Discrepancies in Vessel Density and Blood Flow Distribution in Different Areas of the Iris among Pediatric Type 1 Diabetes Mellitus and Adult Type 2 Diabetes Mellitus Patients

INTRODUCTION: Diabetes mellitus may compromise the vasculature of the iris, thereby leading to severe vision-threatening complications. This study aimed to investigate differences in iris blood flow indices between pediatric type 1 diabetes mellitus (T1DM) patients and adult type 2 diabetes mellitus (T2DM) patients. METHODS: This was a cross-sectional study. Pediatric T1DM patients and healthy children were members of the Shanghai Children and Adolescent Diabetes Eye (SCADE) cohort who visited Shanghai Eye Hospital in February 2022. The adult T2DM patients and healthy adults were patients who visited Shanghai General Hospital from October 2021 to January 2022. Iris OCTA was acquired through a Cirrus HD-OCT 5000 angiography system (Carl Zeiss Meditec, Inc.). A unique iris OCTA quantification method was used, and the vessel area density (VAD) and vessel skeleton density (VSD) were obtained. The area from the pupillary margin to the corneoscleral limbus was taken as the whole iris blood flow index, and the inner third near the pupillary margin of the whole iris was taken as the pupillary margin blood flow index. RESULTS: This study enrolled 34 pediatric T1DM patients, 34 age-matched healthy children, 34 adult T2DM patients, and 34 age-matched healthy adults. The whole iris and pupillary margin VAD and VSD of the pediatric T1DM patients were not different from those of healthy children. The whole iris VAD and VSD of the adult T2DM patients were lower than those of healthy adults, and the pupillary margin VAD and VSD were the same in these two groups. Compared with adult T2DM patients, pediatric T1DM patients had higher whole iris VAD and VSD and lower pupillary margin VAD and VSD values, all with statistical significance. Among diabetic patients, age, BMI, and glycated hemoglobin level were negative independent influencing factors for whole iris VAD and VSD, and age was a positive influencing factor for pupillary margin VAD and VSD. CONCLUSION: There are diverse alterations in iris vessel density and blood flow distribution between pediatric T1DM patients and adult T2DM patients.