Contact lens drying and visual performance: the vision cycle with contact lenses

The Effect of Diquafosol Ophthalmic Solution on Clinical Parameters and Visual Function in Soft Contact Lens-Related Dry Eye

INTRODUCTION

This study evaluated the efficacy and safety of diquafosol ophthalmic solution (DQS) in soft contact lens (SCL)-related dry eye using artificial tear as a control.

METHODS

This study enrolled 26 patients with SCL-related dry eye. DQS and artificial tears (AT) were instilled into the right and left eyes, respectively, with their SCLs on. Dry eye examinations (including tear film breakup time, tear volume, and staining score) were performed and visual function (including contrast sensitivity) was also evaluated before (at baseline) and after treatment (at 4- and 8-week examinations). Subjective symptoms were assessed separately in each eye using a questionnaire on dry eye in contact lens wearers. The results were compared before and after treatment, and between the right eyes treated with DQS (the DQS eye) and the left eyes treated with AT (the AT eye) using the mixed effect model.

RESULTS

Corneal and conjunctival staining scores at 8-week examination were significantly lower than those at baseline in the DQS eye (p = 0.03; p < 0.001, respectively), but no significant changes were observed in the AT eye. Most subjective symptoms improved significantly in both the DQS and AT eyes. However, major subjective symptoms (dryness and blurry vision) improved significantly only in the DQS eye at 8-week examination. Contrast sensitivity at 8-week examination in the DQS eye improved significantly at 12 cycles/degree compared to baseline (p = 0.001) and was significantly better than that in the AT eye (p = 0.03). There were no adverse events related to DQS or AT.

CONCLUSIONS

DQS was effective and safe for SCL-related dry eye. DQS also improved contrast sensitivity.

TRIAL REGISTRATION

University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR), Identification No. UMIN000024064.

Ability of non-invasive tear break-up time to determine tear instability in contact lens wearers

PURPOSE

To evaluate the performance of precorneal and prelens non-invasive tear break-up time (NIBUT) measurements to determine tear instability in contact lens (CL) wearers.

METHODS

In this study, 50 eyes of 25 CL wearers were evaluated. Precorneal first and average NIBUTs and fluorescein tear break-up time (FBUT) were measured before wearing CLs in the morning. Those with FBUT less than 10 s were considered to have tear instability. After wearing CL, first and average prelens NIBUTs were measured at the 30th minute. The receiver operating characteristic (ROC) curve was analyzed to evaluate the performance of NIBUT measurements in the diagnosis of tear instability.

RESULTS

The FBUT value had a significant correlation with first and average precorneal NIBUT values (p < 0.001, r = 0.653 and p < 0.001, r = 0.628, respectively). The FBUT value had no correlation with the prelens first and average NIBUT values (p = 0.542 and p = 0.263, respectively). To understand the relationship between the precorneal and prelens NIBUT values measured by the automated method, their correlation was evaluated. There was no significant correlation between the precorneal and prelens NIBUTs (for all; p > 0.05). The area under curve (AUC) in ROC curve for the first and average precorneal NIBUTs were 0.842 (p < 0.001) and 0.810 (p < 0.001), respectively. The AUC values for the first and average prelens NIBUTs at the 30th minute of CL wear were 0.586 and 0.619, respectively (p = 0.317 and p = 0.166, respectively).

CONCLUSIONS

Precorneal NIBUT measurements may be useful in diagnosing tear instability. Prelens NIBUT values are not yet capable of adequately defining the tear film dynamics in CL wearers.

The association of comfort and vision in soft toric contact lens wear

PURPOSE

This work set out to investigate if there was an association between subjective comfort and both subjective and measured vision during the use of contemporary daily disposable soft toric contact lenses.

METHODS

Thirty-eight habitual soft contact lens wearers wore each of three daily disposable toric lenses for one week in a prospective, crossover, randomised, single-masked study. The following clinical measures were recorded at dispensing and follow-up visits: biomicroscopy scores, lens fitting (including rotation and rotational stability), high and low contrast visual acuity, subjective vision quality and subjective ocular surface comfort. Subjective scores were collected using 0-10 numerical grading scales. Comfort scores were analysed using a linear regression model with age, sex, visit, phase of crossover ('phase'), lens type, lens rotation, lens rotational stability, visual acuity, cylinder power and subjective vision quality as factors of interest and then refined using backward stepwise regression.

RESULTS

Thirty six participants (31.1 ± 13.5 years) completed the study. Comfort scores were found to be associated with subjective vision quality (F = 127.0 ; p < 0.0001), phase (F = 7.2; p = 0.001) and lens type (F = 4.9; p = 0.009). Greater comfort scores were observed with greater subjective vision quality scores. Visual acuity was not statistically significant in the model.

CONCLUSION

This work suggests that symptoms of ocular discomfort may be more intense if there is also perceived visual compromise in daily disposable soft toric lenses. There was a stronger positive correlation between comfort and subjective vision quality compared with comfort and measured visual acuity.

Tear Film Characteristics During Wear of Daily Disposable Contact Lenses

Purpose

To evaluate changes induced over time by three daily disposable (DD) contact lenses on tear meniscus height (TMH), pre-lens non-invasive break-up time (pre-lens NIBUT), tear film osmolarity (TO) and objective quality of vision (OQV).

Patients and Methods

Forty-six subjects enrolled in this prospective open-label unmasked non-randomized simultaneous comparative cross-over study. For the first week of the study, subjects wore a nesofilcon A lens in the right eye and a delefilcon A lens in the left eye. After 3 days of washout, for the second week, subjects wore a nesofilcon A lens in the left eye and a stenfilcon A lens in the right eye. TMH, pre-lens NIBUT, TO and OQV were measured before contact lens fitting and for each contact lens combination on day 1 at 20 minutes and on day 7 after ≥8 hours of wear. OQV measurement included the changes of objective scatter index (OSI), the stability index (SI) and the fluctuation index (FI) calculated in a range of time of 20 s from a blink.

Results

TMH was unchanged at 20 minutes wear of all lenses but was significantly reduced after 8 or more hours wear (on day 7) of delefilcon A and stenfilcon A, respectively. Pre-lens NIBUT was significantly reduced with all lenses, while no significant change in TO was observed with any lens. SI and FI increased significantly for all lenses at both wear times.

Conclusion

While the presence of any contact lens on the eye challenges the tear film, nesofilcon A contact lenses, despite their high water content, compared to delefilcon A and stenfilcon A contact lenses, showed a lower overall effect. We speculate that superior tear film behavior while wearing nesofilcon A lenses may translate to improved subjective comfort, but this remains to be evaluated.

Impact of a Hyaluronic Acid-Grafted Layer on the Surface Properties of Model Silicone Hydrogel Contact Lenses

The introduction of high oxygen transmissibility silicone hydrogel lenses ameliorated hypoxia-related complications, making them the most prescribed type of contact lens (CL). Despite the progress made over the last 2 decades to improve their clinical performance, symptoms of ocular dryness and discomfort and a variety of adverse clinical events are still reported. Consequently, the rate of CL wear discontinuation has not been appreciably diminished by their introduction. Aiming to improve the interfacial interactions of silicone hydrogel CLs with the ocular surface, a biomimetic layer of hydrophilic glycosaminoglycan hyaluronic acid (HA) (100 kDa) was covalently attached to the surface of model poly(2-hydroxyethyl methacrylate- co-3-methacryloxypropyl-tris-(trimethylsiloxy)silane) (pHEMA- co-TRIS) silicone hydrogel materials via UV-induced thiol-ene "click" chemistry. The surface structural changes after each modification step were studied by Fourier transform infrared spectroscopy-attenuated total reflectance and X-ray photoelectron spectroscopy (XPS). Successful grafting of a homogeneous HA layer to the surface of the model silicone hydrogels was confirmed by the consistent appearance of N (1s) and the significant decrease of the Si (2p) peaks, as determined by low-resolution angle-resolved XPS. The HA-grafted surfaces demonstrated reduced contact angles, dehydration rate, and nonspecific deposition of lysozyme and albumin, while maintaining their optical transparency (>90%). In vitro studies demonstrated that the HA-grafted pHEMA- co-TRIS materials did not show any toxicity to human corneal epithelial cells. These results suggest that surface immobilization of HA via thiol-ene "click" chemistry can be used as a promising surface treatment for silicone hydrogel CLs.

Influence of diabetes mellitus on anterior segment of the eye

Diabetes mellitus (DM) has been emerging as one of the most serious health problems worldwide. Ocular complications of DM are currently one of the major causes of blindness in developed countries, among which diabetic retinopathy is relatively well studied and understood. However, although ocular surface complications of DM are common, diabetic complications of anterior segment of the eye, such as, cornea, conjunctiva, and lacrimal glands, are often overlooked. DM is associated with progressive damage to corneal nerves and epithelial cells, which increases the risk of anterior segment disorders including dry eye disease, corneal erosion, persistent epithelial defects, and even sight-threatening corneal ulcer. In this review, the authors will discuss the association of DM with disorders of anterior segment of the eye. Studies indicating the value of corneal nerve assessment as a sensitive, noninvasive, and repeatable biomarker for diabetic neuropathy will also be introduced. In addition, treatment modalities of anterior segment disorders associated with DM is discussed. The studies introduced in this review suggest that early and periodic screening of the anterior segment of the eye, as well as the retina, is important for the optimal treatment of DM.

Predicting Short-Term Subjective Vision Performance of Contact Lenses Used in Myopia Control

OBJECTIVE

To investigate whether initial assessment of contact lenses prescribed for myopia control (MC) predicts short-term visual performance.

METHOD

Retrospective analysis of 43 participants in a double-masked, randomized, cross-over trial wearing at least one lens: single-vision (SV) lens (1-DAY ACUVUE MOIST) or MC lenses (MiSight or Proclear Multifocal-Distance +2.00D). Participants completed questionnaires at the fitting visit, a take-home questionnaire (THQ) 3 days after fitting and finally at the assessment visit (≥5 days after fitting). Questions comprised vision clarity and lack of ghosting (distance, intermediate, near at day/night time); vision stability; driving vision; overall vision satisfaction and comfort (1-10 scale, 1-point steps); and willingness to purchase based on vision and MC benefit of lens (yes/no response). Visual acuity was measured at fitting and assessment visits.

RESULTS

Vision clarity (intermediate and near) was significantly worse at assessment compared with fitting while wearing MC lenses (P<0.001), as was overall vision satisfaction (P<0.001), comfort (P<0.001), and vision stability (P=0.001) while wearing either SV or MC lenses. Participants willing to purchase at assessment visit was 84% with SV and 36% with MC lenses, increasing to 88% (SV, P=1.00) and 61% (MC, P<0.001) if the lenses slowed myopia progression. Visual acuity was no different with either MC or SV lenses at fitting or assessment (P≥0.251).

CONCLUSION

Initial performance at fitting did not predict short-term performance for SV or MC lenses. A significant increase in willingness to purchase if lenses slowed myopia progression was observed while wearing MC lenses. Educating patients on the benefits might increase acceptability of MC lenses.

Predicting Short-term Performance of Multifocal Contact Lenses

OBJECTIVE

To investigate if initial multifocal contact lens (MFCL) performance predicts short-term dispensing performance.

METHODS

A retrospective analysis of 55 participants (Px) in a masked, crossover, clinical trial, using ACUVUE OASYS for Presbyopia and AIR OPTIX AQUA Multifocal. Subjective questionnaires were administered at the following instances: initial fitting, two take home questionnaires (THQ) completed between days 2 and 4 and at assessment, ≥5 days after fitting. Questionnaires included vision clarity and lack of ghosting at distance, intermediate and near at day/night time points rated on a 1 to 10 (1-step, 10 most favorable) rating scale. Vision stability, vision while driving, overall vision satisfaction, willingness to purchase and comfort, as well as acuity-based measures were also collected.

RESULTS

There were no statistical differences in comfort and vision at all distances, in vision stability or driving at either time points between THQ and assessment (P>0.05). However, there was a statistical decline in subjective overall vision satisfaction and comfort between fitting and assessment visits (P<0.001). Willingness to purchase remained the same at fitting and assessment in 68% of Px, whereas only 4% of Px converted to a positive willingness to purchase at assessment. The majority of acuity-based measures remained constant between fitting and assessment visits.

CONCLUSION

Initial performance at fitting was not able to predict short-term performance of MFCL. Subjective measures peaked at fitting and declined thereafter whereas acuity-based measures remained constant. Utility of subjective rating tools may aid practitioners to gauge success of MFCL.

Review of Literature on Measurements of Non-invasive Break Up Times, Lipid Morphology and Tear Meniscal Height Using Commercially Available Hand-held Instruments

Purpose/aims: Dry eye is a common multi-factorial disease characterized by tearfilm dysfunction. Diagnosis of dry eye requires documentation of tear status with non-invasive tear break up times (NIBUT), tear meniscal height (TMH), and tearfilm lipid layer. These parameters objectively assess tear stability and indirectly, the functional impact of meibomian gland dysfunction. While it is obvious that portable instrumentation gives broader access than fixed instrumentation, its value would be limited if it is unreliable and its precision and accuracy substantially worse than fixed instruments.

MATERIALS/METHODS

Because of the lack of systematic reviews concerning the Tearscope, we performed a scoping review of the literature to determine 1. the ranges of the tear parameters as measured by the device, 2. relationship between these measurements and other clinical variables, 3. Information about intra or inter-observer agreement, and comparison with another technique, where available.

RESULTS

We found 22 reports related to NIBUT, 18 reports concerning tearfilm lipid morphology (LM) based on classification of interference patterns, and 8 reports on TMH. While publication of these reports indicates an acceptance of the reliability of portable instruments, we interrogated these studies further to evaluate the results obtained from portable devices and found that there was no equivalent measurements in fixed devices (LM) or measurements differ considerably from fixed devices (NIBUT). In the case of TMH, portable measurements were similar to those by traditional slit-lamp microscopy. There were relatively few studies on TMH measured using handheld devices, but it was found to be correlated to NIBUT but not the Schirmer test values.

CONCLUSIONS

Imaging algorithms in portable tearfilm instruments should be further standardized to facilitate wider adoption and evaluation. In the next few years, new emerging technologies will employ a strategy of non-invasive tear testing that is portable and relatively inexpensive, and these will enhance adoption of such tools in the clinic.

The effect of interrupted defocus on blur adaptation

PURPOSE

Blur adaptation occurs when an observer is exposed to continuous defocus. However, it is unclear whether adaptation requires constant defocus, or whether the effect can still be achieved when the adaptation period is interrupted by short periods of clear vision.

METHODS

The study included 12 emmetropes and 12 myopes. All observers wore full refractive correction throughout the experiment. 1D and 3D of myopic defocus was introduced using spherical convex lenses. An automated system was used to place the blurring lens before the RE for varying periods of blurred and clear vision during adaptation. Participants watched a DVD at 3 m during each 15 min trial. Visual acuity was measured using Test Chart 2000 before and after adaptation.

RESULTS

Blur adaptation occurs to varying degrees depending on the periods of incremental blur exposure. Significant improvements in defocused visual acuity occur with continuous blur, equal blur and clear periods, as well as for longer blur periods. However, longer clear periods showed reduced adaptation and this trial is significantly different to the other three trials for both defocus levels (p < 0.001). No refractive group differences were observed for neither 1D nor 3D defocus (p = 0.58 and p = 0.19 respectively).

CONCLUSIONS

Intervening periods of clear vision cause minimal disruption to improvements in defocused visual acuity after adaptation, indicating that blur adaptation is a robust phenomenon. However, when the exposure to clear vision exceeds the defocused periods, adaptation is inhibited. This gives insight into the effects of real-world tasks on adaptation to blur.

Automated Detection and Quantification of Circadian Eye Blinks Using a Contact Lens Sensor

PURPOSE

To detect and quantify eye blinks during 24-hour intraocular pressure (IOP) monitoring with a contact lens sensor (CLS).

METHODS

A total of 249 recordings of 24-hour IOP patterns from 202 participants using a CLS were included. Software was developed to automatically detect eye blinks, and wake and sleep periods. The blink detection method was based on detection of CLS signal peaks greater than a threshold proportional to the signal amplitude. Three methods for automated detection of the sleep and wake periods were evaluated. These relied on blink detection and subsequent comparison of the local signal amplitude with a threshold proportional to the mean signal amplitude. These methods were compared to manual sleep/wake verification. In a pilot, simultaneous video recording of 10 subjects was performed to compare the software to observer-measured blink rates.

RESULTS

Mean (SD) age of participants was 57.4 ± 16.5 years (males, 49.5%). There was excellent agreement between software-detected number of blinks and visually measured blinks for both observers (intraclass correlation coefficient [ICC], 0.97 for observer 1; ICC, 0.98 for observer 2). The CLS measured a mean blink frequency of 29.8 ± 15.4 blinks/min, a blink duration of 0.26 ± 0.21 seconds and an interblink interval of 1.91 ± 2.03 seconds. The best method for identifying sleep periods had an accuracy of 95.2 ± 0.5%.

CONCLUSIONS

Automated analysis of CLS 24-hour IOP recordings can accurately quantify eye blinks, and identify sleep and wake periods.

TRANSLATIONAL RELEVANCE

This study sheds new light on the potential importance of eye blinks in glaucoma and may contribute to improved understanding of circadian IOP characteristics.

The time course of blur adaptation in emmetropes and myopes

PURPOSE/BACKGROUND

This study examined the effect of myopic defocus on visual acuity (VA) over time, with attention being paid to the first point at which blur adaptation had a significant and measurable effect on defocused VA. Visual acuity was sampled at a higher rate than previous studies in order to assess the time course of blur adaptation processes in myopic and emmetropic observers.

METHODS

Participants were 24 normally-sighted observers (12 emmetropes and 12 myopes, median age: 22.5 years). All ametropic participants wore their full refractive correction throughout the experiment. 1 D and 3 D of myopic defocus were introduced in two separate, randomised sessions. Visual acuity was measured using Test Chart 2000 at 2 min intervals over a 30 min session whilst looking through defocus lenses. Recovery clear VA was also measured every 2 min for a further 20 min.

RESULTS

Defocused VA was found to improve significantly within 4 min after the introduction of defocus for both 1 D (P < 0.0001) and 3 D conditions (P < 0.0001). The improvements reached a plateau shortly after, with no significant further improvements in defocused VA after 6 min. There were no significant differences found in the temporal blur adaptation profiles between emmetropes and myopes (P = 0.267). Data were fitted with an exponential decay function; the lowest R(2) value for this fit was 0.95.

CONCLUSIONS

Blur adaptation has a clinically significant and measurable effect on VA within 4 min of exposure to defocus. This finding indicates that the visual system instigates the neural compensatory mechanisms shortly after the appearance of defocus. Our results relate particularly to real-life vision of uncorrected myopes or myopes who remove their correction for part of the day.

A preliminary investigation into the effects of ocular lubricants on higher order aberrations in normal and dry eye subjects

PURPOSE

To study the effects of ocular lubricants on higher order aberrations in normal and self-diagnosed dry eyes.

METHODS

Unpreserved hypromellose drops, Tears Again™ liposome spray and a combination of both were administered to the right eye of 24 normal and 24 dry eye subjects following classification according to a 5 point questionnaire. Total ocular higher order aberrations, coma, spherical aberration and Strehl ratios for higher order aberrations were measured using the Nidek OPD-Scan III (Nidek Technologies, Gamagori, Japan) at baseline, immediately after application and after 60 min. The aberration data were analyzed over a 5mm natural pupil using Zernike polynomials. Each intervention was assessed on a separate day and comfort levels were recorded before and after application. Corneal staining was assessed and product preference recorded after the final measurement for each intervention.

RESULTS

Hypromellose drops caused an increase in total higher order aberrations (p=<0.01 in normal and dry eyes) and a reduction in Strehl ratio (normal eyes: p=<0.01, dry eyes p=0.01) immediately after instillation. There were no significant differences between normal and self-diagnosed dry eyes for response to intervention and no improvement in visual quality or reduction in higher order aberrations after 60 min. Differences in comfort levels failed to reach statistical significance.

CONCLUSION

Combining treatments does not offer any benefit over individual treatments in self-diagnosed dry eyes and no individual intervention reached statistical significance. Symptomatic subjects with dry eye and no corneal staining reported an improvement in comfort after using lubricants.

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.

Spontaneous eyeblink activity

Spontaneous blinking is essential for maintaining a healthy ocular surface and clarity of vision. The spontaneous blink rate (SBR) is believed to reflect a complex interaction between peripheral influences mediated by the eye surface and the central dopaminergic activity. The SBR is thus extremely variable and dependent on a variety of psychological and medical conditions. Many different methods have been employed to measure the SBR and the upper eyelid kinematics during a blink movement. Each has its own merits and drawbacks, and the choice of a specific method should be tailored to the specific needs of the investigation. Although the sequence of muscle events that leads to a blink has been fully described, knowledge about the neural control of spontaneous blinking activity is not complete. The tear film is dynamically modified between blinks, and abnormalities of the blink rate have an obvious influence on the ocular surface.

Forward light scatter analysis of the eye in a spatially-resolved double-pass optical system

An optical analysis is developed to separate forward light scatter of the human eye from the conventional wavefront aberrations in a double pass optical system. To quantify the separate contributions made by these micro- and macro-aberrations, respectively, to the spot image blur in the Shark-Hartmann aberrometer, we develop a metric called radial variance for spot blur. We prove an additivity property for radial variance that allows us to distinguish between spot blurs from macro-aberrations and micro-aberrations. When the method is applied to tear break-up in the human eye, we find that micro-aberrations in the second pass accounts for about 87% of the double pass image blur in the Shack-Hartmann wavefront aberrometer under our experimental conditions.

Measurement of the time course of optical quality and visual deterioration during tear break-up

PURPOSE

To compare changes in optical quality and visual performance that accompany tear break-up (TBU) during blink suppression.

METHODS

A three-channel optical system was developed that simultaneously measured refractive aberrations (Shack-Hartmann aberrometer), 20/40 letter contrast sensitivity (CS), and TBU (retroillumination, RI). Ten wearers of silicone hydrogel contact lenses were asked to keep one eye open for approximately 18 seconds, while CS, wavefront aberrations, and RI images were collected. The wavefront was reconstructed by zonal methods, and image quality was quantified with a series of metrics including RMS fit error. Novel metrics for quantifying TBU over the contact lens surface were developed by quantifying the contrast of the RI image and by using Fourier descriptors of the first Purkinje (PJ) image shape.

RESULTS

There was a full range of TBU over the lens surface, with four subjects showing TBU across the corneal center and one subject with TBU in the inferior peripheral pupil. Among the four subjects with central corneal TBU, RMS fit error, RI contrast, and PJ Fourier descriptors showed high correlation with CS (r(2) range, 0.9187-0.9414, 0.6261-0.975, and 0.4917-0.8986, respectively). Some of the general optical-quality metrics such as blur strength, neural sharpness, and area of modulation transfer function (MTF) also showed that change correlated with CS loss.

CONCLUSIONS

Optical metrics of tear quality and retinal image quality are associated with the decline in vision that occurs with TBU. The evidence supports the hypothesis that blurry vision symptoms reported by contact lens wearers are caused by poor quality of the retinal image due to TBU.

Visual performance after reduced blinking in eyes with soft contact lenses or after LASIK

PURPOSE

To evaluate visual performance during concentrated visual work in patients wearing soft contact lenses or after LASIK.

METHODS

Thirty-one eyes of 17 patients who had worn soft contact lenses before LASIK were examined by the following tests immediately and 10 seconds after eye opening: 1) functional visual acuity, which is defined as visual acuity measured after prolonged eye opening without blinking; 2) surface regularity index (SRI) and surface asymmetry index (SAI) in corneal topography; and 3) higher order aberration measured with NIDEK OPD-Scan. Results were compared in the same patients before (with soft contact lenses and no eye surgery) and 1 month after LASIK (without soft contact lenses).

RESULTS

Functional visual acuity was significantly decreased 10 seconds after eye opening compared with immediately after eye opening, both with soft contact lenses and after LASIK, and decreased to a greater extent with soft contact lenses. The SRI and SAI were significantly increased 10 seconds after eye opening compared with immediately after eye opening, both with soft contact lenses and after LASIK, and increased to a greater extent with soft contact lenses. Higher order aberration was increased 10 seconds after eye opening with soft contact lenses, but not after LASIK.

CONCLUSIONS

Our results suggest that prolonged eye opening induces a decreased quality of vision in eyes of soft contact lens wearers and after LASIK. Under conditions in which blinking is restricted due to concentrated visual work, such as visual display terminal work, reading, and driving, visual performance may be more compromised with soft contact lens wear than after LASIK.

Prevalence of dry eye disease among Japanese visual display terminal users

OBJECTIVE

To determine the prevalence of dry eye disease (DED) and risk factors among young and middle-aged Japanese office workers using visual display terminals (VDTs).

DESIGN

Cross-sectional prevalence survey.

PARTICIPANTS

Four thousand three hundred ninety-three Japanese young and middle-aged office workers using VDTs.

INTERVENTION

Office workers completed questionnaires sent by e-mail designed to detect dry eye diagnosis and risk factors.

MAIN OUTCOME MEASURES

Clinically diagnosed DED was defined as the presence of a previous clinical diagnosis of DED by dry eye specialists or severe symptoms of DED (both dryness and irritation constantly or often). Current symptoms of DED and possible risk factors such as age, duration of VDT use, type of VDT work, environmental factors, presence of systemic diseases, systemic medicine use, smoking history, and contact lens (CL) use were the main outcome measures. We used logistic regression to examine associations between DED and other demographic factors.

RESULTS

Of the 4393 office workers, 3549 (80.1%) completed the questionnaire. Clinically diagnosed DED was present in 266 (10.1%) of 2640 male subjects and in 195 (21.5%) of 909 female subjects. Severe symptoms of DED were observed in 711 male and in 436 female participants. More than 4 hours of VDT use was associated with an increased risk of DED (odds ratio [OR], 1.68; 95% confidence interval [CI], 1.40-2.02). In addition, CL use (OR, 3.91; 95% CI, 3.37-4.53) increased the risk of severe dry eye symptoms.

CONCLUSIONS

Dry eye disease leading to a clinical diagnosis or severe symptoms is prevalent among young and middle-aged Japanese office workers. The condition is more prevalent among females, CL wearers, and prolonged VDT users. Relevant measures directed against the modifiable risks could provide a positive impact on public health and quality of life of office workers.

FINANCIAL DISCLOSURE(S)

The authors have no proprietary or commercial interest in any materials discussed in this article.

Optical Quality of the Eye Degraded by Time-Varying Wavefront Aberrations with Tear Film Dynamics

PURPOSE

Wavefront aberrations (WFAs) of the eye vary with time because of the tear film dynamics. We investigated, using a simulation method, the variation of optical quality with time-varying wavefront measurements of 13 eyes with different refractions.

METHODS

WFAs of 13 normal eyes of 13 subjects were measured every second for 10 s. First, we simulated WFAs with conventional corneal laser refractive surgery by subtracting the second-order aberrations of the least aberrated measurement from measured consecutive WFAs. Second, we simulated customized refractive surgery by subtracting the second- to sixth-order aberrations of the least aberrated measurement from measured consecutive WFAs. We calculated Strehl ratios and retinal images from these corrected consecutive WFAs.

RESULTS

In one eye, the root mean square (RMS) values of WFAs with a second-order correction were sometimes smaller than those of WFAs with a second- to sixth-order correction, when these were compared at the same time point after a blink. However, in the other 12 eyes, the RMS values with second- to sixth-order corrections were smaller than those with only a second-order correction. In eight eyes, the Strehl ratios with second- to sixth-order corrections were larger than those with second-order corrections. In the remaining five eyes, Strehl ratios with second- to sixth-order corrections were sometimes smaller than those with second-order corrections.

CONCLUSIONS

In a simulation, the correction of time-invariant higher order aberrations usually reduced RMS values, but it did not always result in higher Strehl ratios than those obtained with only second-order corrections.

The Definition and Classification of Dry Eye Disease: Report of the Definition and Classification Subcommittee of the International Dry Eye Workshop (2007)

The aim of the DEWS Definition and Classification Subcommittee was to provide a contemporary definition of dry eye disease, supported within a comprehensive classification framework. A new definition of dry eye was developed to reflect current understanding of the disease, and the committee recommended a three-part classification system. The first part is etiopathogenic and illustrates the multiple causes of dry eye. The second is mechanistic and shows how each cause of dry eye may act through a common pathway. It is stressed that any form of dry eye can interact with and exacerbate other forms of dry eye, as part of a vicious circle. Finally, a scheme is presented, based on the severity of the dry eye disease, which is expected to provide a rational basis for therapy. These guidelines are not intended to override the clinical assessment and judgment of an expert clinician in individual cases, but they should prove helpful in the conduct of clinical practice and research.

Frequency of and Factors Associated With Contact Lens Dissatisfaction and Discontinuation

PURPOSE

To determine the frequency of and factors associated with contact lens dissatisfaction and discontinuation.

METHODS

A cross-sectional survey of 730 subjects was conducted using a self-administered survey instrument. The survey collected information about present age and sex, history of contact lens wear, types of lenses worn, age at starting wear, current wearing schedule (hours per day, days per week), self-perceived contact lens satisfaction, and contact lens-related problems. A variety of statistical analyses including analysis of variance, logistic regression, and repeated-measures logistic regression were used to model the data.

RESULTS

Current or previous experience with contact lenses was reported by 453 (62%) of the subjects. Of these subjects, 119 (26.3%) reported that contact lenses were not the ideal form of visual correction for them (contact lens dissatisfaction) and another 109 (24.1%) had permanently discontinued contact lens wear. Dissatisfied contact lens wearers had reduced self-reported wearing times compared with satisfied contact lens wearers. Previous lens wearers were more likely than current lens wearers to be men, older (by approximately 9.5 years), have started contact lens wear at a later age (approximately 4-5 years later), and have tried either rigid or both soft and rigid lenses. The primary self-reported reason for both contact lens dissatisfaction and discontinuation was ocular symptoms (dryness and discomfort), followed by preference for another corrective modality.

CONCLUSION

A significant number of contact lens wearers are not satisfied with contact lenses and are at risk for discontinuation.

Clinical discussion on the relative efficacy of 2 surfactant-containing lubricating agents in removing proteins during contact lens wear

BACKGROUND

This clinical study aims to evaluate the clinical efficacy of 2 popular rewetting agents, Blink-N-Clean, manufactured by Advanced Medical Optics (Santa Ana, California), and Clens 100, manufactured by Alcon (Ft. Worth, Texas), on protein removal in a nonsymptomatic population of contact lens wearers fitted with etafilcon A soft contact lenses, Acuvue 2, manufactured by Vistakon, a division of Johnson and Johnson Vision Care (Jacksonville, Florida).

METHODS

This randomized, double-blind, crossover study was performed on 22 subjects who had been fitted successfully with etafilcon A soft contact lenses. Each subject was examined on 3 occasions, at 2-week intervals, to evaluate a number of clinical signs related to contact lens wear, with or without the use of ocular lubricants specifically designed to reduce the levels of proteins adsorbed on the lens. A washout period was observed between each of the study's different phases. High- and low-contrast visual acuity levels were measured using the Bailey-Lovie (logMAR) chart under mesopic and scotopic conditions. Protein levels adsorbed on the lenses were determined using a modified Lowry method. Ocular health was assessed under biomicroscopy using conventional techniques. Subjective comfort was also evaluated, using a questionnaire based on a Likert scale graded from 0 to 50.

RESULTS

Objectively, no significant difference in either visual acuity or comfort was found between the use or the nonuse of drops or the use of one specific product. Using Clens 100 allowed for a significant reduction in the quantity of protein on the lens surface. More than 3 subjects of 4 (77%) preferred the Clens 100 product, in large part because they found the size of drops dispensed from the Clens 100 bottle less disturbing during insertion because of the size of the drops and blur.

CONCLUSION

Among healthy contact lens wearers fitted with the same type of contact lens, a significant difference was observed in the quantity of proteins adsorbed on the lens with the use of Clens 100, as compared with the use of either Blink-N-Clean or no product at all. This difference does not seem to have had an impact because clinical signs and symptoms did not vary over the course of the study.

Tear Film Break-up Time Evaluated by Real-Time Hartmann-Shack Wavefront Sensing

PURPOSE

To develop a novel method for measuring tear break-up time (BUT) by continuously measuring higher order wavefront aberrations using a Hartmann-Shack (H-S) aberrometer.

METHODS

Wavefront aberrations up to the sixth order for a 4-mm pupil were measured in six eyes of six normal subjects using an H-S aberrometer. The aberrometry was performed once every second for up to 50 s under topical anesthesia. The sequence of the points was divided into two stages, and the BUT was defined as the wavefront border of the stages (WFBUT). The WFBUT was compared with the BUT by the conventional fluorescein method (FLBUT) or by the disruption of placid-ring images (PLBUT).

RESULTS

In three eyes, the WFBUT (average, 10.9 +/- 1.1 s) was shorter than the PLBUT (average, 17.5 +/- 2.5 s), while in the other three eyes the WFBUT (average, 21.5 +/- 2.2 s) was longer than PLBUT (average, 8.1 +/- 2.2 s). The FLBUT was shorter than WFBUT or PLBUT in most cases.

CONCLUSIONS

The tear break-up time measured by H-S aberrometer may be used as a practical measure of tear break-up.

A novel method for assessing variations in visual acuity after the blink

A novel instrument was developed to assess the visual acuity in correlation with time after blink. The method uses an optical blink detector which triggers the display of a random target symbol on a computer monitor. The delay time between blink and symbol display varies randomly from blink to blink, the exposure duration is fixed at 100 ms. The subject has to identify the correct symbol, a score is kept of the correct responses in correlation to delay time. The recovery of visual acuity after blink was measured for subjects wearing two types of bifocal contact lenses and a control group of non-contact lens wearers. All groups required between 200 and 500 ms to achieve their best visual acuity. Subjects wearing the translating bifocal lenses recovered their vision significantly faster than the subjects wearing no lens or the simultaneous vision bifocal lens.

Effect of Artificial Tears on Visual Performance in Subjects With Dry Eye

PURPOSE

Disruption of the anterior refracting surface of the eye (i.e., the tear layer) reduces visual performance. Tear layer breakup occurs soon after a blink in contact lens wearers and patients with dry eye. This study determined whether artificial tears stabilize the tear film and improve visual performance in contact lens wearers who also exhibit a dry eye.

METHODS

Five subjects with mild to moderate dry eye (probably as a result of an evaporative dry eye) during spectacle and contact lens wear were fitted with a Focus Night & Day hydrogel lens for this study. A temporal, two-alternative, forced-choice paradigm was used to measure contrast sensitivity. The stimuli were vertically oriented sine wave gratings (between 0.5 and 14 cpd) presented for 16.67 msec. The stimuli were presented at two different times after blink detection: 2 sec after blink detection (i.e., before tear layer breakup) or 4 sec after tear film breakup. Four conditions were investigated at 4 sec after tear layer breakup: 1) without artificial tears added, 2) with Clerz2 (Alcon, Fort Worth, TX) instilled, 3) with Sensitive Eyes (Bausch & Lomb, Rochester, NY), and 4) with GenTeal (Novartis, Basel, Switzerland) applied. The artificial tears were instilled at 10-min intervals during the data collection. The short-term visual effects of drop instillation were also investigated by continually monitoring contrast sensitivity for a 14-cpd grating after a single-drop administration.

RESULTS

High spatial frequency contrast sensitivity and visual acuity were found to be reduced after tear film breakup in the absence of supplementation with artificial tears. For the group data (and four of five subjects), the instillation of Sensitive Eyes improved the contrast sensitivity and visual acuity to the level attained before tear breakup, thus prolonging visual performance. Clerz2 and GenTeal did not produce any enhancement in visual performance. A short-term decrease in contrast sensitivity was also observed with a single administration of Clerz2 and GenTeal.

CONCLUSIONS

This study indicates that there was a benefit of Bausch & Lomb Sensitive Eyes tear supplementation on visual performance in subjects with an evaporative dry eye. This may be the result of 1) aqueous supplementation in these subjects and/or 2) the minimal tear layer disruption found with Sensitive Eyes drop administration. The results suggest that practitioners need to identify those patients who can benefit from the use of appropriate artificial tear supplements.

Short-term Effects of Artificial Tears on Visual Performance in Normal Subjects

PURPOSE

Temporal changes in tear film structure can distort the optical wavefront as it passes through the tear layer and reduce contrast sensitivity. Theoretically, any substance applied to the tear layer that alters its structure could affect contrast sensitivity. The purpose of this study is to investigate how different formulations of carboxymethylcellulose sodium (CMC) applied to the tear layer affect contrast sensitivity over time. Additionally, the visual effect of these drops applied over soft and rigid, gas-permeable contact lenses was also investigated.

METHODS

Twenty normal subjects took part in this project. Refresh Celluvisc (Allergan, Irvine, CA, 1.0% high-viscosity CMC) was compared with Refresh Liquigel (Allergan, 1.0% total CMC made by blending 0.35% high-viscosity with 0.65% medium viscosity CMC). Ten of the subjects were habitual soft contact lens wearers and 10 were habitual gas-permeable lens wearers. The stimulus, viewed monocularly, was a stationary, vertically oriented, sine wave grating (14 CPD). A temporal, two-alternative, forced-choice paradigm combined with a self-paced method of limits was used to monitor threshold over time. After baseline data collection, a drop of the artificial tear was applied to the tear layer and the procedure continued for 30 min. This allowed continual tracking of the threshold. Data were collected while viewing the stimulus with the subject's contact lens or with their spectacle prescription.

RESULTS

One drop of Liquigel or Celluvisc decreased contrast sensitivity for a 14 CPD sine wave grating (all p values < 0.005). This decrease in contrast sensitivity was observed during spectacle, soft contact lens, and gas-permeable contact lens wear. Soft contact lens wear resulted in a greater decrease in contrast sensitivity than spectacles when Liquigel was applied to the tear layer. None of the other conditions were different between contact lens and spectacle wear. The return to baseline contrast sensitivity was not significantly different between soft or gas-permeable contact lens wear and spectacles for either Liquigel or Celluvisc. In general, Celluvisc had a greater effect on visual performance than Liquigel.

CONCLUSIONS

These results suggest that Liquigel and Celluvisc alter the tear layer and affect contrast sensitivity. The results agree with patient observations that Celluvisc causes a moderate amount of blur that gradually subsides. In such patients, the shorter duration of blur with Liquigel (about half that of Celluvisc) may be more acceptable. The technique of blending various viscosity CMC materials while maintaining the total CMC concentration of 1.0% may be beneficial in dry eye therapy without causing excessive blur to patients.

Repeatability of the Waterloo Four-Contrast LogMAR Visual Acuity chart and Near Vision Test card on a group of normal young adults

PURPOSES

To investigate the repeatability of logMAR visual acuity (VA) with the Waterloo Four-Contrast LogMAR Visual Acuity (FCLVA) chart and the Near Vision Test (NVT) card. The differences and agreements between near logMAR VA using horizontally- and vertically-presented letters were also determined.

METHODS

Visual acuity of one eye (55 subjects) was first assessed by using the FCLVA chart, comprising four charts of varying contrast, and then with the NVT card (comprising four charts of two contrasts and two presentations). Measurements were repeated after 3 or 4 weeks.

RESULTS

No significant between-visit differences were observed for any of the charts used. The repeatability coefficient for the distance 90, 60, 30 and 10% charts were 0.07, 0.11, 0.15 and 0.16 log units, respectively. The repeatability coefficients of the near vision charts were 0.06, 0.04 (high contrast), 0.11 and 0.10 (low contrast) log units. The agreements between horizontally- and vertically-presented letters were good. The differences were similar to the repeatability coefficient of each chart.

CONCLUSIONS

The repeatability coefficient of the high contrast distance and near chart was about half a line. Repeatability coefficients increase with decreasing contrasts for both distance and near charts, with coefficients of one line or more for low contrast charts. Variabilities in both distance and near VA increase with decrease in contrast. The presentation of the letters does not affect near VA and the agreement between horizontally- and vertically-presented letters (both high and low contrast) was within the repeatability coefficient of each chart.

The Effect of Artificial Tears on Visual Performance in Normal Subjects Wearing Contact Lenses

PURPOSE

Disruption of the anterior refracting surface of the eye reduces visual performance. In the case of a contact lens wearer, this surface is the prelens tear film. This study determined whether artificial tears stabilize the tear film in contact lens wearers and maintained optimal visual performance for a prolonged period.

METHODS

Five normal subjects all in good general and ocular health and adapted to contact lens wear were fitted with Acuvue lenses. A temporal, two-alternative, forced-choice paradigm was used to measure contrast sensitivity. The stimuli were vertically oriented sine-wave gratings (between 0.5 and 14 cpd) presented for 16.67 ms. The stimuli were presented at two different times after blink detection: 2 s after blink detection (i.e., before tear layer break-up) or 4 s after tear film break-up. Three conditions were investigated at 4 s after tear layer break-up: (1) without artificial tears added, (2) with Clerz2 (Ciba Vision) instilled, and (3) with Sensitive Eyes (Bausch & Lomb) applied. The artificial tears were instilled at 10-min intervals during the experimental run.

RESULTS

High spatial frequency contrast sensitivity was found to be reduced after tear film break-up and was not enhanced by either tear solution.

CONCLUSIONS

This study indicates that there is no effect of Clerz2 or Sensitive Eyes in maintaining or improving visual performance beyond the normal prelens tear film break-up time in normal subjects wearing Acuvue lenses.