Eye pain, especially when associated with blurred vision or reduced colour vision, may sometimes be a sign of optic neuritis, an inflammatory condition linked to multiple sclerosis. Early diagnosis can help protect both vision and neurological function.
Not all eye pain originates in the eye itself. Optic neuritis can be the first manifestation of multiple sclerosis and may present with pain on eye movement, vision loss, or colour vision changes, explains Dr Shibal Bhartiya.
Dr Shibal Bhartiya is a neuro-ophthalmologist and glaucoma specialist (trained from Dept of Clinical Neurosciences, University of Geneva), and Mayo Clinic Research Collaborator with over 25 years of experience. Her approach focuses on identifying risk before damage is irreversible, simplifying treatment decisions, and protecting vision long-term. Emphasis on early detection, risk assessment, and continuity of care. She is rated 5 stars across 1,500+ patient reviews on Google.
Why Was This Patient’s Eye Pain Actually a Brain Disease?
Ms RM was 23 when her left eye started hurting. The pain was mild at first, a dull ache deep behind the eye. It was worse when she moved her eye to look sideways. She went to a local clinic, where she was told her eye looked structurally normal. No redness, no inflammation visible on the surface, no sign of infection. She was given lubricating drops and asked to return if it worsened. It did not improve. Three days later, she came to me.
Within two days, she said, the vision in that eye had dimmed, as if I am looking through a veil. Colours looked washed out. Reading my phone screen with that eye alone felt like reading through fog.
Her eye examination was almost entirely normal to look at. But her vision had dropped significantly in that eye, and she had pain on eye movement, which is an unusual and specific finding. When I tested her colour vision, she struggled badly with the reds and greens in that eye alone. Her pupil reacted more slowly to light in the affected eye than in the healthy one.
This pattern, pain on eye movement, reduced colour vision, and a sluggish pupil response, pointed to optic neuritis, inflammation of the nerve that carries vision from the eye to the brain. I arranged an urgent MRI of her brain and orbits.
The scan showed changes consistent with demyelination, areas where the protective coating around nerve fibres in the brain was damaged. RM’s eye was never the real problem. Her optic nerve and her brain were.
Patient details have been changed to protect privacy.
What is Optic Neuritis?
This case is one of the clearest examples of why an eye examination is sometimes a neurological examination. Optic neuritis is the first sign of multiple sclerosis in a substantial proportion of young patients who develop it, often years before any other symptom appears. It is also one of the most commonly delayed diagnoses in ophthalmology, because the eye itself looks deceptively normal. Below, I explain how optic neuritis presents, how it differs from other causes of sudden vision loss, and why an MRI is essential once it is suspected.
Quick Answer: Optic neuritis is inflammation of the optic nerve that causes vision loss, often with pain on eye movement, typically in one eye. It commonly affects young adults, especially women, and is strongly linked to multiple sclerosis. Any suspected case requires an urgent MRI of the brain to look for underlying demyelinating disease.
What Optic Neuritis Actually Is and Why the Eye Looks Normal
The optic nerve carries visual signals from the retina to the brain. In optic neuritis, this nerve becomes inflamed, usually because the body’s immune system has attacked the myelin sheath that insulates the nerve fibres. This disrupts the electrical signal travelling along the nerve, which is why vision drops even though the eye structures themselves, the cornea, lens, and retina, remain completely normal on examination.
This is the central reason optic neuritis is so often missed in its first presentation. A clinician examining the front and back of the eye with standard equipment will see nothing wrong, because nothing is wrong there. The damage is happening further back, in the nerve itself, often at a point that cannot be directly visualised without specific imaging.
Three clinical features distinguish optic neuritis from other causes of vision loss, and all three were present in Riya’s case. Pain that worsens specifically with eye movement, rather than constant pain. Reduced colour vision that is disproportionate to the reduction in visual acuity. And a relative afferent pupillary defect, where the pupil in the affected eye responds more slowly to light than the healthy eye. Any clinician trained to look for this triad will suspect optic neuritis quickly, even when the eye looks structurally normal.
The connection to multiple sclerosis matters enormously for what happens next. Studies following patients with a first episode of optic neuritis show that a meaningful proportion go on to develop MS, particularly when the MRI shows lesions in the brain’s white matter at the time of diagnosis. This is why imaging is not optional once optic neuritis is suspected. It changes the entire management plan, not just for the eye, but for the patient’s long-term neurological health.
Optic Neuritis vs Other Causes of Sudden Vision Loss
| Symptom or Sign | What It Suggests | What To Do |
|---|---|---|
| Pain that worsens with eye movement, vision dimming over days | Optic neuritis, especially in a young adult | Urgent ophthalmology assessment and MRI of brain and orbits |
| Sudden painless vision loss in one eye | Retinal vein or artery occlusion, more common in older adults with vascular risk factors | Same-day emergency eye assessment |
| Reduced colour vision out of proportion to blur | Optic nerve pathology rather than a refractive or surface problem | Pupil testing and colour vision assessment by an ophthalmologist |
| Vision loss with headache and tenderness over the scalp | Giant cell arteritis, an emergency in patients over 50 | Same-day assessment and urgent blood tests |
| Vision loss that fluctuates with body temperature or exercise | Uhthoff’s phenomenon, a recognised feature in patients with prior optic neuritis or MS | Neurology referral if not already under care |
| Eye looks completely normal but vision and colour perception are reduced | Optic nerve disease is likely; the problem is not visible on the eye’s surface | MRI brain and orbits, not just an eye examination |
Why This Diagnosis Is So Often Missed
The most significant reason is that the eye examination looks normal. Clinicians and patients both tend to associate eye disease with visible signs: redness, cloudiness, swelling. Optic neuritis produces none of these. The eye looks exactly as it should, which leads many first assessments to conclude there is no eye problem at all.
The second reason is that the initial symptoms can be mild and easily attributed to eye strain, dryness, or fatigue. Riya’s earlier description, a dull ache and slightly dimmed vision, could plausibly be dismissed as tiredness or screen strain in a young, otherwise healthy woman. The specific detail that distinguishes it, pain worsening with eye movement, is easy to overlook unless directly asked about.
The third reason is that connecting an eye finding to a brain disease requires a specific kind of clinical reasoning that sits between two specialities. An eye doctor without neuro-ophthalmology training may treat the optic nerve finding in isolation. A general physician seeing eye pain may not think to examine pupil reactions or colour vision at all. The diagnosis lives precisely at the intersection of ophthalmology and neurology, which is exactly where it is most easily missed.
When To See a Specialist
Seek urgent assessment from an ophthalmologist or neuro-ophthalmologist if any of the following apply:
- Vision loss in one eye developing over hours to days
- Pain that is worse specifically when you move your eye
- Reduced colour vision in one eye, even if your overall vision seems only mildly blurred
- You are a young adult, particularly a woman between 20 and 45
- Vision loss with no visible redness or surface change in the eye
- Symptoms that fluctuate with heat, fever, or exercise
This presentation should be treated as urgent. An MRI arranged within days, not weeks, gives the clearest picture of what is happening and whether further neurological evaluation is needed.
This page is part of the Neuro-Ophthalmology hub. Read about our full approach to neurological vision conditions. Some vision problems are not eye problems. They are brain problems, nerve problems, or vascular problems, that show up in the eye first. Also read about optic nerve disease, raised intracranial pressure, Vision not clear but tests normal, double vision, and conditions where no diagnosis has yet been reached.
Frequently Asked Questions
Does optic neuritis always mean I have multiple sclerosis?
No. Not everyone with optic neuritis develops MS, but it is one of the most common first presentations of the disease. An MRI helps determine individual risk.
Will my vision recover after optic neuritis?
Most patients regain significant vision within weeks to a few months, often with treatment such as corticosteroids. Some residual changes in colour vision or contrast sensitivity can persist.
Why did my eye look normal even though my vision was affected?
Optic neuritis affects the nerve carrying visual signals to the brain, not the visible structures of the eye itself. This is why a standard eye examination often shows no abnormality.
How soon should I get an MRI after a diagnosis of optic neuritis?
An MRI of the brain and orbits should be arranged urgently, ideally within days of diagnosis, as it guides both treatment and longer-term monitoring. [LINK: neuro-ophthalmology hub]
Book a Consultation
If you are experiencing vision loss with pain on eye movement, particularly alongside reduced colour vision, this needs urgent specialist assessment rather than a routine eye check. The eye may look entirely normal while the real problem lies further back along the visual pathway.
At Dr Shibal Bhartiya Eye Clinic, Gurugram, assessment for suspected optic neuritis includes detailed neuro-ophthalmic examination, pupil testing, and coordination of urgent MRI imaging. [LINK: comprehensive eye exam]
[Book an Appointment → www.drshibalbhartiya.com | +91 88826 38735]
About the Author
This article was written by Dr Shibal Bhartiya, fellowship-trained glaucoma specialist and Mayo Clinic Research Collaborator, Clinical Director at Marengo Asia Hospitals, Gurugram, known for ethical, patient-centred glaucoma care and independent glaucoma second opinions. She is also the Program Director for Community Outreach & Wellness; and for the Marengo Asia International Institute of Neuro and Spine.
She has published peer-reviewed research on glaucoma management, examining how treatment decisions should balance medical evidence, patient preferences, and long-term vision outcomes.
As Editor-in-Chief of Clinical and Experimental Vision and Eye Research and Executive Editor of the Journal of Current Glaucoma Practice (Pubmed Indexed, official journal of the International Society of Glaucoma Surgery), Dr Shibal Bhartiya brings editorial and research depth to every clinical decision. Her 200+ publications, including 90+ PubMed-indexed publications and 28 edited textbooks span glaucoma biology, surgical outcomes, health equity, and emerging diagnostics.
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