Schematic interpretation of indocyanine green angiography in posterior uveitis using a standard angiographic protocol

Abstract

Objective: Indocyanine green angiography (ICGA) detects fluorescence produced by the ICG molecule in the near infrared wave lengths showing choroidal vascular structures. Indocyanine green angiography may prove useful in the workup of uveitis with choroidal involvement. The authors' purpose was to test a standardized ICGA protocol for posterior uveitis to gather systematic and comparable data and to design a schematic approach for the interpretation of angiographic signs.

Design: The proposed ICGA procedure included the search for preinjection fluorescence. In the early phase of ICGA (until +/- 2-3 minutes postinjection), posterior pole frames were taken to detect abnormalities in the retinal and choroidal arteriovenous circulation patterns. During the intermediate phase (12 +/- 3 minutes), posterior pole frames and eight 360 degrees panorama frames were taken to detect fluorescence abnormalities in the background impregnation of the choroid, the same sequence being repeated in the late phase (40 +/- 10 minutes). A cohort of more than 300 patients was analyzed in this standard fashion in 2 centers. PARTICIPANTS AND MAIN OUTCOME MEASURE: Determination of ICGA features and the proposed schematic approach for ICGA interpretation were based on the analysis of 109 cases of posterior uveitis with a well-determined diagnosis.

Results: For uveitis, the intermediate and late phases of ICGA were found to yield the most valuable information showing either ICG hyperfluorescence or hypofluorescence or both. The ICG hyperfluorescence, always reflecting increased leakage or staining but not window defects because there is no pigment epithelium screen in ICGA, could originate either from increased leakage of the choriocapillaris, the large choroidal, or the retinal vessels. The characteristic ICG hypofluorescent dark dots indicating impairment of physiologic impregnation of the choroid could take at least five different patterns.

Conclusion: To date, ICGA features still are difficult to interpret. The proposed standardized ICGA protocol and schematized interpretation for posterior uveitis will help determine ICGA semiology for these disorders and might give new insights into their pathophysiology.