P ERSPECTIVE Ultraviolet-B Phototoxicity and Hypothetical Photomelanomagenesis: Intraocular and Crystalline Lens Photoprotection MARTIN A. MAINSTER AND PATRICIA L. TURNER ● PURPOSE: Ultraviolet-B (UV-B) radiation can cause phototoxic macular injuries in young people who have been sunbathing but not sungazing and in welders. Welders have a reportedly increased risk of uveal mela- noma. We analyze phakic and pseudophakic risks for solar and welding arc UV-B exposure. ● DESIGN: Optical radiation measurement, analysis, and perspective. ● METHODS: Spectral transmittances were measured for UV-transmitting, UV-blocking, and blue-blocking intraoc- ular lenses (IOLs). The photoprotective performances of crystalline and intraocular lenses were analyzed using rele- vant epidemiologic and laboratory data and action spectra for acute retinal phototoxicity and melanoma photocarcino- genesis. ● RESULTS: Crystalline lens UV-B retinal protection is deficient in children and young adults, increasing their potential susceptibility to acute retinal phototoxicity and hypothetical photomelanomagenesis. UV-B radiation has sufficient energy/photon to induce primary melanoma- genic DNA lesions, unlike blue light or UV-A radiation. UV-blocking and blue-blocking IOLs have negligible UV-B transmittance. UV-transmitting IOL transmit- tance of UV-B radiation is equivalent to that of a 15-year-old crystalline lens. ● CONCLUSIONS: If optical radiation exposure is respon- sible for welders’ increased risk of uveal melanoma, then UV-B radiation is the most probable causative agent and spectacle wear is a potential confounding factor in epide- miologic studies of ocular melanoma. Welders under 30 years of age are at greater risk for welding maculopathy than older welders. Children, adults under 30 years of age, and pseudophakic individuals with UV-transmitting IOLs should wear sunglasses in bright environments because of the UV-B window in their crystalline lenses or IOLs. (Am J Ophthalmol 2010;149:543–549. © 2010 by Elsevier Inc. All rights reserved.) U LTRAVIOLET (UV) RADIATION AND VISIBLE LIGHT can cause photochemical retinal damage, also known as retinal phototoxicity or photic retinop- athy. 1,2 International safety standards for photic retinopa- thy are based on photosensitizer-type retinal phototoxicity mediated primarily by lipofuscin in the retinal pigment epithelium (RPE). Phototoxicity decreases with increasing wavelength, so UV-B radiation is more hazardous than UV-A radiation. Similarly, UV radiation is more hazard- ous than violet light, which is more hazardous than longer-wavelength blue light. 1,2 The Table summarizes the optical radiation bands po- tentially involved in retinal phototoxicity or photocarci- nogenicity. Figure 1 presents the spectral dependence of photosensitizer-type retinal phototoxicity 1 in comparison to 1) photokeratitis 3 and mammalian cell mutagenicity 4 and 2) photopic, 5 scotopic, 6 and circadian 7,8 photorecep- tion. 9 Figure 2 shows the protection afforded by the cornea 10 and by crystalline lenses of different ages. 10,11 In general, the cornea completely blocks UV radiation below 300 nm. 10 The crystalline lens protects the retina from most UV-B (280 –320 nm) and UV-A (320 – 400 nm) radiation, but crystalline lenses under 30 years of age transmit potentially harmful UV-B radiation to the retina. 10,11 Solar and welding arc maculopathy and operating mi- croscope and endoilluminator injuries are the only com- mon retinal syndromes of proven phototoxic origin. 1,2,9 Photocarcinogenesis differs from retinal phototoxicity be- cause it involves primarily UV-B radiation damage to DNA molecules, 12,13 a mechanism quite different from the retinal cell apoptosis involved in photopigment-mediated or photosensitizer-mediated photic retinopathies. 1 INTRAOCULAR AND CRYSTALLINE LENS TRANSMITTANCE UV-TRANSMITTING, UV-BLOCKING, AND BLUE-BLOCKING intraocular lenses (IOLs) are all widely used today, 30 years after the recognition that early polymethylmethacrylate IOLs transmitted UV radiation to the retina. 14 Polymers in IOL optics are opaque to UV radiation below 250 nm, but chromophores are needed to block UV-B radiation com- Accepted for publication Nov 25, 2009. From the University of Kansas School of Medicine, Prairie Village, Kansas. Inquiries to Martin A. Mainster, PhD, MD, FRCOphth, Department of Ophthalmology, University of Kansas School of Medicine, 7400 State Line Rd, Prairie Village, KS 66208-3444; e-mail: mmainste@kumc.edu © 2010 BY ELSEVIER INC.ALL RIGHTS RESERVED. 0002-9394/10/$36.00 543 doi:10.1016/j.ajo.2009.11.028