Prevalence and risk factors of lens opacities in rural populations living at two different altitudes in China

AIM： To investigate the prevalence of and risk factors for lens opacities in populations living at two different altitudes in China.·METHODS： A total of 813 subjects aged ≥40y in Lhasa（Tibet Autonomous Region, China. Altitude： 3658 m） and Shaoxing（Zhejiang Province, China. Altitude： 15 m） were underwent eye examinations and interviewed in this cross-sectional study. Participants＇ lens opacities were graded according to the Lens Opacities Classification System II（LOCS II） and the types of opacities with LOCS II scores ≥2 were determined. Univariate and stepwise logistic regression were used to evaluate the associations of independent risk factors with lens opacities.· RESULTS： Lens opacities were significantly more prevalent in the high-altitude than in the low-altitude area（χ2=10.54, P 〈0.001）. Lens opacities appear to develop earlier in people living at high than at low altitude. The main types of lens opacity in Lhasa and Shaoxing were mixed（23.81%） and cortical（17.87%）,respectively. Independent risk factors associated with all lens opacities were age, ultraviolet（UV） radiation exposure,and educational level. Compared with participants aged40-49 y, the risk of lens opacities increased gradually from 2 to 85 times per 10 y [odds ratio（OR）=2.168-84.731,P 〈0.05）. The risk of lens opacities was about two times greater in participants with the highest UV exposure than in those with the lowest exposure（OR=2.606, P =0.001）.Educational level was inversely associated with lensopacities; literacy deceased the risk by about 25%compared with illiteracy（OR=0.758, P =0.041）.·CONCLUSION： Old age, higher UV exposure and lower educational level are important risk factors for the development of lens opacities. Lens opacities are more prevalent among high-altitude than low-altitude inhabitants.

Research on the distribution characteristics of explosive shock waves at different altitudes

There are great differences in the distribution characteristics of shock waves produced by ammunition explosions at different altitudes.At present,there are many studies on plain explosion shock waves,but there are few studies on the distribution characteristics of plateau explosion shock waves,and there is still a lack of complete analysis and evaluation methods.This paper compares and analyzes shock wave overpressure data at different altitudes,obtains the attenuation effect of different altitudes on the shock wave propagation process and proposes a calculation formula for shock wave overpressure considering the effect of altitude.The data analysis results show that at the same TNT equivalent and the same distance from the measuring point,the shock wave overpressure at high altitude is lower than that at low altitude.With the increase in the explosion center distance of the measuring point,the peak attenuation rate of the shock wave overpressure at high altitudes is smaller than that at low altitudes,and the peak attenuation rate of the shock wave overpressure at high altitudes gradually intensifies with increasing proportional distance.The average error between the shock wave overpressure and measured shock wave overpressure in a high-altitude environment obtained by using the above calculation formula is 11.1389%.Therefore,this method can effectively predict explosion shock wave overpressure in plateau environments and provides an effective calculation method for practical engineering tests.