Introduction

Tunnel vision is a type of visual field defect, a narrowing of the visual field. It is defined as the loss of the peripheral visual field, leaving only the central visual field for an individual. Several conditions, such as glaucoma, retinitis pigmentosa, or papilloedema, cause tunnel vision. Individuals with tunnel vision can experience difficulties with daily tasks; therefore, their quality of life is impacted. Early diagnosis is crucial to supporting individuals with appropriate treatment and management options. 

This article explains the diagnostic test that an individual may undergo in identifying tunnel vision.

Purpose of diagnostic tests

Diagnostic tests are essential to confirm the type and severity of peripheral visual field loss, the affected eye or eyes. The test results can support a clinical team for additional tests required to diagnose the underlying condition. This can support a clinical team to devise an appropriate treatment plan for the individual.

Visual field testing

To detect tunnel vision, an individual undergoes a visual field test to identify the visual field defects. Various types of visual fields can be used to identify a visual field defect.

A visual field test can be conducted with both eyes open or each eye separately. For individuals suspected of suffering from tunnel vision, the test is conducted for each eye separately to confirm the visual field defect.

During a visual field test, an individual is required to keep their eye fixed on a central target.^1,2 The assessment tells how well an individual can appreciate objects in their peripheral visual field and central visual field whilst maintaining fixation.²

When testing each eye separately, a visual field test can assess up to 30 degrees in the central vision, up to 60 degrees upwards and nasally, 100 degrees temporally, and 80 degrees downwards.⁴ The blind spot is positioned 10-20 degrees temporally from the central fixation point.⁴

1. A humphrey visual field (HVF) is used with automated static perimetry. This is where an individual’s visual field is mapped using a static stimulus.

The individual is asked to place their chin on a chin rest facing a lit-up dome-shaped bowl.^1,2,3 The individual is asked to fixate on a small static target at the back of the lit-up dome bowl, one eye is covered, and the individual is given a buzzer in their hand.

The individual is asked to press the buzzer when they see a white light in their visual field whilst maintaining fixation on the central target at the back of the dome. There are several subtests that a clinical team can order on the HVF.^1,2,3

• An HVF 24-2 is where an individual’s visual field is examined 24 degrees temporally and 30 degrees nasally
• An HVF 30-2 is where an individual’s visual field is examined 30 degrees temporally and nasally
• An HVF 10-2 is where an individual’s visual field is examined 10 degrees temporally and is focused on the central visual field

2. Kinetic perimetry can be conducted via a Goldman visual field test. This is where an individual’s visual field is mapped per eye by a clinician trained in perimetry using a moving stimulus.¹³

The individual’s chin is placed on a chin rest, one eye is covered, and the patient is asked to look into a lit-up dome-shaped bowl.^12,13 The individual is asked to fixate on a small static target and given a buzzer in their hand.

The clinician moves a white light across the dome in different directions, using different light intensities and stimulus sizes.^12,13 The individual is asked to press the buzzer when they see the white light in their visual field while maintaining fixation on the central target at the back of the dome.

3. An Amsler grid is a printed grid on a small piece of paper with a small black dot in the centre of the grid. An individual can use this to monitor any changes in their central vision.¹⁰

An individual is asked to cover one eye at a time and fixate on the central dot. While holding fixation, the individual is asked to report if there are any grid lines that are missing, wavy, blurred, or different to the previous examination.

This is a common test that is used for individuals who have lost peripheral vision and only have central vision remaining.¹⁰

4. Electroretinography is an examination in which an individual’s retinal light sensitive cells can be assessed to see how well they respond to stimulus.⁹ For the examination an individual would require eye drops to dilate their pupils and drops to numb their eyes. A small device would be used to keep the eyelids open until the examination ends.⁹

In the test, an electrode is placed on the front surface of the eye whilst the individual looks at a pattern of flashing lights. The electrode records the retinal activity to decipher how well it reacts to the stimulus.⁹

5. The confrontation visual field test is a quick method a clinician can use to assess the visual field defect.¹¹ The clinician asks the individual to cover one eye at a time and focus on a specific part of the clinician’s face directly (e.g. the clinician’s nose).

The clinician then will proceed to hold up fingers in different areas of an individual’s peripheral vision and ask them to identify the finger in their vision. This examination is not considered as accurate as other visual field tests, described earlier.¹¹

Additional diagnostic tests

Many diagnostic tests a clinical team may suggest for an individual to undertake to identify the underlying root cause of the tunnel vision identified on the visual field test. 

1. Optical coherence tomography (OCT) is used to produce cross-sectional imaging of the retinal layers. This enables clinical teams to detect any retinal abnormalities and track the progress of these abnormalities related to visual field loss⁵
2. Fundoscopy is where an individual’s retina and optic disc can be assessed for any abnormalities related to the tunnel vision visual field defect using a tool called an ophthalmoscope⁸
3. Colour vision tests can aid in detecting an individual’s difficulty in perceiving specific colours related to a visual field defect⁷ 
4. Contrast sensitivity can measure an individual’s ability to detect objects against backgrounds of a similar colour⁶

Reviewing results 

Clinical teams, specialised in ophthalmology, can support in reviewing the results of diagnostic tests. The combination of a visual field test and additional related tests can help the team narrow down diagnoses and understand the underlying root cause of tunnel vision.

Once a condition is diagnosed the clinical team can provide appropriate care. The clinical team can also utilise diagnostic tests to help monitor the eye condition to support an individual’s care. 

Summary

To summarise, individuals with tunnel vision experience a loss of peripheral visual field leaving only a central visual field; it can be caused by several conditions. Visual field loss can impact patient’s quality of life, including daily activities. Many techniques and tests, viz. Humphrey visual field (HVF), kinetic perimetry, Goldman visual field test, Amsler grid, electroretinography, optical coherence tomography (OCT), and fundoscopy are used to confirm tunnel vision. An individual must undergo diagnostic tests to identify visual field defects for clinical teams to support the individual with appropriate treatment and management options.