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A collagenase that can digest both collagen fibers in the stroma and the native collagen molecule was found in rabbit corneal epithelium, using a tissue culture assay. Calf, chicken and fetal calf serum added to the tissue culture media inhibited the collagenase, while human and rabbit serum were not inhibitory. Edathamil calcium disodium demonstrated a potent inhibitory effect on the enzyme with minimal toxicity to the epithelial cells. The clinical implications of a corneal collagenase are discussed.

The dynamic visco-elastic properties of human, monkey and rabbit lenses have been measured with a dynamic rheometer. The value for the apparent elastic modulus (Young modulus) of the lens was found to be 10 5 –10 6 dyne/cm 2 in humans and 10 4 –10 5 dyne/cm 2 in monkeys and rabbits. The value for the loss tangent was 0·3–0·4 in the human lens and 0·3–0·6 in rabbit and monkey lenses. Elastic moduli and loss tangents of the lenses showed poor dependence on temperature at 15°–55°C and on frequency of oscillation at 0·01–25 c/s. The lenses showed linear viscoelasticity when the amplitude of oscillation was below 0·02 mm, and they showed non-linear visco-elasticity when the amplitude exceeded 0·03 mm.