Abstract
Purpose: :
Acute change of corneal barrier function after instillation of preservatives added to ophthalmic drugs or solutions was evaluated using a novel in vivocorneal trans-epithelial electric resistance (TER) measurement method and an in vitro cytotoxicity test.
Methods: :
Electrophysiologically corneal TER of live rabbit eyes was measured using volt-ohm meter and Ag/AgCl electrodes. Then, TER change after instillation of preservatives was monitored for 60 seconds. Used preservatives were 0.02% , 0.01%, 0.005%, 0.002%, 0.001%benzalkonium chloride (BAC), 0.005%chlorhexidine digluconate (CG), 0.04%paraben (PR; a mixture of methyl paraben and propyl paraben, 13:7 w/w). For the control study, Hank’s balanced salt solution was used. For in vitro study, cultured normal rabbit corneal epithelial cells (NRCE) were exposed to each preservative mentioned above in 60 seconds and cell viability was evaluated by WST-1 Assay.
Results: :
After instillation of 0.02%, 0.01%, 0.005%BAC, TER decreased instantly, TER was significantly lower than that of the control in 10 seconds(P<0.01). TER decreased gradually after instillation of 0.005%CG, TER was significantly lower than that of the control in 60 seconds(P<0.01). After instillation of 0.002% , 0.001%BAC, 0.04%PR, TER was not significantly different from that of the control. Further, TER was decreased according to the concentration dependently in BAC solutions.As for cell viabilities of NRCE, after instillation of 0.02%, 0.01%, 0.005%BAC, and 0.005%CG for 60 seconds, cell viabilities were significantly lower than that of the control (0.02%BAC: P<0.0001, 0.01%, 0.005%BAC, 0.005%CG:P<0.01). After instillation of 0.002%, 0.001%BAC, and 0.04%PR, cell viabilities were not significantly different from that of the control. Decreases in TER and cell viabilities were correlated(rs=0.93, P<0.01).
Conclusions: :
Corneal epithelial disorder after instillation of preservatives was immediate. Corneal epithelial cell death was supposed to be related to the decline of barrier function. In vivo corneal TER measurement method is suitable for assessing toxicity of preservatives added to ophthalmic drugs.
Keywords: cornea: epithelium • cornea: basic science • cornea: clinical science