HWN Suggests

My, What Big Eyes You Have

Finding the cause of a dilated pupil can be a challenging exercise. Trauma, pharmacologic agents and numerous other conditions can cause pupillary dilation. An intracranial aneurysm, with its attendant morbidity and mortality, can also cause a dilated pupil. However, in lieu of any other abnormalities, rest assured that an aneurysm will not likely be the cause of an isolated dilated pupil in an ambulatory patient. Knowing this, should David Bowie ever wander into your practice, don’t refer him for neuroimaging based solely upon his dilated pupil.

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 Unilateral Mydriasis: Emergent or Benign

Unilateral mydriasis can be an ophthalmologic emergency. Emergent evaluation of stroke or aneurysm should be considered anytime an asymmetrically dilated nonreactive pupil is found. The mechanisms of these injuries range from benign causes to an acute third nerve palsy from brain herniation or aneurysm. In a comatose patient, a poorly reactive or dilated pupil would be cause for great concern; however, in a well patient, a third nerve palsy would be a less likely cause. More benign conditions such as iris sphincter abnormalities, pharmacologic dilation, tonic pupil syndrome, or sympathetic irritation are often found.

Articles of Interest

An Unresponsive Pupil in the Urgent Care: Can a Diagnosis be Made From the Bedside History and Exam?

Unilateral mydriasis is a particularly alarming side effect, as it is frequently associated with a more life-threatening condition such as cerebral aneurysm or intracranial hemorrhage. The diagnostic approach in a patient with an isolated cranial nerve palsy should start with considering the age and medical comorbidities of the patient. If an aneurysm is suspected, then an MRI is indicated. The confusion of this side effect with a more serious condition has not only resulted in misdiagnoses, but also exposure to unnecessary neuroimaging and added medical costs.

The Fixed Dilated Pupil

Isolated iridoplegia or internal ophthalmoplegia may be due to impairment of the effector muscles in the eye, defective parasympathetic innervation, or the presence of atropinic substances in the eye. Pharmacologic blockade can be identified by the pupil's failure to constrict to pilocarpine drops. Because of its clarity and technical simplicity, this test should be in general use as an office procedure.

The Truth Behind David Bowie’s Eyes

I couldn’t believe my eyes when I was scrolling through my Facebook feed on Monday. First, I was shocked to hear of the passing of David Bowie, but I also noticed that along with this news, there were several stories about his iconic eye appearance. I had always been told, and always believed, that David Bowie’s unusual eye appearance was due to heterochromia iridis… I guess I was wrong! After reading a few of these articles, I found that the real reason David Bowie’s eyes appeared to be different colors was because he had anisocoria! Did you know that? Or had you also been duped into believing he had heterochromia?!