Normative measurements of the ocular globe position in relation to interzygomatic line, using magnetic resonance imaging among adults in Zaria, Nigeria

Abstract

Introduction: Proptosis and enophthalmos are cardinal signs of many orbito-ocular and systemic diseases which are common in our environment. The need for an imaging parameter that will aid its early diagnosis is necessary as visual compromise is a major consequence if they are not diagnosed and managed early. Aim and Objectives: This prospective study was aimed at using magnetic resonance imaging (MRI), to determine interzygomatic distance, distance between the anterior and posterior borders of the globes and the interzygomatic line (IZL), and then using these parameters to determine the normal position of the ocular globes within the orbits. Methodology: The study was conducted within 6 months spanning November 29, 2011-May 28, 2012, at the Department of Radiology, Ahmadu Bello University Teaching Hospital, Zaria. The distance between anterior border of the globe (corneal apex) and IZL which is referred to as Hertel-index, distance between posterior border of the globe and IZL, and length of the IZL were measured at the level of the lens for 340 normal ocular globes of 170 patients on T1-weighted MRIs. Results: The normal ranges for the orbital measurements are as follows (mean ± standard deviation): The normal position of the posterior pole of the right globe was 6.34 ± 0.99 mm from IZL (ranged 5.40-7.33) while that of the left globe was 6.56 ± 0.93 mm (ranged 5.63-7.50). All measurements in male patients were significantly higher than those in female patients (P < 0.001) and the position of the right globe within the orbit was significantly different from that of the left for both sexes (P < 0.001). Conclusion: The results obtained from this study may help ophthalmologists, radiologists, and other clinicians to quantitatively evaluate patients with enophthalmos, exophthalmos, or other changes in the orbital morphology.