Solution toxicity in soft contact lens daily wear is associated with corneal inflammation

Contact lens-associated solution toxicity manifests as generalized, mild punctate epithelial fluorescein staining and usually is widely reported as asymptomatic, with no substantial clinical sequelae. This study examined the relationship between solution toxicity and corneal infiltrative events (CIEs) in soft contact lens daily wear.

Several nonrandomized interventional clinical trials conducted between May and November 2005 were analyzed retrospectively. Subjects wore commercially available soft contact lenses bilaterally, on a daily schedule, disinfected overnight using marketed lens care solutions for 3 months with monthly disposal. Solution toxicity was defined as diffuse punctate staining in at least four of five areas of the cornea after instillation of sodium fluorescein. First events of corneal staining or corneal infiltrates were used to calculate incidence (per 100 eye months).

Toxic staining was detected in 77 of 609 subjects and all CIEs were mild and symptomatic or asymptomatic. The incidence of CIEs in eyes with a predisposition to toxic staining was 6.7% and in unaffected eyes was 2.3%. CIEs were 3-times more likely to occur in eyes that exhibited solution toxicity compared to unaffected eyes (odds ratio = 3.08, p = 0.008, 95% CI 1.40 to 6.76). Previous events of limbal redness (> or =grade 2.0) were not associated with CIEs (odds ratio = 1.53, p = 0.364, 95% CI 0.63 to 3.70). The rate of CIEs increased as the rate of toxic staining increased for specific lens type-solution combinations (Spearman's rho = 0.558, p = 0.025, n = 16), and peroxide-based solutions consistently resulted in the lowest rates of toxic staining and corneal inflammation.

Eyes that experience solution toxicity are more likely to experience a CIE. Daily wear soft lens wearers should be routinely examined with sodium fluorescein soon after lenses are inserted and alternative solution/lens type combinations should be investigated if toxic staining is detected.