Normative magnetic resonance imaging measurements of orbital structures in pediatric population of North-Eastern India: A retrospective cross-sectional study

Purpose: The people of Northeast India comprise mostly of Mongoloid descent with characteristic craniofacial features. The purpose of this study was to evaluate the normal orbital structures with MRI and determine normative data in the Northeast Indian pediatric population. Methods: MRI images of the 302 orbits of 151 pediatric patients below 16 years of age were retrospectively evaluated to measure the various orbital structures. Both axial and coronal MRI images were utilized for various orbital measurements. An independent sample t-test was done to compare various orbital data according to the sex and side. Linear regression was also done. Results: The mean age of the pediatric population was 9.64 ± 1.47 years with a male: Female ratio of 1.13:1. The mean interzygomatic line was 88.4 ± 9.09 mm and the interorbital line was 22.18 ± 3.62 mm. The mean thicknesses of medial, lateral, superior, and inferior recti muscles were 2.58 ± 0.46, 2.34 ± 0.42, 2.16 ± 0.40, and 2.53 ± 0.49 mm in males and 2.41 ± 0.41, 2.08 ± 0.34, 2.08 ± 0.46, and 2.46 ± 0.49 mm in females. The mean horizontal orbital, vertical orbital diameters, orbital index, mean volume of eyeball, and orbital cavity were 30.27 ± 2.97,3 7.06 ± 3.57, 122.58 ± 7.39, 4.63 ± 0.84, and 15.29 ± 3.52 in males, while 29.16 ± 3.23, 34.96 ± 3.99,119.96 ± 7.31, 4.49 ± 0.87, and 14.65 ± 3.47 in females, respectively. With an increase in age, the interzygomatic line (r = 0.883, r2 = 0.780; P < 0.0005), anterior medial interorbital line (r = 0.808, r2 = 0.652; P < 0.0005), mean volume of eyeball (r = 0.915, r2 = 0.838; P < 0.0005), orbital cavity (r = 0.924, r2 = 0.854; P < 0.0005), and distance between the optic nerve entry site (r = 0.829, r2 = 0.687; P < 0.0005) were increased. Conclusion: This study provides normative data of various orbital structures in a pediatric population and these data likely to be useful for diagnosing various pediatric orbital disorders and helps in the planning of various surgical procedures of orbits