Effect of Contact Lens Wear and a Near Task on Tear Film Break-Up

End-of-day assessment of asymptomatic versus highly symptomatic soft contact lens wearers

PURPOSE

To investigate differences in key clinical parameters between asymptomatic and highly symptomatic soft contact lens (CL) wearers after 14 h of wear.

METHODS

In this pilot investigation, Phase 1 identified asymptomatic (CLDEQ-8 score ≤ 7) and highly symptomatic (CLDEQ-8 score ≥ 20) subjects after fitting with nelfilcon A CLs. Phase 2 investigated the following over a single nelfilcon A CL-wearing day (14 ± 2 h): blinking characteristics, tear meniscus height (TMH), non-invasive tear break-up time (NIBUT), tear film osmolarity and eyelid margin staining. Parameters for the two groups were compared using linear mixed models and post-hoc testing. The relationship between comfort scores and the clinical parameters was also investigated.

RESULTS

Overall, 161 and 42 subjects were enrolled into Phase 1 and 2, respectively. Twenty-five asymptomatic and 17 symptomatic subjects completed Phase 2. Lower eyelid TMH was decreased after 14 h in symptomatic compared with asymptomatic subjects (least square mean [LSM] difference -0.04 mm, 95% CI: -0.07, -0.01). Osmolarity was lower in symptomatic than in asymptomatic subjects at fitting (LSM difference -9.89, 95% CI: -18.91, -0.86). Upper eyelid margin staining was greater after 14 h in symptomatic than in asymptomatic subjects (LSM difference 0.53, 95% CI: 0.01, 1.05) and greater after 14 h than baseline in the symptomatic group (LSM difference 0.61, 95% CI: 0.16, 1.07). There was a significant relationship between comfort and upper eyelid margin staining (r = -0.40, 95% CI: -0.63, -0.11) and blink rate (r = -0.31, 95% CI: -0.57, -0.003).

CONCLUSION

The potential parameters most effective in differentiating asymptomatic from symptomatic wearers were upper eyelid margin staining and lower TMH. The parameter with the strongest relationship to comfort was upper eyelid margin staining, where higher comfort scores were associated with lower levels of staining.

Recognition and evaluation of mental workload in different stages of perceptual and cognitive information processing using a multimodal approach

This study explores the effects of different perceptual and cognitive information processing stages on mental workload by assessing multimodal indicators of mental workload such as the NASA-TLX, task performance, ERPs and eye movements. Repeated measures ANOVA of the data showed that among ERP indicators, P1, N1 and N2 amplitudes were sensitive to perceptual load (P-load), P3 amplitude was sensitive to P-load only in the prefrontal region during high cognitive load (C-load) states, and P3 amplitude in the occipital and parietal regions was sensitive to C-load. Among the eye movement indicators, blink frequency was sensitive to P-load in all C-load states, but to C-load in only low P-load states; pupil diameter and blink duration were sensitive to both P-load and C-load. Based on the above indicators, the k-nearest neighbours (KNN) algorithm was used to propose a classification method for the four different mental workload states with an accuracy of 97.89%.Practitioner summary: Based on the results of this study, it is possible to implement the monitoring of mental workload states and optimise brain task allocation in operations involving high mental workload, such as human-computer interaction.

Evaluating the Performance of Verofilcon A Daily Disposable Contact Lenses in a Group of Heavy Digital Device Users

Purpose

The purpose of this study was to evaluate the performance of verofilcon A daily disposable contact lenses (CL) in CL wearers who identified themselves as heavy digital device users.

Patients and Methods

This prospective, non-masked, open-label study enrolled CL wearers who reported ≥6 hours digital device use per day. Participants were dispensed with the verofilcon A study lenses for 14±2 days, to be worn for at least 5 days a week and 10 hours per day, while continuing their normal routine of digital device use. Participants rated the lens performance at the Day 14 visit using a 0-100 (with 100 being best) scale. Ratings were completed at lens insertion, after 6 hours of digital device use, just before CL removal and for overall experience. Participants also completed a 4-point (strongly agree/disagree, slightly agree/disagree) Likert scale-based questionnaire.

Results

Thirty-two participants were eligible and completed the study (27 females; age 25.8 ± 6.0 years, ranging from 19 to 40). Overall lens performance ratings at the Day 14 visit (mean ± standard deviation) for comfort, dryness, and clarity of vision were 91 ± 11, 88 ± 11, and 92 ± 9, respectively. Subjective ratings were stable throughout the day with no significant differences after insertion, after 6 hours of digital device use and before CL removal (all p>0.05). The majority of participants agreed that the study lenses performed well, provided good all-day comfort (28/32; p<0.01) and good all-day vision (29/32; p<0.01). Participants also agreed that after ≥6 hours of digital device use they were satisfied with CL comfort (27/32; p<0.01), vision (29/32; p<0.01) and that the lenses provided good performance (26/32; p<0.01).

Conclusion

Verofilcon A lenses were found to perform well, with high ratings for comfort, dryness and vision that remained high throughout the day, during extensive digital device use.

TFOS Lifestyle: Impact of contact lenses on the ocular surface

Several lifestyle choices made by contact lens wearers can have adverse consequences on ocular health. These include being non-adherent to contact lens care, sleeping in lenses, ill-advised purchasing options, not seeing an eyecare professional for regular aftercare visits, wearing lenses when feeling unwell, wearing lenses too soon after various forms of ophthalmic surgery, and wearing lenses when engaged in risky behaviors (e.g., when using tobacco, alcohol or recreational drugs). Those with a pre-existing compromised ocular surface may find that contact lens wear exacerbates ocular disease morbidity. Conversely, contact lenses may have various therapeutic benefits. The coronavirus disease-2019 (COVID-19) pandemic impinged upon the lifestyle of contact lens wearers, introducing challenges such as mask-associated dry eye, contact lens discomfort with increased use of digital devices, inadvertent exposure to hand sanitizers, and reduced use of lenses. Wearing contact lenses in challenging environments, such as in the presence of dust and noxious chemicals, or where there is the possibility of ocular trauma (e.g., sport or working with tools) can be problematic, although in some instances lenses can be protective. Contact lenses can be worn for sport, theatre, at high altitude, driving at night, in the military and in space, and special considerations are required when prescribing in such situations to ensure successful outcomes. A systematic review and meta-analysis, incorporated within the review, identified that the influence of lifestyle factors on soft contact lens dropout remains poorly understood, and is an area in need of further research. Overall, this report investigated lifestyle-related choices made by clinicians and contact lens wearers and discovered that when appropriate lifestyle choices are made, contact lens wear can enhance the quality of life of wearers.

Blink Rate Measured In Situ Decreases While Reading From Printed Text or Digital Devices, Regardless of Task Duration, Difficulty, or Viewing Distance

Purpose

To compare blinking measured in situ during various tasks and examine relationships with ocular surface symptoms. The day-to-day repeatability of the blink rate and interblink interval was assessed.

Methods

Twenty-four students (28.6 ± 6.3 years; 8 male and 16 female) completed six reading tasks (printed text, laptop, TV, smartphone, smartphone at 50% brightness, smartphone with complex text), and two nonreading tasks (conversation, walking) in a randomized cross-over study. Ocular surface symptoms and clinical signs were assessed. The blink rate and interblink interval were measured using a wearable eye tracking headset. Blink parameters were compared across tasks and time (linear mixed model and post hoc comparisons with Bonferroni correction). Associations between blinking, symptoms, ocular surface, and clinical signs were assessed (Spearman's correlation). The smartphone reading task was completed twice to determine the coefficient of repeatability.

Results

The blink rate was lower (mean 10.7 ± 9.7 blinks/min) and the interblink interval longer (mean 9.6 ± 8.7 seconds) during all reading tasks compared with conversation (mean 32.4 ± 12.4 blinks/min; 1.5 ± 0.6 seconds) and walking (mean 31.3 ± 15.5 blinks/min; 1.9 ± 1.3s) (P < 0.001). There were no significant differences in blink parameters between any of the reading tasks or between conversation and walking. Changes in blinking occurred within 1 minute of starting the task. No associations were evident between blink rate or interblink interval and ocular surface symptoms or signs. The coefficient of repeatability was ±12.4 blinks/min for blink rate and ±18.8 seconds for interblink interval.

Conclusions

Spontaneous blinking can be measured reliably in situ. The blink rate was decreased and the interblink interval increased during reading compared with conversation and walking. Changes in blinking were immediate, sustained, and not associated with ocular surface symptoms or signs.

Effects of wearing swimming goggles on non-invasive tear break-up time in a laboratory setting

PURPOSE

The use of swimming goggles (SG) has demonstrated to alter different ocular parameters, however, the impact of wearing SG on the tear film stability remain unknown. The main objective of this study was to determine the short-term effects of wearing SG on tear film surface quality break-up time (TFSQ-BUT).

METHODS

Twenty-eight young healthy adults (14 men and 14 women) wore a drilled SG, and TFSQ-BUT was measured before, during and after SG use. Dynamic-area high-speed videokeratoscopy was used for the non-invasive assessment of TFSQ-BUT.

RESULTS

TFSQ-BUT was significantly reduced while SG wear in comparison to the baseline measurement (4.8 ± 4.5 s vs. 8.8 ± 6.9 s; corrected p-value = 0.017, d = 0.57, mean difference = 4.0 [0.6, 7.3]; 45% reduction). Immediately after SG removal, TFSQ-BUT rapidly recovered baseline levels (8.2 ± 5.9 s vs. 8.8 ± 6.9 s; corrected p-value = 0.744). The impact of wearing SG on TFSQ-BUT were independent of the gender of the participants (p = 0.934).

CONCLUSION

The use of SG induces a TFSQ-BUT reduction, with these changes returning to baseline levels immediately after SG removal. These data may be of relevance for the management of dry eye patients, who need to avoid circumstances that exacerbate tear film instability. Nevertheless, these results must be interpreted with caution since the experiment did not entirely mimic real-life conditions (e.g., eye cup piece drilled, time of exposure, environmental conditions). Future studies should consider the inclusion of dry eye patients and older individual in order to explore the generalizability of these findings.

Digital Eye Strain Among Radiologists: A Survey-based Cross-sectional Study

BACKGROUND

Computers have become a fundamental part of clinical radiology departments. Radiologists tend to spend long hours in front of computers, reading and analyzing medical images. This prolonged use of computers is associated with digital eye strain. Therefore, this study aimed to estimate the prevalence of digital eye strain among radiologists and determine its contributory factors.

METHODS

An online survey was sent to radiologists practicing in hospitals in the Eastern Province of Saudi Arabia. The survey addressed demographic information, workload and workstation environment, personal eye care, and evaluation of digital eye strain symptoms as well as the strategies employed to reduce these symptoms. Results were analyzed descriptively using Chi-square tests and logistic regression analyses.

RESULTS

The survey was completed by 198 participants (111 men and 87 women), including residents (40.9%), senior registrars (27.3%), and consultants (27.3%). Most participants (71.2%) were aged below 40 years. Most participants tend to spend 7-9 hours daily reviewing medical images. Overall, 50 participants (25.3%) take a break from work once daily only. A total of 53 participants (26.8%) reported undergoing an eye examination within the past year and 100 participants (50.5%) reported experiencing digital eye strain. Multivariate logistic regression analysis revealed that female sex (odds ratio [OR] = 3.9; 95% confidence interval [95% CI]: 1.6-10.0) and the practice of taking breaks once a day (OR = 15.1; 95% CI: 2.4-94.1) or twice a day (OR = 5.5; 95% CI: 1.1-28.4) only were associated with higher rates of digital eye strain symptoms.

CONCLUSION

Digital eye strain is a prevalent condition among radiologists regardless of their subspecialty. It is more commonly seen among radiology residents. Being a female and not taking frequent breaks were associated with higher rates of digital eye strain.

Low Vision and Dry Eye: Does One Diagnosis Overshadow the Other?

SIGNIFICANCE

The prevalence of dry eye disease and low vision increases with age; they share risk factors and can be the result of underlying common causes. They are generally studied separately; however, combining these perspectives is relevant for research on assistive technology given that sustained focus affects the tear film because of decreased blinking rates.

PURPOSE

The objective of this study was to elucidate to which extent dry eye disease risk factors, signs, and symptoms are assessed in low vision patients who receive an eye examination as part of their vision rehabilitation services.

METHODS

Using a retrospective chart review, dry eye disease risk factors, signs, or symptoms were extracted from 201 randomly selected files that contained an eye examination in the past 5 years from two vision rehabilitation centers.

RESULTS

Demographic variables of charts from the two sites did not differ (mean visual acuity, 0.85 logMAR [standard deviation, 0.53; range, 0 to 2.3]; mean age, 71.2 years [standard deviation, 19 years; range, 24 to 101 years]). Fifty charts (25%) mentioned at least one dry eye disease symptom. Sixty-one charts (30.3%) reported systemic medications that can exacerbate dry eye disease, whereas 99 (49.2%) contained at least one systemic disease thought to contribute to dry eye disease symptoms; 145 (72.1%) mentioned at least one type of ocular surgery. Artificial tears were documented in 74 charts (36.8%). Few specific dry eye tests were performed, with the exception of corneal integrity assessment reported in 18 charts (8.95%).

CONCLUSIONS

Low vision patients have multiple risk factors for dry eye disease; however, dry eye disease tests were not frequently performed in comprehensive low vision eye examinations in this sample. More efforts should be made to assess dry eye disease to enhance comfort and functional vision, especially with the increasing demands of digital devices as visual aids.

CLEAR - Contact lens technologies of the future

Contact lenses in the future will likely have functions other than correction of refractive error. Lenses designed to control the development of myopia are already commercially available. Contact lenses as drug delivery devices and powered through advancements in nanotechnology will open up further opportunities for unique uses of contact lenses. This review examines the use, or potential use, of contact lenses aside from their role to correct refractive error. Contact lenses can be used to detect systemic and ocular surface diseases, treat and manage various ocular conditions and as devices that can correct presbyopia, control the development of myopia or be used for augmented vision. There is also discussion of new developments in contact lens packaging and storage cases. The use of contact lenses as devices to detect systemic disease has mostly focussed on detecting changes to glucose levels in tears for monitoring diabetic control. Glucose can be detected using changes in colour, fluorescence or generation of electric signals by embedded sensors such as boronic acid, concanavalin A or glucose oxidase. Contact lenses that have gained regulatory approval can measure changes in intraocular pressure to monitor glaucoma by measuring small changes in corneal shape. Challenges include integrating sensors into contact lenses and detecting the signals generated. Various techniques are used to optimise uptake and release of the drugs to the ocular surface to treat diseases such as dry eye, glaucoma, infection and allergy. Contact lenses that either mechanically or electronically change their shape are being investigated for the management of presbyopia. Contact lenses that slow the development of myopia are based upon incorporating concentric rings of plus power, peripheral optical zone(s) with add power or non-monotonic variations in power. Various forms of these lenses have shown a reduction in myopia in clinical trials and are available in various markets.

CLEAR - Effect of contact lens materials and designs on the anatomy and physiology of the eye

This paper outlines changes to the ocular surface caused by contact lenses and their degree of clinical significance. Substantial research and development to improve oxygen permeability of rigid and soft contact lenses has meant that in many countries the issues caused by hypoxia to the ocular surface have largely been negated. The ability of contact lenses to change the axial growth characteristics of the globe is being utilised to help reduce the myopia pandemic and several studies and meta-analyses have shown that wearing orthokeratology lenses or soft multifocal contact lenses can reduce axial length growth (and hence myopia). However, effects on blinking, ptosis, the function of Meibomian glands, fluorescein and lissamine green staining of the conjunctiva and cornea, production of lid-parallel conjunctival folds and lid wiper epitheliopathy have received less research attention. Contact lens wear produces a subclinical inflammatory response manifested by increases in the number of dendritiform cells in the conjunctiva, cornea and limbus. Papillary conjunctivitis is also a complication of all types of contact lenses. Changes to wear schedule (daily disposable from overnight wear) or lens materials (hydrogel from SiHy) can reduce papillary conjunctivitis, but the effect of such changes on dendritic cell migration needs further study. These changes may be associated with decreased comfort but confirmatory studies are needed. Contact lenses can affect the sensitivity of the ocular surface to mechanical stimulation, but whether these changes affect comfort requires further investigation. In conclusion, there have been changes to lens materials, design and wear schedules over the past 20+ years that have improved their safety and seen the development of lenses that can reduce the myopia development. However, several changes to the ocular surface still occur and warrant further research effort in order to optimise the lens wearing experience.

Effect of stimulus dimension on perception and cognition

Stimuli characteristics ha a decisive role in our perception and cognition. In the present study, we aimed to evaluate the effects of dimension of stimuli, two-dimensional (2D) versus three-dimensional (3D), on perception and working memory. In the first experiment, using the method of eye tracking, a higher blink rate, pupil size, and the number of saccade for three compared to 2D stimuli revealed a higher perceptual demand of 3D stimuli. In the second experiment, visual search task shows a higher response time for 3D stimuli and an equal performance with 2- and 3D stimuli in spatial working memory task. In the third experiment, four working memory tasks with high and low cognitive and perceptual load revealed 3D stimuli are memorized better in the both low and high load of working memory. We can conclude that 3D stimulus, compared 2D, imposes a higher load on perceptual system, but it is memorized better. It could be concluded that the phenomenon of filtering should occur in the early perceptual system for preventing overload.

Use of digital displays and ocular surface alterations: A review

Digital display use has been accepted to be implicated as a contributing factor for dry eye disease (DED). Abnormal blinking during computer operation, including a reduced blink rate and an incomplete eyelid closure, increased palpebral fissure as consequence of high visualization angles, and meibomian gland dysfunction associated to long-term display use, are behind the increased prevalence of dry eye signs and symptoms found in digital display users. Previous research reveals significant reductions in tear volume and stability, alterations in tear film composition, including increased osmolarity, inflammatory cytokines, oxidative stress markers and reduced mucin secretion, eyelid abnormalities and ocular surface damage, encompassing corneal and conjunctival staining and bulbar redness, as a direct consequence of digital display use. In this regard, individual differences in the way that the various digital displays are typically set up and used may account for differences in their effects on induced dryness signs and symptoms. Furthermore, factors such as the use of contact lenses or inappropriate working environments, usually accompanying the use of displays, may significantly increase the prevalence and the severity of induced dry eye. Other factors, such as old age and female gender are also relevant in the appearance of associated alterations. Finally, clinicians should adopt a treatment strategy based on a multidirectional approach, with various treatments being applied in conjunction.

Prophylactic action of lipid and non-lipid tear supplements in adverse environmental conditions: A randomised crossover trial

PURPOSE

To evaluate the prophylactic benefits of lipid-based and non-lipid-based artificial tear lubricants, in dry eye disease, after adverse environmental exposure.

METHODS

Twenty-eight participants with dry eye disease were recruited in a prospective, double-masked, randomised crossover trial. On separate days, participants were randomised to receive a single application of a lipid-containing tear supplement (Systane Complete) to one eye, and a non-lipid containing eye drop (Systane Ultra) to the contralateral eye. Participants were then exposed to a previously validated simulated adverse environment. Symptoms, non-invasive tear film breakup time, lipid layer grade, and tear meniscus height were assessed at three time points; baseline, following eye drop instillation, and after exposure to the adverse environment.

RESULTS

Both treatments effected improvements in symptoms and non-invasive tear film stability following instillation (all p < 0.05), although an improvement in lipid layer quality was limited to the lipid-containing nano-emulsion tear supplement (p = 0.003). Although protective effects were conferred by both treatments following exposure to the simulated adverse environment, more favourable symptomology scores, non-invasive tear film stability, and lipid layer quality were observed in the lipid-containing tear supplement group (all p < 0.05). No significant changes were observed in tear meniscus height in both treatment groups (all p > 0.05).

CONCLUSIONS

Both the lipid and non-lipid-based artificial tear supplement demonstrated prophylactic benefits in a simulated adverse environment. However, the ability to preserve tear film quality and reduce dry eye symptomology was greater with the lipid-containing eye drop.

TRIAL REGISTRATION NUMBER

ACTRN12619000361101.

Subjective Comparison of Pre-Lens Tear Film Stability of Daily Disposable Contact Lenses Using Ring Mire Projection

PURPOSE

To subjectively evaluate the in vivo tear film stability of three daily disposable contact lenses (DDCLs) using placido ring reflection at lens wear times of 5 mins and 8 and 12 hrs.

PATIENTS AND METHODS

This prospective, randomized, observer-masked, 3-way crossover study evaluated 28 subjects with good tear film stability. In vivo tear film stability was assessed for three DDCLs (nelfilcon A, etafilcon A, omafilcon A) on three different days over 12 hrs of lens wear. Time to first distortion by non-invasive keratography drying-up time (NIK-DUT_f) was assessed by reviewing the captured videos. Lens wettability was also graded subjectively by three investigators using a scale from 0 (no visible distortions) to 3 (distortions in more than one-third of the ring reflection zone). Medians were analyzed statistically.

RESULTS

Mean NIKDUT_f at 8 hrs was longer for nelfilcon A and shorter for etafilcon A and omafilcon A, but the differences were not significant. NIK-DUT_f did not differ significantly among nelfilcon A, etafilcon A and omafilcon A DDCLs at all visits (p=0.36). Subjective wettability grades after 5 mins, 8 hrs, and 12 hrs differed significantly for etafilcon A (P <0.01) and omafilcon A (p < 0.01), but not for nelfilcon A (p = 0.05), DDCLs.

CONCLUSION

Grading was sufficiently sensitive to differentiate the wettability performances of the three lens materials. Nelfilcon A maintained wettability over the wearing period, whereas etafilcon A material showed faster dewetting at 8 and 12 hrs than at 5 mins after lens insertion.

Effects of Blink Rate on Tear Film Optical Quality Dynamics with Different Soft Contact Lenses

Objective

The aim of this study was to investigate tear film optical quality dynamics for four types of silicone hydrogel contact lenses (SHCLs) for daily wear over a 15-day period and for different blink rate (BR) patterns.

Methods

A prospective randomized, double-blind, cross-over pilot study including four SHCLs (A: lotrafilcon B (Air Optix plus HydraGlyde, Alcon Laboratories); B: samfilcon A (Ultra, Bausch & Lomb); C: comfilcon A (Biofinity, CooperVision); and D: filcom V3 (Blu:gen, Mark'Ennovy)). Serial measurements of Objective Scatter Index (OSI) using the HD Analyzer (Visiometrics S.L., Terrassa, Spain) were taken at different blinking patterns: blinking every 2.5 seconds (high BRs) and every 9 seconds (low BRs). They were performed during the first visit before CL insertion (baseline), after 20 minutes of CL wear (Day 1), and during the last visit after 8 hours of CL wear on day 15 of use (Day 15).

Results

Normal young healthy subjects were recruited and fitted with the four lenses. For low BRs, the mean OSI value increased over time for all CLs and the slope of the curve also increased for all CLs, except for CL D. However, for high BRs, the mean OSI value increased only for CLs B and C and the slope of the curve did not change over time for any of them.

Conclusions

These results suggest that the tear film optical quality dynamics after wearing SCHLs for 15 days seems to undergo a slight deterioration only for lowest BR.

Management of digital eye strain

Digital eye strain, an emerging public health issue, is a condition characterised by visual disturbance and/or ocular discomfort related to the use of digital devices and resulting from a range of stresses on the ocular environment. This review aims to provide an overview of the extensive literature on digital eye strain research with particular reference to the clinical management of symptoms. As many as 90 per cent of digital device users experience symptoms of digital eye strain. Many studies suggest that the following factors are associated with digital eye strain: uncorrected refractive error (including presbyopia), accommodative and vergence anomalies, altered blinking pattern (reduced rate and incomplete blinking), excessive exposure to intense light, closer working distance, and smaller font size. Since a symptom may be caused by one or more factors, a holistic approach should be adopted. The following management strategies have been suggested: (i) appropriate correction of refractive error, including astigmatism and presbyopia; (ii) management of vergence anomalies, with the aim of inducing or leaving a small amount of heterophoria (~1.5^Δ Exo); (iii) blinking exercise/training to maintain normal blinking pattern; (iv) use of lubricating eye drops (artificial tears) to help alleviate dry eye-related symptoms; (v) contact lenses with enhanced comfort, particularly at end-of-day and in challenging environments; (vi) prescription of colour filters in all vision correction options, especially blue light-absorbing filters; and (vii) management of accommodative anomalies. Prevention is the main strategy for management of digital eye strain, which involves: (i) ensuring an ergonomic work environment and practice (through patient education and the implementation of ergonomic workplace policies); and (ii) visual examination and eye care to treat visual disorders. Special consideration is needed for people at a high risk of digital eye strain, such as computer workers and contact lens wearers.

Use of a novel extended blink test to evaluate the performance of two polyvinylpyrrolidone-containing, silicone hydrogel contact lenses

Background

Sustained digital display viewing reduces eye blink frequency and tear film stability. To retain water and preserve a smooth optical surface, contact lens manufacturers have integrated the humectant polyvinylpyrrolidone (PVP) into silicone hydrogel contact lenses. In this study, extended blink time (EBT) was used to assess visual stability over a prolonged blink interval of two PVP-containing silicone hydrogel lenses, samfilcon A (SAM) and senofilcon A (SEN).

Materials and methods

This randomized, bilateral, masked, crossover study assessed lens performance in ten subjects after 16 hours of wear. EBT, ie, the time elapsed between cessation of blinking and blur-out of a threshold letter on the acuity chart, was measured. At the end of the wear period, subjects reported duration of computer use and rated visual quality (VQ) and comfort while wearing the assigned lens, and the investigator evaluated lens surface wetting characteristics. Each lens was removed and immediately weighed to determine total water content.

Results

EBTs were 10.42 seconds for SAM and 8.04 seconds for SEN (p = 0.015). Subjective ratings of VQ after 16 hours of wear were 84.6 for SAM and 74.4 for SEN (p = 0.049). Comfort ratings were 85.9 for SAM and 80.2 for SEN (p > 0.05). Median times of computer use were 6-8 hours for both lens types. Post blink, 70.0% of SAM and 30.0% of SEN lenses were completely wet (p = 0.021). Total water content after wear was 43.7% for SAM and 35.5% for SEN (p < 0.001).

Conclusion

EBT measurement indicated more stable vision with the PVP-containing SAM polymer compared with the PVP-containing SEN polymer. The SAM polymer also demonstrated better surface wetting and maintained higher water content after a prolonged period of wear. EBT can be valuable in assessing vision stability of patients after hours of computer use.

Patient-reported Outcomes for Assessment of Quality of Life in Refractive Error: A Systematic Review

SIGNIFICANCE

This review has identified the best existing patient-reported outcome (PRO) instruments in refractive error. The article highlights the limitations of the existing instruments and discusses the way forward.

PURPOSE

A systematic review was conducted to identify the types of PROs used in refractive error, to determine the quality of the existing PRO instruments in terms of their psychometric properties, and to determine the limitations in the content of the existing PRO instruments.

METHODS

Articles describing a PRO instrument measuring 1 or more domains of quality of life in people with refractive error were identified by electronic searches on the MEDLINE, PubMed, Scopus, Web of Science, and Cochrane databases. The information on content development, psychometric properties, validity, reliability, and responsiveness of those PRO instruments was extracted from the selected articles. The analysis was done based on a comprehensive set of assessment criteria.

RESULTS

One hundred forty-eight articles describing 47 PRO instruments in refractive error were included in the review. Most of the articles (99 [66.9%]) used refractive error-specific PRO instruments. The PRO instruments comprised 19 refractive, 12 vision but nonrefractive, and 16 generic PRO instruments. Only 17 PRO instruments were validated in refractive error populations; six of them were developed using Rasch analysis. None of the PRO instruments has items across all domains of quality of life. The Quality of Life Impact of Refractive Correction, the Quality of Vision, and the Contact Lens Impact on Quality of Life have comparatively better quality with some limitations, compared with the other PRO instruments.

CONCLUSIONS

This review describes the PRO instruments and informs the choice of an appropriate measure in refractive error. We identified need of a comprehensive and scientifically robust refractive error-specific PRO instrument. Item banking and computer-adaptive testing system can be the way to provide such an instrument.

TFOS DEWS II pain and sensation report

Pain associated with mechanical, chemical, and thermal heat stimulation of the ocular surface is mediated by trigeminal ganglion neurons, while cold thermoreceptors detect wetness and reflexly maintain basal tear production and blinking rate. These neurons project into two regions of the trigeminal brain stem nuclear complex: ViVc, activated by changes in the moisture of the ocular surface and VcC1, mediating sensory-discriminative aspects of ocular pain and reflex blinking. ViVc ocular neurons project to brain regions that control lacrimation and spontaneous blinking and to the sensory thalamus. Secretion of the main lacrimal gland is regulated dominantly by autonomic parasympathetic nerves, reflexly activated by eye surface sensory nerves. These also evoke goblet cell secretion through unidentified efferent fibers. Neural pathways involved in the regulation of meibomian gland secretion or mucin release have not been identified. In dry eye disease, reduced tear secretion leads to inflammation and peripheral nerve damage. Inflammation causes sensitization of polymodal and mechano-nociceptor nerve endings and an abnormal increase in cold thermoreceptor activity, altogether evoking dryness sensations and pain. Long-term inflammation and nerve injury alter gene expression of ion channels and receptors at terminals and cell bodies of trigeminal ganglion and brainstem neurons, changing their excitability, connectivity and impulse firing. Perpetuation of molecular, structural and functional disturbances in ocular sensory pathways ultimately leads to dysestesias and neuropathic pain referred to the eye surface. Pain can be assessed with a variety of questionaires while the status of corneal nerves is evaluated with esthesiometry and with in vivo confocal microscopy.

TFOS DEWS II pathophysiology report

The TFOS DEWS II Pathophysiology Subcommittee reviewed the mechanisms involved in the initiation and perpetuation of dry eye disease. Its central mechanism is evaporative water loss leading to hyperosmolar tissue damage. Research in human disease and in animal models has shown that this, either directly or by inducing inflammation, causes a loss of both epithelial and goblet cells. The consequent decrease in surface wettability leads to early tear film breakup and amplifies hyperosmolarity via a Vicious Circle. Pain in dry eye is caused by tear hyperosmolarity, loss of lubrication, inflammatory mediators and neurosensory factors, while visual symptoms arise from tear and ocular surface irregularity. Increased friction targets damage to the lids and ocular surface, resulting in characteristic punctate epithelial keratitis, superior limbic keratoconjunctivitis, filamentary keratitis, lid parallel conjunctival folds, and lid wiper epitheliopathy. Hybrid dry eye disease, with features of both aqueous deficiency and increased evaporation, is common and efforts should be made to determine the relative contribution of each form to the total picture. To this end, practical methods are needed to measure tear evaporation in the clinic, and similarly, methods are needed to measure osmolarity at the tissue level across the ocular surface, to better determine the severity of dry eye. Areas for future research include the role of genetic mechanisms in non-Sjögren syndrome dry eye, the targeting of the terminal duct in meibomian gland disease and the influence of gaze dynamics and the closed eye state on tear stability and ocular surface inflammation.

TFOS DEWS II Tear Film Report

The members of the Tear Film Subcommittee reviewed the role of the tear film in dry eye disease (DED). The Subcommittee reviewed biophysical and biochemical aspects of tears and how these change in DED. Clinically, DED is characterized by loss of tear volume, more rapid breakup of the tear film and increased evaporation of tears from the ocular surface. The tear film is composed of many substances including lipids, proteins, mucins and electrolytes. All of these contribute to the integrity of the tear film but exactly how they interact is still an area of active research. Tear film osmolarity increases in DED. Changes to other components such as proteins and mucins can be used as biomarkers for DED. The Subcommittee recommended areas for future research to advance our understanding of the tear film and how this changes with DED. The final report was written after review by all Subcommittee members and the entire TFOS DEWS II membership.

External eye symptoms in indoor environments

Eye irritation, for example dry or irritated eyes, is generally among top three reported symptoms in office-like environments, in particular among workplaces with cognitive demanding visual display unit (VDU) work. The symptoms are especially among middle and advanced ages and particularly among women more than men. The symptoms are also among the most commonly reported complaints in the eye clinic. To be in a position to interpret the high prevalence of eye symptoms, a multidisciplinary and integrated approach is necessary that involves the external eye physiology (separate from internal eye effects), eye diseases (evaporative dry eye (DE), aqueous-deficient DE, and gland dysfunctions), and risk factors that aggravate the stability of precorneal tear film (PTF) resulting in hyperosmolarity and initiation of inflammatory reactions. Indoor environmental, occupational and personal risk factors may aggravate the PTF stability; factors such as age, contact lenses, cosmetics, diet, draft, gender, low humidity and high temperature, medication, outdoor and combustion pollutants, and VDU work. Psychological stressors may further influence the reporting behavior of eye symptoms. The impact of the risk factors may occur in a combined and exacerbating manner.

Evaluation of surface water characteristics of novel daily disposable contact lens materials, using refractive index shifts after wear

PURPOSE

Contact lens wearers today spend much time using digital display devices. Contact lens manufacturers are challenged to develop products that account for longer periods of time where blink rate is reduced and tear-film evaporation rate is increased, affecting both visual acuity and comfort. Two manufacturers recently introduced novel daily disposable contact lenses with high surface water content. The objective of the present study was to compare surface water characteristics before and after initial wear of recently introduced nesofilcon A and delefilcon A high surface water lenses with those of etafilcon A lenses.

PATIENTS AND METHODS

Twenty healthy subjects wore each of the three lens types studied in a randomly determined order for 15 minutes. After each wearing, lenses were removed and the surface refractive index (RI) of each lens was immediately measured.

RESULTS

The mean RI of the unworn delefilcon A lens was 1.34, consistent with water content in excess of 80%. After 15 minutes of wear, the surface RI shifted to 1.43, consistent with its reported 33% bulk water content. In contrast, the mean surface RI of the nesofilcon A lens was 1.38, both initially and after 15 minutes of wear, and that of the etafilcon A lens was 1.41 initially and 1.42 after 15 minutes of wear.

CONCLUSION

The surface of the delefilcon A lens behaves like a high water hydrogel upon insertion but quickly dehydrates to behave like its low-water silicone-hydrogel bulk material with respect to surface water content during wear, while both nesofilcon A and etafilcon A lenses maintain their water content during initial wear. The nesofilcon A lens appears unique among high water lenses in maintaining high surface and bulk water content during wear. This is important because changes in surface RI due to dehydration are reported to lead to visual aberration affecting user experience.

The precorneal tear film as a fluid shell: the effect of blinking and saccades on tear film distribution and dynamics

We conducted a series of experiments to elucidate the behavior of the human precorneal tear film (PCTF) during blinking and horizontal and vertical saccades. Methodology included video-interferometry with subsequent image cross-correlation (tear film lipid layer [TFLL]) and video-microscopy (mucoaqueous subphase [MAS]). We observed that the TFLL interference pattern deteriorates rapidly with successive blinks and degrades slowly with repeated horizontal saccades during blink suppression when dark arcs of thinning appear in the fluorescein-stained PCTF. Furthermore, after full downgaze and a return to the primary position, a transient horizontal bright band appears, deep to the spreading TFLL. It may be followed by local disturbances in the interference pattern. Two horizontal dark bands form in the stained PCTF after the return saccade. PCTF disruption may occur below the lower band during blink suppression. We concluded that shearing during horizontal saccades is insufficient to disturb the tear film structure greatly. The MAS and TFLL move together as a fluid shell. The dark arcs/bands are caused by meniscus-induced thinning, imprinted onto the PCTF at the lid margin. Their stability during blink suppression suggests that the MAS has gel-like properties. The horizontal bright bands are probably due to transient corneal indentation in downgaze. In downgaze, the disturbance of the TFLL and MAS below the dark bands is possibly due to shearing across the MAS in the return phase. This could cause desiccating stress in everyday activities, such as working at a computer.

The effects of increasing ocular surface stimulation on blinking and sensation

PURPOSE

The purpose of this study was to determine how increasing ocular surface stimulation affected blinking and sensation, while controlling task concentration.

METHODS

Ten healthy subjects concentrated on a task while a custom pneumatic device generated air flow toward the central cornea. Six flow rates (FRs) were randomly presented three times each and subjects used visual analog scales to record their sensory responses. The interblink interval (IBI) and the FR were recorded simultaneously and the IBI, sensory response, and corresponding FR were determined for each trial. The FR associated with a statistically significant decrease in IBI, the blink increase threshold (BIT), was calculated for each subject.

RESULTS

Both the mean and SD of IBI were decreased with increasing stimulation, from 5.69 ± 3.96 seconds at baseline to 1.02 ± 0.37 seconds at maximum stimulation. The average BIT was 129 ± 20 mL/min flow rate with an IBI of 2.33 ± 1.10 seconds (permutation test, P < 0.001). After log transformation, there was a significant linear function between increasing FR and decreasing IBI within each subject (Pearson's r ≤ -0.859, P < 0.05). The IBI was highly correlated with wateriness, discomfort, and cooling ratings (Pearson's r ≤ -0.606, P < 0.001).

CONCLUSIONS

There was a dose-response-like relationship between increased surface stimulation and blinking in healthy subjects, presumably for protection of the ocular surface. The blink response was highly correlated with ocular surface sensation, which is not surprising given their common origins. The BIT, a novel metric, may provide an additional end point for studies on dry eye or other conditions.

Rethinking dry eye disease: a perspective on clinical implications

Publication of the DEWS report in 2007 established the state of the science of dry eye disease (DED). Since that time, new evidence suggests that a rethinking of traditional concepts of dry eye disease is in order. Specifically, new evidence on the epidemiology of the disease, as well as strategies for diagnosis, have changed the understanding of DED, which is a heterogeneous disease associated with considerable variability in presentation. These advances, along with implications for clinical care, are summarized herein. The most widely used signs of DED are poorly correlated with each other and with symptoms. While symptoms are thought to be characteristic of DED, recent studies have shown that less than 60% of subjects with other objective evidence of DED are symptomatic. Thus the use of symptoms alone in diagnosis will likely result in missing a significant percentage of DED patients, particularly with early/mild disease. This could have considerable impact in patients undergoing cataract or refractive surgery as patients with DED have less than optimal visual results. The most widely used objective signs for diagnosing DED all show greater variability between eyes and in the same eye over time compared with normal subjects. This variability is thought to be a manifestation of tear film instability which results in rapid breakup of the tearfilm between blinks and is an identifier of patients with DED. This feature emphasizes the bilateral nature of the disease in most subjects not suffering from unilateral lid or other unilateral destabilizing surface disorders. Instability of the composition of the tears also occurs in dry eye disease and shows the same variance between eyes. Finally, elevated tear osmolarity has been reported to be a global marker (present in both subtypes of the disease- aqueous-deficient dry eye and evaporative dry eye). Clinically, osmolarity has been shown to be the best single metric for diagnosis of DED and is directly related to increasing severity of disease. Clinical examination and other assessments differentiate which subtype of disease is present. With effective treatment, the tear osmolarity returns to normal, and its variability between eyes and with time disappears. Other promising markers include objective measures of visual deficits, proinflammatory molecular markers and other molecular markers, specific to each disease subtype, and panels of tear proteins. As yet, however, no single protein or panel of markers has been shown to discriminate between the major forms of DED. With the advent of new tests and technology, improved endpoints for clinical trials may be established, which in turn may allow new therapeutic agents to emerge in the foreseeable future. Accurate recognition of disease is now possible and successful management of DED appears to be within our grasp, for a majority of our patients.

The effects of mild ocular surface stimulation and concentration on spontaneous blink parameters

PURPOSE

This exploratory, pilot study compared the effects of concentrating on a visual task and a very mild ocular surface air stimulus on multiple blink parameters.

METHODS

Ten subjects participated in this study. There were two visits, one with an ocular surface air stimulus (AS) and one without (NS). The AS was set at a level barely perceptible by subjects (approximately 0.6 m/s at the eye). At each visit, subjects performed a high-concentration (HC) and low-concentration (LC) task. Blinking was tracked and tear-film breakup (TBU) was monitored simultaneously to measure blink parameters, including the interblink interval (IBI), blink amplitude, duration, maximum velocity and TBU before and after each blink.

RESULTS

During the HC tasks, IBI was significantly higher and blink duration was lower (repeated measures ANOVA, p < 0.05) than the LC tasks. The IBI in the AS-LC condition was significantly lower and less variable than in the NS-HC condition, whereas blink duration showed the opposite effect (Hotelling T² test, p < 0.005). There was high individual variation in correlations between blink amplitude and maximum velocity. The area of TBU was not significantly correlated with any blink parameter.

CONCLUSIONS

The lack of correlation between TBU and blinking suggests that many blinks are stimulated by internal controls, rather than direct stimulation of the ocular surface by TBU. This pilot study suggests that even very mild ocular surface stimulation produces opposite effects on the timing and duration of the blink, when compared to concentrating on a visual task. The HC task tends to decrease blink frequency and duration, presumably to minimize interruption by the eyelids, whereas mild ocular surface AS increased blink frequency and duration, most likely to increase protection of the ocular surface.

Tear film stability: a review

Tear film stability can be assessed via a number of tools designed for clinical as well as research purposes. These techniques can give us insights into the tear film, and allow assessment of conditions that can lead to dry eye symptoms, and in severe cases, to significant ocular surface damage and deterioration of vision. Understanding what drives tear film instability and its assessment is also crucial for evaluating existing and new therapies. This review examines various techniques that are used to assess tear film instability: evaluation of tear break-up time and non-invasive break-time; topographic and interferometric techniques; confocal microscopic methods; aberrometry; and visual function tests. It also describes possible contributions of different tear film components; namely meibomian lipids, ocular mucins and proteins, and factors such as age, contact lens wear, ocular surgery and environmental stimuli, that may influence tear film instability.

Diadenosine polyphosphates release by human corneal epithelium

Diadenosine polyphosphates are a type of dinucleotides that have been detected in rabbit and human tears. However, their origin and their mechanism of release have not been fully elucidated. In this work we investigated whether the dinucleotides Ap4A and Ap5A can be released from human corneal epithelia as a consequence of shear stress stimuli. In in vitro experiments, concentrations of Ap4A and Ap5A before mechanical stimulus of stratified human corneal epithelial cells were 3.18 ± 0.43 nM and 0.81 ± 0.13 nM, respectively. After shear stimulation, concentrations significantly increased to 12.01 ± 2.19 nM for Ap4A and 2.83 ± 0.41 nM for Ap5A. No significant differences in lactate dehydrogenase activity were detected between non-stimulated stratified human corneal epithelial cells and cells exposed to mechanical shear-stress, indicating that the rise of dinucleotide levels was not due to cell lysis. In in vivo experiments, individuals subjected to a rise in blinking frequency showed a significant increase of Ap4A (∼25-fold when experiment was performed without anaesthetic and 75-fold with anaesthetic) and Ap5A concentration in tears (∼50-fold when experiment was performed without anaesthetic and 125-fold with anaesthetic). Shear-stress stimuli induces Ap4A and Ap5A release from human corneal epithelium, thus explaining the origin of these relevant compounds for the ocular surface biochemistry and physiology.

Scale and spatial distribution of aberrations associated with tear breakup

PURPOSE

We examined the spatial correlation between tear breakup (TBU) and the associated optical anomalies on multiple spatial scales.

METHODS

Five subjects refrained from blinking while the time course and patterns of TBU were sequentially observed using fluorescein, retroillumination, and Shack-Hartmann (SH) aberrometry. Wavefront error maps were developed using Zernike polynomials, as well as local zonal analysis of measured wavefront slopes. The difference between these maps reveals the presence of very high-order aberrations missed by standard modal fitting methods. Size of SH spots was also quantified to estimate optical perturbations on a microscopic scale. The spatial correlation between TBU and optical aberrations was also computed.

RESULTS

Degradation of the tear film increased wavefront aberrations over all spatial scales measured. Consistent with tear thinning, blink suppression induced an irregular pattern of phase advances in regions of TBU. SH spot size also increased in regions of TBU, which indicates the presence of optical aberrations on a scale smaller than individual lenslets.

CONCLUSIONS

The optical signature of TBU caused by blink suppression is a combination of wavefront aberrations on macroscopic and microscopic scales due to non-uniform tear film thinning and possible exposure of a rough epithelial surface. Localized optical defects correspond temporally and spatially with TBU revealed by fluorescein and retroillumination. In addition to gross wavefront aberrations, scatter develops in areas of TBU that will further contribute to image degradation and visual disturbances after TBU.

Validation and verification of the OPI 2.0 System

Purpose

The Ocular Protection Index (OPI) 2.0 System was developed to evaluate ocular surface protection under a natural blink pattern and normal visual conditions. The OPI 2.0 System implements fully automated software algorithms which provide a real-time measurement of corneal exposure (breakup area) for each interblink interval during a 1-minute video. Utilizing this method, the mean breakup area (MBA) and OPI 2.0 (MBA/interblink interval) were calculated and analyzed. The purpose of this study was to verify and validate the OPI 2.0 System for its ability to distinguish between dry eye and normal subjects, and to accurately identify breakup area.

Methods

In order to verify and validate the OPI 2.0 System, a series of artificial images and a series of still image frames captured during an actual clinical session using fluorescein staining videography were analyzed. Finally, a clinical validation process was completed to determine the effectiveness and clinical relevance of the OPI 2.0 System to differentiate between dry eye and normal subjects.

Results

Software analysis verification conducted in a set of artificially constructed images and in actual videos both saw minimal error rates. MBA and OPI 2.0 calculations were able to distinguish between the qualifying eyes of dry eye and normal subjects in a statistically significant fashion (P < 0.001 for both outcomes). As expected, dry eye subjects had a higher MBA and OPI 2.0 than normal subjects (0.232, dry eye; 0.040, normal and 0.039, dry eye; 0.006, normal, respectively). Results for the worst eyes and all qualifying analyses based on staining, forced-stare tear film breakup time, and MBA were numerically similar.

Conclusion

The OPI 2.0 System accurately identifies the degree of breakup area on the cornea and represents an efficient, clinically relevant measurement of the pathophysiology of the ocular surface.

Comparison of the tear film clinical parameters at two different times of the day

PURPOSE

The aim of the present study was to analyse the quality and quantity of the tear film in a young, healthy and non-contact lens-wearing population with measurements taken in the morning and in the afternoon to establish if changes exist in these parameters.

METHODS

In a controlled laboratory setting, morning and afternoon clinical parameters of tear film were assessed. Schirmer test, tear meniscus height, break-up time and non-invasive break-up time were measured in 51 normal subjects on the same day for each individual.

RESULTS

Tear volume showed no significant changes during the day but tear film stability was significantly reduced at the end of the day (p < 0.001), demonstrating that tear film stability is affected by the time of day.

CONCLUSION

Researchers and clinicians might wish to consider these differences when comparisons are made between studies and populations and also when the same patient is observed over periods. Fluorescein instillation can affect the measurements of tear stability in subjects with poor quality tear film.