Posterior vitreous fluorophotometry in normal subjects

M. S. Roy, R. F. Bonner, P. M. Bungay, M. J. Podgor and B. Collier

We performed vitreous fluorophotometry using the Fluorotron Master and intravenous fluorescein injection of 14 mg/kg of body weight in 22 normal subjects. Various methods of analysis were used to evaluate vitreous fluorescein concentration at 3 mm from the retina as well as averaged over the posterior 6 mm. The various methods of calculation yielded mean (+/- SD) postinjection values ranging from 1.7 +/- 1.4 to 4.3 +/- 2.3 ng/mL at 30 minutes and from 7.1 +/- 2.4 to 10.8 +/- 2.7 ng/mL at 60 minutes. The permeability index determined 60 minutes after injection ranged from 0.92 +/- 0.40 X 10(-7) to 1.19 +/- 0.30 X 10(-7) cm/s, according to the protocol used. Replicate pairs of measurements in six subjects demonstrated that the procedure was reproducible to within 17% to 49%, depending on the analysis. The results suggest that if the current methods of data analysis are used, fluorescein leakage might be considered abnormally high if at 60 minutes the 3-mm posterior vitreous fluorescein concentration corrected for background fluorescence exceeds 14.3 ng/mL and/or the permeability index exceeds 2 X 10(-7) cm/s.