Acquired Retinal Macroaneurysm
An acquired retinal arterial macroaneurysm (RAM) forms when arteriosclerosis leads to weakening of the arteriolar wall and consequently, the arterial wall develops an outpouching that results in a macroaneurysm.
Systemic hypertension, cardiovascular disease, and hyperlipidemia are risk factors for RAM formation. Females are more likely to be affected in their sixth or seventh decade.
Histopathologically, there is distension of the affected arteriolar wall, often with surrounding lipid, hemosiderin, blood and proliferation of fibroglial cells.
There may be no symptoms at all in an eye with a RAM if there is no associated hemorrhage or retinal edema and if does not involve the macula. In some eyes, there may be sudden painless loss of vision if acute macular or vitreous hemorrhage occurs.
A complete ophthalmologic examination with pupillary dilation should be performed.
The patient may be asymptomatic or may notice a painless sudden decrease in vision.
On ophthalmoscopy, fusiform or round outpouchings or dilations may be evident along one of the retinal arterioles. About 90% are unilateral. The macroaneurysm is usually located in the posterior pole at one of the first 3 bifurcations of the retinal arterioles, with the superotemporal artery being the most common. Usually, RAM is solitary. RAM usually occurs as a saccular arteriolar dilation at the arterio-venous crossing or bifurcation. Retinal hemorrhage is seen in 50% cases.
In some eyes, multilayer retinal hemorrhage is often noted----subretinal, subhyaloid, preretinal, intraretinal and vitreous hemorrhage may be present, obscuring the macroaneuyrsm itself. The multilayer location of hemorrhage is characteristic in eyes with a ruptured RAM. In cases of vitreous hemorrhage with no view into the fundus, Bscan ultrasonography may demonstrate clues to the multilayer hemorrhage.
Fluorescein angiography can be very useful in making the diagnosis, particularly in those eyes that have associated overlying pre-retinal hemorrhage where the macroaneurysm may light up with the fluorescein where the macroaneurysm usually fills uniformly in the early arterial phase. In the late phase frames, the wall of the aneurysm may demonstrate leakage or staining. Incomplete filling of RAM is due to thrombosis. In some eyes, the pre-retinal blood overlying the RAM may be extensive and block the fluorescence.
Optical coherence tomography is used to document and follow the progression of the macular edema, and subretinal/preretinal hemorrhage.
Patients with an acquired retinal macroaneurysm should be evaluated by their internist for hypertension and lipid disorders.
The following entities should be considered in the differential diagnosis of acquired retinal macroaneurysm when associated with hemorrhage: branch retinal vein occlusion, retinal telangiectasis, proliferative diabetic retinopathy, neovascular age-related macular degeneration when associated with hemorrhagic pigment epithelial detachment. Hemorrhage at multiple levels may also be seen with trauma and anemia.
Instruct the patient to follow-up with the patient's internist to monitor and treat blood pressure and any lipid abnormalities. Smoking should be discouraged.
Some cases of RAM may involute spontaneously due to thrombosis and fibrosis which may appear before or after the development of exudates or hemorrhage.
- If vision and macula are not threated by an isolated RAM.
Laser photocoagulation- when exudation from RAM threatens or involves the macula with or without visual decline. Laser may be applied to the RAM itself or the surrounding area or both. There is a risk of vitreous hemorrhage and branch retinal arteriolar occlusion with laser.
Yag laser hyaloidotomy can be considered in cases of thick pre-retinal hemorrhage with ruptured RAMS.
Intravitreal gas injection with recombinant tissue plasminogen positioning may work in dissipating thick premacular hemorrhage.
Vitrectomy may be helpful in cases with persistent vitreous hemorrhage.
Complications related to the presence of the retinal macroaneurysm include
- chronic leakage-lipid deposition in the foveal center, macular edema.
- subfoveal hemorrhage, intraretinal, preretinal and vitreous hemorrhage.
- rarely epiretinal membrane or choroidal neovascular membrane
- AAO, Basic and Clinical Science Course, Section 12: Retina and Vitreous, 2010-11.