Aneurysms refer to the development of out-pouches of arterial walls due to local weakening caused by systemic disease. Retinal aneurysms refer to the formation of large aneurysms in the retinal arteries of the eye. While smaller aneurysms, known as microaneurysms, are a common complication of other diseases including diabetes, larger aneuryms, known as macroaneurysms, are uniquely found in patients who have chronic systemic hypertension and atherosclerosis.
Retinal macroaneurysms tend to subside once the patient’s bodily hypertension is treated. However, if hypertension remains untreated, retinal macroaneurysms can lead to vitreous hemorrhage. This may cause the development of further complications which can permanently damage the retina and diminish a patient’s vision. Treating retinal macroaneurysms involve laser, pneumatic displacement, and/or vitrectomy surgery to stem the retinal bleeding and clear the vitreous hemorrhage caused by it.
WHAT IS THE DISEASE?
Retinal macroaneurysms arise when a patient has hypertension, or high blood pressure. When the pressure of blood on arterial walls increases dramatically, the walls can weaken causing the artery to widen and bulge, thus forming an aneurysm. Since high blood pressure affects all blood vessels in a patient’s body, aneurysms can also form within the tiny retinal blood vessels of the eye. With enough pressure, blood can break through the retinal aneurysm and cause vitreous hemorrhage and later, ischemia. As long as hypertension is treated immediately, there is a high possibility that the leaked blood will fade away, leaving the vitreous body and retinal cells healthy and intact.
Retinal macroaneurysm formation is a consequence of chronic systemic hypertension. Management of high blood pressure can theoretically reduce the rate of increase in the macroaneurysm, thereby decreasing the chance of rupture. However, generally speaking, the most important mechanism to prevent macroaneurysm is to treat systemic hypertension prior to the development of these aneurysms.
In some patients with retinal macroaneurysms, the macroaneurysm can rupture, leading to bleeding in the retina, sub-retinal space, or vitreous cavity. In these patients, there will be severe visual loss that may resolve spontaneously. This, though, is dependent upon the amount of blood that amasses at the time of the macroaneurysm rupture.
INTRARETINAL & SUBRETINAL BLOOD
The presence of blood within a retinal structure or in the sub-retinal space can compromise visual function in two ways: by blocking light, and over the long term, by causing toxicity to the retina. Once the aneurysm has ruptured, there tends to be no further bleeding and in fact, over time, the blood in both the sub-retinal and intra-retinal spaces will reabsorb, leading to gradual improvement of sight. However, one must remember that, should the blood have been present for an excessively long period of time, the toxicity from the blood product coupled with the chronic distortion of the retinal tissue may lead to impaired visual recovery.
The traditional management for patients with retinal macroaneurysms is a conservative process whereby a retinal surgical team will simply observe and look for other possible complications. In majority of cases, once the macroaneurysm has ruptured and bled, the aneurysm becomes sealed off. Accordingly, without further retinal blood leakage, the blood which is already present from the initial aneurysm tends to reabsorb spontaneously. In most patients, with the re-absorption of retinal blood, there is recovery of sight. However, it must be remembered that sight recovery will never be complete due to the long term toxicity from the presence of blood and the chronic disorganization of the retinal issues.
The best way to prevent the development of major retinal macroaneurysms is to treat the patient’s hypertension before ocular complications arise. Patients should consult their family physicians on how to effectively reduce and maintain a healthy blood pressure.
Thermal lasers can reduce the risk of complications, including vitreous hemorrhage and ischemia, by preventing a patient’s retinal macroaneurysm from bursting. This treatment is used on patients whose retinal macroaneurysms have been detected before they have caused complications.
The use of a pneumatic displacement technique to move the sub-retinal and intra-retinal blood in patients who have retinal macroaneurysms has been pioneered by the Retina Team at OCC Eyecare. The pneumatic displacement technique involves the injection of a C3F8 gas bubble into the eye followed by face-down positioning. Due to the pressure of the bubble pressing against the retina, otherwise known as the tamponade, blood that was previously absorbed by the retina is pushed out of retinal cells allowing the blood that caused the vitreous hemorrhage to naturally fade away without damaging the retinal cells through ischemia.
Vitrectomy surgery is generally reserved for patients who experience severe vitreous hemorrhage, or bleeding, that fails to spontaneously reabsorb. A vitrectomy surgery enables the surgical retina specialist to replace the blood-filled vitreous fluid with a clear saline fluid. Once the opaque vitreous has been removed, patients are able to regain their vision. However, patient’s vision will only be fully restored if there was no damage done to the retinal cells when they experienced the original vitreous hemorrhage.