Corneal and conjunctival toxicity of disinfectants—Assessing safety for use with ophthalmic surgical instruments

We investigated the corneal toxicity of ortho-phthalaldehyde (CidexROPA, Johnson and Johnson K.K.) and its predecessor glutaraldehyde (CidexR, Johnson and Johnson K.K.). We made primary cultures of porcine and human corneal endothelial cells. Commercially available cell lines were also used including human, bovine, and rabbit corneal epithelium and human conjunctival cells. Following incubation for two days, cell survival was measured using a WST-1 assay for endothelia and a MTT assay for the other cells. Test solutions included 2.25% and 3.5% glutaraldehyde and 0.55% ortho-phthalaldehyde. Cell survival was presented as a percentage of the control value. ortho-phthalaldehyde displayed less toxicity than glutaraldehyde for all cell types tested. As expected 3.5% glutaraldehyde was slightly more toxic than 2.25% glutaraldehyde. When primary human corneal endothelial cultures were exposed to ortho-phthalaldehyde, the survival rates were 88% for 100-fold dilutions and 95% for 500-fold dilutions. The survival rates for all cells tested were greater than 90% when dilutions of 1000-fold or more were used. In conclusion, the corneal toxicity of glutaraldehyde and ortho-phthalaldehyde appears to be within safe levels following washing procedures and therefore the use of these disinfectants may be suitable for selected ophthalmic surgical instruments in urgent or under-equipped circumstances.