Dual-Perspective Analysis of Vascular Formations in Sickle Cell Retinopathy

To examine the sickle cell retina in dual perspective (vascular patterns en bloc and structure in serial sections) to gain new insights into sickle cell retinopathy. We analyzed the retinas of two patients with sickle cell disease (a 54-year-old patient with hemoglobin SC, heterozygous for the S and C mutation in the beta chain of the globin gene, and a 20-month-old patient with sickle cell anemia [SS], homozygous for the S mutation) using the previously described adenosine diphosphatase flat-embedding technique. The dual-perspective analysis afforded by our technique revealed that the primary site of occlusions was located at the precapillary level. An unusual neovascular formation, the hairpin loop, was observed in both patients' retinas and appeared to result from recanalization of the wall of an occluded vessel. Many autoinfarcted preretinal neovascular formations were observed in the older SC patient. Two patent preretinal formations were studied in detail and their evolution appeared to be influenced by mechanical factors. The vessels appeared to have been extruded from the retina, perhaps owing to hydrostatic pressure secondary to downstream occlusions. Small pigmented lesions consisting of retinal pigment epithelial cells ensheathing channels that resembled autoinfarcted vessels were found in the eye of the SC patient. This study illustrates unusual morphological features of intraretinal and preretinal neovascularization and of chorioretinal lesions in sickle cell retinopathy and suggests alternative mechanisms for their formation.