An interesting study was published in the October 2013 issue of Optometry & Vision Science. It addresses a situation well known to many contact lens-wearers. Over the course of a day of contact lens wear, discomfort increases for some people. And for some of these people, changing or replacing the lens to a fresh lens part way through the day does not help. Why is that? This study may have an answer and suggests that it is not the lens, it's physical changes happening on the surface of your eyes.
Consequence of Wear Interruption for Discomfort With Contact Lenses
Optom Vis Sci 2013 Oct 17;[EPub Ahead of Print], EB Papas, D Tilia, D Tomlinson, J Williams, E Chan, J Chan, B Golebiowski
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The study examined the comfort reported by patients throughout and at the end of a 10-hour day of wear. Subjects were surveyed on a 0–100 scale for comfort on two separate days.
On the first day, nothing was done to the lenses they wore throughout the day, and study participants reported decreasing comfort during the day. This result was expected, as many optometrists observe this in the clinic. Doctors have long argued about the cause of this discomfort. Was it due to ill-fitting lenses? Or was it due to changes in the surface of the eye caused by contact lens wear?
To answer that question, on the second day the lenses were removed after 5 hours of wear. After removal, either the same lens was reinserted, or it was replaced and a new lens. The assumption was that if lens comfort improved by removing and replacing the same lens, then the surface of the eye was to blame. On the other hand, if comfort improved after switching to a new lens, then the fit of the lens may be at fault. The control group wore lenses continuously for 10 ours with no reinsertion or switching to a new lens.
The results showed that there was no difference between the control group (that wore the lenses continuously for 10 hours) and either the group that removed and reinserted the same lens or the group that switched to a new lens. This lead the researchers to conclude that the increasing discomfort throughout the day was not related to the lenss. They suggested that the likely cause of increasing discomfort was a "fatigue-like response in one or more ocular tissues or stimulation of ocular surface nociceptors induced by the presence of the contact lens."
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