Abstract
Purpose: :
We have previously demonstrated that increased levels of solution-induced corneal staining (SICS) correlates with increased conjunctival chemical sensitivity (IOVS, 2010). This study investigated the relationship between SICS and corneal and conjunctival sensitivity using a meta-analysis approach.
Methods: :
Four studies evaluating SICS and its relationship to pneumatic corneal and conjunctival thresholds (using a modified Belmonte esthesiometer) conducted at the Centre for Contact Lens Research between 2004 and 2009, were included in the analysis. A generalized linear model was employed to combine information from the studies, in which SICS at 2 hours after lens insertion (the time at which corneal staining is greatest) was used as the outcome variable and pneumatic corneal and conjunctival mechanical and chemical thresholds, masked solutions and experiments were used as predictor variables. In addition, symptoms (stinging and burning) were analyzed using the same statistical methods with staining, solutions and thresholds as predictors.
Results: :
The sample sizes of the individual studies varied from 18 to 48 subjects and the total number of cases in the analysis was 292. There were significant relationships between staining, thresholds and solutions (all p ≤ 0.05); in all models, log transformation of conjunctival chemical thresholds was a significant predictor. The ‘best’ model using Akaike's information criterion (AIC) estimates included mechanical and chemical corneal and conjunctival thresholds, solution and study predictors. With symptoms as the outcome - and only corneal thresholds and staining in the model - log transformation of area of staining was a significant predictor.
Conclusions: :
This meta-analysis confirms that SICS is accompanied by an alteration in corneal and conjunctival chemical sensitivity. Conjunctival chemical sensitivity, in particular, appears to be a particularly robust predictor of the area of solution-induced corneal staining.
Keywords: cornea: clinical science • conjunctiva • innervation: sensation