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P. Situ, T. L. Simpson, D. Fonn; Corneal and Conjunctival Mechanical and Chemical Sensitivity in Contact Lens Wearers. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4835.
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To compare pneumatic mechanical and chemical sensitivity at different sites of the ocular surface and in hydrogel and silicone hydrogel contact lens wearers.
41 adapted, asymptomatic daily contact lens wearers, consisting of 25 who currently wore hydrogel lenses and 16 wearing silicone hydrogel lenses were enrolled in the study. Sensitivity was measured at central and temporal mid-peripheral (about 3 mm from the apex) cornea and nasal conjunctiva (about 3 mm from the limbus) at a random order after lens removal. A computer-controlled modified Belmonte esthesiometer was used to deliver mechanical (air at 50 degrees C), and chemical stimuli (air at 50 degrees C with CO2 added). The ascending method of limits was adopted to determine the threshold to these stimuli at each location.
For both mechanical and chemical thresholds, significant differences were found between ocular surface sites (ANOVA both p<0.001). Thresholds at central and mid-peripheral cornea were lower than that at nasal conjunctiva (Tukey test all p<0.002); but the difference between central and mid-temporal cornea was not significant (Tukey test p>0.05). Mechanical and chemical thresholds tended to be higher in hydrogel lens wearers than the silicone hydrogel lens wearers for each corresponding site. However, the differences between lens type were not statistically significant (ANOVA p=0.099 and 0.222 for mechanical and chemical thresholds, respectively).
Sensitivity to mechanical and chemical stimuli in contact lens wearers varied between cornea and conjunctiva but not between the central and mid-peripheral cornea. Silicone lens wearers appear to have higher mechanical and chemical sensitivity than hydrogel lens wearers but the magnitude of the difference was small.
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