Visual Field Testing

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What is this information about?

This leaflet is for patients or carers of patients who have been referred for a visual field test at University Hospitals Sussex NHS Foundation Trust. It explains what the test is, why it is needed, and what to expect. 

Why have I been given this leaflet?

You have been given this leaflet because you, or someone you care for, needs a visual field test. This leaflet will help you understand why the test is important and how it is done. 

What is a visual field test?

A visual field test checks how well you can see around you, especially your peripheral (side) vision. During the test, you will look straight ahead and press a button every time you see a flash of light. 

What is field loss and why does it matter?

Field loss means there are areas in your peripheral vision where your sight is reduced or missing. Testing your visual field helps detect conditions like glaucoma, which, if untreated, can severely reduce your vision. 

How long will the test take?

The test usually takes between three and five minutes for each eye, but this may vary depending on your responses and the type of test used. 

How often will I need the test?

Most patients have the test every six to twelve months. Research shows this is a good interval to detect any changes or worsening of your vision. 

What is a normal result?

Normal visual fields depend on your age, as our vision sensitivity reduces as we get older. Your test results will be compared to normal results for people your age to see if there is any loss. 

Are there other ways to test peripheral vision?

Currently, visual field testing is the best method available. Newer tests are faster and less tiring. If you feel anxious about the test, tell the clinician. They may pause the test or give you more time. 

Why do I need this test?

Visual field tests are often done for people with glaucoma or suspected glaucoma. Other conditions like stroke, droopy eyelids, or neurological issues may also require this test. Your doctor or clinician will explain why you need it. 

My vision is good but I have field loss, why?

You might not notice mild field loss because central vision can remain clear. Also, the loss usually happens slowly, and the brain adapts, especially if only one eye is affected. 

I have 20 / 20 vision: why can’t I drive?

Even if your central vision is good, loss of peripheral vision can make driving unsafe. You might miss hazards coming from the side. If a doctor advises you not to drive, you must stop driving and inform the DVLA. Driving against this advice puts you and others at risk. 

Can cataracts cause field loss?

Yes, some eye conditions like cataracts can cause field loss. When your test results are reviewed, your doctor will consider possible causes. 

If I have field loss, does that mean I have glaucoma?

Not necessarily. The field test is only one part of the overall assessment needed to make a diagnosis. 

Why can’t I wear glasses during the test?

Glasses frames can block part of your peripheral vision. The machine will use lenses inside the device to correct your vision for the test. 

I had this test at my optician. Why do I need it again?

Even if you recently had a test at your optician, the hospital test might use different equipment or settings. For consistency and accuracy, the hospital prefers to do its own test. 

Why do I have to cover one eye?

Sometimes the test is done with both eyes open, usually for DVLA driving assessments. In most cases, each eye is tested separately to check their individual condition. 

I was told I did not do the test correctly. How do you know?

The machine monitors how well you follow instructions. It detects if you move your eyes too much or press the button when no light appears. If the test is not done properly, the results are unreliable. Please ask the clinician to explain the test again if you are unsure. 

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