SUMMARY To clarify the relationship between morphological changes in the corneal endothelium and ultraviolet (UV) radiation, specular microscopic examinations were performed on both eyes of 118 welders and 85 controls. The results showed: a decrease in the hexagonal cells in welders (20-29 years) in comparison with the controls (20-29) (p<005); an increase in the mean cell size of the endothelium and a decrease in the hexagonal cell population with increasing age in both groups; increases in standard deviation (SD) and the coefficient of variation (CV) of the mean cell size in both groups; increases in SD and CV of the mean number of cell sides in both groups; and no difference in the mean cell size between the two groups. These results show that UV radiation damages not only the corneal epithelium but also the endothelium, and suggest that it causes more pleomorphic change (a decrease in hexagonal cell population) than enlargement of the mean cell size.Arc welding generates visible light and much ultraviolet (UV) light. Most of the UV radiation is absorbed by the superficial layers of the cornea. UV light of 265-275 nm wavelength causes photokeratitis (keratitis superficialis diffusa).' UV light of longer wavelength reaches the corneal endothelium, and that over 295 nm reaches the lens and can cause cataracts. However, there has been no report on the effect of UV radiation on the endothelial morphology of the human cornea.UV radiation is now thought to be one of the factors promoting cataracts with aging.23 The endothelium is also affected by aging.4-"' The mean cell size of the endothelium increases4'8 and hexagonal cells of the endothelium decrease with age.' "' The effects of aging on these changes are not clear. We assumed that UV radiation has an important role in the endothelial aging phenomenon and tried to study the relationship between the endothelial changes and UV radiation in welders, who are occupationally exposed to excess UV radiation.Corrcspondcncc to Dr 1. Karai. Subjects and methodsA total of 118 Japanese male welders of mean age 44-1 years (range 24-66 years) in-two welding factories in Osaka were studied. Their mean employment duration as welders was 17 4 years (range 1-39 years). The control group comprised 85 men of mean age of 41-8 years (range 20-73 years), employees in two chemical factories (42 males), and male outpatients (43 persons) without any corneal diseases from the Department of Ophthalmology in two hospitals. The welders were asked about their length of employment as a welder, the welding method used, and personal history of ocular disease. We excluded one welder with corneal disease, and one control who had once worked in welding. We also excluded persons with myopia gravis (over -6 dioptres) from this study.Specular microscopes (Keeler-Konan camera, and Bio-Optics) were used to photograph the central corneal endothelium of both eyes of the subjects three times after treatment with ophthalmic surface anaesthetic (0.4% oxybuprocaine hydrochloride).Kodak film (Tri-X pan, ASA 4...

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