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Measurements and mathematical models in the assessment of optical radiation hazards to the eye

Studies of industrial exposure to infrared radiation and epidemiology of 'infrared cataract' are reviewed, and a programme of optical radiation measurements at UK industrial sites is briefly described. Comparing the results of this study with the threshold limit values recommended by the American Conference of Governmental Industrial Hygienists (ACGIH), it appears that retinal burns and 'blue light' damage are unlikely in the occupations studied, and therefore attention is focused on the infrared exposure of the lens. A mathematical model of heat flow in the human eye has been developed to estimate the temperature rises produced in the lens by a known irradiance level, and thus to assist in furthering the understanding of the mechanism of infrared lenticular damage and in providing a basis for protection standards. It is shown that, for some of the sources in the measurement programme, continuous exposure could lead to temperature rises of several kelvins, particularly at the anterior surface of the lens.