Development of oxidized hydroxyethyl cellulose-based hydrogel enabling unique mechanical, transparent and photochromic properties for contact lenses

With the development of smart devices, higher requirements are put forward for the stimuli-responsive materials. Stimuli-hydrogels as one kind of stimuli-responsive materials with hydrophilicity, demonstrate huge potential in developing intelligent devices for biomedical application. On this basis, we herein report that a sample method was devised to develop a novel composite hydrogel mainly based on oxidized hydroxyethyl cellulose and allyl co-polymer. Subsequently, a series of tests toward this oxidized hydroxyethyl cellulose-based hydrogel due to its structure and performance was applied. Here, the oxidized hydroxyethyl cellulose molecular chains were used as biomacromolecule templates to form Schiff base, borate and hydrogen bonds to obtain unique mechanical properties (fast recovery with almost no-hysteresis and remarkable compressive capacity), while a double bond functionalized spirooxazine (allyl spirooxazine derivative) was applied to endow photo- and pH sensitivity to the oxidized hydroxyethyl cellulose-based transparent hydrogel (T% = 93%) substrate. Furthermore, the oxidized hydroxyethyl cellulose-based hydrogel did exhibit good pH environment adaptability and noncytotoxicity in vitro test. Based on the advanced characteristics, the designed oxidized hydroxyethyl cellulose-based hydrogel has potential applications prospect in the development of safe, fashionable and pH- detectable contact lenses, thereby providing a new strategy for the development of smart, stylish contact lenses.

The Risks and Benefits of Myopia Control

PURPOSE

The prevalence of myopia is increasing around the world, stimulating interest in methods to slow its progression. The primary justification for slowing myopia progression is to reduce the risk of vision loss through sight-threatening ocular pathologic features in later life. The article analyzes whether the potential benefits of slowing myopia progression by 1 diopter (D) justify the potential risks associated with treatments.

METHODS

First, the known risks associated with various methods of myopia control are summarized, with emphasis on contact lens wear. Based on available data, the risk of visual impairment and predicted years of visual impairment are estimated for a range of incidence levels. Next, the increased risk of potentially sight-threatening conditions associated with different levels of myopia are reviewed. Finally, a model of the risk of visual impairment as a function of myopia level is developed, and the years of visual impairment associated with various levels of myopia and the years of visual impairment that could be prevented with achievable levels of myopia control are estimated.

RESULTS

Assuming an incidence of microbial keratitis between 1 and 25 per 10 000 patient-years and that 15% of cases result in vision loss leads to the conclusion that between 38 and 945 patients need to be exposed to 5 years of wear to produce 5 years of vision loss. Each additional 1 D of myopia is associated with a 58%, 20%, 21%, and 30% increase in the risk of myopic maculopathy, open-angle glaucoma, posterior subcapsular cataract, and retinal detachment, respectively. The predicted mean years of visual impairment ranges from 4.42 in a person with myopia of -3 D to 9.56 in a person with myopia of -8 D, and a 1-D reduction would lower these by 0.74 and 1.21 years, respectively.

CONCLUSIONS

The potential benefits of myopia control outweigh the risks: the number needed to treat to prevent 5 years of visual impairment is between 4.1 and 6.8, whereas fewer than 1 in 38 will experience a loss of vision as a result of myopia control.

Dataset on the questionnaire-based survey of the perceived risk of COVID-19 infection and Contact lens (CL) wearers

The data set presents data collected by an online questionnaire, applying closed-ended question types (multiple-choice, Likert scale) and questions Skip Logic. Instruments from previous studies in the field of optometry such as Contact Lens User Experience (CLUE Scales), Quality of Life Questionnaire (CLIQ), Quality of Vision (QoV) Questionnaire, did not meet the needs of this study. Therefore, in order to provide a statistically valid and consistent instrument to examine the psychopathological reactions in Contact lens wearers due to COVID-19, a new questionnaire was designed. The steps followed to collect and manage data were, definition of the objectives of the study, questionnaire design, questionnaire pilot testing (validity, reliability, repeatability), data administration and results interpretation. This descriptive survey employed online data collection using an anonymized questionnaire. The questionnaire was made available via an online link on social networks from 28/09/2020 to 11/10/2020. The questionnaire, in order to record the psychopathological reactions in Contact lens wearers due to COVID-19, was structured according to three psychopathological reactions (COVID-RS scales), (a) disorganized behaviors, (b) avoidant behaviors, (c) maladaptive information consumption. Therefore includes, (a) socio-demographic variables such as, (age, gender, educational level, Professional status, geographical area of habitation), (b) Health and Consumer behavior in Contact lens wearers, (c) Perceived risk of infection due to COVID-19 in Contact lens users, with a total of 22 items and maximum completion time 4 min. The survey included 1676 participants, 1037 were Contact Lens users and completed the online questionnaire. Of them, 76.7% (795) were female and 23.3% (242) were male. The educational level of the participants was, 7.5% (8) primary education, 18.9% (197) Secondary education, 57.9% (601) Undergraduate education, 22.3% (231) Postgraduate education. According to the age groups, 68.2% (707) participants were between 18 and 34 years old, 23.4% (278) participants were between 35 and 54 years old, 4.8% (50) participants were between 55 and 74 years old, 0.2% (2) participants were 75 and over. All data were exported to Excel spreadsheets. Only the completed questionnaires were used in the analyses. Data were analyzed using the Statistical Package for Social Sciences (SPSS) software version 24. Cronbach's alpha showed for the group, Health and Consumer behavior in Contact lens wearers (6 items), to reach acceptable reliability α= 0,881. Cronbach's alpha showed for the group, Perceived risk of infection due to COVID-19 in contact lens wearers (6 items), to reach acceptable reliability α= 0,886. The data set can be used to understand the relationship between the perceived risk of Covid-19 infection and contact lens (CL) use, the potential effect of the pandemic in Health and consumer behavior in Contact lens users, to draft a survey strategy and design, to verify results, etc.

Patients' attitudes and beliefs to presbyopia and its correction

OBJECTIVE

Presbyopia is the gradual inability to focus near objects with age. This study explores patients' attitudes and beliefs towards presbyopia including preferred modes of near refractive correction.

METHODS

In the United Kingdom, twenty-four volunteers completed an online questionnaire and attended a structured, recorded focus group. Participants' age ranged between 36 and 48 years, representing a pre-presbyopic and a presbyopic population. Attitudes and beliefs about presbyopia, its significance, and opinions about current refractive correction including multifocal contact lenses were transcribed and coded using content analysis for overarching themes and patterns.

RESULTS

Six participants (25%) were already wearing a near visual correction while 18 (75%) were not. Five key primary themes with clear inter-participant similarities were identified as 'age-related' (75%), 'acceptance' (50%), clear lack of 'familiarity with the word presbyopia' (65%), a mixed/ reluctant attitude 'towards (multifocal) contact lenses' (62.5%), and 'comfort and convenience' of a presbyopic correction (79%) whereby cost is of less importance.

CONCLUSION

The need for a reading correction was perceived as a sign of age. Spectacles were the most preferred mode of near vision correction, while comfort and convenience were seen as more important than cost. Patient education about presbyopia is lacking. Multifocal contact lenses are not necessarily the preferred visual correction even if the patient already wears contact lenses for distance.

Novel daily disposable therapeutic contact lenses based on chitosan and regenerated silk fibroin for the ophthalmic delivery of diclofenac sodium

The aim of this study was to investigate the possibility of chitosan and regenerated silk fibroin (CS/RSF) blended films as novel biomaterials for daily disposable therapeutic contact lenses based ophthalmic drug delivery system. Diclofenac sodium (DS), a hydrophilic anti-inflammatory agent, was loaded into CS/RSF films by a soaking method. The best conditions of DS loading manifested the loading time of 2 h and pH 6.5 of drug solution. The drug loading capacity and the drug release profile could be controlled by varying the film RSF content. With increasing the film RSF content from 0 to 30%, the amount of loaded DS increased from 12 to 23 µg. Furthermore, the prolong drug released within therapeutic level was obtained with increasing the film RSF content. Consequently, a fast released characteristic within a therapeutic level up to 3 h was observed with the 100CS/0RSF film. On the other hand, the 70CS/30RSF film demonstrated a significant prolonged drug release within therapeutic level up to 11 h. In conclusion, the CS/RSF films are promising as novel biomaterials for daily disposable therapeutic contact lenses-based ophthalmic delivery.

In vitro analysis of the interaction of tear film inflammatory markers with contemporary contact lens materials

PURPOSE

Several clinical studies have suggested that reusable silicone hydrogel contact lens materials exhibit a two-times increased rate of corneal infiltrative events compared to reusable hydrogels. One potential factor contributing to this complication relates to the differential uptake of tear film-based pro-inflammatory cytokines. The purpose of this study was to use an in vitro assay to investigate whether four pro-inflammatory cytokines differed in their uptake onto six contemporary contact lens materials.

METHODS

Conventional hydrogel (etafilcon A, omafilcon A) and silicone hydrogel (balafilcon A, comfilcon A, senofilcon A, somofilcon A) contact lens materials were soaked in solutions containing pro-inflammatory cytokines IL-1β, IL-6, IL-8 and TNF-α. Samples of the soaking solutions were collected over various time points and analyzed using the Meso Scale Discovery system, which served as a measurement of cytokine uptake onto the contact lens materials.

RESULTS

Both conventional hydrogels (etafilcon A, omafilcon A) and two of the four silicone hydrogels tested (balafilcon A, comfilcon A), exhibited some uptake of IL-1β, IL-8 or TNF-α (p < 0.05). Senofilcon A and somofilcon A did not exhibit uptake of any of these cytokines (p > 0.05). There was no uptake of IL-6 onto any of the contact lens materials investigated (p > 0.05).

CONCLUSION

The contact lens materials tested did not exhibit any uptake of IL-6 and furthermore, did not exhibit more than 10 ± 3 % to 25 ± 12 % uptake of IL-1β, IL-8 or TNF-α. Numerous factors could contribute to the reported increase in corneal infiltrative events with reusable silicone hydrogel materials, however, based on these results, it appears that uptake of these four cytokines are unlikely to contribute to this finding.

CLEAR - Evidence-based contact lens practice

Evidence-based contact lens -->practice involves finding, appraising and applying research findings as the basis for patient management decisions. These decisions should be informed by the strength of the research study designs that address the question, as well as by the experience of the practitioner and the preferences and environment of the patient. This reports reviews and summarises the published research evidence that is available to inform soft and rigid contact lens history and symptoms taking, anterior eye health examination (including the optimised use of ophthalmic dyes, grading scales, imaging techniques and lid eversion), considerations for contact lens selection (including the ocular surface measurements required to select the most appropriate lens parameter, lens modality and material selection), evaluation of lens fit, prescribing (teaching self-application and removal, adaptation, care regimen and cleaning instructions, as well as -->minimising risks of lens wear through encouraging compliance) and an aftercare routine.

Prevalence of dry eye syndrome in association with the use of contact lenses in Saudi Arabia

BACKGROUND

Dry eye disease is a tear film disorder which can cause discomfort to patients and negatively affect vision acuity. A number of risk factors has been reported to affect the incidence and severity of dry eye syndrome (DES). The aim is to study the prevalence of DES in Saudi Arabia and the factors affecting the severity of DES in relation to the use of contact lenses.

METHODS

A cross-sectional questionnaire-based study was conducted on 310 participants using the ocular surface disease index (OSDI) questionnaire and the eye dryness part from contact lens questionnaire-8 (CLDEQ-8). Dry eye OSDI scores were compared across different epidemiological and risk factors with focus on the use of contact lenses. Pearson and Spearman's correlation coefficients were used to analyze the frequency of contact lenses usage in relation to OSDI scores. Student's t-test and one-way analysis of variance (ANOVA) tests were used to compare means of two or more than two groups, respectively.

RESULTS

Forty eight (15.5%) of participants did not have any degree of DES, achieving an OSDI score between 0 and 12. Forty participants (12.9%) scored from 13 to 22, (mild DES), 44 (14.2%) were moderate, scoring 23-32 on the OSDI, while those who scored above 33 were 178 (57.4%) had severe DES. The mean score for all participants was 37.8. A high percentage of participants (84.5%) had some degree of DES. There was a strong positive correlation between OSDI score and the frequency of the feeling of dry eye and a moderate positive correlation between OSDI score and the intensity of dryness feeling. Out of 310 participants, 136 (43.9%) indicated using contact lenses. There was no significant association between the use of contact lenses per se and DES, however, those who used contact lenses more frequently had significantly higher OSDI scores.

CONCLUSIONS

Dry eye syndrome is a widespread, underdiagnosed condition in Saudi Arabia. The frequency of contact lenses use may contribute to the incidence of DES.

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.

Ocular and corneal aberrations changes in controlled randomized clinical trial MiSight® Assessment Study Spain (MASS)

Background

To compare ocular and corneal inherent aberrations in the naked eyes of randomly selected children fitted with MiSight contact lenses (CL) for myopia control, versus children corrected with single-vision spectacles (control), over a 24-months period.

Methods

Children aged 8 to 12 years, with myopia (-0.75 to -4.00 D sphere) and astigmatism (< -1.00 D cylinder) were randomly assigned to the lens study group (MiSight) or the control group (single-vision spectacles). The root mean square aberration (RMS) was determined as corneal (RMS_C), corneal high order RMS (HO_RMS_C), corneal low order RMS (LO_RMS_C), ocular (total) RMS (RMS_T), ocular high order RMS (HO_RMS_T), ocular low order RMS (LO_RMS_T), corneal spherical aberration (SA_C) and ocular SA (SA_T) were calculated by aberrometry measures at the baseline, on 12-months and 24-months visits. A 5 mm diameter was defined for the analysis in all visits for all subjects. Only the dominant eye was analyzed.

Results

Seventy-four subjects completed the clinical trial: 41 subjects from the MiSight group (age: 11.01 ± 1.23 years) and 33 from the single-vision group (age: 10.12 ± 1.38 years). RMS_T significantly changed (0.57 ± 0.20 µm, p = 0.029) after 24-months in the control group. In the MiSight group no significant changes were registered (p > 0.05). The SA_C and SA_T did not reveal significant changes between visits or between groups (p > 0.05).

Conclusions

Along 2 years, MiSight CL did not induce significant changes in RMS of anterior cornea or total ocular RMS. Contrary, in control group the RMS_T significantly changed as response of greater eye growth and myopia progression. The results obtained in present study allow to predict corneal or total aberration changes, in children, in response of wearing of MiSight lens along the time.

Trial registration

: ClinicalTrials.gov Identifier: NCT01917110.

Physicochemical characterization of a DMPC-based nanoemulsion for dry eye and compatibility test with soft contact lenses in vitro

INTRODUCTION

The use of contact lenses (CL) is often associated with hallmark symptoms of dry eye disease (DED) such as red eye and dryness. Even though lipid-based artificial tears are already marketed for DED, there is little evidence that supports their use while wearing soft CL.

METHODS

An oil in water (O/W) nanoemulsion was formulated with a highly-stable oily phase composed of castor oil and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). Physicochemical characterization of the DMPC-based nanoemulsion (DMPC-NE) was performed using the Zetasizer Nano ZSP, and its long-term stability was evaluated over 24 months; in addition, the in vitro cytotoxicity of DMPC-NE was determined by Neutral Red Uptake (NRU) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Finally, the physical compatibility of the DMPC-NE with soft CL was tested by measuring the power, diameter, thickness and UV transmittance of two different types of CL.

RESULTS

DMPC-NE had a mean particle size of 86.48 ± 4.22 nm, a polydispersity index of 0.22 ± 0.01 and a zeta potential of -33.23 ± 0.93 mV that remained with no changes after 24 months. DMPC-NE formulation, free of preservatives, showed no cytotoxicity and it was compatible with the physical properties of FDA-class II and -class IV CL.

CONCLUSION

DMPC-NE is a highly stable formulation for dry eye that is safe to be used while wearing soft CL.

Interactions between contact lenses and lens care solutions: Influence in optical properties

PURPOSE

Investigate changes in optical properties of contact lenses materials (transmittance and reflectance) and lens care solutions (absorption and fluorescence) resulting from its interaction.

METHODS

From an experimental study, triplicate measurements of transmittance and reflectance of five contact lenses (Senofilcon A, Lotrafilcon B, Balafilcon A, Comfilcon A, and Omafilcon A), as well as UV-vis absorption and fluorescence of four lens care solutions (LCS) (ReNu MultiPlus, Biotrue, OPTI-FREE PureMoist, and AOSept Plus), were evaluated before and after 8 h, one day and one week in storage. The outcomes were provided by Shimadzu UV3101-PC UV-vis-NIR spectrophotometer equipped with an integrating sphere, between 200-700 nm, and SPEX-Fluorolog 2 FL3-22 spectrofluorometer.

RESULTS

All variables exhibited statistically significant differences over time. Comfilcon A showed the lowest ultraviolet radiation (UVR) A & B attenuation. Balafilcon A and Lotrafilcon B displayed a slight suppression of UVR. Senofilcon A was effective in UVR protection and showed less effect on the fluorescence of lens care solutions. Overall, the reflectance decreased after storage (p < 0.05). AOSept Plus absorbance and fluorescence demonstrated lower interactions than multipurpose solutions (MPS), and Lotrafilcon B induced more remarkable changes in optical properties of LCS than the other materials.

CONCLUSION

The findings suggest that optical variables of lens care solutions and contact lenses changed mutually after storage, probably associated with biochemical and biophysical interactions between components and the release of some polymer compounds. These findings can provide additional information about the interaction of CL materials and LCS in clinical behavior.

Strategies to prolong the residence time of drug delivery systems on ocular surface

Ocular diseases may be treated via different routes of administration, such as topical, intracameral, intravitreal, oral and parenteral. Among them the topical route is most accepted by patients, although it provides in many cases the lowest bioavailability. Indeed, when a topical formulation reaches the precorneal area, i.e., the drug absorption and/or action site, it is rapidly eliminated due to eye protection mechanisms such as blinking, basal and reflex tearing, and naso-lacrimal draining. To avoid this and to reduce the frequency of dosing, various strategies have been developed to prolong drug residence time after topical administration. These strategies include the use of viscosity increasing and mucoadhesive excipients as well as combinations thereof. From the drug delivery system point of view, liquid and semisolid formulations are preferred over solid formulations such as ocular inserts and contact lenses. Furthermore, liquid and semisolid formulations can contain nano- and microcarrier systems that contribute to a prolonged residence time. Within this review an overview about the different types of excipients and formulations as well as their performance in valid animal models and clinical trials is provided.

Müller Muscle-conjunctival Resection with or without Tarsectomy and Combined with Bandage Contact Lens Use in Ptosis Patients with Corneal Graft

PURPOSE

To examine the efficacy of ptosis correction with a Müller muscle-conjunctival resection with or without tarsectomy (MMCR±T), combined with bandage contact lens (BCL) use, in corneal graft patients.

METHODS

Seven patients with corneal grafts who underwent MMCR±T for treatment of ptosis were evaluated retrospectively. A BCL was applied to the grafts at the end of the surgery. The collected data included preoperative and postoperative visual acuity, marginal reflex distance 1 (MRD-1), presence of Hering's dependency by the phenylephrine test, symmetry outcomes, and complications after MMCR±T.

RESULTS

The average duration between the penetrating keratoplasty and MMCR±T was 14 months, with a follow-up time of 10.4 months after MMCR±T. Hering's dependency was observed in four (57.2%) patients before MMCR±T, and MRD-1 was increased in all patients based on preoperative phenylephrine tests. The mean preoperative MRD-1 was -0.14 ± 0.55 mm, and the mean postoperative MRD-1 was 2.35 ± 0.89 mm (p < 0.0001). Symmetry outcomes of perfect (<0.5 mm), good (0.5-1 mm), and fair (≥1 mm) were noted after MMCR±T in three, three, and one patients, respectively. During the follow-up, no obvious corneal epitheliopathy, keratitis, or corneal graft rejection/failure were noted in any cases. BCL use was well tolerated by all patients.

CONCLUSIONS

Most patients achieved good surgical outcomes with the application of the BCL to protect the graft and with the use of the phenylephrine test and Hering's dependency to predict the final eyelid position and symmetry. MMCR±T combined with BCL may therefore represent an alternative approach for correction of ptosis in patients with corneal graft.

Application of systane complete for the treatment of contact lens discomfort

PURPOSE

To understand the safety of treating contact lens (CL) discomfort with a new artificial tear when it is directly applied to a CL-wearing eye.

METHODS

This was a two-week, two-visit, double-masked study that randomized participants with CL discomfort to use Systane Complete (artificial tear), Sensitive Eyes (rewetting drop), or no treatment. Drops were applied before, twice during, and after CL use each day. Corneal staining served as the primary safety metric. Conjunctival staining, tear break-up time, Schirmer's test, CL comfort (Contact Lens Dry Eye Questionnaire-8 [CLDEQ-8]), and dry eye symptoms (Standardized Patient Evaluation of Eye Dryness [SPEED]) were also evaluated.

RESULTS

This study recruited 73 participants with a mean age of 30.3 ± 11.5 years; 18 % of the participants were male. There were no significant changes in ocular surface signs from baseline or between the artificial tear and rewetting drop groups after two weeks (p ≥ 0.05). Participants in the artificial tear and rewetting drop groups had significant improvements in CLDEQ-8 scores after two weeks of treatment compared with baseline (p < 0.0001), though scores for this test were not significantly different between these groups after two weeks (p = 0.94). CLDEQ-8 scores were significantly better in the artificial tear and rewetting drop groups compared with no treatment after two weeks (p < 0.0001).

CONCLUSIONS

Both drops were found to be safe for use with CLs while also significantly improving ocular symptoms compared to no treatment after two weeks of use.

Development of a contact Lens risk survey

PURPOSE

To describe the development and report psychometric properties of the Contact Lens Risk Survey (CLRS) to identify patients at risk for soft contact lens-related complications.

METHODS

Psychometric properties of the CLRS, a web-based survey with branching logic, were determined using data from 5 multi-site fieldings (n = 1059), including re-fielding to sub groups. Responses from participants with and without an active red eye were used to identify risk factors of a red eye event and calculate an overall risk score. A 6th fielding of the CLRS (n = 171) was used to assess discriminate validity.

RESULTS

Participants needed 11-12 min to complete the survey with a negligible difference by age. Internal consistency was excellent (Cronbach's α ≥ 0.70) for 3 of the 5 constructs identified by factor analysis. Twelve of the 17 survey items exhibited excellent within-subject repeatability (Kappa ≥ 0.61). Between-subject agreement, assessed in 18-25 year olds, was high for the majority of items, suggesting good generalizability across different populations of SCL wearers. The ability of the model using individual items of the CLRS to discriminate Controls and participants with a red eye was good with an area under the curve of 0.779.

CONCLUSION

The CLRS tool is a repeatable and valid instrument to standardize documentation of demographic, behavior, and exposure factors which appear to drive the greatest risk of a contact lens related red eye event.

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.

Evaluation of commercial soft contact lenses for ocular drug delivery: A review

Soft contact lenses have generated growing interest in ocular drug delivery due to their potential to enhance drug bioavailability in ocular tissues. Commercially available soft contact lenses offer several advantages for ocular drug delivery as they are manufactured on a large scale, which guarantees the availability of a consistent and reproducible product, and their favorable safety profile is well-established through broad clinical use. Here we review the rationale for using commercially available soft contact lenses for ocular drug delivery; summarize the evolution of the materials used in contact lens fabrication; and explore various methods used to improve the drug release characteristics and its tissue penetration. While significant progress has been made, several issues still require further attention for the commercial launch of a viable drug-eluting contact lens product, including control of initial burst release, shelf-life stability, and drug loss during processing or storage.

Ocular symptoms associated with digital device use in contact lens and non-contact lens groups

PURPOSE

Previous reports indicate that "eye fatigue" occurs in roughly 60 % of the adult population using digital devices and may negatively impact quality of life. However, the construct of eye fatigue remains poorly understood. The goal of this study was to quantify the relationship among symptoms most frequently associated with eye fatigue in those using digital devices.

METHODS

Six hundred and two soft contact lens (SCL) wearers and 127 non-contact lens (non-CL) wearers who reported using digital devices at least 4 hours per day completed a questionnaire assessing the frequency and severity of ten symptoms commonly associated with digital device-related eye fatigue. Subjective ratings were made separately for each symptom using unipolar, five-point Likert scales.

RESULTS

From the initial pool of respondents, 89 % of the SCL wearers reported experiencing eye fatigue more than once per month, while over 60 % reported more than once per week. Notably, eye fatigue frequency did not differ between the soft contact and non-contact lens groups. Although eye strain/pain, dryness, and tired eyes were the most frequently endorsed symptoms by both groups, only dryness and eye irritation were significant factors that discriminated the SCL from the non-CL wearers on the basis of frequency and severity. Principal component analysis indicated that eye strain/pain, soreness, tired eyes, and headaches may comprise a "primary sensations" factor, whereas burning, eye irritation, tearing and dryness comprise a "secondary or surface sensations" factor, and blurred/double vision and words move/float comprise a "visual sensations" factor. Confirmatory factor analysis (CFA) of frequency and severity ratings for SCL wearers yielded excellent fits (RMSEA = 0.046 and 0.050, respectively) with construct reliabilities ranging from 0.729 to 0.824.

CONCLUSION

Frequent and severe eye fatigue is highly prevalent among both soft contact lens and non-contact lens wearers. Those utilizing SCL do not experience symptoms at higher frequency or severity. Key descriptors of digital eye fatigue have been identified and may then be used to help identify and evaluate specific causative, palliative, or ameliorating factors.

Impact of Refractive Errors on Da Vinci SI Robotic System

Objective

To investigate the impact of refractive errors on binocular visual acuity while using the Da Vinci SI robotic system console.

Methods

Eighty volunteers were examined on the Da Vinci SI robotic system console by using a near vision chart. Refractive errors, anisometropia status, and Fly Stereo Acuity Test scores were recorded. Spherical equivalent (SE) were calculated for all volunteers' right and left eyes. Visual acuity was assessed by the logarithm of the minimal angle of resolution (LogMAR) method. Binocular uncorrected and best corrected (with proper contact lens or glasses) LogMAR values of the subjects were recorded. The difference between these values (DiffLogMAR) are affected by different refractive errors.

Results

In the myopia and/or astigmatism group, uncorrected SE was found to have significant impact on the DiffLogMAR (p < 0.001) and myopia greater than 1.75 diopter had significantly higher DiffLogMAR values (p < 0.05). Subjects with presbyopia had significantly higher DiffLogMAR values (p < 0.01), and we observed positive correlation between presbyopia and DiffLogMAR values (p = 0.33, p < 0.01). The cut off value of presbyopia that correlated the most with DiffLogMAR differences was found to be 1.25 diopter (p < 0.001). In 13 hypermetropic volunteers, we found significant correlation between hypermetropia value and DiffLogMAR (p > 0.7, p < 0.01). The statistical analysis between Fly test and SE revealed a significant impact of presbyopia and hypermetropia to the stereotactic view of the subject (p = -0.734, p < 0.05).

Conclusion

Surgeons suffering from myopia greater than 1.75 diopter, presbyopia greater than 1.25 diopter (D), and hypermetropia regardless of grade must always perform robotic surgeries with the proper correction.

Biofilm modelling on the contact lenses and comparison of the in vitro activities of multipurpose lens solutions and antibiotics

During the contact lens (CL) usage, microbial adhesion and biofilm formation are crucial threats for eye health due to the development of mature biofilms on CL surfaces associated with serious eye infections such as keratitis. For CL related eye infections, multi drug resistant Pseudomonas aeruginosa or Staphylococcus aureus (especially MRSA) and Candida albicans are the most common infectious bacteria and yeast, respectively. In this study, CL biofilm models were created by comparing them to reveal the differences on specific conditions. Then the anti-biofilm activities of some commercially available multipurpose CL solutions (MPSs) and antibiotic eye drops against mature biofilms of S. aureus, P. aeruginosa, and C. albicans standard and clinical strains were determined by the time killing curve (TKC) method at 6, 24 and 48 h. According to the biofilm formation models, the optimal biofilms occurred in a mixture of bovine serum albumin (20% v/v) and lysozyme (2 g/L) diluted in PBS at 37 °C for 24 h, without shaking. When we compared the CL types under the same conditions, the strongest biofilms according to their cell density, were formed on Pure Vision ≥ Softens 38 > Acuve 2 ∼ Softens Toric CLs. When we compared the used CLs with the new ones, a significant increase at the density of biofilms on the used CLs was observed. The most active MPS against P. aeruginosa and S. aureus biofilms at 24 h was Opti-Free followed by Bio-True and Renu according to the TKC analyses. In addition, the most active MPS against C. albicans was Renu followed by Opti-Free and Bio-True at 48 h. None of the MPSs showed 3 Log bactericidal/fungicidal activity, except for Opti-Free against S. aureus and P. aeruginosa biofilms during 6 h contact time. Moreover, all studied antibiotic eye drops were active against S. aureus and P. aeruginosa biofilms on CLs at 6 h and 24 h either directly or as 1/10 concentration, respectively. According to the results of the study, anti-biofilm activities of MPSs have changed depending on the chemical ingredients and contact times of MPSs, the type of infectious agent, and especially the CL type and usage time.

The efficacy of low vision aids with contact lenses in pediatric population

PURPOSE

To compare the efficacy of contact lens use with low vision aids (LVA) with the efficacy of spectacle use with low vision aids.

METHODS

Thirty-six pediatric patients with low vision were enrolled in this study between January 2015 and March 2017. The patients were examined for best-corrected visual acuity (BCVA) with spectacles, spectacles with LVA, contact lenses and contact lenses with LVA. Toleration of the patients with contact lenses and LVA were recorded at the final follow-up exam.

RESULTS

The mean BCVA with spectacles was detected as 1.11 ± 0.25 log MAR and the mean BCVA improved to 0.35 ± 0.13 log MAR with the use of spectacles and LVA, which was statistically significant. The mean BCVA with contact lens, which was 0.99 ± 0.22 log MAR, improved to 0.40 ± 0.21 log MAR with contact lens and LVA, which was also significant. There was a statistically significant improvement in BCVA of the patients with contact lenses only when compared to spectacles only. The mean BCVA significantly improved in patients using LVA with contact lenses when compared to LVA with spectacles. Tolerations of the patients with contact lenses and LVA were found to be well at 29 of 36 (80.55%) at final follow-up (26.11 ± 6.85 months).

CONCLUSION

Contact lens use in pediatric patients with low vision especially with LVA offers better visual acuity, a decrease in nystagmus amplitude, wider field of view and comfort.

Could telehealth help eye care practitioners adapt contact lens services during the COVID-19 pandemic?

The COVID-19 pandemic has necessitated government-imposed restrictions on social interactions and travel. For many, the guidance has led to new ways of working, most notably a shift towards working remotely. While eye care practitioners (ECPs) may continue to provide urgent or emergency eye care, in many cases the travel restrictions present a unique challenge by preventing conventional face-to-face examination. Telephone triage provides a useful starting point for establishing at-risk and emergency patients; but patient examination is central to contact lens patient care. The indeterminate period over which conventional practice will be suspended, and the risk that resumption of 'normal' practice could be impeded by a potential secondary peak in COVID-19 cases, hastens the need for practitioners to adapt their delivery of eyecare. Specifically, it is prudent to reflect upon supportive evidence for more comprehensive approaches to teleoptometry in contact lens practice. Smartphone based ocular imaging is an area which has seen considerable growth, particularly for imaging the posterior eye. Smartphone imaging of the anterior eye requires additional specialised instrumentation unlikely to be available to patients at home. Further, there is only limited evidence for self-administered image capture. In general, digital photographs, are useful for detection of gross anterior eye changes, but subtle changes are less discernible. For the assessment of visual acuity, many electronic test charts have been validated for use by practitioners. Research into self-administered visual acuity measures remains limited. The absence of a comprehensive evidence base for teleoptometry limits ECPs, particularly during this pandemic. Knowledge gaps ought to be addressed to facilitate development of optometry specific evidence-based guidance for telecare. In particular, advances in ocular self-imaging could help move this field forwards.

Thirty years of 'quiet eye' with etafilcon A contact lenses

Frequent replacement contact lenses made from the etafilcon A hydrogel lens material were introduced onto the market over 30 years ago, and etafilcon A remains the most widely used hydrogel lens material today. Although the prescribing of silicone hydrogel lenses is increasing, millions of lens wearers globally have been wearing hydrogel lenses for many years and exhibit a physiologically-stable 'quiet eye', with a low profile of adverse events. Hydrogel lenses are demonstrated to maintain a low inflammatory response and infection risk profile during daily wear, which in the case of etafilcon A, may be related to its low modulus, and the naturally-protective, anti-microbial, non-denatured lysozyme absorbed into the lens from the tear fluid. Although improved corneal physiology from decreased hypoxia with silicone hydrogel lenses is well accepted, equivalent levels of corneal oxygenation are maintained during daily wear of low to medium powered hydrogel lenses, which do not impede the daily corneal de-swelling process, and do not induce clinically significant changes in ocular health. Therefore, hydrogel lenses remain an important alternative for daily wear in modern contact lens practice.

Refractive index of soft contact lens materials measured in packaging solution and standard phosphate buffered saline and the effect on back vertex power calculation

PURPOSE

To measure the refractive index (RI) of commonly available soft contact lens (CL) materials, their packaging solutions and compare to the manufacturers' nominal RI. The relationship between RI versus water content, and the effect of inaccurate RI when converting lens power measured in solution to in-air back vertex power were examined.

METHODS

The RI of 18 single vision soft CL materials were measured using CLR 12-70 digital refractometer. Three lenses of each material were measured, in their packaging solution and then after soaking in standard phosphate buffered saline (PBS). The RIs of packaging solution were also measured. Accuracy requirements for correct wet to dry power conversion based on thick lens formula were projected.

RESULTS

The standard deviation between three samples was less than 0.005. The measured RI ranged from 1.3744 ± 0.001-1.4265 ± 0.0004 for PBS soaked and from 1.3739 ± 0.0003-1.4264 ± 0.0024 for packaging solution soaked materials. Comparing nominal with mean measured PBS and packaging solution RIs, 5 and 3 lens materials, respectively, fell outside ISO tolerance. The packaging solution RI of DailiesAquaComfortPlus had the largest difference of 0.0040, compared to RI of standard PBS. For converting lens power measured in PBS to in-air power, the difference between measured and nominal RI of 0.0104 would result in wrongly calculated in-air power 0.99 D for a -6.00 D lens.

CONCLUSION

The CLR 12-70 is reliable and accurate refractometer for the measurement of soft CL materials. Accurate RI measurements are of relevance with increased use of wavefront sensors to measure lens power while they are immersed in solution. Even small errors in solution or material RI can lead to significant errors in converted in-air power. To obtain valid in-air lens power results, measurement conditions must match the material and solution RIs used for the conversion.