A typical view of the conjunctival microcirculation in an SCD patient 1 hour after hospitalization for painful crisis.

Optical magnification, × 4.5; onscreen magnification, × 125. Characteristic landmark features include extreme conjunctival avascularity, complete absence of capillaries, and a further decrease in the presence of arterioles and small venules, giving the bulbar conjunctival surface a more debilitating vascular presentation than the already avascular steady-state blanched appearance. Note the sustained and significant decrease in venular diameter, increased blood sludging caused by the stoppage of blood flow, a sustained and uniform vasocontraction, and the absence of focal occlusion or constriction in the vessels.