Pupil to limbus diameter ratio as an emerging autonomic function test and its correlation with anthropometric parameters in different phases of menstrual cycle

The menstrual cycle is a physiological change in normal females, indicating the proper functioning of both endocrine and reproductive health. The pupil to limbus diameter (PLD) ratio is defined as the ratio of pupil diameter measured at an axial plane to the limbus diameter measured at the same or a parallel axial plane. Alterations in estrogen and progesterone levels may influence cardiac autonomic functions. This study aimed to correlate the PLD ratio with anthropometric parameters, such as body mass index (BMI) and waist circumference (WC), during different phases of the menstrual cycle among medical students.Methods: A cross-sectional study was conducted among first- and second-year female MBBS students aged 17 to 22 years. Anthropometric parameters, including height, weight, BMI, and WC, were measured for all participants. Eye photographs were taken during the follicular and luteal phases of the menstrual cycle, and the diameters were measured manually using the two-box method. The PLD ratios for both eyes showed a significant positive correlation with BMI (right eye: r = 0.682, p < 0.000; left eye: r = 0.430, p < 0.000) and waist circumference (right eye: r = 0.456, p < 0.000; left eye: r = 0.315, p < 0.001). The PLD ratio can serve as a simple, non-invasive, and cost-effective autonomic function test.