Optic Neuritis: ED Evaluation and Management

Authors: Tallib Karaze, DO (EM Resident Physician, Loyola University Medical Center) and Matt Baluzy, DO (Assistant Professor of Emergency Medicine, Loyola University Medical Center) // Reviewed by: Courtney Cassella, MD (Reading Hospital, Assistant Professor of Emergency Medicine, Drexel University); Alex Koyfman, MD (@EMHighAK); Brit Long, MD (@long_brit)

Case 

A 40-year-old female presents to the emergency department (ED) with four days of progressively worsening monocular eye pain and vision loss. The patient reports a dull, achy pain behind the right eye that gets worse with eye movement. She states the pain started first, and then she developed blurry vision, prompting her overnight visit to your ED. There are no reports of trauma or injury to the eye, and the patient cannot recall any event that triggered her eye pain.

Her vital signs are unremarkable. On your initial exam you do not notice any obvious abnormalities with her right eye, but your nurse informs you that her visual acuity in the right eye is 20/100, compared to 20/20 in the left eye. Her intraocular pressure is 15 mmHg bilaterally.

After considering a broad differential, you recognize that some of the patient’s history and initial physical exam findings are consistent with optic neuritis (ON). Questions start to flood your mind: What constitutes a thorough exam for this patient? What tests can help me confirm ON? How do I treat this to prevent further vision loss?

Background

Optic neuritis is characterized by inflammation of the optic nerve. It is typically unilateral but may present bilaterally in rare instances. The incidence of unilateral optic neuritis is approximately 1-2 cases per 100,000 per year.¹

ON is delineated into two types: typical and atypical ON. Typical ON, also known as demyelinating ON, is commonly associated with multiple sclerosis and is the most common type of ON. The atypical form is a catch-all category consisting of ON caused by etiologies unrelated to demyelinating disease.² Atypical causes of ON include:

• Autoimmune diseases
  • Sjögren’s syndrome, systemic lupus erythematosus
  • Inflammatory disease: giant cell arteritis
  • Granulomatous diseases: sarcoidosis, granulomatosis with polyangiitis
  • Antibody-mediated disease: neuromyelitis optica spectrum disorder
• Infections: meningitis, encephalitis, syphilis, tuberculosis, viral etiologies
• Paraneoplastic diseases

Typical ON usually affects Caucasian females ranging from 20-50 years of age.³ It is more common in countries with a northern latitude.¹ Atypical ON can occur more frequently in men and children.²

History

Consider optic neuritis in any patient presenting with acute, atraumatic eye pain and vision loss. Specifically, 97.5% of cases will present with unilateral vision loss that occurs over hours to days. The vision loss is often described as blurring or fogging and typically peaks in severity two weeks into the disease course. Nearly all patients will complain of retro-orbital pain aggravated by eye movement. Many will also present with dyschromatopsia (change in the perception of colors), and some will endorse photopsias (flashes of light).^1-4 Patients may have recurrent episodes of ON if the initial presentation was missed.¹

In cases of atypical ON, patients may present with systemic symptoms that are related to the underlying etiology. This can include headache, neck stiffness, altered mentation, rash, cough, or hemoptysis. Consider an infectious or inflammatory condition in these cases.²

Physical Exam

A complete ocular, facial, and neurological exam should be performed on patients presenting with symptoms of optic neuritis. With most cases of typical ON, the facial exam and neurological assessment will not reveal other significant abnormalities. A slit-lamp exam of the eye and measurement of intraocular pressure (IOP) can rule-out other eye pathologies, including foreign bodies, scleritis, uveitis, and acute angle closure glaucoma. Patients with ON will typically have a normal slit-lamp exam and IOP.^4,5

Visual acuity testing can be performed using a Snellen chart. Most patients will have a decrease in their visual acuity that can range from mild (20/25) to severe (20/200). Visual field testing must also be checked in all quadrants with a focus on the central visual fields, as many patients will have a central scotoma.^1,3,5

A pupillary exam will typically reveal a relative afferent pupillary defect (RAPD) in cases of unilateral optic neuritis. An RAPD results from damage to the afferent fibers in the optic nerve. The best way to elicit this is with the swinging light test.⁵ The figure below details abnormal exam findings when performing a swinging light test.

The Kellogg Eye Center has an excellent video on RAPD that can be reviewed at https://www.youtube.com/watch?v=WrNYqNH3b3A.⁶

Red desaturation testing can aid in the clinical diagnosis as well. This can be done with a dark red object in a well-lit room. The patient should be asked to look at the object with their unaffected eye only and then compare the saturation of the red color to the affected eye. In the case of optic neuritis with dyschromatopsia, the red color would appear lighter with the affected eye.

On fundoscopy, the optic disc may appear edematous in one-third of cases.³ Others will have normal disc margins because of isolated retrobulbar optic nerve inflammation, which can be identified on further imaging.

Point-of-care ultrasound (POCUS) performed by ED physicians assessing patients for ON has high sensitivity and high specificity.⁷ Ocular ultrasound can be used to assess for both optic disc edema and optic nerve sheath diameter. An edematous optic disc can be identified when measurements from the dome of the papilla to the fundus exceed 0.6 mm. An enlarged optic nerve sheath diameter is greater than 5 mm, measured 3 mm from the posterior aspect of the orbit. It should be noted that in the early stages of the disease process, ultrasound findings of ON may not yet be present.⁷

Differential Diagnosis

The differential diagnosis for unilateral eye pain with visual field changes can also include:

– Giant Cell Arteritis

– Acute Angle Closure Glaucoma

– Keratitis

– Anterior uveitis

– Endophthalmitis

– Orbital compartment syndrome

– PRES syndrome

ED Diagnostics

The diagnosis of ON is clinical, but it can be confirmed with additional testing. The preferred confirmatory study is an orbital MRI with gadolinium contrast enhancement and fat suppression. This has been shown to confirm lesions in 95% of patients within the first 20 days following the onset of vision loss.^3,4

CSF studies may also be obtained to aid in the diagnosis of both typical and atypical optic neuritis. CSF testing in typical ON can reveal pleocytosis, elevated protein, immunoglobulin G, and oligoclonal bands.⁹ CSF studies for meningoencephalitis, Lyme disease, syphilis, and angiotensin converting enzymes can be ordered for further evaluation of atypical ON.^2-4

Blood work does not aid in the diagnosis of typical ON and is often normal. Serum studies, such as a complete blood count, complete metabolic panel, erythrocyte sedimentation rate, and C-reactive protein, should be ordered if there is concern for an atypical presentation from an infection, inflammatory condition, or autoimmune disease.

Management

Once ON has been diagnosed clinically or with MRI, treatment is focused on improving optic nerve inflammation. Consulting neurology, ophthalmology, or a neuro-ophthalmologist early in the disease course is recommended. Disposition decisions should be individualized and typically made in conjunction with the specialist. Patients with ON who forgo treatment will often recover vision in a few weeks; therefore, the decision to pursue treatment is guided by consultant recommendations after considering the risks and benefits.

The treatment of ON is centered on steroids and other immunomodulators. In a hallmark study, the Optic Neuritis Treatment Trial demonstrated that 250 mg IV methylprednisolone (MP) administered QID (1000 mg/day) for a total of three days followed by oral prednisone administered at 1 mg/kg/day for 11 days, increases the speed of recovery and yielded better vision at six-months compared to low dose oral prednisone. In this study, prednisone alone did not hasten the recovery process and was shown to increase the recurrence of ON. It should be noted that the final visual acuity, visual fields, and contrast/color perception was similar between groups, indicating that the main benefit of MP was hastening recovery time and preventing recurrence.¹⁰ Additionally, IV methylprednisolone has been shown to delay the conversion to multiple sclerosis in the first two years after treatment.⁴

An alternative treatment regimen is IV methylprednisolone 1000 mg once daily for three days followed by oral prednisone for 11 days. The evidence supporting this approach is not as robust as QID dosing.¹⁰ A more recent study evaluated an oral regimen utilizing high dose prednisone at 1250 mg daily for three days. This study demonstrated similar effectiveness when compared to IV methylprednisolone, suggesting a cheaper alternative that avoids hospital admission.¹¹

The decision to taper steroids should be made in conjunction with your consultants. If there is concern for atypical ON due to an infectious cause, antiviral or antibacterial medications should be administered.

Other potential options for treating ON include plasmapheresis and IV immunoglobulin. The evidence for these treatments is not as strong as steroids but can be considered in cases where vision loss is refractory to steroids.¹

Risk of Multiple Sclerosis

After a patient has been diagnosed with typical optic neuritis, the risk of developing multiple sclerosis by 15 years after the onset of ON is approximately 50%. Patients with demyelinating lesions on initial brain MRI are more likely to develop multiple sclerosis in the future.^9,12

Take Home Points

• Optic neuritis is a clinical diagnosis and presents with acute vision change, pain with eye movements, changes in color vision, and an RAPD on exam. Additional studies such as MRI, POCUS, serum, and CSF studies can aid in the diagnosis.
• Neurology, ophthalmology, or a neuro-ophthalmologist should be consulted to help guide management decisions.
• Treatment options for typical optic neuritis include three days of either IV methylprednisolone or high dose oral prednisone, followed by low-dose oral prednisone and a steroid taper if needed.

References

1. Toosy AT, Mason DF, Miller DH. Optic neuritis. Lancet Neurol. 2014 Jan;13(1):83-99. doi: 10.1016/S1474-4422(13)70259-X. PMID: 24331795.
2. Abel A, McClelland C, Lee MS. Critical review: Typical and atypical optic neuritis. Survey of Ophthalmology. 2019;64(6):770-779. doi:10.1016/j.survophthal.2019.06.001
3. Hammond VM. Optic Neuritis. CorePendium. https://www.emrap.org/corependium/?SearchType=%22text%22. Accessed August 4, 2022.
4. Bennett JL. Optic neuritis. CONTINUUM: Lifelong Learning in Neurology. 2019;25(5):1236-1264. doi:10.1212/con.0000000000000768
5. Germann CA, Baumann MR, Hamzavi S. Ophthalmic diagnoses in the ED: optic neuritis. Am J Emerg Med. 2007 Sep;25(7):834-7. doi: 10.1016/j.ajem.2007.01.021. PMID: 17870491.
6. U-M Kellogg Eye Center in Ann Arbor. Relative Afferent Pupillary Defect. YouTube. 20 June 2014, https://www.youtube.com/watch?v=WrNYqNH3b3A.
7. Yee NP, Kashani S, Mailhot T, et al. More than meets the eye: Point-of-care ultrasound diagnosis of acute optic neuritis in the emergency department. The American Journal of Emergency Medicine. 2019;37(1). doi:10.1016/j.ajem.2018.10.001
8. Sinnott JR, Mohebbi MR, Koboldt T. Papilledema: Point-of-Care Ultrasound Diagnosis in the Emergency Department. Clin Pract Cases Emerg Med. 2018;2(2):125-127. Published 2018 Mar 14. doi:10.5811/cpcem.2018.1.36369
9. Nilsson P, Larsson EM, Maly-Sundgren P, et al. Predicting the outcome of optic neuritis: evaluation of risk factors after 30 years of follow-up. J Neurol. 2005 Apr;252(4):396-402. doi: 10.1007/s00415-005-0655-9. Epub 2005 Mar 22. PMID: 15778816.
10. Wilhelm H, Schabet M. The diagnosis and treatment of optic neuritis. Deutsches Ärzteblatt international. 2015. doi:10.3238/arztebl.2015.0616
11. Morrow SA, Fraser JA, Day C, et al. Effect of treating acute optic neuritis with bioequivalent oral vs intravenous corticosteroids. JAMA Neurology. 2018;75(6):690. doi:10.1001/jamaneurol.2018.0024
12. Optic Neuritis Study Group. Multiple sclerosis risk after optic neuritis: final optic neuritis treatment trial follow-up. Arch Neurol. 2008 Jun;65(6):727-32. doi: 10.1001/archneur.65.6.727. PMID: 18541792; PMCID: PMC2440583.