CORNEAL EPITHELIAL PERMEABILITY DURING EXTENDED WEAR OF DISPOSABLE CONTACT-LENSES VERSUS DAILY WEAR OF SOFT CONTACT-LENSES

Aims-The corneal epithelial permeability during extended wear of dispo sable contact lenses was compared with that during daily wear of soft contact lenses. The study was performed to verify whether the extended wear of disposable contact lenses would result in a higher permeabili ty value than the daily wear of soft contact lenses. A higher permeabi lity makes the cornea more vulnerable for bacterial infections and thu s could explain the higher incidence of bacterial keratitis found in e xtended wear of disposable contact lenses in comparison with the daily wear of soft contact lenses. Methods-The corneal epithelial permeabil ity was determined by fluorophotometry in 33 healthy volunteers after the wear of soft, daily wear contact lenses for at least 6 months. The reafter the determination was repeated in each volunteer after extende d wear of disposable contact lenses for 1 month. The permeability in 3 4 healthy non-contact lens wearing volunteers was determined as a cont rol. The permeability value was calculated from the amount of fluoresc ein that passed into the cornea after application by means of an eyeba th. Results-The mean permeability values after daily and extended wear were 0.032 nm/s and 0.031 nm/s, respectively. The values were not sig nificantly different (WiIcoxon paired test p>0.5). The mean permeabili ty for the non-contact lens wearing controls was 0.042 nm/s. Conclusio n-The results do not sustain the explanation that a difference in perm eability value is the main cause of the increased incidence of keratit is during extended wear of disposable contact lenses in comparison wit h daily wear.