Discrimination of subjective responses between contact lenses with a novel questionnaire.

Purpose: To describe a ranked symptoms scale (RSS) discriminating subjective responses in contact lens (CL) wear in various situations.

Method: Forty experienced clinical trial participants were interviewed for their perceptions of ocular comfort scales, resulting in a numerical RSS. For further evaluation, 20 CL wearers enrolled into a prospective, randomised, crossover trial. Two silicone-hydrogel CLs and a lens care solution (LCS) [Combinations A & B] were selected based on prior performance identifying best/worst combinations for end-of-day comfort. The RSS and a numerical rating scale (NRS) were administered at two time-points (insertion/removal) on alternating days for 6 days.

Results: Both NRS and RSS showed acceptable internal consistency for comfort, vision and handling (Cronbach alpha=0.71 for both scales) and similar repeatability for comfort and handling (coefficients-of-repeatability within 0.1 and 0.2 units, respectively, for each scale). The NRS and RSS discriminated differences between combinations for comfort (p≤0.031) and vision (p≤0.026) at both time-points. Additionally, the RSS showed lens/edge awareness influenced discomfort the most, ranking higher at insertion (p=0.038) and higher for Combination-B at both time-points (p≤0.002). Symptoms of dryness and tired eyes increased for both combinations at removal (p<0.02). The RSS also showed haziness and blurred distance vision influenced vision dissatisfaction with Combination-B at lens removal (p≤0.038) while eye strain/headache increased for both combinations by time of removal (p≤0.013).

Conclusions: The RSS is able to discriminate subjective responses between combinations and time-of-day. The RSS's ability to rank symptoms may be a useful tool in understanding perceptions of discomfort or dissatisfaction with CL wear.