Sequential microdissection and scanning electron microscopy of ciliary microvascular castings.

Intracarotid injection of methylmethacrylate followed by tissue corrosion produces detailed replicas of the ocular microvasculature that can then be studied with the scanning electron microscope. The resultant photographs allow careful scrutiny of even the finest capillaries. However, when applied to the ciliary body, a complicated three dimensional system, we found stereo scanning electron micrography essential to fully appreciate its arteriolar and capillary interconnections. These stereoscopic analyses indicated that specific superficial vessels required excision to visualize deeper, previously hidden microvascular relationships. Using a pneumatically powered ultra microscissors guided by a micromanipulator we successfully removed these vessels. Deeper views were then obtained through repeat stereo scanning electron microscopy. This sequential microdissection and stereo scanning electron microscopy revealed that the major ciliary processes are supplied by two types of arterioles arising from the major arterial circle. Constricted anterior arterioles supply anterior and marginal aspects of the processes as well as interprocess capillary beds. Less constricted posterior arterioles feed capillaries confined to the base of the major processes as well as minor ciliary processes via posterior interprocess connections. Choroidal veins were seen to directly drain both anterior and posterior interprocess capillary beds.