Diabetic Capillary Microaneurysms of the Retina

Saccular dilations arising from one side of the retinal capillaries are part of the typical pathology of diabetic retinopathy and are known as capillary microaneurysms. They were first described by Nettleship1in 1888. However, it seems that little attention was paid to Nettleship's discovery and capillary microaneurysms were rediscovered by Ballantyne and Loewenstein2in 1944. This rediscovery resulted in great interest and an extensive number of papers concerning the structure, development, and significance of the microaneurysms in diabetic retinopathy. Outstanding are those of Ballantyne,3,4Friedenwald,5-7Ashton,8-12and Pope.13 Several theories have been suggested to explain the development of diabetic retinal microaneurysms. Ballantyne3,4considered a combination of stasis and increase of venous pressure caused by thrombosis of smaller retinal veins and additional local weakening of the capillary wall caused by endothelial degeneration as responsible for the saccular dilation. He observed the deposition of fat