|Classification and external resources|
Macroaneursym ICD 9 code: 362.17
Retinal arterial macroaneurysms are acquired, focal dilations of retinal arterial branches (mostly second-order retinal arterioles) that can be classified as hemorrhagic or exudative. Macroaneurysms range from 100 to 250μm in diameter and are most often found on the temporal retina. Associated findings include capillary telangiectasias, vascular remodeling, and retinal edema. While visual prognosis is generally good, vision loss can occur from macular edema, end-arteriole occlusion from thrombosis, or hemorrhage due to rupture of the aneurysm  . Diagnosis is made on clinical exam and via imaging modalities such as fluorescein angiography (FA) and spectral-domain optical coherence tomography (SD-OCT), and treatment is traditionally observation, focal laser photocoagulation, or surgery. More recently, the use of anti-vascular endothelial growth factor (VEGF) intravitreal injections has been suggested but not extensively studied as a possible treatment modality.
Etiology and Pathophysiology
Fichte et al. described vessel wall thickening and the presence of fibrin and foamy macrophages upon histological inspection in retinal arterial macroaneurysms, similar to that seen in age-related arteriosclerotic changes in vessel walls throughout the body . The localized ischemia due to focal embolic damage to the arterial walls from vascular disease can cause increased intimal collagen remodeling and increased permeability of vessels, thus predisposing the vessel to dilation.
Linear breaks found in arterial walls on histopathology lead to a round or fusiform dilation of the arteriolar vessel wall. This weakened arteriolar wall can rupture and cause hemorrhage and exudation at any level of the retina
The Beijing Eye Study has reported on the incidence of arterial macroaneurysms as being 1 case per 9000 eyes primarily among the adult Chinese population . The majority of those affected are elderly and female  , and there is a strong association with hypertension (seen in 75% of patients). In hemorrhagic macroaneurysms, 10% of cases are bilateral  .
Control of hypertension and arteriolar sclerosis risk factors are the mainstay of prevention.
Fluorescein angiography can help visualize macroaneurysms which typically fill in the early arterial phase and staining of the vessel walls with possible leakage may be found in later phases.
Most commonly found incidentally on funduscopic examination in an asymptomatic patient. However, patients may complain of vision loss due to macular edema or hemorrhage. Metamorphopsia or decreased vision are most commonly encountered when macroaneurysms affect the macula. Also presenting complaint may be floaters due to vitreous hemorrhage. Typically patients will have a history of hypertention
Physical Examination and Imaging
Dilated fundus examination may enable visualization of an out-pocketing of the arterial wall, but in the setting of hemorrhage and/or exudation, it may be necessary to use imaging modalities such as FA and SD-OCT to confirm the diagnosis. Round or fusiform dilation of a retinal arteriole within a third degree branch of one of the four main arteries. Most common location for a symptomatic macroaneurysm is from a branch of the superotemporal arcade.
The aneurysm appears as a pulsating round or ovoid pooling of dye on FA, with filling either in the middle to late phase in saccular (sac-like) aneurysms or in the early phase in fusiformic (spindle-shaped) aneurysms. SD-OCT can be helpful in quantifying the exudates in the exudative-type macroaneurysm.
While the presence of a retinal arterial macroaneurysm can be visualized on fundus examination, certain disease processes can present similarly such as Coat’s disease and von Hippel-Lindau disease. Macroaneurysms can also occur secondary to a branch retinal vein occlusion, diabetic retinopathy, radiation retinopathy, and retinal arteritis, in which case the underlying cause should be teased out and treated.
There are currently no approved guidelines for the management of macroaneurysms. Most macroaneurysms resolve spontaneously and can be observed. In all patients with this diagnosis, a systematic work-up for hypertension and systemic vascular disease should be pursued.
Complicated retinal arterial macroaneurysms may be directly treated with moderate-intensity laser photocoagulation with two to three rows of large-spot-size (200-500μm) immediately adjacent to the macroaneurysm, especially if visual function is threatened due to increasing edema  . This treatment course is controversial, as some studies have demonstrated a significant decrease in visual acuity in post-laser eyes  . In eyes with a persistent hemorrhagic aneurysm with severe bleeding or a macroaneurysm too large for laser treatment, surgery to remove the macroaneurysm may be considered.
Cases of submacular hemorrhage can be treated with pneumatic displacement of the clot with or without tissue plasminogen activator, as hemorrhage is toxic to the retinal pigment epithelium and ellipsoid zone. In cases of premacular hemorrhage, YAG laser can be used to perform a posterior hyaloidotomy and release the hemorrhage into the vitreous for faster clearance.
Recent studies have shown promising results using anti-VEGF agents such as bevacizumab and ranibizumab in patients with macroaneurysm-associated macular edema, with one case series by Pichi et al. demonstrating a reduction in macular edema and hard exudates in all 38 eyes evaluated  .
The majority of eyes with the diagnosis of arterial macroaneurysm have good visual prognoses and spontaneous regression. In general, patients with a hemorrhagic macroaneurysm have a better visual prognosis than those with an exudative macroaneurysm. Patients with persistent macular edema or subretinal hemorrhage were found to have the worst prognosis .
ORIGINAL AUTHORS: Michele Lee MD, Ehsan Mozayan MS MD, Peter Karth MD MBA
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