Corneal and conjunctival sensitivity to air stimuli

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Aims:To determine the repeatability of ocular surface sensitivity to mechanical stimulation using air stimuli and the effect of contact lens (CL) wear on sensitivity.Methods:Repeatability: 14 subjects (24–39 years) participated. Mechanical sensitivity to warmed (34°C) and ambient (20°C) air was measured for the central cornea (CC), inferior cornea (IC), and inferior conjunctiva (ICON). Measurements were taken on 12 days; six morning and six afternoon measurements. Differences between sites, time of day, and stimulus temperature were evaluated. CL wear: 10 subjects (22–30 years) participated. Measurements were taken at the same time of day, either following no wear, wear of a CL of oxygen permeability [Dk] of 28×10−9 [cm/s][ml O2/ml mm Hg] or wear of a CL of Dk 140×10−9 [cm/s][ml O2/ml mm Hg]. Differences between sites and wear conditions were evaluated.Results:Repeatability: Sensitivity varied between sites (p<0.01), time of day (p<0.05), and stimulus temperatures (p<0.01). There were no significant differences between days. Mean thresholds for eye temperature stimuli were; CC 64.4 (SD 28.6) ml/min; IC 84.6 (40.0) ml/min; ICON 120.6 (40.4) ml/min and for ambient temperature stimuli were CC 53.9 (16.0) ml/min, IC 59.0 (20.0) ml/min; ICON 72.6 (43.7) ml/min. CL wear: Sensitivity varied between sites and wear conditions (p<0.05). Conjunctival sensitivity was increased after wear of highly oxygen permeable CLs but unaffected by wear of low oxygen permeable CLs.Conclusions:The prototype gas aesthesiometer is able to repeatably measure ocular surface sensitivity and measurements are consistent with previously reported techniques.

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