Abstract
Purpose: :
Previous reports have indicated contact lens replacement during the day does not improve end of day ocular comfort, when single use hydrogel lenses are used. This study assessed whether the same principle applies to silicone hydrogel lenses.
Methods: :
Twenty four participants (Pxs) were instructed to wear new, silicone hydrogel contact lenses for 10 hours on three separate days, with each day corresponding to one stage. During two of the stages, Pxs presented to the clinic after about 5 hours of wear when lenses were removed, then either new lenses were inserted or the same lenses were re-inserted. Pxs were masked to lens condition, and these stages were randomised. For the other stage, lenses were worn uninterrupted for 10 hours. Ocular comfort was assessed using a 1-100 numerical scale at insertion, and after 3, 5, 7 and 10 hours of wear. For those stages where lens wear was interrupted, ocular comfort was also reported prior to lens removal and following lens re-insertion.Mixed linear models were used for statistical analysis
Results: :
Relative to insertion, ocular comfort was significantly worse after 10 hours when lenses were worn uninterrupted (p=0.02). While lens removal and re-insertion was associated with a small improvement in comfort relative to uninterrupted wear, the difference was not significant (p>0.05). There were no significant differences between the 3 stages after 10 hours (p >0.05).
Conclusions: :
These results confirm that for this silicone hydrogel material lens replacement does not improve end of day ocular comfort. Taken with previous findings, this suggests that irrespective of lens type, end of day discomfort is not primarily caused by lens based deterioration but is more likely due to changes within the eye or its adnexa.
Clinical Trial: :
http://www.anzctr.org.au ACTRN12609000430235