In a young woman with acute eye pain and no conjunctival redness, what is the most likely diagnosis and what urgent management is recommended?

Acute Eye Pain Without Redness in a Young Woman

The most likely diagnosis is optic neuritis, and urgent management requires immediate ophthalmology referral within 24 hours, visual acuity assessment, and consideration of high-dose intravenous methylprednisolone to accelerate recovery. 1, 2, 3

Most Likely Diagnosis: Optic Neuritis

Optic neuritis is the most common cause of subacute optic neuropathy in young adults and typically presents with the exact constellation described—acute eye pain without conjunctival redness. 2, 3

Classic Presentation Features

• Ocular pain exacerbated by eye movements is the hallmark symptom, occurring in the vast majority of cases and often preceding or accompanying visual loss 1, 3, 4
• Subacute unilateral visual loss developing over hours to days 2, 3
• Absence of external eye redness—the conjunctiva and sclera appear normal, distinguishing this from conjunctivitis, scleritis, or other external eye diseases 5
• Relative afferent pupillary defect (RAPD) on examination—the direct pupillary light reflex is weaker in the affected eye compared to the consensual response 3
• Age and demographics: Most commonly affects young adults, with higher incidence in women 1, 2

Key Examination Findings to Confirm

• Visual acuity testing will typically show decreased vision in the affected eye 3, 5
• Pupillary examination demonstrating RAPD is critical for diagnosis 3
• Fundoscopic examination: One-third of patients have mild optic disc edema, while two-thirds have a normal-appearing disc (retrobulbar optic neuritis) 3
• Pain with eye movements is nearly pathognomonic when combined with visual loss and no external inflammation 1, 4

Urgent Management Protocol

Immediate Actions (Within 24 Hours)

Refer urgently to ophthalmology for comprehensive evaluation including visual field testing, optical coherence tomography, and consideration of neuroimaging. 5 Eye pain with visual changes constitutes a red flag requiring emergency ophthalmology assessment. 6, 7

Acute Treatment Considerations

• High-dose intravenous methylprednisolone (typically 1 gram daily for 3-5 days) accelerates visual recovery but does not improve long-term visual outcome 1, 3
• Treatment should be initiated promptly after diagnosis confirmation, though visual prognosis remains excellent in 95% of cases regardless of steroid use 1, 3
• Oral corticosteroids alone should be avoided as they may increase recurrence risk based on historical trial data 1

Neuroimaging and Multiple Sclerosis Risk Assessment

• Brain MRI with gadolinium is essential to assess risk of progression to multiple sclerosis (MS), as optic neuritis is often the presenting manifestation of MS 1, 3
• Presence of demyelinating lesions on MRI significantly increases MS conversion risk 1, 3
• Consider disease-modifying therapy (interferon-beta or glatiramer acetate) for high-risk patients to reduce MS conversion 1, 3

Critical Differential Diagnoses to Exclude

Atypical Optic Neuritis Requiring Different Management

If any of the following atypical features are present, serologic testing for AQP4-IgG and MOG-IgG antibodies is mandatory: 2

• Severe vision loss with poor steroid response or steroid dependence suggests neuromyelitis optica spectrum disorder (NMOSD) or MOG antibody-associated disease (MOGAD) 2
• Bilateral simultaneous vision loss is uncommon in typical MS-associated optic neuritis 2, 3
• Prominent optic disc edema may indicate NMOSD, MOGAD, or neuroretinitis 2, 3
• Childhood onset or late adult onset (>50 years) suggests atypical etiology 2

Other Serious Causes of Painful Vision Loss Without Redness

• Acute angle-closure glaucoma typically presents with severe pain, halos around lights, and a mid-dilated fixed pupil—requires immediate tonometry 5
• Posterior uveitis can cause pain without external inflammation but usually has visible vitreous or retinal findings on fundoscopy 8, 5
• Scleritis may have minimal external redness initially but causes severe boring pain and requires slit-lamp examination 5

Common Pitfalls to Avoid

• Do not dismiss eye pain without redness as benign—this combination specifically suggests intraocular or retrobulbar pathology requiring urgent evaluation 5
• Do not delay referral waiting for MRI results—ophthalmology evaluation should occur within 24 hours regardless of imaging availability 5
• Do not confuse with conjunctivitis—conjunctivitis causes redness and discharge without significant pain or vision loss 6, 7
• Do not start oral corticosteroids alone—if steroids are indicated, use high-dose intravenous methylprednisolone 1, 3
• Do not miss bilateral cases—always examine both eyes carefully as bilateral optic neuritis suggests NMOSD or MOGAD requiring different treatment 2

Follow-Up and Monitoring

• Visual recovery typically begins within 2-3 weeks and continues for 3-6 months 1, 3
• Long-term ophthalmology follow-up is essential to monitor for recurrence and assess for development of MS 1, 3
• Patients with brain MRI lesions require neurologic follow-up for MS risk stratification and potential disease-modifying therapy 1, 3