One eye bigger then the other one??

[Mirror Form]

Today one of my residents started pimping me on what it means when one of a patient's pupils is bigger then the other one. Unfortunately I had absolutely no idea and had been assuming the pt was all somatization. Anybody know?

---

Members don't see this ad.

 

[Mitogen79]

Not that i'm an expert by any means, but the first thing that comes to my mind when one pupil is dilated when compared to the other is some sort of mass pressing on the oculomotor nerve; recall that parasympathetic tone is carried with the Oculomotor nerve to the pupil; the parasympathetic response in the pupil is constriction; if a mass is pressing on the nerve, the fibers are irritated and one would expect sympathetic tone to prevail causing dilation of that particular pupil. Among mass effect from a tumor, consider a berry anyeurism forming at the bifurcation of the posterior communicating artery from the posterior cerebral artery... the oculomotor nerve travels right between the PCA and the superior cerebellar artery... If you're suspecting a CN-III issue, also look for other signs such as muscle weakness of the medial rectus, etc...

hope this helps ~

vish~

 

[ckent]

pupils unequal can mean a lot of things. It can mean that the patient is blind in one eye and therefore that one eye is not reacting to light, it can mean that the patient has a cerebral nerve palsy (II or III) of one eye, it could mean that the patient had cataract surgery in one eye, or it could mean that the patient just had a dilating eye drop of cocaine put in one eye. The way that you test to see which eye is the screwed up one (ie is the pupil abnormally dilated, or is the other one abnormally constricted) is you turn off the lights, then shine your light into one eye at a time. The one that doesn't constrict when you shine your light in it is the screwed up one, or the one that doesn't dilate with no light is the screwed up on.

 

[Tenesma]

anisocoria exists in a benign fashion in about 20% of the population (when the difference is <1mm)... so for the most part it is not that interesting of a finding if everythign else is normal

 

[lattimer13]

uncal herniation?

 

[el guapo]

With unequal pupils you first want to determine whether it is a mydriasis in one eye--possibly due to loss of parasympathetic tone in the eye i.e. in CNIII compression-- or due to a miosis in the opposite eye, possibly due to loss of sympathtic tone--perhaps by a Horner's syndome.

As CKent advised, turn to lights down low and shine your light down low and shine your pen light. For testing or pimping purposes, if the bigger one reacts, the bigger one is normal and the smaller one is loss of sympathetic. If the bigger one doesn't react, the smaller one is normal and the bigger one is CNIII tone loss.

 

[omores]

Consolidating information from previous posts and adding more:

First step is to evaluate which pupil is functioning: the bigger or the smaller. Use penlight in darkened room to look for contraction. But you can't stop there: you also have to check for consensual response. When you shine a light into one eye, BOTH eyes should contract (they're wired this way). The consensual response provides important clues about whether the problem is with the transmission of visual information, or with the ability of the pupil to contract.

Penlight in larger pupil causes consensual contraction of opposite pupil ONLY
This indicates that the visual information is getting through (otherwise the opposite pupil wouldn't contract). The problem lies with the contaction mechanism of the affected pupil: could be from trauma or surgery, eye drops, or a problem with CNIII or the parasympathetic tracts that accompany it.

Penlight in larger pupil results doesn't cause contraction of either pupil, but penlight in smaller pupil DOES result in consensual contraction of larger pupil
The dilation/contraction mechanism is intact, but the visual information is not getting through. Could be from trauma or surgery, a problem with the retina, or a non-functioning CNII.

Larger pupil responds to light; it's the smaller pupil that's not functioning
Look for other signs of Horner's syndrome: ptosis and anhydrosis. This is caused by interruption of the sympathetic pathways anywhere along their course (I saw it in someone after neck surgery, for example) and has numerous causes.

Both pupils are reactive, but their sizes are different.
Benign anisocoria: common and not indicative of a problem, though it can look a bit wacky.

Hey Sledge: out of curiosity, what else was going on with the patient?

 

[Caffeinated]

Afferent pupillary defect (APD or Marcus-Gunn pupil) will NOT cause anisocoria. From a neurological standpoint, anisocoria is either benign anisocoria, or a loss of sympathetic or parasympathetic tone to the affected eye. The way to determine this is to check pupil sizes in light and dark. Here's an example:

In normal room light,
R = 4 mm
L = 6 mm

This could be loss of sympathetic tone to the right eye or loss of parasympathetic tone to the left eye. Now check the pupil sizes in the dark. You will need SOME light to check this, but make sure it is a grazing or indirect illumination--you don't want to cause a light reaction.

If in the dark you get the following:
R = 6 mm
L = 6.5 mm

then the anisocoria is worse in the LIGHT. So this is a parasymptathetic denervation to the left eye. If it preganglionic, then you think compressive midbrain defect. If it is postganglionic, then Adies tonic pupil comes to mind. Adies will also show vermiform movements of the pupil on biomicroscopy, near blur, and possibly a loss of deep tendon reflexes.

If, however, in the dark you get:
R = 4
L = 8

then the anisocoria is more pronounced in the dark, this is a sympathetic defecit in the right eye (Horner's), which can be caused by a number of etiologies.

If the difference in pupil size is equal in light and dark, then this is a benign anisocoria.

Beyond the neurological, there are also mechanical factors that could cause anisocoria. For example, trauma secondary to surgery could cause pupil abnormalities. Blunt trauma could cause sphincter muscle rupture.

In short:
1. APD does not cause anisocoria.
2. Larger aniso in the dark is a sympathetic denervation.
3. Larger aniso in the light is parasympathetic denervation.
4. Aniso that is equal in light and dark is benign.

I hope this helps.

 

[Chandler]

Consolidating information from previous posts and adding more:

First step is to evaluate which pupil is functioning: the bigger or the smaller. Use penlight in darkened room to look for contraction. But you can't stop there: you also have to check for consensual response. When you shine a light into one eye, BOTH eyes should contract (they're wired this way). The consensual response provides important clues about whether the problem is with the transmission of visual information, or with the ability of the pupil to contract.

Penlight in larger pupil causes consensual contraction of opposite pupil ONLY
This indicates that the visual information is getting through (otherwise the opposite pupil wouldn't contract). The problem lies with the contaction mechanism of the affected pupil: could be from trauma or surgery, eye drops, or a problem with CNIII or the parasympathetic tracts that accompany it.

Penlight in larger pupil results doesn't cause contraction of either pupil, but penlight in smaller pupil DOES result in consensual contraction of larger pupil
The dilation/contraction mechanism is intact, but the visual information is not getting through. Could be from trauma or surgery, a problem with the retina, or a non-functioning CNII.

Larger pupil responds to light; it's the smaller pupil that's not functioning
Look for other signs of Horner's syndrome: ptosis and anhydrosis. This is caused by interruption of the sympathetic pathways anywhere along their course (I saw it in someone after neck surgery, for example) and has numerous causes.

Both pupils are reactive, but their sizes are different.
Benign anisocoria: common and not indicative of a problem, though it can look a bit wacky.

Hey Sledge: out of curiosity, what else was going on with the patient?

Keep in mind that Horner's syndrome doesn't require ptosis and anhydrosis for it's diagnosis. Interestingly, miosis is always found in Horner's syndrome. The bottomline is that the syndrome is due to a sympathetic block anywhere from the cervical spinal cord to the effector. Don't look for ptosis and anhydrosis as confirmation!

 

[Blake]

Keep in mind that Horner's syndrome doesn't require ptosis and anhydrosis for it's diagnosis. Interestingly, miosis is always found in Horner's syndrome. The bottomline is that the syndrome is due to a sympathetic block anywhere from the cervical spinal cord to the effector. Don't look for ptosis and anhydrosis as confirmation!

Yup, exactly what I've learned so far. The ptosis isn't always there because there's basically 2 eyelid muscles ( Tarsal's muscle = sympathetic pathway; and Levator Palpebrae superior = oculomotor nerve )

Glad to see things are making a lot more sense lately.

 

[johannabartley]

If only one pupil is dilated, however, you may have Adie's syndrome, a condition in which one pupil contracts more slowly than the other in response to light. It's usually caused either by a malfunction in the mechanism that controls the dilation reflex or from a harmless inflammation of the eye nerves.
long term drug rehab

 

[exgatr]

can't forget about something very simple too:

the patient might have narrow angle glaucoma and is on drops to keep that pupil dilated.