Images of Memorable Cases: Case 26 Normal conjunctival circulation (approximately x35). Conjunctiva of a profoundly anemic teenager (approximately x30). 26. Sickle cell disease Inspection of the conjunctiva with the +40 lens of the ordinary ophthalmoscope can be a useful adjunct to the diagnosis of certain types of sickle cell disease, particularly the homozygous form. The characteristic sign consists of sharply defined, dark-red, comma-shaped or corkscrew-shaped vessel fragments that appear isolated from the rest of the conjunctival circulation. These anomalous segments are visible primarily in that part of the lower bulbar conjunctiva covered by the lid. The pathogenesis of this conjunctival sign remains speculative. There is evidence, however, that endothelial proliferation with trapping of erythrocytes occurs in the distal portion of some capillaries; immediately proximal to such involvement, the vessels are dilated and thin-walled. Infusion of blood or inhalation of oxygen can modify, if not temporarily eliminate, the sign. Conversely, eye drops that contain vasoconstricting agents can render the sign more conspicuous.