Which Quantity of Fluorescein and Indocyanine Green Dye Is Needed for Digital cSLO Fluorescence Angiography

Abstract

Abstract: : Purpose: With the advent of confocal scanning laser ophthalmoscopy (cSLO) it is possible to detect lower levels of fluorescence than with previous conventional camera systems. We therefore hypothesized that recommendations regarding the quantity of dyes for i.v. injections (500 mg for fluorescein and 25 mg for indocyanine green – ICG) may no longer be accurate and systematically determined the minimally required amounts of fluorescein and indocyanine green (ICG) dye for digital cSLO fluorescence angiography. Methods: Fluorescein and ICG angiographies were performed in a total of 53 patients with age–related macular degeneration using a cSLO (Heidelberg Retina Angiograph 2, Heidelberg Engineering, Heidelberg, Germany). The amount of dye for bolus injections was gradually tapered while the concentration remained identical:. 500–250–200–166–100 mg for fluorescein and 25–20–15–10–5–2.5 mg for ICG. Standardized acquisition of images was performed at 1, 5, 15 and 30 min following i.v. injection. Assessment of lens opacities was performed using a Scheimpflug camera (EAS–1000, Nidek). Images were evaluated and graded by two independent readers, who were blinded with regard to the amount of dye used for all recorded angiograms. Results: At amounts as low as 166 mg fluorescein in 1.6 ml good image quality was achieved during all phases after injection. Late phase images (15 and 30 min) showed somewhat less contrast which was, however, irrelevant for interpretation of the angiograms or clinical management of the patients as judged by the readers. Nausea occurred less frequent with lower quantities of fluorescein dye injected. 1 and 5 min after injection of ICG all amounts applied also resulted in sufficient image quality during early and late phases. The lower limit for the amount of injected dye to allow readable images was 5 mg in 1 ml. Conclusions: With increased sensitivity of novel confocal scanning laser systems used for routine angiography amounts of fluorescein can be reduced by a third (166 mg) and by a fith for ICG (5 mg) without relevant loss of image quality or information. Given current cost restraints this also allows for relevant savings especially in ‘high–volume’ clinical settings.

Keywords: age-related macular degeneration • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)