Flow and diffusion of indocyanine green and fluorescein dyes in the fovea centralis

Intraretinal leakage of indocyanine green dye

PURPOSE

Indocyanine green (ICG) dye is known to remain selectively in and around choroidal neovascularization (CNV) associated with age-related macular degeneration, and is thought to be cleared from the overlying retinal circulation without leakage. This is the basis of ICG dye-enhanced laser photocoagulation. The authors have observed, however, leakage of ICG dye into cystoid spaces within the retinal and have determined the incidence, clinical features, and angiographic characteristics of this newly described phenomenon.

METHODS

The digital ICG videoangiograms of 149 consecutive patients with exudative age-related macular degeneration and occult CNV were reviewed independently to determine the characteristics of intraretinal ICG dye leakage.

RESULTS

Of the 149 patients with occult CNV, 16 (11%) demonstrated intraretinal leakage of ICG dye between 14 and 34 minutes (median = 20 minutes). The clinical features most commonly associated with this phenomenon are: subretinal fluid (88%), subretinal hemorrhage (88%), subretinal lipid (63%), and retinal pigment epithelial detachment (56%).

CONCLUSIONS

Indocyanine green dye may not be as concentrated in and around CNV as previously reported. The delayed onset of its appearance within intraretinal cystoid spaces may suggest a diffusible choroidal source of leakage. Intraretinal ICG dye may be a relative contraindication for ICG dye-enhanced laser photocoagulation.

Fluorescein. Physiochemical factors affecting its fluorescence

Fluorescein's property of fluorescence is reviewed. Of the many factors which affect its fluorescence, concentration is probably the most important and it best explains why leaking aqueous turns fluorescein bright green during Seidel's test. The intensity and pattern of fluorescein staining of corneal lesions is probably due to the concentration and distribution of fluorescein in the cornea. The concentration of fluorescein achieved in the retinal blood vessels during fluorescein angiography affects its fluorescence.