Purpose: To investigate eyes with solitary large aneurysms arising from retinal capillaries.
Methods: Consecutive patients with aneurysms greater than 200 µm in diameter were evaluated with a comprehensive ophthalmologic examination including optical coherence tomography, optical coherence tomography angiography, and fluorescein angiography. The aneurysms were solitary in the sense, and there was only one aneurysm larger than the threshold diameter and a few or no other aneurysms.
Results: There were 5 patients, 3 male patients, who had aneurysms that reached a maximal mean size of 273.4 µm. One patient had stable diabetic retinopathy and had a documented growth of a capillary aneurysm to 331 µm over an 8-year 7-month period until the aneurysm was associated with widespread edema. The remaining 4 patients did not have diabetes or any discernable retinal vascular disease. Anti-vascular endothelial growth factor treatment was associated with a partial response in one patient and no apparent response in the others. Laser photocoagulation of the aneurysms resulted in resolution of the edema and involution of the lesions.
Conclusion: Large aneurysms arising from retinal capillaries occur and have a candidate name of retinal capillary macroaneurysms. Histologic evaluation of retinal capillary aneurysms shows the presence of matrix metalloproteinase-9, which may function to decrease the wall strength in the face of increasing wall tension from aneurysmal expansion, as predicted by LaPlace's law. Thus, retinal capillary macroaneurysms may have multiple forces driving their formation.