The retina (the light-sensitive layer of tissue at the back of the eye) needs a lot of oxygen and other nutrients carried to it by the red blood cells in the blood. The retina also produces a lot of waste materials (such as carbon dioxide, CO2) that must be removed by the red blood cells. Therefore, any disturbance to the red blood cell movement through the blood vessels, especially through the capillaries (the smallest diameter vessels); can have a significant effect on the health of the retina. Red blood cells are too small to be seen using regular tests, so it has been impossible to see their movement through the retinal blood vessels to determine how they are related to various retinal diseases.

The purpose of this study is to examine how the red blood cells move through the capillary vessels of the retina and the choroid of the eye by using the new procedure of injecting indocyanine green dye directly into the red blood cells.