A leak between the carotid artery and the venous space behind the eye. Arterial pressure is transmitted into the veins of the orbit, and the eye becomes red, swollen and pulsatile — a picture regularly mistaken for infection or thyroid eye disease.
Direct high-flow fistulas often follow head injury and develop over days. Indirect low-flow fistulas arise spontaneously, more often in older patients, and come on gradually — which is precisely why they are treated as conjunctivitis or thyroid eye disease for weeks first.
CT or MRI of the orbit shows a swollen eye and an enlarged draining vein. Catheter angiography establishes the diagnosis definitively, distinguishes direct from indirect fistulas, and maps the route for treatment.
Closure is endovascular. The fistula is reached either through the artery or, more often, through the venous route, and sealed with coils, liquid embolic material, or a stent placed across the tear. Direct traumatic fistulas usually need prompt treatment. Some indirect fistulas close on their own, so observation is reasonable when vision is not threatened and pressure in the eye is controlled.
After successful closure, the redness and protrusion settle over days to weeks and the noise usually stops immediately. Double vision takes longer to recover, as the affected nerves need time.
An eye that is losing sight should be treated without delay. If vision has changed, call +91 76780 63385 rather than waiting for an outpatient appointment.
That is usually the right question, and often the answer is no. Send the scans and you will get a straight opinion — including when the safest course is to do nothing and watch.