A retinal macroaneurysm (RMA) is a localized, acquired abnormality involving one of the small arteries within the retina. The retina is the light-sensitive tissue lining the back of the eye. An RMA appears as an abnormal, bubble-like dilation or bulge on the wall of a retinal artery, often occurring in only one eye. This condition can potentially affect vision when the weakened vessel wall leaks fluid or blood.
Defining the Condition and Identifying Risk Factors
A retinal macroaneurysm represents a focal expansion of a retinal arteriole, a small branch of the central retinal artery. These aneurysms commonly develop within the first three bifurcations of the major retinal arteries, often at a point where an artery and a vein cross over each other. The physical stress at these arterial-venous crossings, combined with underlying systemic conditions, contributes to the weakening of the vessel wall.
The primary underlying systemic cause for the formation of an RMA is chronic systemic hypertension, or high blood pressure, which is identified in a significant number of patients, sometimes up to 75% of cases. Uncontrolled high blood pressure and arteriosclerosis (hardening of the arteries) place continuous stress on the arterial walls. This constant pressure can lead to focal damage and a subsequent outpouching of the vessel wall.
RMAs are most frequently diagnosed in individuals in their 60s and older. There is a notable gender predilection, with women being diagnosed with RMAs more often than men; some studies report women making up 70% to 80% of cases. Management of the underlying systemic diseases, such as hypertension and elevated lipid levels, is crucial.
Recognizing the Warning Signs
While some retinal macroaneurysms can remain quiescent and asymptomatic, the most common presentation of a symptomatic RMA is a sudden, painless reduction in visual acuity. This acute vision change typically happens when the macroaneurysm begins to leak or ruptures, causing blood or fluid to enter the retinal layers or the vitreous cavity. The resulting hemorrhage can be multi-layered, appearing in the preretinal, intraretinal, or subretinal spaces.
Patients may also notice floaters, which are small specks or shadows in their visual field, particularly if the bleeding is severe enough to spill into the vitreous humor. A scotoma, or a blind spot, can also be a warning sign, depending on the location and size of the hemorrhage. The severity of the visual symptoms is directly related to whether the leakage or rupture affects the macula, the small central part of the retina responsible for sharp, detailed central vision.
Diagnostic Procedures and Imaging
The initial step in diagnosing an RMA involves a comprehensive eye examination, including a dilated fundus examination, which allows the ophthalmologist to directly view the retina. During this examination, the macroaneurysm may appear as a round or fusiform dilation on a retinal artery, often surrounded by hemorrhage or yellow-white lipid deposits in a circinate pattern. However, the presence of dense blood can sometimes obscure the lesion, necessitating further imaging.
Optical Coherence Tomography (OCT) is a non-invasive tool that provides cross-sectional images of the retina, allowing for detailed visualization of the retinal architecture. OCT helps confirm the diagnosis by showing the macroaneurysm as a hyper-reflective, round or oval lesion within the inner retinal layers. It is also essential for assessing the complications, such as the extent of intraretinal or subretinal fluid, edema, and hemorrhage, which guides treatment decisions.
Fluorescein Angiography (FA) is another important diagnostic test where a fluorescent dye is injected into a vein, allowing the retinal circulation to be photographed. This test confirms the vascular nature of the lesion by showing early hyperfluorescence at the site of the aneurysm. FA helps to differentiate the RMA from other conditions and reveals the degree of leakage, although dense hemorrhage can sometimes block the visualization of the lesion.
Management Approaches and Visual Outcomes
The management of a retinal macroaneurysm is tailored to the individual case, depending on the size of the lesion and the degree of associated complications, especially macula involvement. Many uncomplicated RMAs, where the leakage or hemorrhage does not threaten the macula, are managed with simple observation. Spontaneous thrombosis (clotting) of the aneurysm and reabsorption of leaked blood and fluid often occur over several months.
Active intervention is considered when the macroaneurysm causes persistent macular edema or a significant, non-clearing hemorrhage that threatens central vision. One common treatment is laser photocoagulation, which involves applying a focused laser to the macroaneurysm or the surrounding area to seal the leaking vessel and reduce intraluminal pressure. Direct laser application is used cautiously to avoid damaging the underlying retina.
Intravitreal Anti-Vascular Endothelial Growth Factor (Anti-VEGF) injections, such as bevacizumab, are frequently used to treat the resulting macular edema and exudation. These injections block a protein that causes blood vessels to leak, helping to dry up fluid and improve visual acuity. For severe, non-resolving vitreous hemorrhage, a surgical procedure called a pars plana vitrectomy may be necessary to physically remove the blood from the eye’s cavity.
The visual outcome following an RMA is often favorable, even when the initial vision loss is profound. Most patients experience preservation or a return of functional vision, especially if the macula was not permanently damaged. The location of the hemorrhage is a strong determinant of prognosis, with submacular hemorrhages carrying the poorest visual outcome. Managing underlying systemic hypertension is necessary long-term to prevent new macroaneurysms.