What is the Humphrey visual field test?

The most common field test for glaucoma uses a computer called the Humphrey visual field analyser, which projects a series of lights that flash on and off one at a time to find the dimmest light you can see. You sit with your forehead and chin against the rests and keep looking at the central orange dot throughout the test, pressing a buzzer whenever you notice a spot of light. The lights appear randomly at different angles, sizes and brightness, and the other eye is then tested. Some lights are bright and some very dim, so periods without seeing any lights are normal. Blink normally (best just after pressing the button), let the technician know if you cannot see the lights or they are out of focus, and alert them if you need help. The test is not designed to assess whether your vision is good enough to drive.