Normal Measurements of Optic Nerve in Pediatric Population

Objective: The aim of this study was to examine the normal values of the optic nerve in different segments of the nerve trace in the pediatric population using magnetic resonance imaging (MRI). Methods: Two radiologists retrospectively reviewed images obtained with a 1.5 tesla MR device of 426 youngsters (213 males/213 girls). Measurements were performed on the T2 sequence. Parts of the orbital region, prechiasmatic region, and optic tract were measured. Participants were divided into 5 different age groups. Results: The mean age of the population is 8.3 ± 1.5 years. The average diameter of the orbital segment of the entire population was 3.58 ± 0.53 mm, 4.74 ± 0.48 mm for the prechiasmatic segment, and 3.61 ± 0.48 mm for the optic tract section. Age correlates positively with the orbital plane (OP), prechiasmatic portion (PP), and optic tract (OT) values. All age groups have considerably varying mean OP, PP, and OP diameters. Good interobserver reliability was observed for all 3 diameter measurements (OP cap value = 0.62, PP cap value = 0.58, OT cap value = 0.67). Conclusion: Normal diameters of the optic nerve can be measured by MRI at above mentioned sections with a good interobserver reliability. These normal values can be used to detect obscure thickness changes/abnormalities in optic nerves of the children.