| IntroductionUltraviolet Radiation is one of important factors for cataract. The incidence of cataract in colored people is higher than white people. Now we are entering a society of more elder people, so it is urgent to develop the risk evaluation of cataract induced by Ultraviolet Radiation.To evaluate the individual UV exposure exactly is the necessary precondition for dose -effect relationship research of ultraviolet radiation and opacity of lens. UV exposure dose of different people may differ much because of different work and life style. So it is not appropriate to evaluate individual UV exposure using the ambient UV level. And the biological effects of ultraviolet radiation are results of exposure constantly, so we need to find a kind of recording method which can simulate ocular UV exposure realistically and combine the data from this method with lifetime outdoor time to calculate individual ocular UV exposure dose. In Hainan, the UV level is high and the latitude,sun latitude and sunshine time are all suitable to do dose - effect relationship research of ultraviolet and opacity of lens. And there also have population with stable composition and simple life history.We took questionnaire survey of UV exposure history and eye examination of population in Yacheng, Hainan and used a circling - model method to simulate individual ocular UV exposure during daytime. Then we constituted a formulation for calculating individual ocular UV exposure dose combing with outdoor time.Objects and MethodSpectral Sensitivity of Solar UV sensor was put in the eye position of circling - model. It faced vertical to the horizontal level nearly and was fixed by a piece of special - made wood. The model circled constantly at a speed of 10 rounds /min in the open air. We recorded the cumulated UV dose of the sensor in eyes every 15 minutes.We chose population in one village in Yacheng as our research objects by cluster sampling method. Then we took a questionnaire survey to get the outdoor time of people's major stage of life and took examination including using eye chart to test visual acuity, cranny light to examine eyeground and EAS - 1000 to get opacity of eyes.We selected the means of data received by simulated - monitoring and made curve estimation to get two formulations calculating individual UV exposure time and dose. Then we worked out the individual UV exposure time and dose of population in Yacheng by taking the out door time into the formulations.ResultsThe monitoring results of circling - model in Shenyang showed that the daily distribution of individual ocular UV exposure dose presented different current in different seasons. The curve of daily distribution was campanulate in winter and trapeziform in spring, autumn. In summer there curve was sunken in noon. The curve of Yacheng is similar with the curve in spring and autumn in Shenyang.The results of Yacheng population showed high, low, high again and stable current feature of average UV exposure of every age. The average annual outdoor time of Yacheng population showed lowest at school age, highest at elder age, and kept stable at other ages.The opacity of lens related most with age, then with the UV exposure dose and related least with the UV exposure time.Cataract people received more UV exposure dose and time between 3 ~ 12years old than normal people (p = 0.03, p=0.022).The cumulated UV exposure dose and time of population in Hainan are much higher than population in Zhangwu (p <0.05). But there is no difference between the mean value of lens opacity of two groups (p=0. 223). And there is no difference between the mean value of len's opacity in each age group expect 50 -60 group(p =0.021). Taking T - test of the opacity of lens after dividing the paired people by age, the results showed there was difference between people from two area after 45 years old( p=0.008).DiscussionExcessive UV exposure will increase damage to eyes. Either in developing or developed countries, cataract has become a critical problem. Report of WHO showed the number of cataract patient had reached to one billion and fifty - eight million. A lot of epidemiological evidence support that ultraviolet radiation is a factor for formation of cataract, but some epidemiological conclusion are contrary because of the loss of precise evaluation to cataract and individual UV exposure dose.We used circling - model to simulate the daily ocular UV exposure, then created formulations and combined them with outdoor time to calculate individual ocular UV exposure dose. And we also examined the opacity of lens with the EAS - 1000 supplied by Japan.Results from circling - model monitoring showed that the daily distribution of ocular UV exposure looked like trapeziform and this current is different from that of environmental UV exposure. The daily distribution current of simulated monitoring showed that reflecting UV light took a great part in all UV exposure received in lens and eye socket visibly keep UV light out of lens. Though the reflecting ratio of material used on sensor is different from human eyes, this finding exhibited important significance to future study in UV exposure of eyes.The average annual UV exposure, dose of every year (age3 - 85) in Hainan showed high, low, high again and stable; the average annual UV exposure time of every year showed lowest at school age, highest at elder age, and kept stable... |
