Photochemotherapy and the eye: photoprotective factors.

The photosensitizer, 8-Methoxypsoralen, binds reversibly to a greater extent to human serum albumin than to human lens in the absence of UVA irradiation. Since experimental and clinical evidence suggests that peak levels in skin exceed those in plasma, which in turn exceed those in the lens, 5 to 10 fold more UVA is required to induce lenticular injury than to produce a threshold skin effect. To prevent the potential photoactivation of residual of 8-MOP in the lens, UVA opaque wraparound sunglasses should be worn for 24 hours after drug ingestion. Glasses with limited UVA transmission but good visible transmission should be worn after the 24 hour period following drug ingestion or indoors during the first 24 hours as a substitute for the wraparound. Every effort should be made to insure complete compliance in the wearing of UVA photoprotective lenses by all psoralen photosensitized patients.