Retinal macroaneurysm: natural history and guidelines for treatment.

Retinal artery macroaneurysms: clinical and fluorescein angiographic features in 34 patients

“…This may be due to the fact that where the perfusion pressure is high as in the first three orders of the arterial tree, the thin stretched arterial sac is relatively easily perforated, whereas the perfusion pressure is lower in the smaller arterioles predisposing more to exudation. 5 Our study suggests that whereas, there is a preponderance of haemorrhagic over exudative changes in the first three orders of the arterial tree, those exudative changes that do occur, do so with decreasing frequency the further away from the optic disc the MA occurs. Arteries close to the disc have larger diameters and increased flow rates compared to peripheral vessels.…”

“…7 In most cases, MAs arise on the first three orders of the arterial tree, though occasionally they arise on small branches of the major arterial tree. 5 The latter tend to reach a very large size and promote severe exudative phenomena in the retina. Fusiform MAs are thought to be more prone to exudation, though our study, have shown that haemorrhage predominates.…”

“…1 Subsequent changes may include arteriolar constriction proximal to the MA, arteriolar sheathing distal to the MA, and pigment clumps resulting from intratretinal haemorrhage and disruption of the RPE. 5 The 'Z-shaped' kinked ( Figure 7) appearance at the site of the resolved MA may result from fibrotic changes in the media of the arterial wall causing traction on the adventitial portion in that segment, leading to shortening of the artery. Counterforces between the fibrous contracture and the tensile strength of the adventitial attachments to the internal limiting membrane of the retina will lead to the appearance of the Z-shaped kink.…”

“…Counterforces between the fibrous contracture and the tensile strength of the adventitial attachments to the internal limiting membrane of the retina will lead to the appearance of the Z-shaped kink. 5 Other angiographic findings include widening of the capillary free zone and intra-arterial collateral vessels. Areas of microangiopathy are often associated with fluorescein leakage in the area around the MA 2 ( Figure 4).…”

“…These terms have also been described as 'blow-out' and 'cuffed', respectively. 5 Fusiform MAs are characterized by a circumferential widening of the retinal artery (Figure 4), whereas saccular MAs represent localized outpocketings of the retinal artery wall 6 ( Figure 5). Where the anatomical nature of the aneurysm was unclear, the MA was described as 'indefinable'.…”