How to Test Visual Fields With a Penlight

The visual field test measures how well an individual can look straight ahead but still use her peripheral vision. This test helps to diagnose many disorders, including brain disorders, optic nerve problems and vision disorders. A narrowing visual field is an early sign of glaucoma. Today optometrists will use machines to perform the visual field test but you can also do it more informally by using a penlight.

Things You'll Need

• Eye patch
• Penlight
• Black paper
• Tape

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Instructions

• 1

  Have the patient close her left eye. To ensure that the left eye is completely closed, cover the eye with an eye patch or the patient's left hand.

• 2

  Instruct the patient to stare straight ahead in space. Tape a piece of black paper on the wall for him to focus on.

• 3

  Stand in front of the patient but slightly to one side. Avoid standing in the spot where she is staring. Stand so you are facing the patient.

• 4

  Hold the penlight in your hand. Raise your arm so it is fully extended to the side but at the patient's eye level: about 50 cm in front of the patient.

• 5

  Turn the light on and move the light from the side into the central spot where the patient is staring. Have the patient raise her hand when she can see the light. At this point, stop moving the light and turn it off.

• 6

  Repeat the light movement in Step 5 for all sides; left, right, top and bottom. Perform the test on the right eye followed by the left eye. Make a note of the distance when the patient raised her hand.

• 7

  Compare the results with those of patients with perfect eyesight. Individuals who have a narrow visual field or do not see the light in one spot may have an eye disorder such as glaucoma. Further tests are needed for a conclusive diagnosis. The wider the visual field, the better your eyesight.