Orbital Index in Human Dry Skulls of East Indian Origin: A Cross-sectional Study

Introduction: Orbital index demonstrates the proportion of the orbital length to the orbital width and varies with race, geographic region, and ethnicity. Aim: To evaluate the normal reference orbital parameters for the adult Bihar population of east Indian region. Materials and Methods: A cross-sectional study was conducted at Mata Gujri Memorial Medical College, Kishanganj, Bihar, India for a period of one month from September 2022 to October 2022. A total of 41 dry adult skulls irrespective of sex were included. The digital Vernier caliper was used to measure the maximum orbital height and width. The orbital index was determined by using the formula maximum orbital length (height)/maximum orbital width×100. Based on the average orbital index as standard, three categories of orbits have been described-Megaseme (large): the orbital index is 89 or over, Mesoseme (intermediate): the orbital index varies between 89 to 83, and Microseme (small): the orbital index is 83 or less. Statistical analysis was performed using Statistical Package for Social Sciences (SPSS) version 20.0. Orbital index between the right-side and left-side were compared using an unpaired two-tailed t-test at a 95% confidence limit. Results: Mean orbital length of right orbit of the dry skulls was 33.14±1.95 mm and left orbit was 33.44±1.92 mm. The mean orbital width of right orbit was 39.43±2.47 and left orbit was 39.13±2.49 mm. The mean orbital index was found to be 84.26±5.59 mm and 85.62±5.17 mm on the right and left orbit respectively (p-value=0.244). According to the orbital index the studied group of east Indian population comes under the mesoseme category. Conclusion: The study provides useful baseline orbital morphometric data of east Indian population which are very important during forensic research.