No abstract

PurposeTo investigate whether carrying out various interventions part way through the day influences comfort in symptomatic daily disposable (DD) contact lens wearers.MethodsA subject-masked, randomized, controlled clinical trial was conducted in thirty symptomatic soft lens wearers who wore their habitual DD contact lenses bilaterally for 12 h on two separate days. Five hours after lens application, one of the following three interventions or a control was performed on each eye: replacing the existing lens with a new lens; removing and reapplying the same lens; performing a ‘scleral swish’; and no action (control). Comfort scores were recorded using SMS text messages every hour following lens application using a 0 (causes pain) to 100 (excellent comfort) scale. Comfort scores before lens application, at 6 mins post-application, and at 6 mins post-intervention were also recorded.ResultsThere was a significant reduction in comfort from pre-lens application to 6 mins post-application for all groups (all p<0.05). Comfort gradually decreased from 6 mins to 5 h after lens application for each group (p<0.0001) with no significant difference between groups over the 5-h period (p = 0.09). There was no significant difference in comfort 6 mins post-intervention for any group (all p>0.05). After the intervention, comfort continued to decline (p<0.0001) with slightly lower mean scores for the control group compared to the new lens group (p = 0.003). Change in comfort relative to pre-intervention (5 h) was similar for all groups (p = 0.81). There was no difference in comfort at 12 h between groups (p = 0.83).ConclusionThis work has confirmed that comfort shows a continual and significant decline over a 12-h wearing period in symptomatic DD contact lens wearers. None of the interventions investigated had any significant impact on end-of-day comfort. These data suggest discomfort in lens wearers is more heavily influenced by changes to the ocular environment rather than to the lens itself.Trial RegistrationControlled-Trials.com ISRCTN10419752 http://www.controlled-trials.com/ISRCTN10419752

Author contributions: MNC & MLR: involved in all aspects of study conception and design; data acquisition, analysis and interpretation; and drafting and critically revising the manuscript. PBM & CMC: involved in study design; data interpretation; and critically revising the manuscript.

This work has demonstrated that the marginal conjunctiva is the most sensitive conjunctival region. After 12 hours, symptomatic lens wearers showed decreased sensitivity of the lower marginal conjunctiva and increased lower lid margin lissamine green staining compared with those of the nonwearers.