MACULAR CAPILLARY PARTICLE VELOCITIES - A BLUE FIELD AND SCANNING LASER COMPARISON

Background: Two different techniques are available for measurement of macular capillary particle velocities. The psychophysical blue field s imulation technique gives data on macular leukocyte flow velocities, w hile the scanning laser technique provides information on capillary bl ood velocities of hypofluorescent segments in the macular network. Pub lished velocity data differ considerably between the two methods. The current study was undertaken to compare the two measuring techniques i n a group of healthy volunteers. Methods: Thirty-two healthy subjects (12 man, 20 women, mean age 27 years) participated in this study. All subjects underwent entoptic leukocyte visualization by means of blue f ield simulation followed by fluorescein angiography using scanning las er ophthalmoscopy. Results: The capillary blood velocities measured us ing the scanning laser technique were significantly higher (P < 0.01) than the now velocities estimated with the blue field simulation techn ique (2.68 +/- 0.3 mm/s vs 0.89 +/- 0.2 mm/s). No significant correlat ion between the flow velocities was found (r = -0.22). Conclusion: The differences may be related to different measuring locations and/or me asurements of different phenomena. The blue field technique estimates average leukocyte flow in the macular network, whereas the scanning la ser technique quantifies the velocity of erythrocyte aggregates in the capillary lumen of the para- and perifoveal network. A combination of both techniques may be helpful in interpreting physiological responsi veness and altered velocity pattern in diseased eyes.