Abstract
Purpose: :
Many soft contact lens (SCL) wearers report a decrease in comfort and vision as their lenses approach scheduled replacement time. It is not clear whether these symptoms are driven by changes in the SCLs as they age from wear or have some other etiology. This evaluation was conducted to investigate differences in subjective comfort (SC) and vision (SV) with masked replacement (MR) between symptomatic SCL wearers (SYM) habitually reporting a decrease in comfort at replacement time, and asymptomatic wearers (ASYM).
Methods: :
78 subjects (41 SYM and 37 ASYM) were enrolled. All subjects wore their habitual SCLs and used habitual care products for two randomized, 30 day cycles of daily lens wear. Study visits occurred at days 0, 28 and 30 in each cycle. In one cycle (A), lenses were replaced after 28 days (28D) of lens wear and these new lenses were worn for a further 2 days. In the other cycle (B), a visit occurred at 28D but lenses were not replaced for the final 2 days of the cycle. Subjects were not aware that a replacement was made and investigators were masked with respect to cycle (A or B). SC and SV were graded (0-100 unit scale) at three time points, on days 1, 14, 27 and 29 in each cycle.
Results: :
SC and SV decreased with lens age (mean change in ratings: ASYM 10 units, SYM 20 units, both p<0.001) and wearing time (mean change in ratings: ASYM by 10 units, SYM by 20 units, both p<0.001). SYM subjects had lower SC and SV than ASYM subjects (p<0.001) and a greater decline in SC with wearing time (p<0.001). Masked replacement at 28 days did not significantly affect SC or SV ratings for SYM or ASYM subjects at the day 29 time point (p=0.524).
Conclusions: :
Masked replacement of SCLs towards the end of a 30 day cycle of lens wear did not appear to have any impact on SC or SV for both subjects who habitually report inferior performance with lens age and for subjects who are relatively asymptomatic. Further investigation into the effect of unmasked replacement on SCLs wearers’ perception of subjective performance is required.
Clinical Trial: :
http://www.clinicaltrials.gov NCT01198600
Keywords: contact lens • clinical research methodology