A review of meibomian gland structure,function, and contact lens wear

PurposeTo provide a balanced literature review of the studies that have evaluated the effect of contact lenses on meibomian gland (MG) health.MethodsA PubMed.gov literature search was conducted on or before May 15, 2021. No other time constraints were applied. Search terms included the following: “meibomian gland(s)” plus “contact lens(es)” or “meibography” plus “contact lens(es)”. Only full text articles written in English were considered. The reference lists of recovered papers were used to identify articles missed during the primary search. Included articles were required to discuss the impact of contact lenses on MG morphology or function and were graded according to the level of evidence presented.ResultsThe literature indicates that contact lenses impact MG function; however, the data are equivocal regarding contact lenses inducing MG structural changes. The literature likewise indicates that the mechanism(s) by which contact lenses impact the MGs are likely multifactorial. Recent data suggests that MGs may have some plasticity. Detected differences between studies likely stem from varied populations evaluated, study designs, and the duration of the evaluation periods.ConclusionsWith this literature review finding conflicting relationships between MG health and contact lens use, future longitudinal studies with standardized clinical MG assessments are needed to determine the true impact of contact lenses on MG health. Until these data are obtained, contact lens wearers should undergo a full MG evaluation, especially because recent data suggest that MG treatments may restore MG structure and function.     

Damage of the ocular surface from indoor suntanning—Insights from in vivo confocal microscopy

PurposeTo evaluate the ocular surface at the microstructural level of adults who habitually undertake indoor-suntanning utilising in vivo confocal microscopy.MethodsParticipants were prospectively recruited and enrolled into either а study group (n = 75) with a history UV indoor tanning, or a control group (n = 75) with no prior history of artificial tanning. The study group participated in voluntary tanning sessions performed with standard equipment and maintained their usual routine for eye protection. Slit lamp biomicroscopy and in vivo confocal microscopy were performed at baseline before undertaking a series of suntanning sessions (10 sessions of 10 min duration over a 15 day period), within three days after the last session, and four weeks after the last session. Control group participants were examined at baseline and 8 weeks later and did not participate in tanning sessions.ResultsAll participants were female with a mean age of 25 ± 4 years and 24 ± 4 years in the study and control groups, respectively. No clinically significant changes were observed in either group over time using slit lamp biomicroscopy (all p ≥ 0.05), however, statistically significant differences were observed between the study and the control group for all corneal layers imaged using confocal microscopy (all p ≤ 0.03). Characteristic cystic conjunctival lesions with dark centres and bright borders were observed in 95% of the study group before and in 100% after the suntanning sessions.ConclusionIndoor suntanning resulted in statistically significant microstructural changes in the cornea and the bulbar conjunctiva that are undetectable with slit lamp biomicroscopy.     

The differences between patient and optometrist experiences of contact lens hygiene education from the perspective of a Scottish university teaching hospital

BackgroundContact lens related keratitis is a frequent presentation to acute ophthalmology services. Patients often do not recall being counselled regarding the safe use of contact lenses therefore fail to comply with guidance.This study aimed to identify the content and format of advice given to patients with contact lens keratitis concerning appropriate hygiene practices, determine their compliance with this and finally characterise optometrist practices regarding contact lens advice provided to patients.MethodsAll adult patients presenting with contact lens related keratitis to the acute ophthalmology clinic were asked to complete a survey. Information was collected on lens type, format of advice received and compliance.Community optometrists were asked to complete an electronic survey on their contact lens review practices and routine patient education.ResultsAll patients surveyed recalled counselling on initiation of contact lenses; however 12% (6/50) were given no advice on return visits. This advice was in written format for 20% (10/50) of patients on initiation increasing to 32% (16/50) on renewal.Many patients slept (22%), showered (44%) or swam (36%) in lenses. 92% cleaned their contact lenses appropriately, but cases were washed infrequently (19% of cases cleaned < monthly) or with tap water (27%).All optometrists surveyed claimed to provide advice to patients in either written or verbal format for new and returning contact lens users. 49% (16/33) of optometrists gave written advice to patients on initial contact lens fitting, but only 1/33 continued with written advice for repeat customers.ConclusionThis study identified that although most patients were informed of appropriate hygiene requirements, compliance was poor. Optometrists regularly provide verbal advice but do not routinely offer written support and there is a mismatch between patient recollection and self-reported optometrist practice. It is suggested that patient education needs greater emphasis and both verbal and written information should be regularly provided on initial review and follow up assessments.     

Does placebo effect exist in contact lens discomfort management?

PurposeTo study the effect of daily disposable contact lens (DDCL) refitting in monthly contact lens (CL) wearers suffering from contact lens discomfort (CLD), and to assess if there is a placebo effect associated with this CLD intervention.MethodsSymptomatic CL wearers, according to the Contact Lens Dry Eye Questionnaire 8 (CLDEQ-8 ≥ 12 points), were divided into two groups. The study group was provided with DDCLs (delefilcon A) and the control group with a masked pair of their habitual monthly CLs (placebo effect) and were assessed after one month. Then, the control group was provided with the same DDCLs and evaluated one month later. The symptoms were recorded with the CLDEQ-8 and global rating of change scale (GRCS). Non-invasive tear break-up time (NITBUT), conjunctival hyperaemia, fluorescein staining, and lid wiper epitheliopathy (LWE) were evaluated. Changes between visits, groups, and the effect of each intervention were analysed.ResultsThirty-one participants (mean age: 23.2 ± 5.3 years) were recruited. The study group (n = 14) showed an improvement of -39.6 ± 25.8 % (p < 0.001) in CLDEQ-8 and 31.3 ± 14.6 points in GRCS (p < 0.001) after one month of DDCL use, while no changes in clinical tests were found. In the control group (n = 17), symptoms improved significantly after wearing the masked monthly CL (CLDEQ-8: -26.1 ± 31.0 %, p = 0.03; GRCS: 14.9 ± 17.0, p = 0.002), however a worsening in bulbar (26.5 ± 40.0 %; p = 0.02) and limbal hyperaemia (21.6 ± 34.7 %, p = 0.02) and an improvement of -19.1 ± 37.0 % (p = 0.049) in LWE was found. When the control group was fitted with the DDCL, improvements in GRCS (20.5 ± 25.5, p = 0.02), NITBUT (37.9 ± 42.3 %, p = 0.002), and conjunctival staining (-47.1 ± 59.9 %, p = 0.005) were noted.ConclusionsRefitting symptomatic monthly CL wearers with Delefilcon A DDCL is effective in reducing symptoms related to CLD. However, clinicians and researchers must be aware of the existence of a placebo effect when assessing the effectiveness of any CL refitting.     

Cooperative Cover of Uniform Demand

Networks and Spatial Economics - We investigate the total covered area by multiple facilities applying the cooperative cover model. We found that the cooperative cover area is much larger than the...     

Manipulating user resistance to large-scale information systems through influence tactics

This study examines how influence tactics can be used to manipulate user resistance and subsequent usage behaviors in the context of large-scale, newly implemented information systems (IS). To do so, we integrate the theory of interpersonal influence and leadership, adaptive structuration theory, and the literature on user resistance and behavioral IS theories, and develop a comprehensive theoretical model anchored in (a) social influence tactics, (b) IT artifact perceptions, and (c) user resistance and subsequent behaviors. The resultant theoretical model explains how influence tactics modulate user perceptions, user resistance to the system, and ultimately the unfaithful use of the system. This model is tested in the context of an electronic medical record (EMR) system implementation, with a sample of 442 clinicians who were exposed to various influence tactics and with the use of SEM techniques. The results indicate that certain influence tactics are beneficial in reducing user resistance while others can unintentionally increase resistance. Resistance, in turn, drives adaptive user behaviors in the form of unfaithful use of the system. Thus, it is possible to manipulate resistance and resultant adaptive behaviors through influence tactics, without necessarily altering the IT artifact. This is particularly important, as many off-the-shelf IT artifacts cannot be substantially modified.     

Videokeratoscopic assessment of silicone hydrogel contact lens wettability using a new in-vitro method

PurposeThe aim of the study was to assess the surface wettability of new-generation silicone hydrogel (SiH) contact lenses (CLs) videokeratoscopically using a new in-vitro method under office conditions.MethodVideokeratoscopic methodology was used to compare time-dependent CL wettability on an in-vitro cornea model. The model cornea was a polished chrome surface coating a Teflon form. It was prepared with a base curve of 8.7 mm and a diameter of 15 mm. Laboratory temperature and humidity were controlled. Before and after placing CLs on the on the model cornea, Bausch + Lomb Biotrue® multi-purpose solution (MPS) was dropped to simulate the pre-lens and post-lens film layer. Fanfilcon A, Senofilcon A, Samfilcon A, and Lotrafilcon B CLs with -3.00D were used, and images were taken with the videokeratoscopic method for testing. In the control group, the same procedure was performed without placing CLs. The images of CLs at 0, 60, 90, 120, 150, and 180 s were taken. Distortions and gaps seen in rings were recorded. The areas in rings were calculated in pixels using İmageJ.ResultsWhen CLs were examined, statistical differences were found among average pixel values (p < 0,001). The average pixel value was 131877.4 in the Samfilcon group, 116125.5 in the Senofilcon group, 137893.2 in the Fanfilcon group, 125578.3 in the Lotrafilcon group, and 124984.6 in the control group. No difference was found between the average values of the Lotrafilcon group and the control group. Differences were found between the average values of all other groups.DiscussionThe results obtained showed that videokeratoscopy was an effective method for in-vitro testing of CL wettability. It was found that SiH lenses displayed different performance under office conditions depending on materials and technologies used for wetting the lens surface. It was shown that lens surface wettability could be measured with a repeatable and new method when the factors affecting surface wetness and image quality were ruled out.     

Impact of meibomian gland width on successful contact lens use

PurposeTo evaluate meibomian gland (MG) width and determine its impact on successful contact lens (CL) use and ocular health.MethodsA five-site study was conducted by recruiting 18- to 45-year-old subjects who had dropped out of CLs because of discomfort. CL dropouts were compared to age- and sex-matched successful CL wearers. Right eyes were evaluated for tear break-up time, tear meniscus height, MG expressibility, meibum quality, and meibography. Central MG widths were evaluated with a custom MATLAB program.ResultsCL dropouts (n = 56) and successful CL (n = 56) wearers had similar grades for upper (p = 1.0) and lower (p = 0.22) MG atrophy, upper (p = 0.07) and lower (p = 0.89) MG tortuosity, and upper (p = 0.92) and lower (p = 0.97) MG widths. Upper eyelid MG widths were narrower than lower eyelid MG widths (p = 0.03). Upper and lower MG tortuosity (p < 0.001) and widths (p = 0.03) were associated, but not atrophy (p = 0.42). Lower eyelid MG widths were associated with MG expressibility (p = 0.01), but MG widths were not with any other factors.ConclusionsSuccessful CL wear does not appear to be clinically influenced by MG width or other measures of MG structural integrity. Lower eyelid MGs were wider than upper eyelid MGs and narrower lower eyelid MGs were associated with worse MG expressibility, suggesting that narrower MGs may produce abnormal meibum. Data also suggests that MG factors of both eyelids should be evaluated in practice.