Sudden vision loss? Why doctors say it could be an early sign of multiple sclerosis

Vision problems are often dismissed as simple eye strain, fatigue, or the need for a new pair of glasses. But in some cases, sudden blurred vision, pain behind the eyes, or difficulty seeing colours may signal something far more serious happening deep within the nervous system. Doctors warn that optic neuritis - an inflammation of the optic nerve - can sometimes become one of the earliest warning signs of multiple sclerosis (MS), a chronic autoimmune disease that affects the brain and spinal cord.

Multiple sclerosis occurs when the body’s immune system mistakenly attacks myelin, the protective covering surrounding nerve fibres. This damage disrupts the communication between the brain and different parts of the body, affecting functions such as movement, sensation, balance, and vision. Since the optic nerves are also covered by myelin, vision-related symptoms may appear early in the course of the disease, even before other neurological signs become noticeable.

Globally, the burden of multiple sclerosis has been steadily rising, with estimates increasing from nearly 2.2 million cases in 2016 to around 2.8 million in 2020. Health experts say optic neuritis is considered one of the most significant early indicators of MS, making timely recognition extremely important for early diagnosis and treatment.

We spoke to Dr B. K. Madhusudhan, Lead Consultant – Neurology at Aster RV Hospital, to understand how optic neuritis is linked to multiple sclerosis, the symptoms people should not ignore, and why early medical attention can make a difference.

Why optic neuritis can become the first warning sign of MS

Dr Madhusudhan explained that optic neuritis develops when the optic nerve - responsible for carrying visual signals from the eye to the brain - becomes inflamed. In multiple sclerosis, the immune system mistakenly attacks myelin, the protective sheath surrounding nerve fibres, disrupting nerve communication.

“When this inflammation affects the optic nerve, visual symptoms may appear even before other neurological signs of multiple sclerosis become obvious,” Dr Madhusudhan said.

He added that for some patients, sudden vision disturbances may be the very first indication that inflammatory damage is occurring within the central nervous system.

Symptoms people should never ignore

Dr Madhusudhan noted that optic neuritis commonly affects young adults between the ages of 20 and 40 years and is seen more frequently in women, mirroring the broader trend observed in multiple sclerosis.

He said patients often experience sudden or rapidly worsening vision loss, usually in one eye, though both eyes may occasionally be involved. Vision may appear blurry, dim, foggy, or washed out.

“One of the hallmark symptoms is pain behind the eye, particularly during eye movement,” he explained.

Apart from reduced vision, many patients also report difficulty distinguishing colours, especially red shades, along with reduced contrast sensitivity.

Dr Madhusudhan stressed that optic neuritis should never be dismissed as a routine eye issue, especially in younger individuals with no previous history of eye disease.

“In nearly 15 to 20 per cent of multiple sclerosis patients, optic neuritis may be the first clinical event,” he said. “At the same time, a single episode does not automatically confirm MS, but it does significantly increase future risk, particularly if MRI scans reveal demyelinating lesions.”

Why early diagnosis and MRI evaluation matter

Dr Madhusudhan emphasised that diagnosing optic neuritis requires both neurological and ophthalmological assessment, as several conditions can mimic similar symptoms.

He explained that MRI scans of the brain and orbit play a crucial role because they can identify inflammation along the optic nerve and detect silent demyelinating lesions elsewhere in the brain that are suggestive of multiple sclerosis.

“Visual evoked potential tests may also be used to measure how quickly the brain responds to visual signals, while blood investigations help rule out infections and other autoimmune disorders,” he said.

He further highlighted the role of cerebrospinal fluid (CSF) analysis in selected cases.

“CSF testing can detect oligoclonal bands, which may indicate abnormal immune activity linked to multiple sclerosis. It also helps exclude infections and other neurological conditions that can resemble optic neuritis,” Dr Madhusudhan explained.

Treatment, recovery, and the emotional impact

According to Dr Madhusudhan, high-dose intravenous corticosteroids are commonly used to reduce optic nerve inflammation and accelerate visual recovery.

“Most patients recover a substantial part of their vision over weeks to months, although some may continue to experience reduced contrast sensitivity or difficulty seeing in low light,” he said.

He added that patients showing MRI findings suggestive of multiple sclerosis may require disease-modifying therapies (DMTs) to reduce future relapses and slow disease progression.

“Early intervention is becoming increasingly important in MS care because timely treatment may delay long-term disability and improve neurological outcomes,” he noted.

Beyond the physical symptoms, Dr Madhusudhan also highlighted the emotional burden associated with sudden vision loss.

“Many patients experience anxiety, fear, and uncertainty, especially when visual symptoms appear unexpectedly in otherwise healthy young adults,” he said.

He stressed that prompt medical attention for unexplained vision changes can help not only in managing optic neuritis early but also in identifying multiple sclerosis at a stage where treatment and rehabilitation may be more effective.

This story is done in collaboration with First Check, which is the health journalism vertical of DataLEADS