Optic Neuritis (Papillitis and Retrobulbar)

Optic neuritis is an inflammatory disease of the optic nerve, frequently associated with demyelination due to multiple sclerosis (approximately 50% of cases). However, it may also be associated with other autoimmune and inflammatory conditions including diabetes, neuromyelitis optica (NMO) spectrum disorder and chronic relapsing inflammatory optic neuropathy (CRION).

Optic neuritis affects women more than men and typically presents in those younger than 50 years of age. Affected individuals present with monocular vision loss occurring progressively over several hours to days and is typically accompanied by pain on eye movements. Red cap desaturation and relative afferent pupillary defect may be present in the affected eye. Visual field defects are variable, ranging from a general field depression and centrocecal scotoma through to altitudinal defects.

The signs and symptoms of optic neuritis may be exacerbated by an increase in body temperature (warm bath, exercise, fever etc), known as Uhtoff’s phenomenon. Patients recovering from optic neuritis may also note difficulty in depth perception when looking at moving objects (Pulfrich phenomenon).

Depending on the location of involvement, it may present with swelling and elevation of the anterior part of the optic nerve (papillitis) or with no visible funduscopic signs of inflammation (retrobulbar optic neuritis). Visible disc swelling occurs in approximately one half to one third of cases.
- In cases of papillitis, disc oedema and RNFL thickening can be seen initially.
- Retrobulbar optic neuritis is not associated with an acute elevation of the optic disc as inflammation is occurring more posteriorly along the nerve. The other signs and symptoms noted above however still occur including reduced vision, visual field defects, pain on eye movement and red desaturation.

Resolved optic neuritis of either type is associated with RNFL thinning, making it one differential to consider when making a glaucoma diagnosis.

The Optic Neuritis Treatment Trial (ONTT) showed a 5-year cumulative probability that a patient with optic neuritis would be diagnosed with multiple sclerosis was 30%. This risk however was highly dependent on the number of lesions present on brain MRI at first presentation. The study also found however that having no brain lesions present on MRI at first presentation did not preclude the development of multiple sclerosis (Neurology 1997).

Visual recovery was also monitored over time in the ONTT. Results showed that in 93% of cases, vision started to improve within 5 weeks of an acute presentation. 15 year follow up of patients in this study found that visual acuity and visual function was normal or near normal in most patients at that time but patients with multiple sclerosis were more likely to have deficits in normal visual function (Ophthalmology, 2008).