Objective To explore the distribution ofchoroidal thickness and its influence factors in university students.Methods A cross-sectional study.A total of 896 eyes of 896 college students were included in the study.Among them,there were 350 males (350 eyes) and 546 females (546 eyes).All the eyes were right eyes.The average age was 19.18 ± 1.36 years old.According to the spherical equivalent refraction (SER),the eyes were divided into non-myopia group,low myopia group,moderate myopia group and high myopia group,which were 59,251,356 and 230 eyes,respectively.The subfoveal ChT (SFCT) was measured using a swept-frequency source optical coherence tomography scanner.According to the ETDRS,the choroid within 6 mm of the fovea was divided into three concentric circles centered on the fovea of the macula,which were the central area with a diameter of 1 mm,the inner ring area of 1-3 mm and the outer ring area of 3-6 mm.The outer ring area of 3-6 mm has a total of 9 zones.The inner ring and outer ring 4 regions were superior,inferior,nasal and temporal,respectively.The distribution characteristics of ChT in different regions,genders and diopter groups were observed.Bivariate correlation analysis were used to analyze the correlation of ChT and SER,axial length (AL).Results The average SFCT of 896 eyes was 221.28± 67.35 μm.The mean SFCT of males and females were 227.20 ± 69.38 and 217.50± 65.80 μm,respectively.The difference of SFCT between different genders was statistically significant (t=2.075,P=0.038).Compared with the central region ChT,there was no significant difference in ChT between the outer ring and the outer region (t=0.086,P=0.932).The difference of ChT in other regions was statistically significant (t=-21.973,-5.818,36.328,-3.065,-18.017,-10.595,57.007;P＜0.001,＜0.001,＜0.001,＜0.002,＜0.001,＜0.001,＜0.001).In the horizontal direction,ChT gradually thickens from nasal to temporal (F=2 251.558,P＜0.001);in the vertical direction,ChT gradually decreases from superior to the central,but have a little increased from central to inner inferior,then decreased to outer inferior again (F=45.425,P＜0.05).Correlation analysis showed that SFCT was negatively correlated with AL (r=0.478,P＜0.01) and a negative correlation with axial length (r=-0.395,P＜0.01),and positively correlated with SER (r=0.478,P＜0.01).SFCT decreased by 12.29 μm for every in myopic refractive error of 1 D,or by 20.14 μm for every increase in AL of 1 mm.Conclusions ChT is changed by different location.The horizontal direction is gradually thickened from nasal to temporal.The vertical direction is thicker than the center.The inferior inner ring area is thicker than the outer ring area.Gender,SER and AL are the influencing factors of SFCT.

Objective:To observe the prevention and control effect of 1% atropine on the progression of form deprivation myopia (FDM) in guinea pigs and the potential biological mechanism.Methods:Sixty-nine 3-week-old tricolor guinea pigs with normal refraction were randomly divided into a normal control group ( n=19), a FDM group ( n=19), a FDM+ atropine group ( n=19), and an atropine group ( n=12). No intervention was given to guinea pigs in normal control group.The FDM model was established by covering the right eye of guinea pigs with a semitransparent latex facemask for 4 weeks in FDM and FDM+ atropine groups.For the FDM+ atropine group, 1% atropine gel was topically administered to the form-deprived right eyes once a day for 4 weeks.For the atropine group, the right eye was treated with 1% atropine gel once a day for 4 weeks.Refraction and axial length of guinea pigs were measured by retinoscopy and ophthalmic A-scan ultrasonography respectively at baseline, experiment week 2 and week 4.In experiment week 4, eyeballs were enucleated to make sections via the paraffin wax processing procedure, and the microstructural and ultrastructural changes of the sclera were observed under the light microscope and transmission electron microscope, respectively.The isobaric tags for relative and absolute quantitation labeling combined with liquid chromatography-tandem mass spectrometry were used to identify the differentially expressed proteins.Use and care of the animals complied with the Regulation for the Administration of Affairs Concerning Experiment Animals by State Science and Technology Commission.The study protocol was approved by the Institutional Animal Care and Use Committee of Tianjin Medical University (No.TJYY2020111028). Results:There were statistically significant differences in the diopter of guinea pigs at different time points among the four groups ( Fgroup=138.892, P<0.001; Ftime=167.270, P<0.001). Compared with normal control group, the diopter of guinea pigs in FDM group at experiment weeks 2 and 4, and FDM+ atropine group at experiment week 4 developed toward myopia, showing statistically significant differences (all at P<0.001). Compared with FDM group, the diopter of guinea pigs in FDM+ atropine group at experiment weeks 2 and 4 developed toward hyperopia, showing statistically significant differences (both at P<0.001). There were statistically significant differences in the axial length of guinea pigs at different time points among the four groups ( Fgroup=32.346, P<0.001; Ftime=353.797, P<0.001). The axial lengths of FDM group at experiment weeks 2 and 4 and FDM+ atropine group at experiment week 4 were longer than those of normal control group, and the axial lengths in FDM+ atropine group at experiment weeks 2 and 4 were shorter than those in FDM group, and the differences were statistically significant (all at P<0.001). The collagenous fibers of posterior sclera of guinea pigs were loose and disordered in FDM group, and were regular in FDM+ atropine group.The posterior scleral thickness of normal control group, FDM group, FDM+ atropine group and atropine group was (141.74±16.98), (101.46±9.15), (112.74±6.24) and (134.30±18.19) μm, respectively, with a statistically significant difference ( F=6.709, P=0.005). The posterior sclera was significantly thinner in FDM group than in normal control group and FDM+ atropine group (both at P<0.05). The diameter of posterior scleral collagen fiber gradually increased from inside to outside in normal control group, FDM+ atropine group and atropine group, and the diameters of the inner, middle and outer posterior scleral collagen fibers were smaller in FDM group than in normal control group.Proteomic analysis revealed 85 differentially expressed proteins (fold change>1.30) between FDM group and normal control group, FDM+ atropine group and FDM group, of which 38 were up-regulated and 47 were down-regulated after atropine treatment.Gene Ontology enrichment analysis showed that biological processes mainly involved were biological regulation, cell process, localization and metabolic process.Molecular function mainly involved were binding, catalytic activity, molecular function regulator, structural molecule activity and transporter activity.Cell components mainly involved were in cellular anatomical entity, intracellular and protein-containing complex. Conclusions:Atropine can increase the diameter of scleral collagen fibers in guinea pigs of FDM model, improve the arrangement of scleral collagen fiber, inhibit scleral thinning.The mechanism of atropine to control myopia progression is closely related to the tight junction between scleral cells, cytoskeleton and extracellular matrix remodeling.