Fluorescein in the human optic disc. II. The fluorescein appearance rate.

Automatic intravenous infusion of fluorescein with constant speed during 25 sec is followed by a gradual increase of fluorescein in the retinal arteries and in the disc tissue. The slope of this increase Sd divided by the maximum fluorescein Md in an area of the disc Sd/Md is called Fd, the same for a retinal artery is called Fr. Fr was found to be independent of intraocular pressure in the range examined (mean pressures 15--30 mm applanantion). Fd/Fr = omega, the "fluorescein appearance rate" is correlated to the linear velocity of blood in the capillaries of the observed disc area and hence to its circulation. omega was found to be diminished in 6 out of 9 cases with ocular tension between 26 and 38 mm applanation, but not in 3 cases. It was not diminished in 4 cases with 22-25 mm applanation. Further studies are necessary to elucidate these findings suggesting some adaptation of disc circulation to intraocular pressure but not proving it: fluorescence from vessels behind the lamina cribrosa has the tendency to seemingly "normalise" omega.