Macular vasculature, visual acuity, and irreversibly sickled cells in homozygous sickle cell disease

ABSTRACT

Observations of visual acuity and the conjunctival, macular, and perimacular vascularity have been assessed in patients with homozygous sickle cell (SS) disease. There were 17 matched pairs, each consisting of one patient with a high count (>15 percent) and one with a low count (<5 percent) of irreversibly sickled cell (ISCs). The macular vascular bed was assessed by measurements of the foveal avascular zone (FAZ), perimacular zones, and counts of perimacular vascular abnormalities (perimacular counts). Small foveal avascular zones and high perimacular counts were commoner in younger than older patients and there was a significant inverse correlation between size of the FAZ and the perimacular count. These observations were compatible with the hypothesis that perimacular vessel anomalies represent the early vaso-occlusive phase which progresses to ischaemia and the formation and enlargement of avascular areas. Visual acuity was assessed by Snell's test type and by measuring contrast sensitvity. There was no obvious relationship between acuity measured by the 2 methods and no relationship between acuity and observations of mascular vascularity. High ISC counts were significantly related to abnormalities of conjunctival vasculature, but no relationship was noted with abnormalities of the macular vasculature or with visual acuity (AU)