Magnetic Resonance Imaging Nomogram For Optic Nerve And Extraocular Muscles In Nigerian Subjects

Background: The role of optic nerves and extraocular muscles as critical in conveying visual signals to the brain and controlling movement of the eyeballs to ensure precise vision cannot be overemphasized. Objective: The study aimed at the assessment of optic nerves and extraocular muscles of 195 brain images generated by Magnetic Resonance Imaging (MRI) to establish normal sizes of these tissues. Methods: Direct measurement of the size of optic nerves and extraocular muscles was carried out respectively on the magnetic resonance images with the aid of a Digital Imaging and Communications in Medicine (DICOM) image viewer. The data was analyzed using Microsoft Excel 2007 by subjecting to descriptive statistics, student’s t-test and Pearson’s correlation statistical tools. Result: The mean size of the right optic nerve of the subjects was 4.89 ± .77mm and the left was 4.87 ± .69mm. There was no significant difference (p>0.001) between the size of the right and the left optic nerves. The sizes of extraocular muscles of subjects studied were: 3.15 ± .49mm for Right Lateral Rectus Muscle (RLRM); 3.06 ± .46mm for Left Lateral Rectus Muscle (LLRM); 3.13 ± .39mm for Right Medial Rectus Muscle (RMRM) and 3.20 ± .39mm for Left Medial Rectus Muscle (LMRM). There were no significant differences between sizes of extraocular muscles (p<0.001). Conclusion: The findings have provided a standard for future quantitative comparison and will serve as predictive indicators or radiologic reference for the diagnosis of patient with associated visual problems.