The effect of a new rigid gas-permeable contact lens design on lactic dehydrogenase activity in rabbit tears.

BACKGROUND Most corneal damage induced by contact lenses is due to interference with corneal oxygenation. OBJECTIVE To investigate the effect on the rabbit cornea of a rigid gas-permeable contact lens with a newly designed periphery. METHOD We fitted New Zealand white rabbits (n = 12) with RGP contact lenses that were identical in all respects except for the design of the periphery. In each animal, one contact lens had an innovative periphery consisting of a microscopic diffractive relief lathed on the back surface; the other contact lens was of a conventional design. The lenses were worn continuously for 7 days. During this experimental period and for 1 additional week we assessed the corneal damage by daily testing lactic dehydrogenase activity in the tears. RESULTS On the last day of the experimental week and the first 3 days of the healing period, mean tear LDH activity was significantly lower in the eyes with the new contact lens design than in eyes with the conventional lenses. CONCLUSIONS The novel periphery design reduces corneal damage resulting from contact lens wear, as reflected by LDH levels in the tears. The new design probably facilitates the flow and exchange of tears under the contact lens, resulting in improved metabolism of the cornea. These findings may also prove applicable to soft contact lenses.