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Disease Entity
Etiology
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.
Risk Factors
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. The incidence is reported to be approximately 1 in 5000 persons.
General Pathology
Histopathologically, there is distension of the affected arteriolar wall, often with surrounding lipid, hemosiderin, blood and proliferation of fibroglial cells.
Diagnosis
History
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 hemorrhage or vitreous hemorrhage occurs.
Physical examination
A complete ophthalmologic examination with pupillary dilation should be performed. The vision may be compromised if the leakage or hemorrhage from the macroaneurysm affects the macula.
Symptoms
The patient may be asymptomatic or may notice a painless sudden decrease in vision.
Clinical diagnosis
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. Exudation may occur around RAM without any retinal hemorrhage.
The multilayer location of hemorrhage is characteristic in eyes with a ruptured RAM. In some eyes, multilayer retinal hemorrhage is often noted----subretinal, subhyaloid, preretinal, intraretinal and vitreous hemorrhage may be present, obscuring the macroaneuyrsm itself. Rupture after Valsalva has been reported. [1] Optical Coherence Tomography (OCT) may demonstrate clues to the multilayer hemorrhage. In cases of vitreous hemorrhage with no view into the fundus, a B scan ultrasonography may be required to assess the status of retina.
Diagnostic procedures
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.
Laboratory test
Patients with an acquired retinal macroaneurysm should be evaluated by their internist for hypertension and lipid disorders.
Differential diagnosis
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, leukemia, [2]neovascular age-related macular degeneration when associated with hemorrhagic pigment epithelial detachment. Hemorrhage at multiple levels may also be seen with trauma and anemia.
Management
General treatment
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.
Observation
- If vision and macula are not threated by an isolated RAM.
Surgery
Laser photocoagulation- when exudation from RAM threatens or involves the macula with or without visual decline. Argon laser may be applied directly to the RAM itself or indirectly to the surrounding area or both. Direct laser to the aneurysm utilizes low power with long duration yo avoid rupture. Indirect laser reduces the blood flow to the aneurysm with the goal of slow spontaneous resorption of the lesion. 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
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
Additional Resources
- American Academy of Ophthalmology. Arterial Macroaneurysms. Basic and Clinical Science Course, Section 12. Retina and Vitreous. San Francisco: American Academy of Ophthalmology; 2022-2023:165-166.
- Porter D, Vemulakonda GA. Blood Pressure. American Academy of Ophthalmology. EyeSmart/Eye health. https://www.aao.org/eye-health/anatomy/blood-pressure-list. Accessed January 06, 2023.
