Effects of granulocyte colony stimulating factor on retinal leukocyte and erythrocyte flux in the human retina

PURPOSE. The blue-field entoptic technique was introduced more than 20 years ago to quantify perimacular white blood cell flux. However, a final confirmation that the perceived corpuscles represent leukocytes is still unavailable. METHODS. The study design was randomized, placebo-controlled, and double masked with two parallel groups. Fifteen healthy male subjects received a single dose of granulocyte colony stimulating factor (G-CSF, 300 μg) and 15 other subjects received placebo. The following parameters were assessed at baseline and at 12 minutes and 8 hours after administration: retinal white blood cell flux, with the blue-field entoptic technique; retinal blood velocities, with bidirectional laser Doppler velocimetry; retinal venous diameter determined with a retinal vessel analyzer; and blood pressure and pulse rate determined by automated oscillometry and pulse oxymetry, respectively. RESULTS. After 12 minutes, G-CSF reduced total leukocyte count from 5.5 ± 1.4 10⁹/L at baseline to 1.9 ± 0.4 10⁹/L. This was paralleled by a 35% ± 11% decrease in retinal white blood cell density. After 8 hours G-CSF increased total leukocyte counts to 20.0 ± 4.4 10⁹/L. Again, this increase in circulating leukocytes was reflected by an increase in retinal white blood cell density (110% ± 48%). All effects were significant at P < 0.001. By contrast, none of the other hemodynamic parameters was changed by administration of G-CSF. CONCLUSIONS. The results clearly indicate that the blue-field entoptic technique assesses leukocyte movement in the perimacular capillaries of the retina. Moreover, white blood cell density appears to adequately reflect the number of circulating leukocytes within the retinal microvasculature. Hence, an increase in retinal white blood cell density does not necessarily reflect retinal vasodilatation.