Abstract
Purpose: :
Certain silicone hydrogel (SH) lens materials used on a daily wear (DW) basis with specific care regimens have been reported to produce unacceptably high levels of relatively asymptomatic corneal staining. The purpose of this study was to investigate the correlation between corneal staining and bulbar and limbal redness in subjects using daily wear SH lenses and various care regimens.
Methods: :
A meta–analysis of four double–masked, randomized, cross–over clinical trials (sample size ranging from 20 to 36) in which 106 adapted soft lens wearers wore various combinations of SH lens materials on a DW basis while using a variety of care regimens for periods of one month was undertaken. Participants were examined at baseline and after 1, 7, 14 and 28 days, resulting in over 500 subject visits. Corneal staining, limbal and bulbar redness were measured subjectively by a masked investigator and bulbar redness was measured objectively with a Spectrascan650 photometer at each visit. Repeated measures ANOVA and Pearson correlation coefficients were used to examine the interactions between staining and limbal and bulbar hyperemia at the time in each study when staining was maximum.
Results: :
In each experiment, there were significant levels of staining (each p<0.05). There were no significant correlations between subjective bulbar, subjective limbal or objective redness and staining in any of the studies (all |r|< 0.39; p>0.05 for each study).
Conclusions: :
These studies indicate that subjects who are asymptomatic and exhibit low levels of ocular redness should be examined for signs of corneal staining, as staining may not be correlated with other signs and symptoms. How it is physiologically possible to exhibit corneal staining in an otherwise unchanged (at least in terms of redness) and asymptomatic eye remains to be clarified.
Keywords: cornea: epithelium • conjunctiva • contact lens