Ocular axial length measurement among normal adults using magnetic resonance imaging

Abstract

Background/Introduction: Macrophthalmia and microphthalmia are cardinal signs of many orbito-ocular and systemic diseases which are seen in northern Nigeria. Some cases of refractive error may also be directly related to the ocular axial length (AL). The need for an imaging parameter that will aid their early diagnosis is necessary, as visual compromise is a major consequence if they are not diagnosed and managed appropriately.

Aim and Objectives: To use magnetic resonance imaging, to determine the normal AL of the eyeball and to establish the association, if any, between AL and inter-zygomatic line (IZL), age and sex.

Materials and Methods: The study was conducted over a 6- month period (29^th November 2011 to 28^th May 2012) at the Department of Radiology, Ahmadu Bello University Teaching Hospital, Zaria. The anterio-posterior dimension of the globes (AL) and the length of IZL were measured at the level of the lens for 340 normal ocular globes of 170 patients on T₁-weighted MR images.

Results: The normal ranges for ocular measurements were as follows (mean ± SD): AL of the right globe, 23.32 ± 1.34mm (range 22.0–24.7) and AL of the left globe, 23.29 ± 1.22mm (range 22.10–24.51). The length of the IZL was 103 ± 4.78mm (range 98.2–107.78). All measurements in male patients were significantly higher than those in female patients (P < 0.001).

Conclusion: The results obtained from this study may help ophthalmologists, radiologists and other clinicians to quantitatively evaluate patients with macrophthalmia, microphthalmia and/or refractive errors.

Keywords: Inter-zygomatic line, magnetic resonance imaging, normal adults, ocular axial length