Hemorheologic Abnormalities Associated with HIV Infection: In Vivo Assessment of Retinal Microvascular Blood Flow

PURPOSE: To evaluate retinal microvascular blood flow in human immunodeficiency virus (HIV)-infected individuals using scanning laser Doppler flowmetry (SLDF) and to seek correlations between flow and various laboratory measures that may predict alterations in flow. METHODS: The Heidelberg Retina Flowmeter and SLDF software were used to acquire in vivo retinal blood flow data from 24 HIV-infected individuals and 16 HIV-negative control subjects. In each subject, separate scans were performed in each of six retinal regions: nasal parapapillary retina; macula; and the superior, nasal, inferior, and temporal periphery. Erythrocyte aggregation (assessed in vitro by a fully automatic erythrocyte aggregometer and by zeta sedimentation ratio [ZSR, a hematocrit-independent sedimentation rate]), serum fibrinogen level, plasma viscosity, and leukocyte rigidity (assessed in vitro with a cell transit analyzer) were compared with flow in selected regions. RESULTS: Flow was significantly higher in the periphery (superior, nasal, inferior, temporal) than in the posterior retina (nasal parapapillary retina, macula). Flow was highest in the temporal periphery for both HIV-infected subjects and control subjects. Flow in the posterior retina was significantly lower in HIV-infected subjects than in control subjects (P < 0.0001). Among HIV-infected individuals, flow in the macula correlated negatively with ZSR (r = -0.397, P = 0.0547) and leukocyte rigidity (r = -0.505, P = 0.0119). CONCLUSIONS: Microvascular blood flow in the posterior retina is reduced in HIV-infected individuals. Both increased erythrocyte aggregation and increased leukocyte rigidity contribute to this hemorheologic abnormality.