Optic Neuritis Presenting with Painful Monocular Visual Loss in a Young Adult: A Case Report

Abstract

Optic neuritis is an acute inflammatory optic neuropathy characterized by visual dysfunction, often accompanied by pain that worsens with eye movement. It commonly affects young adults and may represent the initial clinical manifestation of an underlying demyelinating disorder, particularly multiple sclerosis. We report the case of a 26-year-old woman who presented with painful loss of vision in one eye, with worsening pain during eye movements. She also reported previous episodes of numbness involving both legs, raising suspicion for a previous demyelinating neurological event. The clinical presentation was highly suggestive of optic neuritis. Typical examination findings include reduced visual acuity, impaired color vision, a relative afferent pupillary defect, and either a normal optic disc or optic disc swelling. Magnetic resonance imaging of the brain and orbits with contrast is an important investigation because it can demonstrate optic nerve enhancement and associated demyelinating lesions. This case highlights the importance of recognizing the characteristic clinical presentation of optic neuritis and evaluating young patients for an underlying demyelinating disorder.

Introduction

Optic neuritis is an acute inflammatory disorder of the optic nerve that commonly presents with unilateral visual impairment in young adults. It is an important cause of acute visual loss in this age group and may occur as an isolated inflammatory condition or in association with neurological diseases such as multiple sclerosis (MS), neuromyelitis optica spectrum disorder (NMOSD), and myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD).

The classical presentation includes acute or subacute monocular visual loss, reduced color perception, and pain that is characteristically aggravated by eye movement. A relative afferent pupillary defect may be present in unilateral or markedly asymmetric disease. The optic disc may appear normal, particularly in retrobulbar optic neuritis, or may demonstrate optic disc swelling.

The association between optic neuritis and multiple sclerosis is particularly important because optic neuritis may precede the development of clinically definite MS. Magnetic resonance imaging (MRI) of the brain and orbits with contrast is therefore an important component of the diagnostic evaluation. MRI can demonstrate optic nerve inflammation as well as white-matter lesions suggestive of a demyelinating disorder.

We report a case of a young woman presenting with the classic clinical features of optic neuritis and a history suggestive of previous neurological episodes, emphasizing the importance of recognizing optic neuritis as a possible early manifestation of a demyelinating disease.

Case Report

A 26-year-old woman presented with painful loss of vision in one eye, with the pain becoming more pronounced during eye movements. The patient reported a history of previous episodes of numbness involving her legs. The combination of acute monocular visual loss, pain associated with eye movement, and previous neurological symptoms raised clinical suspicion of an inflammatory demyelinating disorder involving the optic nerve.

The patient had no specific ocular history provided in the available clinical vignette. The presentation was considered characteristic of optic neuritis, particularly given her young age and the associated neurological history.

Ophthalmic evaluation in suspected optic neuritis typically demonstrates decreased visual acuity and impaired color vision, particularly red desaturation. A relative afferent pupillary defect, commonly referred to as a Marcus Gunn pupil, may be present when the disease is unilateral. Examination of the optic disc may reveal either optic disc swelling or an apparently normal optic disc in cases of retrobulbar optic neuritis.

Based on the characteristic clinical presentation, a provisional diagnosis of acute optic neuritis, with possible underlying demyelinating disease, was made.

Investigations

Further investigation with MRI of the brain and orbits with contrast is indicated in this clinical setting. MRI may demonstrate enhancement of the affected optic nerve and can identify additional demyelinating plaques within the brain. The presence and distribution of characteristic white-matter lesions can help determine the likelihood of an underlying multiple sclerosis diagnosis.

Visual evoked potentials (VEP) may demonstrate delayed conduction along the optic pathway and can provide supportive evidence of optic nerve dysfunction. In patients with atypical presentations, additional investigations may include cerebrospinal fluid analysis and serological testing for alternative inflammatory or demyelinating causes, including AQP4-IgG and MOG-IgG.

Management and Outcome

Treatment of acute optic neuritis depends on the severity of visual dysfunction and the underlying cause. For typical acute demyelinating optic neuritis, high-dose corticosteroid therapy can accelerate visual recovery, although it does not substantially improve long-term final visual outcomes in otherwise typical cases. The Optic Neuritis Treatment Trial demonstrated faster visual recovery following intravenous methylprednisolone compared with placebo, while oral prednisone alone at the studied dose was associated with an increased risk of recurrent optic neuritis.

A commonly used acute treatment approach is high-dose intravenous methylprednisolone followed by an oral corticosteroid taper when clinically indicated. Treatment should be individualized according to the severity and clinical context.

Because this patient had previous episodes of leg numbness, neurological evaluation and assessment for multiple sclerosis or another demyelinating disorder would be particularly important.

Follow-up

Long-term follow-up is important in patients presenting with optic neuritis, particularly when there are additional neurological symptoms suggestive of a demyelinating disorder.

Follow-up should include:

• Assessment of visual acuity
• Color vision testing
• Visual-field assessment
• Pupillary examination
• Optical coherence tomography when appropriate
• Neurological evaluation
• MRI surveillance when clinically indicated
• Assessment for subsequent neurological or visual episodes

If MRI demonstrates characteristic demyelinating lesions, the patient may require further neurological evaluation for multiple sclerosis and consideration of disease-modifying therapy according to the overall diagnostic criteria and clinical course.

Discussion

Optic neuritis is a clinically important inflammatory optic neuropathy that frequently affects young adults. The combination of unilateral visual loss and pain aggravated by eye movement is particularly characteristic and should immediately raise suspicion for optic neuritis.

The patient in this case was a 26-year-old woman who presented with the classic symptom complex of painful monocular visual loss. The additional history of previous episodes of leg numbness is clinically significant because it suggests that the optic nerve episode may not be an isolated ocular event. Instead, it raises the possibility of previous neurological involvement as part of a central demyelinating process.

Visual dysfunction in optic neuritis may include decreased visual acuity, impaired color discrimination and visual-field defects. Red desaturation can be particularly useful clinically. A relative afferent pupillary defect is expected when unilateral optic nerve dysfunction is sufficiently asymmetric. The optic disc may be normal because inflammation can occur posterior to the optic nerve head, resulting in retrobulbar optic neuritis.

MRI plays a central role in evaluating suspected optic neuritis. Contrast-enhanced MRI of the orbits can demonstrate enhancement of the affected optic nerve, while brain MRI may identify lesions characteristic of multiple sclerosis. MRI findings are also useful for assessing the future risk of developing clinically definite MS in patients presenting with a first demyelinating event.

The differential diagnosis of optic neuritis has expanded beyond MS-associated disease. NMOSD and MOGAD can also produce optic neuritis and may have different clinical patterns and treatment strategies. Current evidence emphasizes that treatment should be tailored to the underlying cause. In particular, NMOSD-associated optic neuritis may require urgent escalation therapy, including plasma exchange in appropriate patients who respond inadequately to corticosteroids.

Corticosteroid therapy is primarily used to accelerate recovery from acute visual dysfunction. The landmark Optic Neuritis Treatment Trial showed that intravenous methylprednisolone followed by oral prednisone accelerated visual recovery, but the long-term difference in visual acuity was not substantial. Importantly, oral prednisone alone at the studied conventional dose increased the risk of recurrent optic neuritis and should not be used as the sole treatment for typical acute optic neuritis.

This case therefore emphasizes an important clinical principle: optic neuritis should not be viewed solely as an ophthalmic problem. In a young patient, particularly when accompanied by previous sensory or neurological symptoms, it may represent an early manifestation of a systemic or central demyelinating disorder.

Prognosis

The visual prognosis of typical optic neuritis is generally favorable, with most patients experiencing substantial visual recovery over time. However, the underlying etiology has important implications for recurrence risk, neurological disability, and long-term management.

Patients with optic neuritis associated with multiple sclerosis require appropriate neurological assessment because optic neuritis can represent a clinically isolated demyelinating syndrome or part of established MS. Conversely, atypical or recurrent optic neuritis should prompt consideration of NMOSD, MOGAD, infectious, inflammatory, or other alternative causes.

Regular ophthalmic and neurological follow-up is therefore essential to monitor visual function and identify subsequent neurological events.

Conclusion

Optic neuritis is an important cause of acute painful monocular visual loss in young adults. The characteristic combination of decreased vision, pain worsened by eye movement, impaired color vision, and a relative afferent pupillary defect should prompt consideration of the diagnosis.

In this 26-year-old woman, the history of previous episodes of leg numbness provided an important neurological clue suggesting a possible underlying demyelinating disorder. MRI of the brain and orbits with contrast is an important component of evaluation, particularly when multiple sclerosis is suspected.

Early recognition, appropriate neuro-ophthalmic assessment, MRI evaluation, and timely corticosteroid therapy when indicated can facilitate visual recovery and enable early identification and management of an underlying demyelinating disease.

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