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The Afferent Pupillary Pathway The Pupil: Black Hole of • The body has AFFERENT neurons (nerves) that carry ‘sensory’ messages to the brain (like images & light!) Valuable Information • Afferent = “A Feeling” (message to the brain) • The AFFERENT pupillary pathway is: – Retina – Optic Nerve (II CN) – Optic Chiasm – Optic Tract • “Light” message branches off; “visual” message continues on different path! – Pretectal Nucleus Lecturer: M. Patrick COLEMAN, COT & ABOC – Edinger Westphal Nucleus (part of III CN nucleus) Kerrville, TX

The The Efferent Pupillary Pathway Afferent Pupillary • Once the “brain” receives Pathway the Afferent (sensory) (cont.) message & interprets it, it sends out an Efferent You can see that (motor) message to adjust the afferent the pupil’s size “pupillary pathway” never • Remember EFFERENT = makes it to the: “Exit the brain”…(a motor LGB, Optic message to the muscles or Radiations, or glands) Visual Cortex!

The Efferent Pupillary Pathway (cont.) The Efferent Pupillary Pathway (cont.) • The Efferent neurons (nerves) carry ‘motor’ messages to nerves & glands to operate muscles or secrete chemicals which change things in body • The EFFERENT pupillary pathway is: – Edinger-Westphal (accessory III CN) – III Cranial Nerve (two axons; one extends to each eye) – Ciliary ganglion (one on each side of head) leads to the Short Ciliary Nerves – Iris sphincter muscle (one in each eye) • The ciliary ganglion axon extends to the iris sphincter muscle & innervates it, as needed, to get the pupil at the ‘correct’ size

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The Efferent Pupillary Pathway (cont.) How to properly assess the pupils (PERRLA & APD) Did you notice that the “EFFERENT” • When you test pupils, you are testing the Afferent and Efferent pathways pathway • When you shine a bright light into the eyes… does not use any – An AFFERENT message goes to the brain (the of the “AFFERENT” Edinger Westphal Nucleus – an ‘accessory’ part pathway structures? of the III CN nucleus) for processing – The brain “sees” that the light is very bright & sends an EFFERENT message to the iris With that in mind, could a totally BLIND sphincter muscles (the constrictor muscles) to EYE show any pupillary constriction? pull the pupils smaller.

How to properly assess the pupils How to properly assess the pupils (PERRLA & APD) (cont.) (PERRLA & APD) (cont.) For pupil testing - • P E R what should you – Pupils Equal & Round assess? • Pt looks @ 20/400 letter – you look at 1. P ER RL A their pupils (NO LIGHT USED YET!) The darker the room, the better  2. Any Afferent • R L Pupillary Defect – Reacts to Light (…now you use the light!) (APD) present? • Check DIRECT reaction • Maybe you know • Check CONSENSUAL reaction it as “Marcus Gunn” [MG] • (Pt still looking at 20/400 letter!)

How to properly assess the pupils (PERRLA How to properly assess the pupils & APD) (cont.) (PERRLA & APD) (cont.) A = Accomodation! APD or MG testing (People tend to skip this one & that’s bad!) (also called the “swinging flashlight test”) • Start with pt looking @ the 20/400 letter • Pt looks @ the 20/400 letter • Hold a pen about six inches (6”) in front of the pt’s • Shine light directly into OD; wait a second, then… eyes... • NOW, have patient look at the pen tip (near object): • Move quickly to the OS… Did the pupils CONSTRICT? – Was it the same size (constricted?) = GOOD! • If YES, that is great! That’s what you want. – Did it constrict first, then grow slightly? = GOOD • If NO, that is a problem. Repeat to be sure; if – Did it DILATE as if the light was not there? = BAD! still no reaction or it is a very slow/poor reaction, • Now move quickly back to the OD to assess it LET THE DOCTOR KNOW

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How to How to properly properly assess the assess the pupils pupils (PERRLA (PERRLA & APD) & APD) (cont.) (cont.)

How to How to properly properly assess the assess pupils the pupils (PERRLA (PERRLA & APD) & APD) (cont.) (cont.)

How to Documenting Pupil Testing Results properly This is your patient & everything checks assess out fine. How would you record it? the pupils (PERRLA & APD) (cont.)

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Documenting Pupil Testing Results (cont.) Documenting Pupil Testing Results (cont.)

This is your patient & everything checks out Another way to document pupil testing is by fine. How would you record it? showing pupil sizes in dim light, bright light, & rapidity of response to a near object

Documenting Pupil Testing Results (cont.) Documenting Pupil Testing Results (cont.) • Pupil testing irregularities can indicate: – Hodgkin's disease, Lung tumor, trauma to the neck, or • Record the way your doctor(s) want it done! migraines (Horner’s Syndrome) You work for them. • Ptosis, miosis, anhydrosis (skin dryness); on one side • Tested w/cocaine or apraclonidine eye drops; if smaller • If you see something wrong during your pupil pupil fails to dilate, Horner’s is confirmed testing, DO NOT DILATE THE PT!!! – Optic neuritis or retrobulbar neuritis (both signs of M.S. {multiple sclerosis}) = + Afferent Pupillary Defect – Get the doctor so he/she can assess & • Only shows during the “swinging flashlight test”; but make the diagnosis. usually pupils are unequal & Visual Acuity (VA) is poor in one eye – Once you dilate, that is it. No assessment – Syphilis (Argyll Robertson pupils) can be made. That is NOT the time to tell • Miotic, poor (or no) reaction to light, but good the doctor, “Maybe the right pupil was off a accommodative response; both pupils affected – Viral infection (Adie’s Tonic Pupil) little.” • Unequal pupils, poor light response (slow to constrict & slow to dilate), but decent accommodative response

Pupillary Pathway & Testing

As you can see, w/ your naked eye & a simple penlight, YOU might be able to detect a life threatening disease! • Do NOT ‘pencil-whip’ your pupil testing; your full attention & time are required to get it right! • If you see ANYTHING that doesn’t seem right, GET THE DOCTOR. – You DON’T have to “diagnose” what problem is! – You DO have to be able to tell if there IS a problem!

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