Complete Blood Count and Retinal Vessel Calibers

Objective: The influence of hematological indices such as complete blood count on microcirculation is poorly understood. Retinal microvasculature can be directly visualized and vessel calibers are associated with a range of ocular and systemic diseases. We examined the association of complete blood count with retinal vessel calibers. Methods: Cross-sectional population-based Blue Mountains Eye Study, n = 3009, aged 49+ years. Complete blood count was measured from fasting blood samples taken at baseline examination, 1992-4. Retinal arteriolar and venular calibers were measured from digitized retinal photographs using a validated semi-automated computer program. Results: All analyses adjusted for age, sex, systolic blood pressure, diabetes, smoking and fellow vessel caliber. Higher hematocrit, white cell count and platelet count were associated with narrower arteriolar caliber (p = 0.02, 0.03 and 0.001 respectively), while higher hemoglobin, hematocrit, red cell count, white cell count and platelet count were associated with wider venular caliber (p < 0.0001 for all). Each quintile increase in hematocrit, white cell count and platelet count was associated with approximately 0.5 mu m narrower arteriolar caliber; whereas each quintile increase in all of the complete blood count components was associated with approximately 1-2 mm wider venular caliber. Conclusions: These associations show that elevated levels of hematological indices can have adverse effects on the microcirculation.