The Eye Care Advocate

A purple-toned watercolor illustration of a person holding a medical penlight horizontally below their eyes. Centered pink text reads: "Introducing Beyond PERRLA: Decoding the Pupil. A course by The Eye Care Advocate."

Why “PERRLA” is Often a Lie: How to Master Effective Pupil Assessments

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by

Jason Searle
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Have you ever seen “PERRLA” written in a patient’s notes, only to realise they are 80 years old and have artificial lenses? Since accommodation (the “A” in PERRLA) is physically impossible for a pseudophakic patient, that clinical recording tells us the assessment was likely rushed or “auto-filled”.

Pupil assessment is the bridge between the eye and the brain. It takes 30 seconds, but it tells you more about the patient’s central nervous system than almost any other test in your room. Yet, for many students, it’s a source of anxiety.

Whilst I have produced this FREE Skill Centre article on the pupil, I have developed a course that goes far beyond and fully covers pupil assessment, the pitfalls that go around it and tackles why each one occurs. If you enjoy the free article, please consider the full course. This course moves you past “ticking the box” and turns you into a “Pupil Sleuth”.

Join for Access to Beyond PERRLA: Decoding the Pupil Course Today!

The Only “Lie Detector” in Your Room

Subjective tests rely on the patient’s effort, but the pupils do not lie. When a patient has reduced vision but the back of the eye looks normal, the pupil assessment helps to provide your answer.

  • If there is a Relative Afferent Pupillary Defect (RAPD), the debate is over: there is a problem with the “input train” (the signal going into the optic nerve).
  • If the pupils are normal, the nerve is functioning, and you can look elsewhere for the cause.

Mastering the Swinging Flashlight Test

The most misunderstood part of any assessment is the swinging flashlight test. It is the gold standard for finding an RAPD, but it is a “comparative” test – as you are asking the brain which eye is sending the stronger signal.

If your rhythm is off, you’ll manufacture defects that don’t exist. We use custom diagrams and animations to help you visualise these neural pathways in action, showing you exactly why the pupil “escapes” or dilates when the signal is weak. You’ll learn the “3-second rule” to ensure your timing is as precise as a metronome.

A purple-toned watercolor illustration of a person's face during a pupil assessment. A hand holds a medical penlight (pentorch) near the subject's left eye. The side of the penlight features a pupillary gauge with black dots ranging from 2mm to 7mm, used by clinicians to accurately measure and compare pupil size in millimeters. This is an essential test to determine PERRLA.
The course covers correct pen torch positioning, movement and pupil size measurements to avoid inaccurately recording PERRLA.

Solving the Mystery of Different Sized Pupils

A common mistake is trying to use the swinging flashlight test to diagnose things like Horner’s Syndrome or an Adie’s Pupil. In this course, we clarify the “detective work” required for anisocoria (unequal sizes):

  • The Light-Dark Comparison:
    We teach you why a difference that gets worse in the dark points to a Horner’s (a “dilation” problem), while a difference that is worse in the light points to a 3rd Nerve Palsy or Adie’s (a “constriction” problem).
Alt-text: Adie’s Tonic Pupil Presentation A four-panel purple watercolor illustration titled "Adie's Tonic Pupil, Right Eye," demonstrating clinical findings that deviate from PERRLA: Dim Light: Shows mild anisocoria (unequal pupil size); the right Adie’s pupil is slightly larger than the normal left pupil. Bright Light: Displays increased anisocoria; the normal left pupil constricts significantly, while the right Adie’s pupil remains dilated, failing the "Reactive to Light" portion of PERRLA. Response to Light: A close-up confirming the right pupil’s minimal-to-absent constriction when light is applied directly. Response to Near Target: Demonstrates that the right pupil eventually constricts when focusing on a near object, though the reaction is typically slow or "tonic," showing a dissociation where accommodation is preserved despite a loss of light reflex.
The course allows for understanding the different pupil abnormalities that can arise – and how to differentiate them.
  • The Red Flags:
    We break down the “Do Not Miss” scenarios, such as the painful 3rd Nerve Palsy, which is a potential surgical emergency caused by an aneurysm.
A purple watercolor illustration of a pair of human eyes demonstrating a right Third Nerve Palsy. The affected eye (on the left side of the image) is positioned in a characteristic "down and out" gaze deviation and exhibits a significantly dilated pupil compared to the normal left eye.
A blown pupil in a right CNIII Palsy. This is a major red flag that needs immediate attention.

Avoiding the “Pitfalls” Clinic

Even the best clinical knowledge is useless if your technique is flawed. Our Troubleshooting Clinic covers the 20 most common mistakes, including:

  • The “Glass Eye” Trap:
    How to check if a nerve is working even when the iris is physically unable to move.
  • Accommodation Contamination:
    How to stop the patient’s brain from “cheating” the test by looking at your light.
  • The Dark Iris Defeat:
    Pro-tips for seeing pupil movement in patients with very dark brown eyes.

Learn to stop hoping you don’t find an anomaly and start learning how to hunt for them. This course doesn’t just prepare you for an OSCE; it prepares you for the 1-in-1,000 patient whose life might depend on your 30-second pupil check.

A screenshot of an online learning platform featuring a course titled "Beyond PERRLA: Decoding the Pupil." The course syllabus is organized into four sections: Part 1 covers "The Why" (Wiring & Warning), Part 2 "The How" (The Routine), Part 3 "The 'Abnormal' Pupils," and Part 4 "The Troubleshooting Clinic." Part 4 is expanded, displaying six video thumbnails with purple watercolor backgrounds. These thumbnails include titles such as "The 'Bright Room' Pitfall," "The 'Accommodation' Contamination," "The Dark Iris," "The 'Lazy Swing' Pitfall," "The 'Biased Light' Pitfall," and "The 'Pupillary Escape' Pitfall."
A snapshot of the course. Beyond PERRLA: Decoding the Pupil Course is a comprehensive course delivered through The Eye Care Advocate community. It contains 26 lessons and a quiz at the end to test your understanding and knowledge of the content within.
Join for Immediate Access to this Course

Exclusive Founding Member Offer

Master the pupil assessment skills and join a network of experts dedicated to clinical excellence. Join the community before the end of January 31st 2026, to lock in these lifetime rates:

  • Students: Just £10/month
    (Membership is £15/month from February 1st 2026)
  • Professionals: Just £20/month.
    (Membership is £30/month from February 2026)
Join the Community Today

This includes access to our Beyond PERRLA: Decoding the Pupil course, the “Ret Mess to Ret Success” course, “The Student Blueprint”, as well as member benefits, access to a supportive community, a daily picture/word quiz, access to all online events, support from Jason (The Eye Care Advocate) and digital access to the popular textbook “History and Symptoms: The Eye Examination”.

This community provides exceptional value for money and resources, case studies and other learning/supporting resources are being added constantly. Lock in your membership before February to secure that Founding Member offer and join over 30 other members working towards a better, more resilient future in eyecare.

Just want the course?

Want just the access to the course and none of the other benefits of the community? You can sign up for lifetime access to this individual course here for a standalone fee of £30.00.

Beyond PERRLA Course Only = £30.00 One Time Purchase

Frequently Asked Questions

Is this just for students preparing for OSCEs?

While this is an essential resource for university and pre-reg OSCE preparation, it is designed for every Eye Care Professional (ECP). Whether you are a newly qualified optometrist or a seasoned professional, the course helps you sharpen your clinical “lie detector” and ensures your recordings are accurate and professionally resilient.

How do I access the course?

You have two ways to access the “Beyond PERRLA” course:

One-Time Purchase: If you prefer not to join the community, you can purchase lifetime access to this specific course for a one-time payment of £30.

The Eye Care Community: Membership gives you full access to this course, plus “Ret Mess to Ret Success,” “The Student Blueprint,” and our supportive network. The community will always remain the best value way of accessing the courses on The Eye Care Advocate.

Why should I join the community instead of buying the course individually?

Joining the community offers the best value. For less than the cost of the one-time purchase, you get a month of access to everything—including the digital version of the “History and Symptoms” textbook, live events, and direct support from Jason. Plus, if you join before January 31st, 2026, you lock in your Founding Member rate for life.

Can I cancel my membership?

Of course. While we aim to be the network you need for your entire career, you have full control over your membership. However, remember that if you cancel, you will lose your exclusive Founding Member price lock if you decide to rejoin later.

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