Station B: Neurological
Thermometer
Pupillary Assessment
Mission: Perform a cranial nerve assessment to check the brain’s “wiring.”
PART 1: THE PROTOCOL (PERRLA)
Watch the video tutorial above. Then, follow these steps.
The Acronym:
Doctors use PERRLA to remember what to look for. If a patient passes all these tests, their brain stem is healthy.
| Letter | Stands For | The Check |
| P | PUPILS | Are the black centers clear? |
| E | EQUAL | Are they the same size? (>1mm difference is bad). |
| R | ROUND | Are they perfect circles? |
| RL | REACTIVE TO LIGHT | Do they shrink when light hits them? |
| A | ACCOMMODATION | Do they shrink/cross when looking at a close object? |
PART 2: THE PROCEDURE (Instructions)
Pair up. One student is the Doctor, one is the Patient. Use the Penlight.
Step 1: The Pre-Check (Baseline)
Dim the lights (or cup your hand over the patient’s eyes to block ceiling glare).
Measure: Look at the pupils without the penlight. Use the pupil gauge card to estimate their size in millimeters (e.g., 4mm).
Check: Are they Equal and Round?
Step 2: Reaction to Light (The “Swing” Test)
The Approach: Turn on the penlight. Come in from the SIDE (the ear side), not directly from the front. Why? It’s kinder to the patient.
Direct Response: Shine the light in the Right Eye. Watch the Right Pupil. It should snap shut (constrict).
Consensual Response: Shine the light in the Right Eye again, but this time look at the Left Pupil. It should also shrink, even though the light isn’t hitting it! This proves the brain is connecting both sides.
Repeat on the other eye.
Step 3: Testing Accommodation (Distance)
Far: Ask the patient to stare at the wall across the room.
Near: Hold your finger or a pen about 6 inches from their nose. Say, “Focus on my pen.”
The Reaction: You should see Convergence (eyes cross slightly inward) and the pupils should get tiny.
PART 3: CLINICAL NOTES
How to talk like a pro.
1. Documentation
Write the size change as a fraction: Resting / Reactive.
Example: “Pupils were a 4, then went down to a 2. Write 4/2.
2. The Red Flag: Anisocoria
Definition: When pupils are unequal in size (more than 1mm difference).
The Cause: If a patient has just hit their head, and one pupil is “blown” (huge) and doesn’t react to light, it indicates brain swelling or bleeding.1 This is a surgical emergency.
3. Why do we do this?
As the nurse in the video said, this simple 30-second test gives us vital information about the Nervous System, Blood Supply, and Brain Health.
Learn more about Pupillary Assessment
Reflex Test
Test 2: The Patellar Reflex (Spine Check)
Sit: The patient must sit on a high surface (table edge) so their legs dangle freely. If the foot touches the floor, it won’t work!
Locate: Feel the patient’s knee. Find the hard kneecap (Patella). Slide your finger down about 1 inch to find the soft tendon connecting the kneecap to the shin bone.
The Strike: Hold the Reflex Hammer loosely by the handle (let it swing like a pendulum). Strike the soft tendon briskly.
Observe: Does the leg kick forward?
The Reflex Arc (Why do we kick?)
When you tap the knee, the leg kicks before the brain even knows what happened.
The Loop: The signal goes from the Knee to the Spinal Cord to the Knee.
Why? It is a survival mechanism. Your body reacts to protect itself faster than you can think.
Medical Clue:
No Kick (Hyporeflexia): Possible nerve damage or spinal injury.
Crazy Kick (Hyperreflexia): Possible stroke or severe anxiety.