Diffuse solar UV radiation and implications for preventing human eye damage

Ocular UV exposure is a function of both the direct and diffuse components of solar radiation. Broadband global and diffuse UV measurements were made in the morning, noon and afternoon. Thirty sets of measurements were made i n summer and 50 in each of the other seasons at each of the periods in full sun. Corresponding sets were made in the shade of Australian evergreen tre es: 42 trees in summer and 50 in each of the other seasons,The percentage d iffuse UV was higher for the shorter 320-400 nm range (UVB) than for 280-32 0 nm (UVA). The percentage diffuse UVB ranged from 23 to 59%, whereas the p ercentage diffuse UVA ranged from 17 to, 31%. The percentage diffuse UV was lower at noon than in the morning and afternoon with the difference more p ronounced for the UVB, The average percentage diffuse UVB over all the meas urements in the tree shade for the morning, noon and was 62, 58 and 71%, re spectively, and the average percentage diffuse UVA was 52, 51 and 59%, resp ectively.