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Jiangtao Chen, Trefford L. Simpson; A Role of Corneal Mechanical Adaptation in Contact Lens–Related Dry Eye Symptoms. Invest. Ophthalmol. Vis. Sci. 2011;52(3):1200-1205. doi: 10.1167/iovs.10-5349.
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To compare corneal mechanical adaptation measured psychophysically in contact lens wearers with or without dry eye symptoms.
Two groups of contact lens wearers were recruited. One group (symptomatic) consisted of subjects with dry eye symptoms (according to the subjective evaluation of symptom of dryness [SeSoD] questionnaire). The second control group (asymptomatic) consisted of subjects reporting no symptoms. There were 32 (aged 20 to 42 years, 6 males and 26 females) and 29 subjects (aged 21 to 36 years, 9 males and 20 females) in the symptomatic and asymptomatic groups, respectively. Mechanical stimulus thresholds of the cornea were determined using a Belmonte pneumatic esthesiometer and the ascending method of limits. Then three stimulus intensity groups (subthreshold, threshold, and suprathreshold) were applied to the eye in random order, each 20 times. Subjects rated the intensity of the stimuli using a scale of zero to four. The rating data from the two groups were compared by Friedman nonparametric ANOVA. Adaptation was defined as the reduction in subsequent ratings compared with earlier ones.
No significant difference was seen in subjects' thresholds in both groups (P = 0.22). The symptomatic group rated their sensations to suprathreshold stimuli higher than the asymptomatic group. More importantly, there was significant adaptation with suprathreshold mechanical stimulation in the asymptomatic group (P = 0.006) but not in the symptomatic group (P = 0.08). There was no adaptation during threshold and subthreshold stimulus sessions in either group.
Adaptation was found to suprathreshold mechanical stimuli in the asymptomatic group but not in the symptomatic group.
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