Visual field test

What is a visual field test?

A visual field test is the name given to a specific type of eye test that is designed to evaluate your central and side vision to determine how much you can see around what you’re looking at, also known as your field of vision. It’s painless and takes just a few minutes per eye.

Visual field testing isn’t performed as part of a routine eye exam. Instead, it’s usually recommended if:

• you have a family history of certain eye conditions, such as glaucoma
• you are showing signs of raised intraocular pressure (IOP) or optic nerve disease
• you are experiencing symptoms such as unexplained headaches or blind spots in your vision
• you have underlying health conditions which could affect your vision, such as diabetes, high blood pressure or multiple sclerosis.

What is a visual field test also known as?

A visual field test may also be referred to as a peripheral vision test, field vision test, eye field test or perimetry test. If you’re ever unsure about the type of testing being carried out, always ask your medical team to explain it to you.

What are the different types of visual field tests?

There are several different types of visual field tests. The main varieties are:

• Confrontation testing: this refers to a quick in-clinic screening assessment where your examiner checks your side vision by comparing what you can see with what they see.
• Automated static perimetry: the most common type of visual field testing; this uses a machine where you are asked to stare at a central image while lights flash in different places around it. You’re asked to focus only on the image, but to push a button when you can see the lights flash.
• Kinetic visual field testing: instead of flashing lights, this is where your examiner moves a light target from the outer edges of your peripheral vision until you can see it, which is an effective way of mapping the boundaries of your outer vision.
• Frequency doubling perimetry: this test uses flickering, striped patterns to detect certain types of visual field loss. It’s most often used in glaucoma screening.
• Electroretinography: this diagnostic eye test measures the electrical activity of the light-sensitive cells inside your eye (your retina) when exposed to flashes or patterns of light.
• Amsler grid testing: an Amsler grid is a 10x10cm grid pattern with a dot in the centre to monitor your central vision. It’s used to detect distortions, wavy lines or blind spots caused by conditions affecting your macula, which is responsible for the fine details you can see, such as age-related macular degeneration.

What is the difference between a visual field test and other eye tests?

Your vision is extremely complex, and all eye tests and examinations are performed to evaluate a specific part of how you can see. Together, they provide a comprehensive overview of how well all parts of your eyes and vision are working. Visual field testing is the specific test that is used to measure your overall area of vision.

What conditions can a visual field test detect?

Visual field testing is most effective at detecting patterns of vision loss, and in particular, loss of peripheral vision or the development of blind spots. This makes it a reliable tool for identifying a range of conditions, including:

• glaucoma
• stroke, or other problems with the connection between your eyes and brain
• brain tumours and other growths that could be pressing on visual pathways
• diabetic retinopathy, and other diabetes-related eye damage
• macular degeneration
• retinal detachment
• problems with your optic nerve, which is the nerve that sends messages from your eyes to your brain
• neurological disorders, such as multiple sclerosis
• cataracts.

Visual field testing can also be used to assess how much damage to your eyesight may have been done following an eye injury or trauma.

How serious is visual field loss?

Visual field loss has the potential to be very serious, as it can be an indicator that you have damage to your eye, optic nerve or even your brain. It can also make everyday tasks such as walking, reading and driving difficult and unsafe. If you think you may have any issues with your field of vision, you must make an appointment with your optician to discuss your symptoms as soon as possible.

Who is most at risk of visual field problems?

Visual field problems can affect anyone, but you may be at higher risk of developing issues in this area of your vision if you:

• are over the age of 50
• have been diagnosed with a neurological disorder, such as multiple sclerosis, or if you’ve had a stroke
• have a chronic health condition like diabetes or high blood pressure, especially if it's not well controlled
• have a family history of glaucoma or other inherited retinal problems
• have particularly high myopia (short-sightedness).

Your optician or ophthalmologist should tell you if you are at increased risk of issues with your field of vision.

Who is a visual field test suitable for?

Anyone who is suspected of having issues with their visual field, or who has been flagged as having conditions that increase their risk of developing visual field loss can and should undergo visual field testing.

Who may find visual field testing difficult?

Visual field testing requires a significant amount of concentration and can cause visual fatigue, and this means that certain types of people can find completing it challenging. This includes young children, older adults, people with ADHD, anxiety or panic disorders and people on the autistic spectrum1. People with physical limitations may also find it hard to sit in the same position for a sustained period, such as those with severe arthritis, restricted neck mobility or tremors, such as those seen in Parkinson’s disease.

How should I prepare for a visual field test?

There’s no specific physical preparation required for a visual field test, but it’s generally recommended to make sure you attend feeling well rested, as it will require sustained concentration.

If you currently wear prescription glasses, you should bring these with you. Alternatively, if you wear contact lenses, you can wear them. This is because the machine needs to check your corrected, rather than uncorrected, vision.

What happens during a visual field test?

Visual field testing is non-invasive, so there’s no need for anaesthetic. Each eye will be tested separately, so you’ll be asked to wear a patch over the other. You’ll be asked to sit at a machine and place your chin onto one rest, with your forehead against another. This puts your head into the correct position and keeps it secure.

You’ll be asked to focus on a target which will be in the centre of your field of vision. It’s essential that you stare directly at this target (you can blink) and not follow the flashes with your eyes. You’ll be given a small handheld device with a button on the top and told to press the button every time you notice a flash of light. Some flashes will be bigger, smaller or brighter than others, and you should push the button every single time.

The test usually takes between 5 and 10 minutes per eye.

What happens after a visual field test?

After a visual field test, the results will be sent to your examiner for review. Your optician or ophthalmologist can then discuss them with you and make recommendations for treatment if they feel that any is needed.

What happens if my visual field test result is abnormal?

If your visual field test shows that you have missing or reduced vision, several things could happen. Firstly, the test may be repeated to ensure that the results remain the same after the second test, to rule out tiredness or other external factors that could cause inaccuracies.

If the initial test was accurate, you may be referred for further examinations and assessments to determine the cause of your vision loss. These can then be used to give you an accurate diagnosis and create a treatment plan that focuses on restoring your vision (if possible) and/or preventing any further vision loss.

Can I drive after a visual field test?

Yes. Your eyes may feel a little tired, but there’s no reason you will be unable to drive.

Limitations of visual field testing

Visual field testing is the gold standard test used for evaluating the field of vision, but like any human test, it can be affected by several factors, and these can impact its accuracy.

Some of these factors include:

• Whether it’s your first or a subsequent test. Studies show that people tend to do better on later tests as they’ve learned what to expect and how to respond.
• Poor concentration, due to tiredness or cognitive disorders.
• Inability to sit still, as moving your head can affect your results.
• Having certain eye conditions, such as cataracts, as these can affect how much light reaches your retina. This could mean that missed flashes are due to cataracts rather than generalised visual field loss.

It’s also important to note that mild field loss can be normal for some people and is not always indicative of an eye disease.

How accurate is a visual field test?

Visual field testing is considered one of the most accurate ways to determine loss of visual field.

How much does a visual field test cost at Nuffield Health?

For pricing information, please contact your local hospital. The hospital or your healthcare team will give you a fixed all-inclusive price for the treatment following your initial consultation.