Characterizing how contact lens wearers use their lenses is important because it helps to understand the environmental challenges to their ocular and contact lens surfaces. Analysis of these data provides new information about the environmental stressors to which lens-wearing eyes are exposed and the ability of subjects to cope with their effects. It also reveals situations that may limit lens wear.
This survey shows that the most common “exposures” to challenging environments involve routine everyday activities included in the wearer’s lifestyle. Over 90% (92%) of these subjects reported wearing their contact lenses while driving at night, 89% while using a computer, 87% while in a heated or air-conditioned car, and 79% while sitting under a heating or air-conditioning vent in a building. These activities define the typical routine of everyday life for adults with jobs and active lifestyles. Even though highly air-conditioned environments can disrupt the prelens tear film13 and can result in ocular,3,6,14 skin, and mucous membrane symptoms,1,2,15,16 this study shows that hydrogel contact lens wearers must and do maintain lens wear in those environments. Use of lenses during occupational and domestic activities is the norm and therefore contact lens wear must be comfortable enough for the wearer to continue lens wear. If silicone hydrogels can help deliver better lens comfort during everyday activities and environments, perhaps their use could help slow the rate of discontinuation of lens wear17–19 as lens discomfort or dryness are most often cited as the reason to cease lens wear.20
Interestingly, the least common environmental exposures (sitting under an air vent, being in low humidity and dry air, being in a smoky, dusty or polluted environment) were also associated with lower comfort ratings with habitual hydrogel lenses. That is, lens wearers seemed to avoid wearing lenses in the most uncomfortable environments such as dusty, smoky, or windy environments as shown in Fig. 2. Harsher environments like these are probably more able to predict and therefore avoid, such as going to a smoky tavern with friends or working with a sanding machine on a weekend project. Because of the ability to remove lenses when they please, lens wearers are able to and do self-manage their lens wear in order to avoid the situations that may prove unpleasant while wearing lenses.
Napping while wearing lenses was the only factor that theoretically could be experienced by all subjects but, in the study, was reported by only a few. Only 27% of this group reported napping while wearing their habitual daily wear hydrogel lenses, and only 14% reported doing so “always” when they took a nap. That represents fair compliance with the warning against closed-eye wear of the low transmissibility hydrogel lenses that they were wearing on entering the study. The higher transmissibility materials have the advantage of avoiding corneal hypoxia during brief periods of closed-eye wear for patients who nap in lenses while also maintaining good comfort. Lower water content in the silicone hydrogel materials reduces the amount of on-eye dehydration during closed-eye wear as well.12
For many lens wearers, after being refit with one of the silicone hydrogel test lenses, many environments that had previously challenged comfort with their habitual hydrogel lenses no longer appeared to pose such a challenge. The subjects with senofilcon A, and galyfilcon A lenses reported significantly improved comfort in most situations. One exception was for galyfilcon A while using a computer. Subjects who were refit with lotrafilcon B lenses, however, reported fewer symptoms in many environments but did not report a significant improvement in comfort in the most frequently experienced challenging environments; night driving, computer use, or while sitting in a car with heat or air-conditioning. The authors note that the galyfilcon A and lotrafilcon B groups were smaller than the other test lens groups, but were similar in size for most of the exposures as shown in Table 3. This smaller sample size for these lenses would have an impact on the power to detect a difference in the test vs. habitual lens in those environments. Because the first goal of this analysis was to determine the usage patterns, it was not possible to balance the sample of subjects who were exposed to each lens type and environment in combination. Although the exposed number of subjects for night driving, computer use, sitting in air-conditioned or heated rooms, and reading was nearly identical between the galyfilcon A and lotrafilcon B lens groups, as shown in Table 3, the results were quite different. The data displayed in Figs. 5 A and B shows the proportions of subjects with good comfort with habitual or test silicone hydrogel lenses so that the patterns of change in symptoms can be viewed regardless of the number of subjects in the sample.
Although a study such as this cannot pinpoint the cause of the discomfort from habitual lenses, an improvement that resulted from refitting with a new lens type may be due to use of materials that resist dehydration, stay cleaner, avoid corneal hypoxia, or have smoother surfaces. Provision of a new pair of lenses alone cannot account for all of the improvement reported in this study, as approximately 70% of the subjects habitually wore 2-week replacement disposable lenses and more than 7% wore daily disposable lenses. Although not a feature of this study, a design in which the subjects were crossed back into their habitual lens design would have more clearly identified the role of lens replacement in the improvement in symptoms.
The environments in which the subjects reported the worst comfort with habitual lenses improved the most after refitting with silicone hydrogel lenses, regardless of lens type. These exacerbating conditions included sitting under an air-conditioning or heating vent, spending time in a low humidity or dry air environment, being in a smoky, dusty or polluted environments, and napping while wearing lenses and comprise the activities that may limit lens wear if not managed properly. This study shows that lens wearers continue to put up with environmentally triggered discomfort because they need to continue wearing lenses while working or in other situations. In these situations, the option of removing the lenses may be unavailable or inconvenient. Improved comfort with silicone hydrogel lenses in environments that caused discomfort from particulates, such as dusty or windy conditions may occur because the lens surface retains more surface moisture which, in turn, facilitates clearance of particles from the surface through blinking.
This study was limited primarily by uneven sample size across environmental exposures and lens groups, and the short duration of lens wear (2 weeks) before sampling the subjective assessment of the silicone hydrogel test lenses. The lotrafilcon B group was under-represented in the West, which may have reduced the baseline dryness reports in that group. However, because a paired analysis was applied, each subject is compared to themselves, thereby reducing the effect of differences across groups at baseline. In addition, because of the 2 week sampling time, only a small number of subjects in each lens type experienced air travel or spending time in high altitude. These small sample sizes make it unwise to conduct statistical tests on these variables. However, examination of the slopes in Figures 5A and B between the proportions of subjects who reported their lenses were always or frequently comfortable in environments before and after refitting will show the relative improvement within that cohort regardless of sample size.
How much do environmental factors that are known to affect the comfort of the natural surface of the eye, such as low humidity, high temperature, and air turbulence, affect the comfort of hydrogel and silicone hydrogel contact lenses? This study indicates that the use of hydrogel lenses is avoided in a few harsh environments, such as windy, polluted, and dusty areas. These may be environments that actually limit lens wear. However, to function in their everyday life, contact lens wearers must wear lenses in a wide variety of other dry or turbulent conditions to ride to work in their car, and heat or cool their homes and offices. The sampling of experience with silicone hydrogel lenses in this study indicates that they were tolerated more easily and worn more comfortably in the wide range of conditions when compared with the subjects’ habitual hydrogel lenses. If silicone hydrogel lenses begin to be prescribed as the standard of care for soft lens wearers, the proportion of patients experiencing discomfort and poor tolerance of lenses should decrease over time in the next few years. Lens materials that were primarily designed to increase the oxygen transmissibility to the cornea may have provided another very tangible benefit for contact lens wearers.
This study was sponsored by Vistakon, a division of Johnson & Johnson Vision Care, Inc. Graeme Young, Chris Hunt and Robin Chalmers are paid consultants for both Vistakon and CIBA Vision, a Novartis Company. Colleen Riley is employed by Vistakon.
Robin L. Chalmers
2097 East Lake Rd,
Atlanta, GA 30307
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Keywords:© 2007 American Academy of Optometry
adverse environments; silicone hydrogel lenses; symptoms; signs; contact lenses