Indocyanine Green Angiography: Choroidal Dye Contributes to Retinal Assessment

Abstract

Abstract: : Purpose:Previous studies have shown a lack of correlation between ICG and fluorescein angiography (FA) arteriovenous passage (AVP) times. However, these studies failed to identify the source of the discrepancy. The purpose of this study was to determine whether choroidal fluorescence contributes to the lack of agreement between ICG AVP times and FA AVP times. Methods: All procedures were approved by an IRB, and informed consent was obtained. Sixteen patients with primary open angle glaucoma (POAG) (63.5 ± 10.8 years, 9 male, 7 female) were recruited. ICG angiography was attained on four occasions using a Rodenstock scanning laser ophthalmoscope (SLO 101, Germany). Choroidal and retinal hemodynamics were measured using a digital image analysis system. Choroidal measurements were obtained using six 63x63 pixel areas, two peripapillary and four perifoveal. Brightness was plotted over time to attain choroidal filling dynamics. Filling times, filling slopes, and dye duration ( the width of the filling curve) were quantified. AVP time was calculated using 3x3 pixel windows placed on the superior temporal retinal artery and vein pair adjacent to the optic disc. Results: ICG AVP times did not correlate with choroidal filling times or slopes; however ICG AVP times were significantly correlated to dye duration in 7 instances (p ≤ 0.05 and r² ≥ 0.3 for each). Conclusions: ICG AVP times are confounded by light from the choroid and represent choroidal circulation time.

Keywords: blood supply • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • imaging/image analysis: clinical