The absence of corneal toxicity with low-level topical anesthesia

By means of an osmotic pump we infused 0.3% proparacaine solution continuously into the central stroma of a rabbit cornea. An area of anesthesia about 6 mm in diameter was maintained for several days. The epithelium remained unaffected and healed normally where it was scraped away in the anesthetic area. Similarly, the repeated instillation into the rabbit's eye of 0.05% proparacaine eyedrops at ten-minute intervals throughout the day resulted in continual anesthesia without signs of epithelial dystrophy. It seems that the toxic level of proparacaine is above that required for anesthesia.