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William Ngo, Yunwei Feng, Nancy J Keir, Trefford L Simpson; Selecting a Sensory Panel to Judge Contact Lens Discomfort. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4666.
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To determine individuals from a population of contact lens wearers who are able to discriminate contact lens discomfort well.
44 adapted soft lens wearers were enrolled in this prospective, randomized, study. Corneal mechanical sensitivity threshold (CMST) was determined for each participant on one randomly determined eye prior to inserting a randomly determined contact lens (lens A, B, or C) in the contralateral eye. A customized Belmonte pneumatic esthesiometer was used to induce discomfort in the non-lens wearing eye by administering a controlled flow of air to the cornea. The participants were asked to match the magnitude of discomfort to the contact lens wearing eye by adjusting a potentiometer that controlled the flow rate of the air. The participants were also asked to give a subjective score (0 to 100) to rate the discomfort of the lens. This procedure was repeated for the other two lenses on two separate days. CMST variance was calculated and the sample was split into two equal sized groups: the participants in the lower CMST variance half were defined as the sensory panel group, and participants in the higher CMST variance half were defined as the control group. McNemar’s test was used to quantify the significance of the ordinal rank of the lenses based on subjective discomfort scores. The three lens comparisons tested were A vs. B, A vs. C, and B vs. C.
The mean CMST variance of the sensory panel group (58.43±53.92(ml/min)2, 0.00-175.75(ml/min)2) was significantly lower (p<0.05) than the control group (688.80±554.83(ml/min)2, 196.33-2325.00(ml/min)2). Based on ordinal ranking derived from the subjective discomfort ratings, the sensory panel group was able to significantly discriminate between A vs. B and A vs. C (both p≤0.05), but not B vs. C (p=NS). The control group was only able to discriminate between A vs. C (p=0.05).
Low CMST variance is one possible criterion that could be used to find individuals who are good contact lens discriminators. Future work will include refining and exploring different strategies to define a sensory panel, and determine how different the two groups will perform when wearing lenses throughout the day. A limitation of this study is that it uses mechanical stimuli to match lens discomfort, which may not be representative of true lens discomfort.
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