Updated on  February 21, 2024
8 min read

What to Expect During the PERRLA Eye Exam

9 sources cited
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The pupil is the dark opening at the center of the eye through which light enters. It can adjust its size according to the amount of light you need for better focus and clearer vision.

Doctors recommend regular eye checkups at least once a year to ensure your pupils and other parts of the eyes are healthy. Several primary tests are conducted during a routine eye exam, including the PERRLA eye test.

In this article, we’ll discuss this standard but important eye test, focusing on the following:

  • Conditions diagnosed using the PERRLA test
  • How PERRLA exam is conducted
  • Interpreting PERRLA results
  • Common queries about PERRLA

What is the PERRLA Eye Exam?

The PERRLA eye exam is a test to assess the health and functionality of your pupils. It examines how well the pupils respond to light and movement.

extreme closeup of female green eyes

PERRLA is an acronym for “pupils are equal, round, and reactive to light and accommodation.” It’s non-invasive, painless, and has no side effects.

How Does the PERRLA Assessment Work?

The test is conducted in a dark room at the doctor’s office. Using the PERRLA system, your eye doctor can diagnose certain health issues, including eye and neurological (nervous system) diseases.1

They check for the following:

  • Pupil equality. How equal the pupils are in terms of size
  • Pupil shape. Normal pupils should be perfectly round
  • Pupil reaction. How pupils react to light (constricting in bright light and dilating in dim light)
  • Pupillary accommodation. How pupil size decreases or increases based on object distance from the eye

This pupillary response test is essential to emergency room patient assessments and routine eye exams.

Why is the PERRLA Eye Exam Necessary?

The PERRLA eye exam helps doctors identify any issues with pupillary dilation and constriction reflexes. Any issues with your pupils can cause vision problems, so the eye exam also enables them to implement appropriate measures to save your vision.

Pupils play an important role in your visual acuity by controlling how much light enters your eyes. The light is focused on the retina, a light-sensitive layer at the back of the eye.

The retina sends the light signals to the central nervous system (brain) for interpretation. This enables you to see and identify objects in your surroundings.

Common symptoms that may necessitate a PERRLA eye exam include:

What Conditions Can the PERRLA Eye Exam Diagnose?

There are many potential causes of pupillary defects. Consult your eye doctor or the emergency room if you notice unusual pupil structure or vision changes.

Eye doctors can use the PERRLA test to diagnose the following health and vision issues:

1. Anisocoria

Anisocoria is when the pupils’ sizes are uneven due to underlying health conditions. It affects about 20% of the population, and symptoms can vary depending on the cause.2

2. Third Nerve Palsy

Third nerve palsy is the dysfunction of the third cranial nerve that controls eye muscle movements.3 The defects affect the constriction of the pupil, the position of the upper eyelid, and the eye’s focusing ability.

A complete third nerve palsy presents with a completely closed eyelid with the eye positioned outward and downward. The eye’s inward and upward movement is impaired.

3. Adie’s Tonic Pupil

Adie’s Syndrome, otherwise known as Adie’s tonic pupil or Holmes-Adie Syndrome, is a neurological condition. It’s characterized by a pupil abnormally dilated at rest and reacting sluggishly to bright or direct light.4

Adie’s tonic pupil usually affects one eye. However, both may be affected too.

4. Horner’s Syndrome

Horner’s syndrome is a nervous system defect. On the affected side of the face, you will see a drooping eyelid, shrunken pupil, and decreased sweating.

Horner’s syndrome may result from a stroke, tumor, or spinal cord injury.

5. Marcus Gunn Pupil

Marcus Gunn Pupil is a visual problem characterized by abnormal pupillary reaction to bright lights. It’s also called a Relative Afferent Pupillary Defect or RAPD.

With this condition, one pupil may constrict while the other eye is exposed to light. However, the constricting pupil may refuse to react when exposed to the same light.

6. Argyll Robertson (AR) Pupil

An AR pupil is a condition indicative of late syphilis.5 It’s characterized by bilaterally small pupils that do not constrict in bright light but do so when accommodating nearby targets (light-near dissociation).

7. Brain Tumor 

A critical symptom of a brain tumor is the dilation of the pupil in one eye. This symptom requires immediate medical treatment.

8. Head or Eye Trauma

Trauma to the head or eye during a car accident or fall can cause severe injury to your ocular system. It can result in enlarged or differently-sized pupils.

9. Increased Intracranial Pressure (ICP)

Increased pressure in the brain due to trauma or an underlying condition can cause one pupil to be dilated or fixed.6 Further deterioration can cause changes in pupillary reactivity and the size of the opposite pupil.

10. Glaucoma

Glaucoma is a condition caused by optic nerve damage. The optic nerve has nerve pathways that transmit light signals from the eyes to the brain. Damage to these nerves causes unequal pupils that do not respond to light.

11. Drug Abuse

Common eye symptoms of drug abuse include drooping eyelids, abnormal pupil size, and nonreactivity of the pupil to light signals. If drug abuse is suspected, the PERRLA eye test can examine pupil function before confirmatory fluid tests are done.7

How is the PERRLA Eye Exam Conducted?

The PERRLA test is a routine test during comprehensive eye exams. This test is done in a dimly lit exam room and involves three parts:

  1. Pupil irregularity check. The eye doctor will examine your pupils for any abnormalities in shape and size
  2.  Swinging light test. The doctor will use a small penlight to illuminate each eye independently and observe the pupils’ reaction to light
  3. Focus check. The doctor will move an object (index finger or pen) close and far away from your eyes and side to side while observing the pupillary reaction and each eye’s focusing ability

The PERRLA eye exam requires no special equipment and can be done in about 5 minutes.

What Do the Results of a PERRLA Eye Exam Mean?

The optometrist will have the results ready immediately after the exam and determine whether your pupils are normal.

In healthy adults, the normal pupil size ranges between 2 to 4 mm in bright light and 4 to 8 mm in less light.8 They are also regularly round in shape and reactive towards light or moving objects. Any significant deviation from these characteristics may indicate a problem. Abnormal PERRLA results may show the following:

  • Unequal pupil size (anisocoria). It may indicate damaged neck blood vessels, brain aneurysms, or cranial nerve damage. It can also be a side effect of medications like anti-nausea or motion sickness. 
  • Sluggish pupil reaction (Adie’s pupil syndrome). It may indicate the presence of an infection, trauma, eye surgery, tumors, or migraine.
  • Pinpoint pupil and drooping eyelid (Horner’s syndrome). This may indicate a damaged carotid artery, lymphoproliferative disorders, or tumors (neck and lungs)

The PERRLA test cannot detect a specific underlying condition. It also does not measure pupil size, shape, or reaction speed to light and motion. However, it can be a good starting point since it gives your doctor clues about any possible disorders to be investigated further for more accurate results.

Common Treatments for Pupil Defects

If your PERRLA test indicated pupillary abnormalities, your eye doctor may prescribe treatment depending on the underlying condition.

Common treatment options include:

  • Eye drops. Pilocarpine eye drops can support pupil constriction in Adie’s tonic pupil.
  • Prism eyeglasses. These may help relieve diplopia (double vision) symptoms due to a brain tumor, aneurysm, or a stroke. An eye patch can also achieve this.
  • Sunglasses. These are recommended for use outdoors to deal with light sensitivity.
  • Pupil cerclage.9 This surgical technique involves running a suture around the margin of the affected pupil to shrink it. This procedure minimizes stretching of the iris (front colored part of the eye), thus maintaining the desired pupil size and round shape. It can correct abnormally dilated pupils like in traumatic mydriasis or Adie’s tonic pupil.

Common Queries About PERRLA Eye Exam

Below are common questions people ask about PERRLA eye exam:

What does it mean if pupils are not reactive to light or accommodation?

If your pupils are nonreactive to light and accommodation, it may indicate a neurological issue (problem with cranial nerves) or eye disease. Possible causes of an unreactive or non-accommodative pupil include infection, trauma, eye surgery, tumors, or Increased intracranial pressure (ICP). 

Can a PERRLA eye exam detect vision anomalies?

Yes. Healthy pupils play an important role in enabling clear vision. The PERRLA test can detect any abnormalities in the pupils, which can form a basis for your eye doctor to understand the cause of your vision issues.

What preparations are required before the test?

There is no special preparation for the PERRLA test. The test is often done during your routine vision check. Ensure you have all your vision insurance information and arrive on time for your appointment.

Does a normal PERRLA result indicate healthy eyes?

No. Normal PERRLA test results do not necessarily indicate healthy eyes and abnormal results do not indicate a conclusive diagnosis.  Your doctor will discuss the results with you to determine the need for more tests for a more accurate diagnosis.


The PERRLA eye exam is a test to assess the health and functionality of your pupils. It’s quick, non-invasive, painless, and has no side effects.

Using the PERRLA eye test, your eye doctor can assess pupil size, shape, reaction to light, and accommodation. During the test, the doctor will expose your eyes to bright light and examine how your pupils react to light intensity and motion.

The test can help diagnose certain health issues, including eye and neurological (nervous system) diseases. Consult your eye doctor if you notice any changes to your pupil to rule out any serious underlying condition.

Updated on  February 21, 2024
9 sources cited
Updated on  February 21, 2024
  1. Neuro-Visual Disorders.”  Johns Hopkins Medicine.
  2. Anisocoria.” National Library of Medicine, 2023.
  3. Cranial Nerve III Palsy.” National Center for Biotechnology Information (NCBI), 2023.
  4. Xu et al. “Adie’s Pupil: A Diagnostic Challenge for the Physician.” National Center for Biotechnology Information (NCBI), 2022.
  5. Argyll Robertson Pupil.” National Library of Medicine, 2021.
  6. Mader et al. “Initial pupil status is a strong predictor for in-hospital mortality after aneurysmal subarachnoid hemorrhage.” Springer Nature, 2020.
  7. Tennant, F. “The rapid eye test to detect drug abuse.” National Center for Biotechnology Information (NCBI), 1988.
  8. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition,” National Library of Medicine, 1990.
  9. Frisina et al. “Pupil cerclage technique for treatment of traumatic mydriasis.” National Center for Biotechnology Information (NCBI), 2020.
The information provided on VisionCenter.org should not be used in place of actual information provided by a doctor or a specialist.