Effect of hydrogen peroxide neutralisation onthe fitting characteristics of group IV disposable contact lenses

Twenty subjects took part in a single-masked, randomised, cross-over study to investigate the fitting characteristics and comfort found after disinfecting ionic disposable contact lenses with a two-step hydrogen peroxide (H2O2) disinfection system, after using both overnight disinfection and overnight neutralisation.Lenses inserted after overnight disinfection and 20 minutes neutralisation resulted in a statistically significant reduction in comforton insertion compared to overnight neutralisation (p=0.0005). After 10 minutes there was no difference in comfort between the two groups. There was a wide scatter in the comfort scores for the 20-minute neutralisation group, indicating significant inter subject variation, with 70% (±20%) of subjects grading comfort as 7/10 or better. Lenses neutralised for 20 minutes were generally immobile on insertion, requiring almost 10 minutes to begin movement. After 60 minutes there was no difference in movement between the two neutralisation systems.The study indicates that if H2O2 is to be used to disinfect group IV lenses, then a small percentage of subjects may complain of lensdiscomfort on insertion if the lenses are only neutralised for 20 minutes. The results also show that most lenses show an acceptable clinical fit within 60 minutes of insertion, whichever neutralisation method is used. woRDs: Hydrogen peroxide, disinfection, neutralisation, Acuvue,