Hypersensitivity to Cold Stimuli in Symptomatic Contact Lens Wearers. Issue 8 (August 2016) - Situ, Ping
ABSTRACT: Purpose: To examine the cooling thresholds and the estimated sensation magnitude at stimulus detection in controls and symptomatic and asymptomatic contact lens (CL) wearers, to determine whether detection thresholds depend on the presence of symptoms of dryness and discomfort. Methods: Forty-nine adapted CL wearers and 15 non–lens wearing controls had room temperature pneumatic thresholds measured using a custom Belmonte esthesiometer, during Visits 1 and 2 (Baseline CL), Visit 3 (2 weeks no CL wear), and Visit 4 (2 weeks after resuming CL wear). CL wearers were subdivided into symptomatic and asymptomatic groups based on comfortable wearing time (CWT) and CLDEQ-8 score (<8 hours CWT and ≥14 CLDEQ-8 stratified the symptom groups). Detection thresholds were estimated using an ascending method of limits and each threshold was the average of the three first-reported flow rates. The magnitude of intensity, coolness, irritation, and pain at detection of the stimulus were estimated using a 1–100 scale (1 very mild, 100 very strong). Results: In all measurement conditions, the symptomatic CL wearers were the most sensitive, the asymptomatic CL wearers were the least sensitive, and the control group was between the two CL wearing groups (group factor p < 0.001, post hoc asymptomatic vs. symptomatic group, all p's < 0.015). Similar patterns were found for the estimated magnitude of intensity and irritation (group effect p = 0.027 and 0.006 for intensity and irritation, respectively) but not for cooling (p > 0.05) at detection threshold. Conclusions: Symptomatic CL wearers have higher cold detection sensitivity and report greater intensity and irritation sensation at stimulus detection than the asymptomatic wearers. Room temperature pneumatic esthesiometry may help to better understand the process of sensory adaptation to CL wear.