The Study Of Vascular Parameters Relate To Macular Area In Different Degrees Of Myopia By Using Optical Coherence Tomography Angiography

Objective:To measure macular related vascular parameters of the retinal and choroidal systems in patients with different degrees of myopia by Optical coherence tomography angiography,so as to evaluate the correlation between the structure and function,and to guide the prevention of myopia.Methods:Patients with high myopia who visited the ophthalmology clinic of the First Affiliated Hospital of Kunming Medical University from August 2019 to March 2021 were recruited into the cohort study for baseline examination,and age-and sex-matched moderate and low myopia patients were collected as the control group during the same period.Among them,some patients were excluded due to other ocular diseases,low examination quality and other problems,and after strict screening,the total number of patients finally included in this study was 84 patients,142 eyes,ranging in age from 14 to 67 years old,who were divided into two groups according to refraction:high myopia group(SE≤-6.0D,72 eyes)and moderate and low myopia group(SE>-6.0D,70 eyes),and all study subjects underwent basic visual acuity,best-corrected visual acuity,refraction,slit-lamp microscopy,axial length,intraocular pressure examination,fundus photography,and OCTA examination.Retinal macular thickness values and percentage of vascular density were recorded.Subfoveal choroidal thickness was manually measured by built-in software after OCT high-definition mode scanning.Choriocapillaris density was calculated on the binarized images by adaptively local threshold binarization of the original choroidal images.The magnification of the myopic eye was corrected with the Littmann magnification formula(t=p × q × s),the differences in retinal and choroidal thickness and foveal avascular area(FAZ)related parameters before and after correction were analyzed,and the correlation between parameters was compared ultimately.Results:The mean age of the patients in this study was 33.64±13.11 years old,the mean refraction was-7.16±4.20 D,the mean axial length was 26.14±1.87 mm,and the mean best-corrected visual acuity(log minimum angle of resolution logMAR)was 0.07±0,13,and there was no significant difference in age or gender between the two groups(P>0.05).In multivariate analysis,the overall superficial and deep retinal vascular density was significantly lower in high myopia(P>0.001).In the superficial retina,the vascular density in both the foveal region(central 1 mm diameter)and the parafoveal(central 1-3 mm diameter ring)or perifoveal regions(central 3-6 mm diameter ring)was lower in the high myopia group than in the medium and low myopia group,while in the deep retina,only the vascular density in the fovea and perifovea was lower in the high myopia group than in the medium and low myopia group,and the vascular density in the parafoveal region was not significantly different between the two groups.Choriocapillaris density also showed a significant difference between the high myopia(55.7±3.1%)and moderate to low myopia groups(58.0±2.6%)(P>0.001).Before myopic magnification correction,there was no difference in the mean foveal thickness between the two groups,while the mean retinal thickness,parafoveal,and perifoveal thickness in the high myopia group were significantly lower than those in the medium and low myopia group(P>0.001).Similarly,subfoveal choroidal thickness(SFCT)was thinner in the high myopia population(P>0.001).As for the foveal avascular zone(FAZ),there was no significant difference between the two groups(P>0.05).After correction,the high myopia group generally had thicker retinal thickness than the medium and low myopia groups,whether it was whole retinal thickness,or foveal(inner,outer),parafoveal,or perifoveal regions.SFCT remained thinner in the high myopia group.With the deepening of myopia,both FAZ area and perimeter were significantly enlarged(P<0.001).Correlation analysis of each parameter:refraction(SE)was positively correlated with whole vascular density in the superficial retina(r=0.57,P<0.001),whole vascular density in the deep retina(r=0.46,P<0.001),choriocapillaris density(r=0.48,P<0.001),and subfoveal choroidal thickness(r=0.46,P<0.001),was negatively correlated with best-corrected visual acuity(r=-0.73,P<0.001),retinal thickness(r=-0.41,P<0.001),FAZ area(r=-0.37,P<0.001),and FAZ perimeter(r=-0.43,P<0.001),foveal inner thickness was positively correlated with mean vascular density in the foveal region in the superficial retina(r=0.59,P<0.001),and foveal outer thickness was not significantly correlated with mean vascular density in the foveal region in the deep retina(P=0.8)Subfoveal choroidal thickness was negatively correlated with age(r=-0.39,P<0.001)and positively correlated with choriocapillaris density(r=0.43,P<0.001).Conclusions:1.The density of macular subdivisions of superficial retinal capillary plexus,deep capillary plexus and choriocapillaris in patients with high myopia was significantly lower than that in patients with moderate to low myopia.Furthermore,the higher the myopic refraction,the lower the capillary density.2.Correction of optical magnification is necessary for the study of myopia related parameters.After correction,the retina(including the fovea,parafovea,and perifoveal full-thickness retina)was significantly thickened in all regions of the macula in high myopia,and the inner foveal thickness was positively correlated with the mean vascular density in the foveal region of the superficial retinal plexus.3.The FAZ area and perimeter were significantly increased in patients with high myopia compared with moderate to low myopia.Moreover,the deeper the myopia,the bigger of FAZ area and perimeter,the early macular ischemic status can be assessed by FAZ,and the progression and prognosis of retinal ischemia-related diseases can be followed up and observed.4.Choroidal thinning is one of the earliest signs of non-pathological myopic changes.The choroid of patients with high myopia is significantly thinner than that of patients with moderate to low myopia.With the deepening of myopia,the thinning effect in the foveal region is more prominent,and the choriocapillaris density is lower.