Reactivity of white blood cell flux to hyperoxia in patients infected with human immunodeficiency virus

Purpose: The aetiology of the apparently vasoocclusive phenomena in human immunodeficiency virus (HIV)-related retinopathy is not well understood. Several hypotheses, including infectious damage of the retinal vasculature and altered retinal haemodynamics, have been postulated. Direct measurement of oxygen tension in the retina is not possible in vivo and indirect methods have to be employed. The objective of this study was to investigate the retinal vascular response to 100% oxygen breathing in patients with HIV. Methods: Twelve patients infected with HIV and 12 healthy individuals, matched for age, sex and smoking habits, were studied in an open study using the blue-field entoptic technique for the measurement of retinal white blood cell (WBC) flux. Reactivity in retinal blood flow during 100% O₂ breathing over 15 min was measured and expressed as percentage change over baseline. Results: WBC velocity during oxygen inhalation decreased over baseline by 9.0 ± 5.8% in HIV-infected patients and by 18.6 ± 5.4% in healthy participants (p < 0.04 between groups, anova). The decrease in WBC velocity was paralleled by a decrease in WBC density. This decrease tended to be more pronounced in healthy participants (13.6 ± 7.9%) than in HIV-infected patients (8.0 ± 10.8%), but the difference was not statistically significant (p = 0.1 between groups, anova). WBC flux decrease was 16.2 ± 11.4% in HIV-infected patients and 29.5 ± 9.5% in the control group and was significant between groups (p = 0.007 between groups, anova). Conclusion: Our results indicate a reduced reactivity of WBC flux to systemic hyperoxia in patients with HIV. Whether abnormal retinal haemodynamics in HIV-infected persons contributes to the pathogenesis of HIV-related microvascular diseases or is a consequence of the structural changes associated with the disease is unknown.