Two Types of Retinal Capillary Path in Humans using Fluorescein Leukocyte Angiography

ABSTRACT

PURPOSE: To explain hypothesis that there are two types of human retinal capillary pathways. One is simple type and the other is complex type. The former plays a role in blood flow regulation and the latter does capillary function itself. METHODS: We measured the length, tortousity, and flow velocity of human retinal capillaries using Fluorescein Leukocyte Angiography (FLA) with a Scanning Laser Ophthalmoscope (SLO) on two healthy adult male volunteers. We studied distribution and pathways of human retinal capillaries on the posterior pole. RESULTS: The lengths of capillaries were distributed with two peak incidence. One was 70 microgram and the other 240 microgram. There was no relationship between capillary length and tortousity. The correlation between capillary length and leukocyte velocity showed that the shorter capillary group has a wide range of velocity but the longer group has a narrow range of velocity. CONCLUSIONS: Two types of retinal capillary pathways exist on human retina. Compared with two types of capillaries on the cat retina described by Ben-nun et al, we found that the shorter capillary type plays a role in blood flow regulation and the longer type in capillary function itself.