VARIABILITY IN CHORIOCAPILLARIS BLOOD-FLOW DISTRIBUTION

Purpose. To investigate variability of choriocapillaris blood flow pat terns. Methods. After the intravenous injection of indocyanine green, angiograms were recorded at 30 images per second in rhesus monkey eyes using a fundus camera equipped with a pulsed laser diode light source , synchronized with a gated (5 msec), intensified charge-coupled devic e, or CCD, video camera. Images of choriocapillaris filling alone were extracted. Plastic corrosion casts were made of two of the monkey's c horoidal vasculatures for subsequent scanning electron microscopy exam ination. Results. Pulsed laser indocyanine green fluorescence excitati on produced better definition of choriocapillaris filling than had bee n achieved using continuous illumination. No correlation was found bet ween the choriocapillaris plexus architecture revealed by the plastic corrosion casts and the observed choriocapillaris lobular filling. Ove rall posterior pole choriocapillaris dye-filling patterns were relativ ely stable for periods of days, but they changed gradually for periods of weeks. Localized minor pattern changes occurred on a much shorter time scale. Choriocapillaris filling patterns were altered by acutely elevating intraocular pressure, by O2 and CO2 breathing, and by argon laser retinal photocoagulation of adjacent areas. Conclusions. Chorioc apillaris filling patterns appear to be determined by the network of p erfusion pressure gradients that exist among the interspersed feeding arterioles and draining venules connected to the choriocapillaris plex us. Changes in intraocular pressure and in blood P-O2 and P-CO2 levels can produce marked changes in the distribution of choriocapillaris bl ood flow. Retinal laser photocoagulation of adjacent fundus areas alte rs choriocapillaris blood flow to the extent that the altered flow mig ht be an important factor in the beneficial results attributed to reti nal laser treatment.