Psoralen--long-wave ultraviolet therapy and human cataractogenesis.

Cataract formation associated with psoralen--long-wave ultraviolet (P-UVA) therapy has been documented in experimental animals. Presumptive P-UVA cataracts in humans have also been reported recently. Cataracts from two patients on P-UVA therapy were subjected to high-resolution phosphorescence spectroscopy. The lens homogenates from these two patients showed phosphorescence peaks identical (in shape and lifetime) with the previously reported 8-methoxypsoralen lens protein photoproduct seen in P-UVA-treated cataractous rat lenses. The data provide objective proof that these phototherapeutic drugs can generate specific P-UVA photoproducts in human lenses. Similar photoproducts have previously been demonstrated in experimental (rat) P-UVA cataracts.