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

Background: 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. Methods: 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. Results: Ultrasound biomicroscopy demonstrated choroidal thickening and ciliary body effusion with forward rotation of the lens-iris diaphragm altering refraction and mechanically limiting iris movements. Conclusions: 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.