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K. Maruyama, N. Yokoi, S. Kinoshita; Effect of Temperature and Humidity on Tear Film during Soft Contact Lens Wear . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3695.
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Purpose: Dry eye symptoms are often associated with soft contact lens (SCL) wear and are possibly affected by environmental conditions. This study aimed to explore the effect of temperature and humidity on tear film on SCL. Methods: Enrolled subjects were all daily SCL wearers and aged 23.5±5.2 (mean±SD, n=11). Subjects were adapted in an environmental chamber (The environmental chamber®, Tabai Espec Co. Ltd., Osaka, Japan; 34.8m3 in size) and four conditions were set regarding the air temperature (AT) and relative humidity (RH): [Test1 (AT: 5°C/RH: 10%); Test2 (15°C/20%); Test3 (25°C/40%); Test4 (35°C/50%)]. Subjects wore two different types of hydrogel SCLs (CL-a: 72.0% in water content; CL-b: 37.5%) only on right eyes. These lenses were compared in the same environmental conditions. Meniscus tear volumes by measuring tear meniscus radius (TMR) before and during the wearing of SCLs were evaluated by a video meniscometer (Yokoi, Cornea, 2001). Tear interference patterns (TIP) on SCLs were graded into one of 5 original grades (Increased grades for thinner film). Pre-corneal non-invasive tear film breakup time (NIBUT) before SCL wearing and pre-lens NIBUT were assessed using a video interferometer (Yokoi, AJO, 1996). Eye dryness before and during the wearing of SCLs were scored by asking each subject. Results: No significant difference was found in TMR before and during the wearing of SCLs in either environmental condition. Grades of TIP in each type of SCLs significantly increased as the AT/RH decreased (p<0.05). Pre-corneal NIBUTs before SCL wearing were not significantly changed. Pre-lens NIBUTs (sec.) were significantly decreased as the AT/RH decreased (CL-a: test1; 2.73±1.49, mean±SD; test2; 2.73±1.74, test3; 5.36±4.23, test4; 8.00±3.32; CL-b: test1; 3.09±1.76, test2; 2.82±3.06, test3; 6.91±2.77, test4; 7.64±3.41, each p<0.05 without test 1 vs test 2). Scores of dryness were significantly increased in each SCLs (p<0.05) as the AT/RH decreased; however, severer scores of dryness were noted in wearing CL-a than CL-b in all environmental conditions (p<0.05). Conclusions: In SCL wear, tear volume was considered to be independent of AT and RH. It was found that tear film on SCL became thinner, pre-lens NIBUT became shorter and dryness during the wearing of SCLs increased as the AT and RH decreased. Dryness was more commonly found to be felt in SCL of higher water content.
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