Ciliary Body/Iris Appositioning Producing Mechanical Pupillary Defects in Carotid-Cavernous Sinus Fistula: An Overlooked Pathophysiologic Mechanism

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Variable pupillary responses have been described with carotid-cavernous sinus fistulas. These often are associated with a decrease in visual acuity and attributed to retinal ischemia. We propose a novel pathophysiologic mechanism for changes in pupillary reactivity involving anatomic changes secondary to choroidal effusion.


To demonstrate proof-of-concept, we investigated 2 consecutive patients with carotid-cavernous sinus fistulas and pupillary disturbances using repeated refractions and anterior segment ultrasound biomicroscopy.


Ultrasound biomicroscopy demonstrated choroidal thickening and ciliary body effusion with forward rotation of the lens–iris diaphragm altering refraction and mechanically limiting iris movements.


Where there are acute elevations in orbital venous pressure causing ciliary body effusion, changes in visual acuity and pupillary abnormalities can be produced by mechanical effects.

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