Dynamic Changes Of Retinal Vascular Diameter And Arteriolar-to-venular Diameter Ratio In Full Term Newborns Within 10 Days Of Birth

Objective: Retinal blood vessels are the only blood vessels that can be directly observed in vivo and is one of the indices to evaluate microcirculation.A newborn’s environment changes greatly from inside to outside in a short time during delivery,which affects its microcirculation.Observing the dynamic changes of retinal blood vessels during this period can indirectly reflect the changes in neonatal microcirculation.Herein,digital measurement software was used to measure the diameter of retinal blood vessels of full-term newborns from the first day to tenth day and arteriolar-to-venular diameter ratio(AVR)was calculated.By comparing the results of each day,dynamic change process of retinal blood vessels during this period was examined.Methods: We screened the data of newborns collected by Star Pupil Medical Cloud Data System(XBDS)in primary hospitals in An Hui Province from October 2020 to March 2022.We reviewed the data of 700 full-term,normal-weight,newborns(1400eyes)within 10 days of birth.Data on newborns on the 1st-6th day of life was divided into group 1 to 6 and that on the 7th-10 th day of life was included into group 7.We studied 96 cases(182 eyes)in the first group,101 cases(196 eyes)in second group,187 eyes in third group,195 eyes in fourth group,177 eyes in fifth group,110 cases(208 eyes)in sixth group and 97 cases in seventh group.The fundus image selection criteria of the subjects was that the optic disc is roughly in the center,and the retinal blood vessels are less deformed and clear.We imported the selected images into Image-Pro-Plus software.Firstly,the diameter of the optic disc was measured.Subsequently,the diameter of the main vascular branches of retinal artery and the accompanying vein in the four quadrants were measured at a distance of 0.5-1.0PD from the edge of the optic disc and AVR value was calculated accordingly.Finally,retinal vascular diameter and AVR of each group was compared to determine their dynamic changes.In addition,differences in retinal vessels in different quadrants were deciphered by comparing the diameter and AVR values of retinal vessels in each quadrant.Results: The average AVR within 10 days after birth was 0.565(95%CI 0.562-0.568).There was a significant positive correlation between the diameter of retinal arterioles and venules(Pearson correlation coefficient was 0.605,P<0.001).Central retinal artery equivalent diameter(CRAE),central retinal vein equivalent diameter(CRVE),and AVR did not correlate with sex,weight,gestational age,and corrected gestational age.When CRAE,CRVE,and AVR of different groups were compared,there were significant differences between the first and second day,third and fourth day,fourth and fifth day,as well as fifth and sixth day(P<0.05).There were significant differences in CRVE between the first day of birth and second day,and sixth and seventh to tenth day of birth(P<0.05).The differences of AVR between different days after birth were statistically significant(P<0.05).CRAE,CRVE,and AVR were different in different quadrants.CRAE was the largest in the inferior temporal quadrant,followed by superior temporal quadrant,inferior nasal quadrant,and superior nasal quadrant,respectively.CRVE was the largest in the inferior temporal quadrant,followed by superior temporal quadrant,inferior nasal quadrant,and superior nasal quadrant.In addition,AVR was the largest on the nose and under the nose followed by superior and inferior temporal quadrants,respectively.There were significant differences in CRAE,CRVE,and AVR between the upper and lower retina,and between temporal and nasal retina(P<0.05).There were also some differences in CRAE,CRVE,and AVR between different groups in each quadrant.Conclusion: After birth,the central retinal vascular system of newborns experienced urgent and adaptive changes.Its AVR value is significantly lower than that of adults.CRAE and AVR showed a consistent S-shaped change trend within ten days of birth.At the same time,the change trend of CRVE is small,and there is no significant difference among multiple age groups.The changes of CRAE and CRVE can affect AVR,but it is mainly caused by the changes of retinal artery.The diameter of retinal blood vessels in different quadrants changes asymmetrically.The diameter of retinal blood vessels and the ratio of arteriovenous caliber have nothing to do with neonatal sex,weight,gestational age and corrected gestational age.The method of observing the microcirculation in the body through the retinal vessels of newborns can play an important role in monitoring the early vital signs of newborns.