Selmaj Optical coherence tomography in multiple sclerosis Thickness of the retinal nerve fiber layer as a potential measure of axonal loss and brain atrophy

Multiple sclerosis (MS) is a primary demyelinating disease of the central nervous system with a variable spectrum of clinical and pathological presentation. Although pathologic damage in MS involves the myelin sheath, recent data showed that axonal degeneration might be equally important and occur during early phases of the disease [2]. For assessment of axonal loss in vivo in MS patients several MRI techniques, such as T1 lesion load [21], atrophy measures, and brain parenchymal fraction (BPF) [12], have been applied. All these techniques require advanced technology and extensive examination times. The retina represents the most proximal part of optic nerve, with a unique structure composed of unmyelinated axons and with some contribution from glial cells [8, 13]. This axonal distribution creates a retinal nerve fiber layer (RNFL) and its thickness correlates with changes in axonal function [4]. A reduction in the RNFL has been observed in patients with several optic neuropathies [1]. Qualitative changes in RNFL in MS patients was first reported by Frisen and Hoyt [7]. Quantitative changes in RNFL in optic neuritis were first described by Parisi et al. [14], Trip et al . [19] and Fisher Received: 18 August 2007 Received in revised form: 21 April 2008 Accepted: 24 April 2008 Published online: 25 September 2008