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Ryan Dimit, William L. Miller, Norman E. Leach, Jan P. Bergmanson; Comparison of Morning and Afternoon Osmolarity in Silicone Hydrogel Wearers and Non-contact Lens Wearers. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6538.
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Tear film osmolarity is thought to be an important marker for dry eye disease. A major complaint of contact lens wearers is end of day discomfort, which may be related to dry eye disease. It is also known that there is an association between tear film osmolarity and ocular comfort. However, little is known of the changes in osmolarity between lens material types and morning versus afternoon osmolarity of asymptomatic patients. This study sought to evaluate the daily variations in tear film osmolarity in a group of daily wear silicone hydrogel contact lens wearers and compare them to normal non-contact lens wearers.
Experienced silicone hydrogel (SiHy) contact lens wearers and normal, non-contact lens wearers were recruited to participate. Contact lens subjects were instructed to apply their lenses at least 1 hour prior to the first osmolarity measurement. Tear film osmolarity was assessed on each eye while the subject was wearing the lens using a TearLab system. This system determines osmolarity by measuring the electrical impedance of a 50 nL tear sample retrieved from the tear meniscus at the lateral canthal region of the lower lid. A repeated measurement was also taken in the afternoon after the subject had worn the lenses a minimum of seven hours. Non-contact lens wearers were assessed once in the morning and again at a minimum of seven hours later.
The mean for the morning readings for contact lens wearers was 303.32 (±8.41) mOsms/L and for the afternoon it was 300.10 (±10.51) mOsms/L. For non-contact lens wearers the morning readings averaged 296.90 (±8.51) and the afternoon average was 298.90 (±8.71). No statistical differences were found between contact lens wearers versus non-contact lens wearers for the morning (p=0.067) or afternoon (p=0.725) readings. There was also no statistical significance between morning and afternoon visits for either contact lens wearers (p=0.220) or non-wearers (p=0.617).
In summary, it appears that silicone hydrogel contact lens wear does not increase the tear film osmolarity in asymptomatic subjects. Silicone hydrogel wear also does not significantly increase tear osmolarity over that of non-contact lens wearers. All lens types tended to show a slight decrease in tear osmolarity in the afternoon, however larger decreases tended to occur with earlier generations of silicone hydrogel materials.
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