Ocular and Vision Problems in Patients After Fontan Operation

Numerous authors have described optic disc edema, globe flattening, choroidal folds which were thought to be part of the well-defined but still idiopathic syndrome of idiopathic intracranial hypertension. The pathogenesis of idiopathic intracranial hypertension is not well understood. Recent reports, however suggest that elevated cerebral venous pressure underlines the process. The close relationship that exist between spinal fluid pressure and cerebral venous pressure has been definitely established. It was found that patients with increased venous pressure due to heart failure had an increase in spinal fluid pressure as well. Furthermore, numerous authors have described venous stasis retinopathy, bilateral choroidal detachments, intraretinal hemorrhages, vessel tortuosity, microaneurysms, capillary leakage, central retinal vein occlusion, open angle glaucoma, choroidal effusion, etc. in patients with pulmonary arterial hypertension. Elevated venous pressure found in pulmonary arterial hypertension is responsible for the delayed choroidal perfusion and the reduced venous blood outflow. This explains the clinical findings of venous stasis retinopathy, choroidal detachments, etc. which are related to elevated episcleral, retinal and choroidal venous pressure secondary to elevated systemic venous pressure (increased pulmonary vascular resistance in patients with pulmonary arterial hypertension leads to right heart failure and subsequent elevation in systemic venous pressure). Systemic venous pressures in Fontan patients are comparable with those in patients with significant right heart failure in a 2- ventricular circulation. With Fontan anatomy the elevated central venous pressure is transmitted to the dural venous sinuses of the brain through jugular veins and the paraspinal venous plexus and after the Fontan procedure brain venous pressure are chronically elevated. The investigators believe that the long-term effects of the Fontan operation can result in a spectrum of ocular changes similar to those occurring in patients with idiopathic intracranial and pulmonary arterial hypertensions due to chronically elevated cerebral venous pressure. It has been reported that intraocular pressure is directly related to the episcleral and jugular venous pressure in patients without underlying ophthalmic diseases. Several previous studies have shown a linear correlation between central venous pressure and intraocular pressure. Therefore, the investigators believe that the monitoring of intraocular pressure may be simple and effective method for estimating central venous pressure in patients with Fontan circulation.