ABSTRACT
Objective:To analyze the prevalence of poor vision and spatial distribution characteristics among primary school students in Shenzhen.Methods:A cross-sectional study was conducted.Vision screening among primary school students in Shenzhen was carried out by myopia screening hospitals organized by Shenzhen Myopia Prevention and Control Center for Children and Adolescents using the logarithmic visual acuity chart in 2019.The prevalence of poor vision in different districts, different genders and different grades was calculated.Spatial distribution of the prevalence of poor vision was analyzed with Arcgis 10.2 software.This study adhered to the Declaration of Helsinki.Written informed consent was obtained from guardian of each subject.The study protocol was approved by an Ethics Committee of Shenzhen Eye Hospital (No.20201230-06).Results:A total of 1 044 545 students received the visual acuity examination.The prevalence of poor vision among primary school students in Shenzhen in 2019 was 53.4%(557 748/1 044 545). The prevalence of poor vision among primary school students in the former Shenzhen Special Economic Zone was 56.7%(172 771/304 532), which was higher than 52.0%(384 977/740 013) in areas outside the former Shenzhen Special Economic Zone, and the prevalence of poor vision among girls was 56.7%(268 201/473 164), which was higher than 50.7%(289 547/571 381) among boys, and the differences were statistically significant ( χ2=192.412, 375.434; both at P<0.001). As the grade increased, the prevalence of poor vision firstly decreased and then increased, showing an increasing tendency in general.The prevalence rate of poor vision among primary school students among grade 1 to 6 was 49.8%(99 615/200 203), 44.0%(86 521/196 800), 47.2%(82 848/175 331), 54.5%(89 737/164 731), 60.8%(96 271/158 298), and 68.9%(102 756/149 182), respectively, and a significant difference was found ( χ2=2 871.017, P<0.001). The global Moran I index in Shenzhen was 0.278.The local Moran I index and Geary coefficient in Guangming District were 0.933 and 0.78, respectively.The prevalence of poor vision in Guangming District and its surrounding areas was a low-low cluster. Conclusions:The prevalence of poor vision among primary school students in Shenzhen is spatially aggregated.
ABSTRACT
Objective To observe the effects of the topical benzalkonium chloride on the cornea of experi-ment animals and evaluate the safety of topical benzalkonium chloride.Methods 36 rabbits were randomly divided into two groups according to the random number table,18 rabbits(36 eyes)in each group.The benzalkonium group was assigned as preservative benzalkonium chloride(0.05%)gutta,the control group was served as blank control. Rabbits were examined by the slit lamp,non-contact corneal endothelial microscope and Ultrasonic Wave instrument for corneal endothelial cell density and corneal thickness before and the 3rd weeks,the 6th weeks after the medica-tion.In vitro cornea was stained by typan blue and alizarin red,corneal endothelial cells were observed and calculate the viability of corneal endothelial cells (CECs).Results The differences of corneal thickness at the 3rd weeks and the 6th weeks were not statistically significant between the two groups(t =1.876,1.876,all P >0.05);The differ-ences of the corneal endothelial cell density and the viability of corneal endothelial cells(CECs)between the two groups at the 3rd weeks and the 6th weeks were not statistically significant(t =0.321,1.541,all P >0.05);The tear meniscus height of the benzalkonium group were lower than the control group at the 6th weeks[(142 ±36)μm vs. (198 ±31)μm,t =2.462,P <0.05].Conclusion Benzalkonium chloride has no impact on the corneal endothelial cells in short period,but the affection on the tear is obvious.