Effect of anticholinergic eye drops on intraorbital, periorbital and brain pulsation power

The study aims to investigate the effect of pharmacologically reducing parasympathetic activity on ocular and cerebral pulsations, inspired by recent discoveries of a glymphatic-like system in the eye driven by physiological pulsations.

Forty-six healthy volunteers were subjected to fMREye imaging, with 23 receiving topical tropicamide and 23 serving as controls. Additionally, 83 healthy volunteers were scanned using 3D whole-brain magnetic resonance encephalography (MREG). Ocular pulsation power across very low-frequency, respiratory and cardiac bands was quantified in each individual.

Topical tropicamide significantly reduced physiological pulsation power throughout the eye, including the cornea, lens, vitreous body, retina and optic nerve. Similar reductions were observed in the untreated eye, indicating potential systemic effects. In the brain, significant pulsation changes were noted in the venous sinus and internal carotid artery following tropicamide application.

The findings suggest parasympathetic activity is crucial in modulating physiological pulsations in both ocular and cerebral glymphatic pathways. This interplay may have implications for conditions involving impaired fluid dynamics, such as glaucoma and traumatic brain injury.