Habitual Contact Lens Wearers Research Articles

Ocular thermography and clinical measurements in symptomatic and asymptomatic soft contact lens wearers.

Symptoms of dryness and discomfort are the main reasons for contact lens dropout. Clinical tests for this purpose are invasive or subjective. Ocular thermography may help to assess the ocular discomfort and dryness in noninvasive and objective manner. This study aimed to investigate the relationship of ocular thermography with clinical measurements in habitual symptomatic and asymptomatic soft contact lens wearers. Forty habitual contact lens wearers were evaluated in two age- and gender-matched asymptomatic and symptomatic groups (Contact Lens Discomfort Questionnaire scores ≤8 and ≥14, respectively). Clinical measurements took place during visit 1 (with contact lens in situ and after contact lens removal) and at baseline after a 2-week washout period (visit 2). The Ocular Surface Disease Index (OSDI) questionnaire, noninvasive tear breakup time, bulbar conjunctival hyperemia, and corneal staining were assessed. Thermal cooling rate was computed in the central and lower cornea during natural blinking (30 s) and sustained eye opening (10 s). Dry eye symptoms (OSDI score) were significantly higher in the symptomatic group during contact lens wear (p<0.001) and at baseline (p = 0.001). Thermal cooling rate was significantly higher in the symptomatic group in the lower cornea (10 s, p=0.013) with the contact lens in situ and in the central cornea (30 s, p=0.045) after contact lens removal. At baseline, dry eye symptoms (OSDI score) significantly correlated with cooling rate in the central cornea region for the symptomatic group (30 s: r = -0.5, p=0.03; 10 s: r = -0.63, p=0.005). Noninvasive tear breakup time correlated with cooling rate in the central cornea region at baseline in the symptomatic group (30 s, r = 0.6, p=0.005; 10 s, r = 0.55, p=0.018). Cooling rate in the central cornea region (10-s duration, p<0.0001) and noninvasive tear breakup time (p<0.0001) were identified as significant predictor variables for dry eye symptoms at baseline. Noninvasive tear breakup time and thermal cooling rate were identified as significant predictor variables for contact lens-induced dry eye. These findings may suggest the potential for the additional application of ocular thermography in the evaluation of contact lens discomfort.

Evaluation of Perfluorohexyloctane Eyedrops in Habitual Contact Lens Wearers.

Dry eye disease is one of the most common disorders we see in practice today. Perfluorohexyloctane (PFHO) ophthalmic solution (MIEBO®) (©Bausch + Lomb) is a novel, non-aqueous, single entity, preservative-free ophthalmic drop recently approved by the FDA for treatment of the signs and symptoms of dry eye disease. While the safety and efficacy of PFHO has been demonstrated in non-contact lens wearers, its safety and potential benefits in habitual contact lens wearers have not been explored. This report presents the results of a trial designed to evaluate the safety of PFHO and its effect on contact lens comfort, specifically in established contact lens wearers. The study included 47 patients who were adjusted contact lens wearers with a best corrected visual acuity of 20/25 or better at distance. All the patients were healthy contact lens wearers with no dry eye symptoms. A significant improvement in comfort scoring was observed without any significant changes in osmolarity, meibography scores, and total fluorescein staining. These findings suggest that PCHO is safe for contact lens wearers to use and shows promise to reduce contact lens dropout.

Tear-film evaporation flux and its relationship to tear properties in symptomatic and asymptomatic soft-contact-lens wearers

PurposeWith soft-contact-lens wear, evaporation of the pre-lens tear film affects the osmolarity of the post-lens tear film and this can introduce a hyperosmotic environment at the corneal epithelium, leading to discomfort. The purposes of the study are to ascertain whether there are differences in evaporation flux (i.e., the evaporation rate per unit area) between symptomatic and asymptomatic soft-contact-lens wearers, to assess the repeatability of a flow evaporimeter, and to assess the relationship between evaporation fluxes, tear properties, and environmental conditions. MethodsClosed-chamber evaporimeters commonly used in ocular-surface research do not control relative humidity and airflow, and, therefore, misestimate the actual tear-evaporation flux. A recently developed flow evaporimeter overcomes these limitations and was used to measure accurate in-vivo tear-evaporation fluxes with and without soft-contact-lens wear for symptomatic and asymptomatic habitual contact-lens wearers. Concomitantly, lipid-layer thickness, ocular-surface-temperature decline rate (i.e., °C/s), non-invasive tear break-up time, tear-meniscus height, Schirmer tear test, and environmental conditions were measured in a 5 visit study. ResultsTwenty-one symptomatic and 21 asymptomatic soft-contact-lens wearers completed the study. A thicker lipid layer was associated with slower evaporation flux (p < 0.001); higher evaporation flux was associated with faster tear breakup irrespective of lens wear (p = 0.006). Higher evaporation flux was also associated with faster ocular-surface-temperature decline rate (p < 0.001). Symptomatic lens wearers exhibited higher evaporation flux than did asymptomatic lens wearers, however, the results did not reach statistical significance (p = 0.053). Evaporation flux with lens wear was higher than without lens wear but was also not statistically significant (p = 0.110). ConclusionsThe repeatability of the Berkeley flow evaporimeter, associations between tear characteristics and evaporation flux, sample-size estimates, and near statistical significance in tear-evaporation flux between symptomatic and asymptomatic lens wearers all suggest that with sufficient sample sizes, the flow evaporimeter is a viable research tool to understand soft-contact-lens wear comfort.

Exploring the factors which impact overall satisfaction with single vision contact lenses

PurposeTo explore the impact of subjective factors (lens handling, comfort and vision) on overall single vision contact lens satisfaction. MethodsCorrelation analysis of a prospective, randomised, double-masked, bilateral crossover study involving 55 adapted lens wearers fitted with somofilcon A (SiHy) (clariti® 1 day, CooperVision) and etafilcon A (Hy) (1 DAY ACUVUE® MOIST, Johnson & Johnson Vision) was conducted. Subjective ratings of lens handling, comfort and vision collected after 1 week of lens wear for each lens type were correlated with overall satisfaction. Data were analysed by combining data for both lens types and also for each lens separately. ResultsFor the combined analysis, significant correlations (p < 0.01) were found between subjective ratings of overall satisfaction and ratings of handing for application (r = 0.64), handling for removal (r = 0.50), comfort upon application (r = 0.59), comfort at end of day (r = 0.61), overall satisfaction with comfort (r = 0.88) and overall satisfaction with vision (r = 0.64).Correlation analysis of the per lens data showed that lens specific correlations of overall satisfaction with handling for lens application varied greatly with lens material (SiHy: r = 0.26, p = 0.05 vs Hy: r = 0.72, p < 0.01). Correlation strength of comfort upon application/at end of day with overall satisfaction also varied with lens material (Application: SiHy: r = 0.40 vs Hy: r = 0.61; End of day: SiHy: r = 0.76 vs Hy: r = 0.58; all p ≤ 0.01). ConclusionOverall satisfaction was significantly correlated with the specific subjective evaluations of handling, vision and comfort. Correlations of overall satisfaction and ease of handling for each lens type suggest that, for habitual contact lens wearers, dissatisfaction with handling at the time of lens application can play a major role in overall dissatisfaction with a lens. Handling for application had a similar correlation (r) value as vision, suggesting that handling for application should not be underestimated when considering overall patient satisfaction.

Review of 20 years of soft contact lens wearer ocular physiology data

BackgroundSince the introduction of Silicone hydrogel (SiHy) contact lenses 20 years ago, industry has continued to modify lens materials, designs, lens care products and manufacturing processes, striving to improve contact lens physiological performance, comfort, and convenience for wearers. The purpose of this study was to investigate whether the ocular health of habitual soft contact lens wearers today is better than it was in previous decades. MethodsBaseline ocular physiology data for 3624 participants from a The Brien Holden Vision Institute clinical trials database were retrospectively reviewed. Records were grouped into 3 time periods; A: >2 decades ago (1997–1999), B: one decade ago (2009–2014) and C: recent years (since 2015). Physiology data for both neophytes and habitual contact lens wearers included; bulbar, limbal and upper palpebral conjunctival redness, corneal and conjunctival staining and conjunctival indentation from contact lenses. ResultsCorneal staining levels are similar between neophytes and contact lens wearers at time points A and C but worse for contact lens wearers at time point B. Limbal redness was greater in contact lens wearers than in neophytes at time point A but at time points B and C they are not different to the non-contact lens wearing population. In recent years, most ocular physiological variables in habitual contact lens wearers are similar to neophytes. ConclusionsWhile there have been changes over the past two decades in ocular physiological responses to contact lens wear, it appears that ocular health with current day contact lens wear is similar to no lens wear in most respects.

Conjunctival Vascular Adaptation Related to Ocular Comfort in Habitual Contact Lens Wearers

We sought to investigate the bulbar conjunctival vascular responses in habitual contact lens (HCL) and non-contact lens (NCL) wearers after short-term lens wear and their relationships with ocular comfort. A prospective, comparative before-and-after study. Twenty-seven subjects (13 HCL and 14 NCL wearers) were enrolled. Microvasculature and microcirculation on the temporal bulbar conjunctiva were imaged at baseline and 0.5 and 6 hours after wearing contact lenses (1-Day Acuvue TruEye; base curve, 8.5mm; power,-0.50 diopters) on both eyes. The measurements included vessel diameter (D), axial (VA), and cross-sectional (VS) blood flow velocities, blood flow volume (Q), and vessel density (Dbox) and complexity (D0). A Contact Lens User Experience (CLUE) questionnaire was used to assess ocular comfort. No significant change (P > .05) was observed in D, VA, VS, Q, Dbox, and D0 in the HCL wearers after contact lens wear. By contrast, VA, VS, Q, Dbox, and D0 increased significantly after lens wear (after 0.5 and 6 hours) in NCL wearers compared with baseline (P < .05). Moreover, the changes from the baseline to 0.5 hours (VA, VS, and Dbox) and 6 hours (VA, VS, Q, Dbox, and D0) after contact lens wear in NCL wearers were significantly greater than that in HCL wearers (P < .05). The CLUE score 6 hours after lens wear was higher in HCL wearers than in NCL wearers (P < .05). It was also significantly correlated with VA, VS, and D0 after 6-hour lens wear in HCL wearers (P < .05). This is the first study to reveal the relationship between ocular comfort and conjunctival vascular responses in habitual contact lens wearers.

Inter-visit measurement variability of conjunctival vasculature and circulation in habitual contact lens wearers and non-lens wearers

BackgroundThe inter-visit variation of measuring bulbar conjunctival microvasculature and microcirculation needs to be considered when the results from multiple visits are interpreted. This study examined the inter-visit variability of measuring conjunctival microvasculature and microcirculation in habitual contact lens (HCL) wearers and non-contact lens (NCL) wearers.MethodsTwenty-eight subjects were recruited including 13 HCL wearers (10 females and 3 males; mean age ± standard deviation, 25.8 ± 4.6 years) who had worn contact lenses on a daily basis for at least 3 years and 15 NCL wearers (10 females and 5 males, age 25.5 ± 4.0 years) were recruited. The temporal bulbar conjunctiva was imaged using a functional slit-lamp bio-microscope (FSLB) imaging system. FSLB imaging was performed in the morning when the HCL wearers did not wear their lenses. The measurements included conjunctival vessel diameter, vessel density, blood flow velocity and flow volume. In addition, conjunctival microvasculature was analyzed using monofractal (Dbox, representing vessel density) and multifractal (D0 representing vessel complexity) analyses. The repeated measurement was conducted at least one week after the first visit and both eyes of each participant were imaged. The coefficient of variation (CV) was calculated as the standard deviation of the differences between test and re-test then divided by the mean of the measurements. The intra-class correlation coefficient (ICC) was also calculated.ResultsNo significant differences of all vascular measurements in both the right and left eyes were found between two groups (P > 0.05). Between two measurements on two different visits, the CV was from 2.4% (vessel density D0) to 63.5% (blood flow volume Q) in HCL wearers and from 3.4% (D0) to 40.6% (blood flow volume) in NCL wearers. The ICC was from 0.60 (vessel diameter) to 0.81 (axial blood flow velocity VA) in HCL wearers and from 0.44 (Q) to 0.68 (cross-sectional blood flow velocity VS) in NCL wearers.ConclusionsThe measurement variability of the vessel density of the bulbar conjunctiva appeared to have the smallest inter-visit variation. The measurement variability of the vasculature and circulation in HCL wearers were similar to that in NCL wearers.

Satisfaction of astigmatic patients with toric nesofilcon A contact lenses.

PurposeThe purpose of this evaluation was to compare the experience of habitual contact lens wearers with that of nonwearers when fitted with a novel toric nesofilcon A contact lens (Biotrue ONEday for Astigmatism lens; Bausch & Lomb Incorporated, Rochester, NY, USA), for wearer comfort, vision, and satisfaction in a real-world setting.Materials and methodsParticipating eye care practitioners (ECPs) prescribed toric nesofilcon A lenses to their astigmatic patients as part of their routine clinical practices. Accordingly, 1,253 patients successfully completed the evaluation; of these, 51% wore contact lenses habitually, 41% wore eyeglasses, and 8% had no prior vision correction. All wore the lenses for at least 4 days, and 74% wore them for an average of 9 hours or more per day. After at least 4 days of wear, each patient completed an online survey to evaluate his or her level of satisfaction regarding comfort and vision. As this postmarket evaluation was observational, data were analyzed to determine whether more patients than not agreed with individual statements regarding lens performance, and whether there was any difference in response between habitual contact lens wearers and nonwearers.ResultsAs a measure of general satisfaction, 96% of patients indicated that their overall opinion of the toric nesofilcon A lens was good to excellent. Further, more patients than not agreed that the lens performed well with regard to all aspects of vision and comfort queried (P<0.001). There was no difference in response between habitual contact lens wearers and nonwearers.ConclusionAll astigmatic patients with spherical contact lenses, other toric lenses, or eyeglasses, as well as those who had no prior correction, who had converted to the toric nesofilcon A lens expressed a high level of satisfaction with vision and comfort. ECPs should expect high success rates when converting astigmatic patients to the novel toric nesofilcon A lens.

Evaluated Conjunctival Blood Flow Velocity in Daily Contact Lens Wearers.

This study examined conjunctival microvasculature development in long-term habitual contact lens (HCL) wearers after a night of sleep. Twenty HCL wearers (15 women and 5 men, aged 28.6±6.9 years, mean age±standard deviation) who had worn contact lenses on a daily basis for at least 3 years and 40 noncontact lens (NCL) wearers (23 women and 17 men, aged 36.5±6.6 years, mean age±standard deviation) participated in the study. A functional slitlamp biomicroscopy imaging system was used to image the temporal bulbar conjunctiva. Imaging was performed in the morning while the contact lens wearers were not wearing their lenses after a night of sleep. The conjunctival vessel diameters, blood flow velocities, and flow rates were measured. In addition, fractal analyses were performed to obtain the vessel network density (Dbox) and complexity (D0). The average blood flow velocity in HCL wearers after a night of sleep was 0.59±0.19 mm/s, which was significantly higher than that in NCL wearers (0.48±0.17 mm/s, P<0.05). The microvessel network density and complexity levels (Dbox=1.64±0.05 and D0=1.71±0.05, respectively) in the HCL wearers were significantly higher than those in NCL wearers (Dbox=1.61±0.05 and D0=1.69±0.04, both P<0.05). The blood flow velocity was positively correlated with the duration of contact lens wear (r=0.46, P<0.05) and with the daily number of lens-wearing hours (r=0.49, P<0.05) in HCL wearers. This study identified microvascular alterations in the conjunctiva in response to daily contact lens wear after a night of sleep in long-term daily contact lens wearers. The unrecovered changes may indicate that para-inflammation occurs on ocular surfaces because of contact lens wear and that overnight sleeping with no lenses may not sufficiently restore the ocular surface to an intact state.

Factors Affecting Microvascular Responses in the Bulbar Conjunctiva in Habitual Contact Lens Wearers.

PurposeTo investigate the factors affecting microvascular responses in the bulbar conjunctiva of habitual contact lens (HCL) wearers.MethodsA functional slit-lamp biomicroscope (FSLB) was used to image the temporal bulbar conjunctiva of habitual contact lens (HCL) wearers and non–contact lens (NCL) wearers. The vessel diameters and blood flow velocities (BFVs) were measured. Fractal analysis using Dbox as vessel density and D0 as vessel complexity were used to quantitatively analyze the microvascular network. One eye each of 91 NCL wearers and 75 HCL wearers was imaged.ResultsThe BFV of NCL wearers was 0.50 ± 0.14 mm/s, which was negatively correlated with age (r = −0.22, P < 0.05). The BFV, vessel diameter, Dbox, and D0 of HCL wearers was significantly higher than NCL wearers (P < 0.05). In these HCL wearers, BFVs were positively correlated with contact lens (CL) hours of wear per day and CL days of wear per week. BFV, Dbox, and D0 were not related to CL years of wear, CL power, CL base curve, and CL diameter (P > 0.05).ConclusionsVascular responses on the bulbar conjunctiva occurred in HCL wearers and appeared to be unrelated to sex or age, CL years of wear, and lens parameters, indicating that wearing a CL itself may be the predominant factor inducing these responses.

Daily Wear Contact Lenses Manufactured in Etafilcon A Are Noninferior to Two Silicone Hydrogel Lens Types With Respect to Hypoxic Stress.

This study hypothesized that a traditional high-water contact lens of moderate oxygen transmissibility (Dk/t) is noninferior to common silicone hydrogel (SH) lenses worn for daily wear with respect to measures of hypoxic stress. Thirty-six habitual contact lens wearers completed wear of three lens types worn in a randomized order: etafilcon A (ACUVUE 2, control), lotrafilcon B (Air Optix Aqua), and comfilcon A (Biofinity). Central corneal thickness (CT) and limbal hyperemia were measured >2 hr after waking and after 6 to 8 hr of wear on days 1 and 7. Endothelial bleb formation was measured on day 1 of each lens type. Noninferiority of etafilcon A, with respect to the other two lens types, was assumed if the following difference margins of equivalence were met: <1.5% for corneal swelling, <0.5 grade for limbal hyperemia, and <1% area of endothelial blebs. Outcomes were modeled using generalized linear mixed modeling techniques. All lenses showed reductions in least-square mean estimates of CT on both days: etafilcon A -0.26% at day 1 and -0.31% at day 7; lotrafilcon B -1.11% at day 1 and -1.06% at day 7; comfilcon A -0.63% at day 1 and -0.84% at day 7. The difference in mean swelling between etafilcon A and lotrafilcon B was 0.85% at day 1 (95% confidence interval [0.4%-1.3%]) and 0.75% at day 7 (0.3%-1.2%). The difference in mean swelling between etafilcon A and comfilcon A was 0.37% at day 1 (-0.1% to 0.8%) and 0.53% at day 7 (0.1%-1.0%). For limbal redness, etafilcon A fell within 0.1 grade of lotrafilcon B and 0.18 grade of comfilcon A. For endothelial bleb formation, etafilcon A fell within 0.45% of lotrafilcon B and 0.23% of comfilcon A. The etafilcon A control lens resulted in corneal deswelling throughout the day as did the SH lens types. Limbal hyperemia and endothelial bleb formation with all lenses were negligible, and noninferiority assumptions were met between the lens types for all outcomes. Equivalence of etafilcon A with respect to the two SH lenses for three measures of hypoxic stress was demonstrated.

Effect of contact lens surface properties on comfort, tear stability and ocular physiology.

Retrospective analysis of different contact lens wearing groups suggests lens surface lubricity is the main factor influencing contact lens comfort. However, the examined commercially available contact lenses differ in material and design as well as surface properties. Hence this study isolates the contribution of lens surface properties using an ultra-thin coating technology. Nineteen habitual contact lens wearers (21.6±1.7years) wore formofilcon B soft monthly disposable contact lenses with and without coating technology modified surface properties for a month each in a randomised double-masked cross-over study. OBJECTIVE NON-INVASIVE: breakup time (NIKBUT), NIKBUT average and ocular redness (Jenvis grading scale) were evaluated (Keratograph 5M) after 1 week and 1 month of wear. Symptoms were assessed using the Contact Lens Dry Eye Questionnaire (CLDEQ-8); perceived vision quality and subjective lens comfort at insertion, mid-day and end of the day were rated with four Visual Analog Scales. Perceived visual quality (F=5.049,p=0.037), contact lens dry eye symptoms (F=14.408,p=0.001) and subjective lens comfort (F=28.447,p<0.001) were better for coated compared to uncoated lenses. The surface coating postponed the lens dewetting (F=8.518,p=0.009) and increased the pre-lens tear film stability (F=5.626,p=0.029), but bulbar (F=0.340,p=0.567) and limbal (F=0.110,p=0.744) redness were similar for both contact lenses. No parameter changed significantly between a weeks' and months' wear (p>0.05). Lens surface wettability and ocular redness were not correlated to changes in symptoms (p>0.05). As previously hypothesised, enhancing the physical surface properties of a soft contact lens improves subjectively rated wearer comfort, which, in turn, should result in reduced contact lens discontinuation.

Mental Health Status of the Keratoconus Patients Visually Corrected with Contact Lens Compared to Spectacles

1.1.Aim of the Study:To analyse the mental health status and psychological well being of the keratoconus patients using rigid contact lenses compared to spectacle corrected ones. The objective is to study if the correcting vision with contact lenses impacts the mental health status of the patients suffering from keratoconus. 1.2.Methodology:In the month of January to April, 2015 a cross sectional study was conducted in Ahooja eye hospital, Gurgaon, Haryana, India and Rajan eye care hospital, Tnagar, Chennai, Tamilnadu, India. Thirty two keratoconus patients were enrolled for the study and subjects were asked to the mental health status questionnaire MHI 38 with informed consent. Fifteen were habitual contact lens wearers and seventeen non contact lens wearers who volunteered to participate this study. Study included those contact lens users who wore lenses all waking hours and had been wearing them for atleast one year. All the questions were score coded for entering the data in Microsoft Excel sheet. The status of mental health was based on eight indicises which provided information on mental well being. 1.3.Results:17 males and 15 females participated in this study. The mean age of the participant was 28.03± 5.56 (range 20-39 years). The mean score of keratoconus patients of non contact lens wearer and contact lens wearer in Anxiety was 32.84 ± 2.99 &18.79 ± 3.67, Depression 13.34 ± 4.08 & 7.71 ± 2.19, Loss of behavioural / Emotion Control 30.29 ± 2.22 & 22.77 ± 6.70, General Positive Affect 49.00 ± 3.86 & 29.73 ± 4.48, Emotion Ties 10.17 ± 1.44 & 5.28 ± 1.71, Life Satisfaction 3.44 ± 0.96 & 4.94 ± 0.73, Psychological Distress 81.28 ± 4.48 & 53.15 ± 9.62, Psychological Well Being 41.15 ± 4.75 & 69.08 ± 5.26, Mental Health Index 119.81 ± 5.53 & 185.82 ± 11.03 respectively. Our results show that P value is <0.05 is statistically significant in all subscales and on the global scale variable of MHI 38. It suggests those who wear contact lenses have significantly better life satisfaction and Mental Health. Proper contact lens option as vision correction in Keratoconus patients improves the mental health status and are more positive in attitude compared to non users. A successful contact lens fit influences the mental health status compared to those who do not opt to wear it. 1.4.Conclusion:Eye care practitioners should motivate and proactively advise contact lenses to patients with Keratoconus as they will have better life satisfaction and psychological well being.

Eyelid Margin and Meibomian Gland Characteristics and Symptoms in Lens Wearers.

To describe the lid margin characteristics of contact lens wearers and relate them to comfort during lens wear. Three study sites enrolled habitual contact lens wearers. Subjects completed the Comfort domain of the Contact Lens User Experience (CLUE) questionnaire, and each eye was graded for the presence of mucocutaneous junction (MCJ) displacement, lid margin irregularity, and lid margin vascularity. Examiners counted the number of meibomian gland (MG) orifices in the central centimeter of the lower eyelid and the number of those that showed pouting/plugging and vascular invasion. MG expressibility was graded according to the Shimazaki schema. Subjects were grouped based on presence/absence of each characteristic, total number of orifices (≥5 vs. <5), and expressibility (grade 0 vs. >0). Descriptive statistics are reported. A linear model was used to assess the fixed effect of each characteristic on combined CLUE score and each CLUE statement, if the effect on combined CLUE score showed p < 0.10. The study included 203 subjects (67.5% female) with mean age (±SD) of 30.3 ± 9.6 years. The most commonly observed characteristics were orifice pouting/plugging, compromised MG expressibility, and lid margin vascularity (35.0, 30.3, and 20.4%, respectively). MCJ displacement and MG expressibility had an effect on the combined CLUE score such that individual CLUE statements were analyzed (p = 0.01 and p = 0.06, respectively). MCJ displacement had an effect on comfort upon insertion (p = 0.01), comfort after 5 minutes (p = 0.03), end-of-day comfort (p = 0.01), and ability to maintain ocular moisture (p = 0.030). MG expressibility had a significant effect on general comfort (p = 0.01), comfort throughout the day (p = 0.02), and the ability to maintain ocular moisture (p = 0.02). MCJ displacement and MG expressibility have an effect on contact lens comfort.

The Effect of Refractive Lenses on Perceived Direction

The accuracy of directional localization with refractive lenses was determined by open-loop pointing for four myopic habitual contact lens wearers. The target was a single point of light at random locations (dark), or was embedded in a horizontal array of lights (light). In the dark, the regression slope of indicated vs actual target position was significantly less for spectacles than for contact lenses, as predicted from the prismatic effects of the spectacles. In the light, slopes for spectacles and contacts were not significantly different. These results suggest that spectacle wearers do not utilize eye position information in making direction judgments in the light. Copyright © 1996 Elsevier Science Ltd.