Diagnostics
Ophthalmic diagnoses in the ED: optic neuritis

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Abstract

Optic neuritis is the most common cause of decreased vision due to optic nerve dysfunction in patients who are 20 to 40 years of age. Optic neuritis, or inflammation of the optic nerve, is primarily due to idiopathic demyelination. Demyelinative lesions seen in optic neuritis are not unlike those seen in plaque associated with multiple sclerosis. In fact, acute inflammatory demyelination of the optic nerve commonly occurs as an initial manifestation of multiple sclerosis. Key features of optic neuritis include a vision loss occurring over 1 to 10 days, color vision impairment, eye pain with motility, and an afferent pupillary defect. This significant diagnosis can be challenging to an emergency physician as it is relatively infrequently observed.

Introduction

In the United States, the annual incidence of optic neuritis in a predominately white community is approximately 5 per 100,000 per year, whereas the prevalence is 115 per 100,000 [1]. Most cases occur in patients between 15 and 45 years old, with women affected more frequently than men.

Most cases are due to inflammatory demyelination of the optic nerve. The pathophysiology leading to the demyelination is most often idiopathic. Occasionally, optic neuritis may be due to an infectious process involving the orbits or paranasal sinuses. Optic neuritis caused by inflammatory demyelination carries a strong association with multiple sclerosis (MS), but cases may occur in isolation.

The diagnosis of this disease is made based on history and physical exam findings. However, magnetic resonance imaging (MRI) may yield prognostic information in terms of the patient's future risk for development of MS. Despite a large amount of recent research regarding the therapy for optic neuritis, the treatment remains controversial.

Section snippets

Case example

A 28-year-old woman arrived at the emergency department (ED) complaining of a 3-day history of progressive headache, eye pain, and unilateral blurred vision. She denied a history of chronic headache and stated that she had previously been in good health. There is no history of recent trauma.

On physical examination, the patient was alert and oriented. Her vital signs were normal. The visual acuity was tested at 20/20 on the right side and 20/200 on the left. Cranial nerves II through XII were

Pathophysiology and clinical manifestations

Optic neuritis represents an inflammatory and demyelinating condition of the optic nerve. The most common form arises from idiopathic demyelination of the nerve. This degeneration of the optic nerve represents the most common cause of optic nerve disease. Pathologically, the nerve is surrounded by inflammatory cells initiating swelling and fragmentation of the nerve tissue. Further degeneration occurs as macrophages phagocytize myelin breakdown products [2]. The other, less common causes of

Diagnosis

Optic neuritis is generally a clinical diagnosis based on history and physical examination. In cases with typical clinical symptoms, laboratory testing is unlikely to be revealing [7], [8]. Symptoms often include a reduced visual acuity and color perception, ocular pain, and APD in the affected eye [9], [10], [11], [12]. The first 2 symptoms can be tested by using a standard eye chart and pseudoisochromatic plates.

Most cases of optic neuritis are retrobulbar and the fundoscopic examination will

Treatment

There is no known cure for optic neuritis. Much of the current understanding of the treatment comes from the Optic Neuritis Treatment Trial (ONTT), which was a multicenter trial composed of 457 patients with optic neuritis. The primary objective of this study was to assess the benefit of corticosteroid treatment of optic neuritis. Numerous follow-up studies were performed to investigate the potential benefit of steroids for treatment of optic neuritis and prevention of MS.

In the ONTT, patients

Key points

  • Optic neuritis is a clinical diagnosis that often includes eye pain, a relatively abrupt vision and color differentiation loss, and an afferent papillary defect.

  • Intravenous steroids have been shown to speed the recovery of vision without affecting the final visual outcome.

  • Steroids may also decrease the symptom onset of MS over the first 2 to 3 years after optic neuritis.

  • Brain MRI is the most useful predictor of subsequent development of MS.

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