Overview

A traumatic brain injury (TBI) can happen when someone receives an external force to the head that is so impactful it disrupts normal brain function.¹ This can be from a fall, a car accident, or a sports collision. Each year, millions of people sustain such injuries worldwide, ranging from mild concussions to severe trauma that can permanently alter cognitive functions. In fact, globally, there were an estimated 20.8 million new cases of TBI in 2021, with around 38 million people living with the ongoing effects of a previous injury.²

TBI can impair an individual’s cognition, behaviour, personality, and sensorimotor function.³ Additionally, because around a third of the human brain is involved in processing vision, and most of the sensory information our brain receives comes from our eyes, the visual system is particularly vulnerable to such injuries.⁴

Many TBI survivors experience visual difficulties, such as:

• Double vision
• Dizziness
• Partial sight loss
• Reading difficulties³ 

One particularly distinct symptom is tunnel vision. The term might sound familiar as a metaphor for being narrow-minded, but it originates from the condition in which peripheral vision is restricted, leaving the affected individual with only a narrow view straight ahead in their line of sight. Tunnel vision isn’t just a problem of the eyes: it reflects broader changes in how the brain processes visual information after injury.

What is tunnel vision?

Tunnel vision, or visual field constriction, is a real and measurable consequence of TBI. The eye struggles to process information efficiently from the edges of the visual field, particularly when the brain is under cognitive load, for example, when attention is divided between tasks.⁵

For those who experience it, the world appears as though everything is happening through a dark tube; everyday tasks such as driving, reading, or navigating crowded spaces become challenging and disorienting.

Tunnel vision, as a result of TBI, can be temporary or permanent. The first year after a TBI is critical for recovery and functional improvement; however, many of the impairments, including visual field loss, often persist past the one-year mark of their injury.^1,6,7 

Tunnel vision can be caused by eye conditions, such as glaucoma (a disease that damages the optic nerve), but they are recognised consequence of TBI. Tunnel vision occurs in around 18% of patients with TBI, without co-occurring eye injury, suggesting that this condition is also caused by damage further along the neural pathways of the visual processing system.¹ 

How the brain sees

The processing of visual information relies on a complex network that begins with taking in information through the eyes, which is carried through to the brain, where it is processed. This complicated process involves numerous communication pathways and multiple brain regions for comprehensive visual perception.

Light first enters through the eye, which is focused onto the retina: a thin layer of light-sensitive cells residing at the back of the eye. These cells then convert light into electrical signals, which act like messages that are sent via bundles of nerve fibres that form the optic nerves. These signals then go through complicated travel routes and are eventually taken to a structure deep inside the brain called the thalamus, specifically, an area known as the lateral geniculate nucleus. The lateral geniculate nucleus acts as a relay station of information, passing visual messages to the primary visual cortex at the back of the brain in the occipital lobe, where basic shapes, edges, and colours begin to form more detailed pictures.^3,8

The brain then breaks this information down into multiple processing streams that work together: a concept called distributed processing. There are two pathways: one helps us recognise what we are looking at, i.e., faces, objects, and details, and the other helps us locate those objects in space, relative to the self and coordinate movements like reaching for an object. These visual areas also interact with other regions responsible for eye movement and visual focus, ensuring that both eyes work together in collaboration.^1,3,9

Although this is only a snippet of the visual processing system, we can see that vision relies on an intricate processing network. Because of this, damage anywhere along this system (from the optic nerve to the visual cortex) can distort what visual information a person can process, thus affecting their vision. As is the case with many TBIs, the eyes themselves are often found to be healthy, yet the individual has difficulties processing visual stimuli. This points to a problem within the brain.^3,8,9

The neurology of tunnel vision

After a TBI, the force of impact can disrupt the brain's visual network. Even if the eyes are spared, the pathways that carry signals from the eyes to the relevant visual processing structures in the brain can become stretched, bruised, or compressed. TBIs can cause visual field disturbances through trauma anywhere along the visual pathway.^3,10

This can be due to several reasons. TBI can cause intracranial oedema, which is swelling of the brain due to fluid buildup. It can also cause hematoma or haemorrhages, which are pockets of blood that form when vessels are damaged and leak into surrounding tissues, and bleeding in the brain tissue or spaces around it, respectively.^3,10

All of these factors can cause swelling and increased intracranial pressure, which leads to compressed brain tissue and reduced blood flow, which can disrupt the function of brain structures.^3,10

When this happens, the areas responsible for receiving, interpreting, and integrating visual information can be interrupted, as is with tunnel vision. The extent of the impairment often depends on the severity and location of the injury, particularly when the occipital or parietal lobes are affected, as these regions are essential for processing and interpreting visual information.¹¹

In some cases, the problem isn’t necessarily due to trauma to specific brain regions (known as focal trauma), but rather from microscopic tearing of nerve fibres (a condition known as diffuse axonal injury), which is often a product of TBI. Diffuse axonal injury disrupts the communication between visual regions, thus affecting the visual field. Other types of brain injury, such as stroke or oxygen deprivation, can also cause similar effects of tunnel vision if blood flow to these visual processing regions is reduced.^10,11

Every day life with tunnel vision

For those living with tunnel vision after a TBI, tasks that once felt automatic, such as crossing the street, driving, or reading, can become sources of frustration and anxiety. In particular, driving can be dangerous because of the loss of peripheral vision.¹²

Even walking through crowded places such as supermarkets or pavements can be challenging, as it’s easier to bump into obstacles or lose balance in visually complex environments.^3,13 

Reading is another common struggle. Because the eyes move in quick jumps across text, any loss in the visual field can cause skipped lines, the need to re-read, or even make words appear to move or blur.¹³

What makes this even more complicated is that many people with tunnel vision don’t initially realise they’ve lost part of their sight. This is because the brain is remarkably good at “filling in” missing information, creating the illusion of a complete visual image. This can make vision loss harder to detect until it begins to seriously interfere with daily life.^3,14

All of these manifestations together can become very draining and can take a toll on the individual. The combination of reduced independence, safety concerns, and the frustration that comes with it can lead to feelings of anxiety and isolation. Understanding that these problems stem from the brain, rather than just the eyes themselves, can help patients and specialised clinicians work together towards rehabilitation and recovery.

Diagnosis and rehabilitation

Prompt diagnosis of visual and cognitive impairments is crucial for the recovery from TBI, because failure to do so can significantly delay functional recovery and independence. The useful field of view test (UFOV) is a computer-operated test that measures visual information processing and functional peripheral vision. Specialists will also assess peripheral vision deficits with perimeter tests.^1,12

A failure to treat sensorimotor and visual deficits early in the rehabilitation process can delay functional recovery. Treatment of tunnel vision predominantly focuses on helping people adapt rather than restoring lost sight. Tools like prism glasses or mirrors can slightly expand the visible area, while visual scanning training teaches people to move their eyes and head more intentionally to notice what they can’t see in their restricted field of view. While recovery is variable, rehabilitation and adaptive training can help many people regain confidence in their vision and everyday life.³ 

Summary

• TBI can damage the brain’s visual pathways, causing problems like tunnel vision
• Tunnel vision limits sight to a narrow central area due to a brain injury
• It affects daily tasks such as driving, reading, and navigating spaces