyndon Jones is the most impactful author, with a hCL-20-index of 32. The University of New South Wales (Australia) produces the most impactful contact lens-related papers, and the United States is the most highly-ranked country. Optometry and Vision Science is the most impactful journal in the contact lens field. Conclusions: Contact lens materials and lens-associated keratitis are topics of high interest in the contemporary contact lens literature, with an emerging interest in orthokeratology for myopia control and glucose monitoring. Impactful 21st century authors, institutions, countries and journals are identified. Optometry is revealed as the leading profession in relation to the publication of impactful contact lens-related papers.

The official guide to scleral lens terminology

PurposeIn absence of scleral lens standards, this article aims to provide an official definition of terms related to scleral lens fitting and manufacturing, in order to make more uniform the use of appropriate terms when describing, writing or lecturing about scelral lenses. Adoption of a common terminology may also favor more fruitful exchanges between eyecare practitioners and manufacturers. MethodsA committee of 12 advances scleral lens clinicians met and develop a list of terms related to scleral lens fit and manufacturing. Litterature review was made using PubMed database with the keywords “scleral lenses” and “terminology”. Other related publications such as textbooks were also considered valid references. Validation of the terms selected and their suggested definition was made by consultation of other experts in the field, over 2 years. A final version was adopted by the Scleral Lens Education Society late in 2018. ResultsThis article contains three main sections. Section I provides the definition of a scleral lens. Section II addresses the general terminology habitually applied to contact lens field but in the context of scleral lens usage. Finally, Section III suggests a decription of terms specifically used when fitting or manufacturing scleral lenses. At the end, recommendations are made to manufacturers about the essential elements to provide to eyecare practitioners in order to help them understanding the lens design and to customize their fit. ConclusionA common language is key to advancing the science and clinical practice of scleral lens fitting. The current terminology will help standardize this field, helping eyecare practitioners, educators, speakers and manufacturers to talk with the same language.

Spatiotemporal electrochemistry on flexible microelectrode arrays: Progress towards smart contact lens integration

We demonstrate a real-speed spatiotemporal electrochemical map showing both time- and position-varying concentration of an analyte in contact with a flexible microelectrode array. A polymer-based device of 11 μm in thickness comprising patterned gold metallisation on a polyimide substrate was fabricated, with eight individually addressable working electrodes (diameter 30 μm) and an integrated counter electrode. We performed a repeated sequence of high-speed chronoamperometric measurements at each electrode and processed the data to generate a spatiotemporal concentration map, in which a number of fluid effects, including bulk flow, diffusive mixing and homogenisation of two miscible fluids of different concentration were observed. This device was fabricated using processes compatible with an existing smart contact lens platform, with a view to develop integrated sensors in future work. We believe this technique has significant potential in the field of electrochemical smart contact lenses, both in introducing new functionality and in improving our ability to draw accurate and clinically-relevant conclusions from measurements made in the tear film.

Specialist practitioners

Specialist practitioners

Chronic wide-field imaging of brain hemodynamics in behaving animals.

Chronically monitoring cerebral activities in awake and freely moving status is very important in physiological and pathological studies. We present a novel standalone micro-imager for monitoring the cerebral blood flow (CBF) and total hemoglobin (HbT) activities in freely moving animals using the laser speckle contrast imaging (LSCI) and optical intrinsic signal (OIS) methods. A new cranial window method, using contact lens and wide field optics, is also proposed to achieve the chronic and wide-field imaging of rat's cerebral cortex. The hemodynamic activities of rats' cortex were measured for the first time without restriction of cables or fibers in awake and behaving animals. Chronic imaging showed the increase of CBF and HbT in motor cortex when the rats were climbing on the cage wall. Interestingly, the CBF activation of supplying vessel was smaller than that of parenchyma. Furthermore, after the climbing, CBF demonstrated fully return to the baseline while HbT showed a delayed recovery. The standalone micro-imager technology provides new possibilities of brain imaging in cognitive neuroscience studies.

Scleral lens for keratoconus: technology update.

Scleral lenses are large diameter lenses which rest over the sclera, unlike the conventional contact lenses which rest on the cornea. These lenses are fitted to not touch the cornea and there is a space created between the cornea and the lens. These lenses are inserted in the eyes after filling with sterile isotonic fluid. Generally, scleral contact lenses are used for high irregular astigmatism as seen in various corneal ectatic diseases such as keratoconus, pellucid marginal degeneration, or/and as liquid bandage in ocular surface disorders. In this article, we review the new developments, that have taken place over the years, in the field of scleral contact lenses as regard to new designs, materials, manufacturing technologies, and fitting strategies particularly for keratoconus.

Contact lens citation metrics – The Spanish connection

To eye care practitioners, citation metrics may seem to be a somewhat esoteric and irrelevant concept, far removed from the realities or real world, day-to-day clinical practice. However, quantitative analysis of the published literature is becoming increasingly important, and a beautiful example of this is presented in this issue of the Journal of Optometry. My former PhD student, Genis Cardona, has teamed up with Joan Sanz to undertake a thorough and telling analysis of current worldwide publishing trends in the contact lens field. When held in the mirror, this work reflects the growing contributions from Spanish researchers to the field...

Citation parameters of contact lens-related articles published in the ophthalmic literature.

This study aimed at exploring the citation parameters of contact lenses articles published in the Ophthalmology thematic category of the Journal Citation Reports (JCR). The Thompson Reuters Web of Science database was accessed to record bibliometric information and citation parameters of all journals listed under the Ophthalmology area of the 2011 JCR edition, including the journals with main publication interests in the contact lens field. In addition, the same database was used to unveil all contact lens-related articles published in 2011 in the same thematic area, whereupon differences in citation parameters between those articles published in contact lens and non-contact lens-related journals were explored. Significant differences in some bibliometric indicators such as half-life and overall citation count were found between contact lens-related journals (shorter half-life and fewer citations) and the median values for the Ophthalmology thematic area of the JCR. Visual examination of all Ophthalmology journals uncovered a total of 156 contact lens-related articles, published in 28 different journals, with 27 articles each for Contact Lens & Anterior Eye, Eye & Contact Lens, and Optometry and Vision Science. Significant differences in citation parameters were encountered between those articles published in contact lens and non-contact lens source journals. These findings, which disclosed contact lenses to be a fertile area of research, may be of interest to researchers and institutions. Differences in bibliometric indicators are of relevance to avoid unwanted bias when conducting between- and within-discipline comparisons of articles, journals, and researchers.

Do educators need educating?

Actual text: I was recently at the Spanish College of Optometry biennial conference and attended a meeting of contact lens lecturers from around Spain and Portugal. We discussed various ideas, mainly about how to share good practice and improve standards. What came to my mind was ‘is there a blueprint for training trainers?’ Well probably not but there are many things that we need to acknowledge such as the way students learn for example. Many educators themselves were taught by lecturers who would write on a blackboard or use acetate on an overhead projector, then came the 35 mm slide era followed by the Powerpoint era. More recently there is a move towards a much more integrated approach of various teaching methods. At my university our contact lens and anterior eye lectures generally follow a format where a narrated Powerpoint lecture is uploaded onto our internal virtual learning environment. This narrated version of the slides is designed to give the didactic element of the topic. The students listen to that before attending an interactive seminar on that topic. The seminar is also recorded so that students can listen to that afterwards. The seminar is designed to give additional information, such as case reports, or to clarify key points or for live demonstrations. It is a good way of doubling the contact time with the students without imposing further on an already packed formal timetable as the students can work in their own time. One problem that we noticed with this approach was that attendance can vary. If the students feel that they will gain something from the interactive seminar then they are more likely to attend – exam tips usually win them over! At the Spanish meeting the educators decided that they wanted to have regular meetings. The industry colleagues in attendance said that they were happy to help but could not necessarily give money, but they could offer meeting rooms, pay for lunch and evening meals. They even said that that they were happy to host meetings and invite other companies too (except to manufacturing plants). In the UK the British Committee of Contact Lens Educators (BUCCLE) meets for one day on three occasions in the year. The American Optometric Contact Lens Educators (AOCLE) meets annually at a three day event. Both these organisations get some help from industry. BUCCLE usually has one of its meetings at a university, one at a company training centre/manufacturing plant/national headquarters and one meeting the day before the BCLA annual conference. BUCCLE usually has its pre-BCLA meeting in conjunction with the International Association of Contact Lens Educators (IACLE). So when educators meet what would they discuss; well probably the focus should be on education rather than actual contact lens knowledge. For example sharing ideas on how to teach toric lens fitting would be better than discussing the actual topic of toric lenses itself. Most universities will have an education department with an expert who could share ideas on how to use the internet in teaching or how to structure lectures or assessments etc. In the past I have helped with similar training programmes in other countries and sharing good practice in pedagogy is always a popular topic. Anyone who is involved in education in the field of contact lenses should look at the IACLE web page and look out for the IACLE World Congress in 2015 in the days preceding the BCLA. Finally, IACLE, AOCLE and BUCCLE all exist as a result of generous educational grants from contact lens companies and anyone interested in finding out more about should refer to their respective web pages.

BCLA Pioneers Lecture – Evidence basis for patient selection: How to predict contact lens success

A prediction (Latin præ-, “before,” and dicere, “to say”) or forecast can be defined as “a statement about the way things will happen in the future, often but not always based on experience or knowledge. Although guaranteed information about the future is in many cases impossible, prediction is necessary to allow plans to be made about possible developments” (Wikipedia). Some predictions in the field of contact lenses have been very high profile and controversial, such as the predicted demise in rigid gas permeable contact lenses (RGPs) by Nathan Efron [1], whereas others, such as the presumed safety of multipurpose contact lens care solutions that have met specified regulatory criteria, have proved disastrously wrong (resulting in the Fusarium outbreak) [2].

Publication analysis of the contact lens field: What are the current topics of interest?

PurposeTo determine the main current research interests of scientists working in the contact lens field. MethodsAll articles published in the 2011 issues of all journals included in the Journal Citation Reports subject category Ophthalmology were inspected to expose those papers related to the contact lens field. Information regarding source journal was obtained and authorship details were recorded to determine the top most prolific authors, institutions and countries. A comprehensive list of key words was compiled to generate a two-dimensional term map in which the frequency of occurrence of a particular term is defined by label size and the distance between two terms is an indication of the relatedness of these terms, based on their co-occurrences within groups of key words. Clusters of related terms were also identified. ResultsVisual examination of all articles uncovered a total of 156 papers, published in 28 different journals. Contact Lens & Anterior Eye, Eye & Contact Lens and Optometry and Vision Science had 27 articles each. The most prolific authors and institutions revealed the predominance of countries with long research tradition in the contact lens field. Ten different word clusters or areas of interest were identified, including both traditional, yet unresolved issues (e.g., comfort or dry eye), and the latest research efforts (e.g., myopia control). ConclusionsThese findings, which revealed contact lenses to be a fertile area of research, may be of relevance to new researchers as well as to those interested in exploring the latest research trends in this scientific discipline.

Overview of factors that affect comfort with modern soft contact lenses

The past few years have been dynamic in the soft contact lens (SCL) field, resulting in a number of new research tools and new products to successfully fit and manage SCL wearers. In particular, the field has recently seen important developments that were designed to improve the SCL comfort in the quest for the “ultimate contact lens”. This comfort topic remains very timely and complex. Contact lens discomfort remains the primary reason for discontinuation of wear [ 1 Dumbleton K. Woods C.A. Jones L.W. Fonn D. The impact of contemporary contact lenses on contact lens discontinuation. Eye Contact Lens. 2013; 39: 93-99 Crossref PubMed Scopus (7) Google Scholar , 2 Richdale K. Sinnott L.T. Skadahl E. Nichols J.J. Frequency of and factors associated with contact lens dissatisfaction and discontinuation. Cornea. 2007; 26: 168-174 Crossref PubMed Scopus (62) Google Scholar ] and the number of discontinuations approximates the number of new fits annually, creating a significant drain on overall growth of the wearer base [ [3] Fonn D. Targeting contact lens induced dryness and discomfort: what properties will make lenses more comfortable. Optom Vis Sci. 2007; 84: 279-285 Crossref PubMed Scopus (51) Google Scholar ]. In the future, if novel applications of SCLs are to be successful, such as lenses to retard the development of myopia or to monitor diabetes, patients must be able to maintain years of comfortable use in order to receive the benefit from these innovations.

Are nanotechnology and robotics alternatives for therapeutic and theragnostic ophthalmic applications technologies for eye care services

Objective: To identify new technological advances in biotechnology, nanotechnology and robotics and their application in diagnosis and therapeutics for visual health. Methodology: The systematic review was made in Journal of Engineering, Journal of Biomedical Nanotechnology, NIH Public Access, Investigative Ophthalmology & Visual Science, Intechweb open access journal and books, among others for a total review of 43 articles and 6 books. The databases used were: NLM Catalogue, (NCBI), Scirus, CiteSeer and open access (Intechopen, Hindawi) with the advances in nanotechnology, artificial vision and robotics applied to visual health. Results: Retina implants, ocular memristors, ocular electrodes and chips, digital cameras and smart phone applications for low vision patients are some of the new alternatives in technology for the diagnosis based on biotechnology and nanotechnology and on the several years of job of interdisciplinary and multidisciplinary researchers of different fields to make innovation useful for visual impairment, ocular microbiology and molecular immunodiagnostics. The FDA recently approved the retina implants and this opened a new field to allow converting light signals into electrical signals. On the other hand, in the field of pharmacology, ocular nano-carrier molecules for sustained release of drugs and other devices to vitrectomies are some of the significant health advance studies for the future in visual health. Additionally, in the field of contact lenses and artificial corneas: biopolymers for biosensors have been developed for early detection of keratoconus and systemic diseases. Conclusions: Nanotechnology, biotechnology, robotics and bio-molecular biology are emerging and convergent sciences that when applied to visual sciences will be helpful for the patients, and are an increase in papers on innovation of this field, involving a multidisciplinary team requiring new divulgation in the role and performance of the visual health professionals of the future. To know and divulgate these new technologies is important for continued joint efforts around global education, and to create a database with new keywords, in order to know who and where these innovations are improving around the world, to planning researcher mobility and to include these new valuable technologies in the curriculum of visual health and get the patient safe.

An international survey of daily disposable contact lens prescribing

PurposeThe aim was to determine the extent of daily disposable contact lens prescribing worldwide and to characterise the associated demographics and fitting patterns.MethodsUp to 1,000 survey forms were sent to contact lens fitters in up to 40 countries between January and March every year for five consecutive years (2007 to 2011). Practitioners were asked to record data relating to the first 10 contact lens fits or refits performed after receiving the survey form. Survey data collected since 1996 were also analysed for seven nations to assess daily disposable lens fitting trends since that time.ResultsData were collected in relation to 97,289 soft lens fits, of which 23,445 (24.1 per cent) were with daily disposable lenses and 73,170 (75.9 per cent) were with reusable lenses. Daily disposable lens prescribing ranged from 0.6 per cent of all soft lenses in Nepal to 66.2 per cent in Qatar. Compared with reusable lens fittings, daily disposable lens fittings can be characterised as follows: older age (30.0 ± 12.5 versus 29.3 ± 12.3-years for reusable lenses); males are over‐represented; a greater proportion of new fits versus refits; 85.9 per cent hydrogel; lower proportion of toric and presbyopia designs and a higher proportion of part‐time wear. There has been a continuous increase in daily disposable lens prescribing between 1996 and 2011. The proportion of daily disposable lens fits (as a function of all soft lens fits) is positively related to the gross domestic product at purchasing power parity per capita (r2 = 0.55, F = 46.8, p < 0.0001).ConclusionsThe greater convenience and other benefits of daily disposable lenses have resulted in this modality capturing significant market share. The contact lens field appears to be heading toward a true single‐use‐only, disposable lens market.

Citation Analysis of the Contact Lens Field

To identify, analyze, and celebrate the most highly cited articles relating to contact lenses and the leading authors, journals, institutions, and countries associated with these publications. To capture all contact lens articles published since 1900, a search equation targeting specific contact lens-related terms in the titles of articles was derived and entered into "Web of Science." A rank order list of the 1000 most highly cited articles was assembled, each having received at least eight citations. The most prominent articles, authors, journals, institutions, and countries were identified from this list by simple counts. The most highly cited article relating to contact lenses (although cited exclusively in the physical sciences literature) is that of Phillip and Schmidt (J Non Cryst Solids 1984;63:288-92), reporting the application of the sol-gel process for the fabrication of rigid contact lenses. Eight of the top 10 articles ranked according to average number of citations/year relate to contact lens-associated microbial keratitis. Of the top eight authors, six have spent all, or a substantial proportion, of their academic careers in Australia and seven have worked in optometric research environments. Optometry and Vision Science is the leading journal. The top-ranked institution is The University of New South Wales, Sydney, Australia. The United States is the most prominent publishing country in the field, and Australia ranks highest when the numbers of highly cited articles are considered per head of population. This work provides a unique snapshot of significant articles relating to contact lenses.

Editorial

My role as an editor means that I need to try and stay on top of the literature of new developments in the field of contact lenses and anterior eye. I am sure others too, do the same in their respective roles, but maybe they do not have the privilege to access new information like I do. So, you can imagine my surprise when my friend and colleague, Mr Ali Mearza (Consultant Ophthalmologist at Charing Cross, London), called regarding a patient he saw who had complications after having undergone a new surgical technique of coloured anterior chamber implants overseas. Searching through the literature I found a handful of publications on these implants. Unsurprisingly, I was keen to publish this fascinating case report and share it with you, especially after I had a sneak preview of the images he took. So many questions come to mind when you read the report. Why have this type of surgery as a cosmetic procedure being the most obvious one. Also, the ethical question arises. To perform a purely cosmetic, elective procedure on an otherwise healthy eye! I do remember a time when we would question laser refractive surgery in the same way, but I cannot imagine that anterior chamber cosmetic implants will become acceptable to the majority of eye care practitioners in the way that laser refractive correction has become – let me know what you think.

Hyaluronic acid in hydrophilic contact lenses: Spectroscopic investigation of the content and release in solution

Two experimental spectroscopic methods for the determination of the content of hyaluronic acid in solution are provided based on the formation of complexes between the hyaluronic acid and cationic dyes with sensitivity down to concentrations of either 0.25 or 2.5 microg/ml. These techniques were applied to commercial hydrophilic contact lenses and allowed (i) distinguishing among contact lenses either loaded or non-loaded with hyaluronic acid, (ii) determining, for the loaded ones, the content of hyaluronic acid, (iii) evaluating the release of hyaluronic acid by the lens in solution, and (iv) determining the role of the hyaluronic acid in preventing the adsorption and the successive release by the contact lens of other components which can be present, for example, in the conservation solutions and/or in the blisters of the lenses. The results represent new physical chemistry insights for the field of contact lenses with impact on the advancement of current technology.