PERRLA Eye Assessment: What It Is and How It Works

Medically Reviewed by Whitney Seltman, OD on November 09, 2022
Written by Sharita Hanley
3 min read

You’ve probably had a PERRLA eye exam during a checkup with your doctor or before an eye exam. Your doctor uses it to measure how well your pupils work. It can help point to eye diseases and conditions that can affect your brain and nervous system. The acronym “PERRLA” explains what your doctor measures when they do the test.

“PERRLA” stands for:

Pupils, which are the dark dots in the center of your eyes. They shrink or widen to control how much light gets into your eye. During the test, your doctor will make sure your pupils are in the right part of your eye.

Equal. Your pupils should be the same size. If they aren’t, you doctor will do more tests to find out why.

Round. Healthy human pupils are perfectly round circles.

Reactive to. This refers to how well your pupils react to the next steps.

Light. When there’s too much light, your pupils close a little to protect your vision. To test this, your doctor will shine a bright light in your eyes and watch what your pupils do. If they don’t get smaller, there might be a problem and your results will come back abnormal.

Accommodation. Accommodation is your eyes’ ability to change focus. Healthy pupils dilate when you look at something far away and shrink when you look at things that are near. If yours don’t adjust at all, your test results will show abnormal reaction to accommodation.

The PERRLA test happens in a dim room in three parts.

  1. First, your doctor looks at your pupil and notes if they have an odd shape or size.
  2. Next, they do a swinging flashlight test. They’ll move a small flashlight back and forth in front of your eyes while you look straight ahead. They may do this a few times to see if your pupils react to the light.
  3. Lastly, your doctor will ask you to look at their index finger or a pen. They’ll move it close, far away, and from side to side. As your pupils react, they’ll check how well or poorly they focus.

Abnormal results can mean you have:

Anisocoria, which means that your pupils aren’t equal in size. About 20% of people live with this condition. Most times, it’s physiologic, which means it isn’t related to any underlying health conditions. If there’s more than a 1-millimeter difference in the size of your pupils, it might be a sign of other health issues. Your doctor will do more tests to confirm.

Adie’s pupil syndrome, a neurological disorder that causes your pupil to close slowly instead of quickly when you look at bright lights. One of your pupils will also be larger than the other. If you need treatment, glasses and eye drops can help.

Horner’s syndrome, a rare condition that happens when something interferes with the nerve pathways that connect your brain and your face. It causes a small pupil and a drooping eyelid on one side of your face. The affected pupil will also open slowly in dim lighting and won’t open very much.

Argyll Robertson pupil, a condition that causes small pupils that shrink down to focus on objects nearby, which is normal. But the pupils have trouble closing when exposed to bright light. It can be related to certain diseases like syphilis.

PERRLA is an easy way for your doctor to measure your eye health and pinpoint signs of other conditions. But it does have some limitations. PERRLA doesn’t diagnose a specific condition. It can only give your doctor clues about any disorders you may have. So if you have an abnormal test, your doctor will do more tests.

The test also doesn’t include the actual size and shape of your pupil or how quickly your pupils respond to light or moving objects. These small details can help reveal more accurate results. But PERRLA is a good first test to check for conditions.