Optic or Retrobulbar Neuritis

This is an important cause of unilateral sudden loss of vision in a white eye in a young person. The patient complains of pain behind the eye on attempting to move it and there is often a grey or coloured patch in the centre of the field of view. In severe cases,the sight of the affected eye can be lost completely. On examination, a relative afferent pupil defect on the affected side might be the only objective evidence of disease. It is essential to test the pupil before dilating it with eye drops. The fundus is often normal initially (retrobulbar neuritis), although there can be slight swelling of the optic disc (optic neuritis). After two or three weeks the optic disc starts to become pale. The visual prognosis is generally good. Most patients make a complete or nearly complete recovery after 6-12 weeks. The attack is unilateral in 90% of cases, although there is a risk that the other eye can be affected at a later date and recurrent attacks in one or both eyes can cause permanent damage to the vision. Fortunately, it is extremely rare for a patient to be made blind by multiple sclerosis.

The diagnosis at the time of the acute attack relies on the history and noting the pupil reaction. It is often advisable to make the diagnosis in retrospect. The patient might give a history of visual loss in one eye, which has recovered, and at a later date, presents with other nonocular signs and symptoms of demyelinating disease. If it can be confirmed that the patient has had a previous attack of optic neuritis, this can help in the confirmation of the diagnosis of disseminated sclerosis. Under these circumstances, the pallor of the disc can be helpful, but careful assessment of the colour vision, visual acuity and measurement of the visually evoked potential can provide conclusive evidence. At the time of the acute attack, testing the visual field might reveal a central scotoma. The size of this defect diminishes as healing occurs, often leaving a small residual defect between blind spot and central area.

Corticosteroids administered systemically can speed up recovery of vision. However, the final visual outcome is unchanged by such treatment.

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