Multiple Sclerosis (MS) is a central demyelinating disease involving multifocal demyelination of white matter. It often affects young people under 40 years of age. A secured diagnosis requires multiple attacks of demyelination separated in time and anatomical locations. A thorough neurological history is important at the time of presentation. Nuclear magnetic resonance imaging (MRI) offers some help in diagnosis but does not substitute for good history taking.
The most common ocular manifestation of MS is optic neuritis. It is the presenting feature in 25% of cases and occurs during the course of established disease in 70% of cases. Between 50% and 70% of patients in the 20 - 40 years age group presenting with optic neuritis subsequently develop systemic demyelination.
Optic neuritis typically presents as sudden unilateral blurred vision progressing over a few days. The vision is often described as being 'washed out'. Colours appear desaturated and there is often retro/peri-ocular pain aggravated by eye movements. Signs include reduced acuity of variable severity from minimal to 'no perception of light'; an afferent pupillary defect (pupil dilates during the 'swinging light' test); and dyschromatopsia (poor colour discrimination performance).
The most common visual field defect is a central scotoma. Ophthalmoscopy may reveal a swollen optic disc although the disc is often normal in the retrobulbar type of MS. Optic atrophy (from previous attacks) may be found in the ipsi- or contra-lateral eye. Visual recovery is slower than the initial loss and usually takes four to six weeks. About 90% of sufferers recover normal visual acuity. Minor defects in colour vision and brightness appreciation may persist. The effects of subsequent attacks are additive. There is no correlation between the degree of visual defect during the attack and the final visual outcome.
An applicant with a suspected or confirmed history of Multiple Sclerosis, or a history of optic neuritis should be considered as having a condition that is of aeromedical significance.