What is PERRLA eye test? Things to know

The PERRLA test is a comprehensive eye examination that can help healthcare professionals identify a broad range of health issues, like vision problems and some neurological conditions.

People can undergo a PERRLA test as part of a physical exam, in the emergency room, or during a regular eye exam.

Keep reading to learn more, including what PERRLA stands for, how doctors use this exam, and what the results mean.

What does PERRLA stand for?

A healthcare practitioner can use a PERRLA test to identify vision issues.
A healthcare practitioner can use a PERRLA test to identify vision issues.

PERRLA is an acronym that stands for:

P: pupils

E: equal

R: round

R: reactive to

L: light

A: accommodation.

How’s it working out?

The pupil is a hole in the eye centre. The colored portion of the eye looks like a black spot in the iris. Healthy pupils work by dilating to let more light in or restrict to let less light in. These adjustments help a person see under different lighting conditions, and they also prevent eye damage.

A doctor will check, during a PERRLA test, whether the pupils are:

  • Equal: The pupils should be equal in shape and size. If one pupil is larger than the other, this may signal a problem.
  • Round: Healthy pupils are round. If the shape of the pupils is unusual, this could signify an injury to the eye.
  • Reactive to light and accommodation: Healthy pupils get smaller in bright or direct light, as well as when a person focuses on something very close to their eyes.

To evaluate the pupils, the doctor will:

  • look at the eyes and note the shape and size of the pupils
  • shine a light into the eyes to see whether the pupils constrict in response to bright light
  • ask a person to focus on something close to the face to see how the pupils respond

The pupils ‘ actions and appearance are influenced by many factors. Muscle and eye injuries or brain and spinal cord damage may cause irregular PERRLA outcomes. For that reason, doctors often use this examination as a preliminary assessment of neurological injuries as well.

The PERRLA check isn’t a full eye health assessment. This excludes other important steps, such as:

  • the size of each pupil
  • the specific shape of each pupil
  • how quickly the pupils dilate or constrict
  • certain differences between the pupils, such as constricting more quickly or dilating to different sizes

Many guidelines for evaluating PERRLA suggest that the doctors add a dark room dimension to the analysis. Assessing how the pupils dilate in a dark room will make testing pupil activity simpler and this is an significant first check for some brain lesions.

Is it a reliable test?

Some research suggests that the PERRLA exam has become so routine that doctors can either simply look at the eyes and then claim they have finished the examination or fail to fully take care of the findings.

For example, a 2012 study found that 2 percent of people with only one eye documented medical records as having a normal PERRLA outcome. That is impossible, however, because the test requires two equal pupils.

Another 8 percent of reports suggested that PERRLA was just the left or right eye, which is not true since the examination compares the eyes to each other.

Results

The muscles, nerves and brain regions that control the pupils must all function well to get normal PERRLA test results. Consequently, anomalies in the test will signal a wide range of conditions.

A diagnosis of a medical condition based solely on the PERRLA test is not possible in most cases but the test is a good first step in the diagnostic process. The test results can help a physician decide which tests to take next.

Adie syndrome, or Adie tonic pupil, is one of the most common causes of an excessive PERRLA test results. The condition causes one pupil’s abnormal dilation although sometimes both pupils are larger than usual, which can cause bright light pain. There are also poor reflexes in some people with this syndrome, though many have no other symptoms.

Many medical conditions can cause Adie syndrome, including syphilis, damage to the eye and, in rare cases, varicella-zoster infection. But physicians may not be able to identify a cause at times.

The check can also act as a warning sign for severe health conditions. PERRLA’s test results will predict different medical conditions, depending on the results.

Irregular pupil shape

If the pupils are not round, this could indicate:

  • Trauma to the eye: A scratch or other eye injury can damage the muscles in the iris, causing irregularly shaped pupils.
  • Tadpole pupil: This syndrome causes areas of one or both pupils to become larger, sometimes during or after a migraine episode. Doctors think that a spasm in a muscle in the iris causes tadpole pupil.
  • Damage to the midbrain: If the pupils are oval or another odd shape, this may be due to damage to the pupil fibers that attach in the midbrain.

Abnormal constriction or dilation

When the pupils do not constrict or dilate in the way that a doctor would expect, this might be a sign of:

  • Drug misuse: Stimulant drugs, such as cocaine, may cause the pupils to remain dilated, while opioid drugs, such as heroin, may cause very small pupils.
  • Damage to the central nervous system: A brain injury may affect the brain’s ability to either send or interpret signals to dilate or constrict the pupils. Severe head injuries can damage the nerves that help dilate or constrict the pupils.
  • Brain tumors or lesions: For example, when the pupils dilate at different rates, this may be a sign of a tumor or lesion on the optic nerve.
  • Damage to the blood vessels of the brain: Sometimes, an aneurysm presses on a nerve, reducing the ability of the pupils to dilate correctly.

Summary

The PERRLA test is one way of assessing the susceptibility of a person to certain neurological conditions. It may also aid health care professionals in diagnosing eye health problems and eye injuries.

Although this is useful and acts as a good first step in testing for an underlying condition, not all factors are taken into account by the PERRLA test.

Regular results of the PERRLA test do not automatically mean a person is healthy and an abnormal outcome of the test does not allow for a definitive diagnosis.

People who undergo a PERRLA test should discuss the results with their doctor and ask them if further testing could allow for a more precise diagnosis.

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