Orbital structures in the pediatric age group: A normative assessment using magnetic resonance imaging

Many diseases of traumatic, infectious, endocrinologic and neoplastic origin can lead to orbital involvement and related morphological changes. In the present study, we aimed to determine the age-based normal orbital measurements using magnetic resonance imaging (MRI) in pediatric patients.Our retrospective study included 186 patients with normal orbital MRI findings. The patients were divided into the following five groups based on their age. Group 1: 1-24 months; Group 2: 25-60 months; Group 3: 61-120 months; Group 4: 121-168 months; and Group 5: 169-216 months. Globe position relative to interzygomatic line (IZL) and orbital rim, optic nerve-sheath complex, extraocular muscle diameters, were measured.The differences among the age groups for the distances between cornea and sclera in relation to IZL, for the distances between cornea and sclera relative to orbital rim, and for the extraocular muscle diameters were statistically significant. In terms of the extraocular muscle diameter, it was found that the thinnest muscle of all groups was the lateral rectus muscle while the thickest was the medial rectus muscle.In pediatric patients who were divided into five groups based on their age, the positions of bulbus oculi relative to IZL or orbital rim and the normal diameter ranges of extraocular muscles and of the optic nerve-sheath complex in orbital MRI were determined. We are of the opinion that the presence of such a scale could be a guide in the evaluation of orbital MRI in pediatric patients.