THE EFFECTS OF INTRAOCULAR LIDOCAINE ON THE CORNEAL ENDOTHELIUM

Objective: The study aimed to evaluate the direct effect of intraocula r lidocaine hydrochloride (HCI) 1% on corneal endothelial cell functio n, ultrastructure, and viability using an in vitro perfusion specular microscope system. Design: Paired rabbit and human corneas were isolat ed and mounted in an in vitro specular microscope for endothelial perf usion evaluation, Corneas were perfused with a control solution (BSS P lus for humans, glutathione bicarbonate Ringer's [GBR] for rabbits) fo r a I-hour stabilization period. After the stabilization period, one c ornea of each matched pair was perfused with preservative-free lidocai ne HCI 1% for 15 minutes followed by control solution for an additiona l 2 to 3 hours. The control cornea continued to receive either GBR or BSS Plus. Corneal thickness measurements were taken every 15 minutes t hroughout the perfusion period, Corneal swelling and deswelling rates were calculated by linear regression analysis, At the end of the exper iment, corneas were fixed for scanning and transmission electron micro scopy, In another group of corneas, the endothelial viability was assa yed after direct perfusion with lidocaine HCI 1%. Results: Lidocaine H CI 1% caused endothelial cell edema, which reversed on removal of lido caine from perfusion media. Corneal swelling and deswelling rates did not differ significantly between the lidocaine and control groups, Ele ctron microscopy showed the effects of transient endothelial cell edem a with an otherwise normal mosaic pattern and ultrastructure for both treatment groups. Endothelial cell viability was maintained after the direct lidocaine exposure and a 2-hour washout. Conclusions: Lidocaine HCI 1% causes a transient endothelial cell edema to the in vitro perf used endothelium of human and rabbit corneas, Proper attention should be given to the type of lidocaine injected intraocularly (i.e., concen tration, vehicle, preservatives, pH, osmolarity). Although lidocaine H CI 1% appears to be safe to both human and rabbit endothelium during s hort-term in vitro exposure, further in vivo and in vitro studies are needed to determine long-term effects of intraocular lidocaine on the corneal endothelium.