Correlation of optic neuritis and retinal nerve fibre thickness using optical coherence tomography in a cohort of multiple sclerosis patients

Abstract

Background: Optical coherence tomography (OCT) is a fast, non-invasive imaging technology that produces 3D, high-resolution images of the retina. Direct visualisation of the retina allows a unique opportunity to study the effects of multiple sclerosis (MS)-associated neurodegeneration on retinal ganglion cells as well as effects of retrobulbar demyelination on axonal and retinal architecture through measurement of retinal nerve fibre layer (RNFL) thickness and total macular volume (TMV). These findings are clinically important as axonal loss is irreversible and correlates with disability.

Aim: To determine the role and usefulness of OCT in a local cohort of MS patients.

Setting: Neurology Clinic, Inkosi Albert Luthuli Central Hospital, KwaZulu-Natal, South Africa.

Methods: Nineteen patients with MS currently being treated with interferon β-1b underwent OCT examination of both eyes. RNFL thickness and macular volume were measured and correlated with clinical disease characteristics, history of optic neuritis and level of disability.

Results: Mean RNFL thickness was 77.3 μm with no significant difference in mean RNFL in eyes with a history of optic neuritis (ON) and those without (p = 0.4). Eyes with a history of ON did, however, have significantly thinner RNFL compared with the contralateral eye (p = 0.04). Despite a strong correlation between TMV and RNFL (p = 0.001), a subset of patients with normal RNFL had TMV that was less than 1% of what was expected. There was no correlation between RNFL and disability scores.

Conclusion: OCT enables a direct axonal ‘optical biopsy’, for monitoring disease progression and treatment response in MS. RNFL thinning occurs independently of a history of optic neuritis and may represent a chronic optic neuropathy in patients with MS.

Keywords: Multiple sclerosis; optical coherence tomography