| Objective:1.To explore differences in biological parameters of the cornea between people living in hypoxic environment at high altitude and people living in the plains,and to locate the reference range for normal value of biological parameters of the cornea in Tibetan junior school students living in areas of hypoxic environment at high altitude.2.To find out the effect of the high-altitude and hypoxic environment on the histological structure of the cornea of SD rats.Methods:1.Cross-sectional Study.Sex,age,grade and other basic information of Tibetan junior school students without ametropia living in Maizhokunggar,Lhasa(the high-altitude group)and junior school students with low myopia in Beijing(the low-altitude group)is collected,their diopter tested via mydriatic refractometry,and spherical equivalent refraction(SE)of the low-altitude group calculated.he thinnest point thickness(Thk),central corneal thickness(CCT),anterior chamber depth(AD),iris corneal angle,simulated K1、simulated K2、thinnest point position were collected using the Italian Sirius 3D corneal topography and anterior segment analysis system.The left eye or right eye data of each student included are selected using the random number table for a statistical analysis.Distribution of continuous variables is studied with histogram and Q-Q plot,among which those agreeing with normal distribution are described with mean value ± standard deviation.After correcting biological parameters of the cornea of students in the low-altitude group by diopter using Pearson linear regression,the two groups are further compared using Student’s t-test.2.24 8-week-old SPF SD rats(18 females and 6 males)are divided into the high-altitude group and the low-altitude group using the random number table.12 rats(9 females,3 males)of the high-altitude group are transported to a hypoxic area at high altitude(Laboratory Animal Room,Tibet University,Lhasa)for a week’s adaptation and then mated according to the proportion of female:male as 3:1;all pregnant rats experience natural parturition.After raising the third-generation rats to 8-week-old,the central corneal thickness(CCT)is measured with A-scan,and the eyeballs removed to make paraffin sections for subsequent H.E.staining,toluidine blue staining and immunohistochemical staining.Histological differences in the cornea between the two groups are observed with an optical microscope.Differences in the expression of matrix metalloproteinases(MMPs)-2 and-9 in the corneal tissue are also analyzed.Results:1.There were 690 subjects with mean age(14.85±1.27)in the high altitude group,Of the 345 right eye data,Of the 175 girls,170 groups were from boys;Of the 345 left eye data,149 from girls,The 196 groups came from boys.Right eye Thk、CCT、AD、iris cornea angle,K1、K2 and HVID were(504.99 ± 30.73)respectively(509.10 ± 35.82)μ m,(3.31±0.27)mm,47.45°± 5.70°,(43.15±1.89)D,(44.16±2.29)D and(11.39±0.55))mm.The above parameters of left eye were(503.34 ± 29.22 μ m,respectively(508.36±28.75)μ m,(3.26±0.26)mm,47.82°± 5.88°,(43.06 ± 1.40)D,D(44.16±1.53)and(11.55±2.26)mm.The thinnest point of the right mainly concentrated in180-270°,But the left eye is mainly concentrated in 270-360°.A total of 378 subjects of average age(14.60±1.029)in the low altitude group,Of the 189 right eye data,Of the 95 groups,Group 94 was from boys;Of the 189 left eye data,Of the 96 groups,Group 93 was from boys.Right eye Thk、CCT、AD、iris cornea angle,K1、K2 and HVID were(554.13±34.78)respectively(556.63±34.77)μ m,(3.35±0.24)mm,45.26°±4.76°,(42.37±1.40)D,(43.51±1.61)D and(11.97±0.41)mm.;and The above parameters of the left eye were(553.26±39.25μ m,respectively(553.84±47.37)μ m,(3.36±0.25)mm,45.60°± 5.16°,(42.36±1.43)D,(43.63° 1.69)D and(11.99° 0.46))mm.At the thinnest point of the right cornea,the focus is ° 180-270,But the left eye is mainly concentrated in 270-360°.The ThK and AD of both eyes were different between high altitude and low altitude(P<0.05),and the low altitude was significantly higher than that of high altitude.2.The CCT of SD rats in high altitude area were:(139.05±16.57)μ m.(134.26±11.70)in low altitude areaCentral corneal thickness in high and low altitude rats was not statistically significant(P=0.406).According to H.E stained and toluidine blue stained sections,the collagen arrangement in the corneal stroma of rats in the high-altitude group is loose and layered,with a lot of gaps between the layers;but the direction of collagen fibers remains ordered.Immunohistochemical staining shows significantly higher expression of MMP-2 and MMP-9 in the corneal stroma of rats in the high-altitude group than that in the low-altitude group.Conclusion:1.There are differences in corneal thickness between adolescents living in high altitude hypoxia area and adolescents living in low altitude area,but it is not certain that it is caused by ethnic factors or altitude factors.Ophthalmologists should make appropriate adjustments in the diagnosis and treatment of corneal and refractive diseases in Tibetan adolescents.2.The cornea of SD rats reared and grew in a high altitude hypoxic environment developed corneal stroma osteoporosis,which was speculated to be caused by the hypoxic environment at high altitude. |
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