Protection from acute exposure to ultraviolet radiation by ultraviolet-absorbing RGP contact lenses.

One eye in each of 12 female pigmented rabbits was irradiated with UVB while wearing an EqualensR I rigid gas-permeable contact lens. The other eye served as a control. The irradiance level was 625 microW cm-2 (285-315 nm total bandpass) with exposure times up to 2364 s. Eyes were evaluated 24 h and 48 h after exposure by biomicroscopy and pachometry, and later by scanning electron microscopy (SEM). The contact lens was found to protect the central cornea from radiant exposures up to 60 times threshold. The exposed areas of cornea showed characteristic ultraviolet damage with an arc of demarcation indicating the position of the lens. With time the area formed a ridge of damaged cells (confirmed by SEM). At radiant exposure over 0.75 J cm-2 some oedema was seen in the 'protected' region, apparently by extension rather than as a direct effect. These findings suggest that in the human being exposed to ultraviolet radiation this ultraviolet-absorbing RGP lens would permit nasal and temporal photoketatitis with sparing of the central cornea and provide some protection of more posterior ocular structures.