Potential Ocular Complications from PUVA Therapy and Their Prevention

Abstract

During the last decade psoralens have become increasingly popular in treating psoriasis. The well-known photosensitizing action of these drugs has led to increasing concern regarding potential ocular complications, particularly in patients receiving prolonged psoralen therapy. We have demonstrated that this drug can be found in lenses of rats injected (intraperitoneally) with 4-8 mg/kg of 8-methoxypsoralen (8-MOP) and that its presence can lead to a photosensitized enhancement of lenticular fluorescence. Our experiments suggest one mechanism regarding the photosensitizing properties of 8-MOP within the ocular lens. Photo-addition products are generated with certain amino acid residues in the lens proteins which may result in the permanent retention of this compound within the ocular lens. We have recently shown that free 8-MOP can also be detected in human lenses for at least 12 hr following oral ingestion. Since the free 8-MOP tends to diffuse out of the lens during this period of time (as long as photic stimulation is prevented) it may be possible to prevent these photochemical reactions if the patient avoid exposure to ambient light for 12-24 hr immediately following ingestion of the drug. It may also be possible to protect these patients with special glasses which are capable of reflecting all UV radiation (up to 400 nm) while completely transmitting the visible radiation (400-750 nm).

Ocular psoriasis

“…80,83,84 Therefore, patients are counseled to protect their eyes during therapy and to wear UV-blocking sunglasses for 12 to 24 hours after treatment. 83 Increased risk for anterior cataract formation was seen in early guinea pig studies; however, these studies used high doses of UV radiation and subsequent studies using psoralen doses comparable with standard therapeutic human doses failed to show similar risk. 85,86 Table I provides an outline of PUVA and cataract formation in both psoriatic and some nonpsoriatic patient populations.…”

The lens and PUVA therapy

“…After 24 hours more than 90% of the 8-MOP has been evacuated from the body. 8-MOP had been demonstrated in the lens of the enucleated eye of a patient who was given 0.75 mg 8-MOP per kg body weight 12 hours before the enucleation (Lerman et al, 1980). Lerman has also found 8-MOP in the lens in rats and seals (Lerman et al, 1981); this was possible up to 24 hours after administration.…”

“…These spectacles must also be worn in the house as UV-A light passes through normal window glass. During the UV-A irradiation the patient wears red plastic spectacles which prevent the passage of UV light (Lerman et al, 1980;Wennersten, 1978).…”

Current Approach to Phototherapy Applications in Dermatology Practice: Part 1. History, Lamps, Ultraviolet Radiation Levels Measurement and Phototherapy Modalities

“…8-MOP, oral kullanımdan sonra en az 12 saat süreyle lenste saptanabilir (41). Ancak, psoriasis nedeniyle PUVA uygulanan hastaların izlendiği prospektif kohort özellikteki Amerikan çalışmasında, PUVA'nın katarakt riskini artırmadığı gösterilmiştir (42).…”