Normal Sonographic Optic Nerve Sheath Diameter among Children in South Western Nigeria

Introduction: Optic Nerve Sheath Diameter (ONSD) correlates with intracranial pressure and can be utilised for monitoring in emergency situations. Aim: To determine the reference values of optic nerve sheath diameter in healthy school going children in South western Nigeria by using B-mode sonography. Materials and Methods: A cross-sectional study was conducted in children from three selected schools after consent and approval from the parents and Institutional Health Research Ethics committee, respectively. B-mode sonography using a 4-12 MHz probe was carried out on children with normal visual acuity and fundoscopy. Demographics of the children and the optic nerve sheath diameter were recorded in a proforma. Data was analysed with SPSS version 21 and were represented as mean and standard deviation. Paired t-test was used to compare ONSD between the right and left eye. Independent t-test was used to compare ONSD between males and females. Significance was set at p-value <0.05. Results: Optic nerve sheath diameter was measured in both eyes of 468 children. There were 235 (50.2%) boys and 233 (49.8%) girls (M:F Ratio= 1.01:1) and age range was 2 to 16 years. Mean ONSD in the right eyes was 0.56 +/- 0.08 cm while in the left eye it was 0.58 +/- 0.09 cm for boys, while in girls in the right eyes it was 0.55 +/- 0.08 cm and in left eye it was 0.57 +/- 0.07 cm. The mean ONSD of the left eyes was longer than the right eyes. (p=<0.001). There was no significant difference in ONSD measurement between males and females (p=0.275). Conclusion: Mean ONSD in children was longer in the left eye than the right, and increases with age.