A 39 y.o. female comes in with daily headaches and unequal pupils
she notes she has had unequal pupils for two years but today her pupil is more dilated and she has blurred vision in the R eye.
What is the differential?
Our patient was sent to the ED to rule out a third nerve palsy from a posterior communicating aneurysm. What she actually had was an Adie’s pupil.
BASIC EYE REVIEW
In distance vision, the lens does not have to change size because light rays are entering the eye in a parallel fashion. As we change to near vision the lens must constrict to focus on the retina and the pupil size decreases. This is called accommodation.
Adie’s pupil- THE ADIES PUPIL CONSTRICTS WITH ACCOMODATION. The pupil is dilated and reacts slowly to light but shows more response to accommodation as shown above.
The syndrome is caused by damage to the parasympathetic innervation of the eye, usually by a viral or bacterial infection that causes inflammation in the eye. It is frequently seen in females with absent knee or ankle jerks and impaired sweating. Because the eye is dilated the patient complains of blurred vision.
Third nerve palsy – IN A THIRD NERVE PALSY THERE WILL BE NO DECREASE IN PUPIL SIZE WITH ACCOMODATION.
The third nerve has outer parasympathetic fibers that supply the ciliary muscles and the sphincter pupillae so when the nerve is compressed the pupil dilates. The ciliary muscle changes the shape of the lens when the eye focuses on a near object. This decreases the size of the pupil if the ciliary muscle is intact but it is not intact when the third nerve is compressed by a posterior communicating aneursym.
In both Adie’s and third nerve palsy the dilated pupil is the abnormal one.
David Bowie had anisocoria because he was punched in the eye at age 16 and damaged his ciliary muscle
The pupil is so dilated a red reflex from retinal vessels could sometimes be seen.
CAUSES OF ANISOCORIA
Anisocoria- affects 20% of the population and it is often a benign finding.
Horner’s syndrome- causes a constricted pupil on one side because of a defect in sympathetic fibers running along the carotid. This can be caused by a carotid dissection, Pancoast tumor of the lung or cervical tumor. The abnormal pupil is the small one and the pupil will not dilate in darkness.
Primary eye pathology- can cause a dilated pupil including uveitis and glaucoma.
Third nerve palsy can cause a dilated pupil whether ischemic or compressive
Multiple sclerosis can cause a dilated pupil because of optic nerve demyelination and decreased light perception.
Adie’s syndrome – is related to damage to the parasympathetic innervation of the eye and causes a dilated pupil.
Migraines can sometimes be associated with unilateral mydriasis.
Toxins- touching your eye after you touch a scopolamine patch will result in a dilated pupil .
Trauma- can cause damage to the ciliary muscle .
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