June 2023
Volume 64, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2023
Indocyanine green (ICG) angiography: What do we see?
Author Affiliations & Notes
  • Dan Mejlachowicz
    Centre de Recherche des Cordeliers, Paris, Île-de-France, France
  • Seiki Achiedo
    Centre de Recherche des Cordeliers, Paris, Île-de-France, France
  • Theano Eirinopoulou
    Institut du Fer a Moulin, Paris, Île-de-France, France
  • Min Zhao
    Centre de Recherche des Cordeliers, Paris, Île-de-France, France
  • Francine F Behar-Cohen
    Centre de Recherche des Cordeliers, Paris, Île-de-France, France
    Hopital Cochin, Paris, Île-de-France, France
  • Footnotes
    Commercial Relationships   Dan Mejlachowicz None; Seiki Achiedo None; Theano Eirinopoulou None; Min Zhao None; Francine Behar-Cohen None
  • Footnotes
    Support  ANR-20-CE17-0034
Investigative Ophthalmology & Visual Science June 2023, Vol.64, 3505. doi:
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    • Get Citation

      Dan Mejlachowicz, Seiki Achiedo, Theano Eirinopoulou, Min Zhao, Francine F Behar-Cohen; Indocyanine green (ICG) angiography: What do we see?. Invest. Ophthalmol. Vis. Sci. 2023;64(8):3505.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : ICG is an albumin and lipid binding dye absorbing in the far red and used in angiography to visualize choroidal vessels (ICG-A). But ICG-A also show non vascular, poorly characterized structures. To improve clinical interpretation of ICG-A, we studied ICG transport in different layers of rat retina.

Methods : Different rat strains (wild-type (WT), transgenic (TG) animals overexpressing human mineralocorticoid receptor (MR), pigmented and non-pigmented) were used. RPE/choroid were incubated for 45 min in 10% ICG at 37°C (5% CO2) or RPE/choroid and neural retina were examined 1 and 6 hours after intravenous ICG injection. Ultra-deep red confocal microscope allowed to localize ICG in flat-mounted tissues and immunohistochemistry for Tryptase (mast cells), TUBB3 (nerves), IBA1 (macrophages) and caveolin-1 (caveolae) was performed.

Results : In RPE/choroid organoculature, ICG enters homogeneously in the RPE of WT rats whilst heterogeneous staining was observed in the TG RPE (vesicle-like shapes and at the cell membrane). Co-localization with caveolin-1 indicates caveolae transport at the membrane. ICG also localized at the external wall of the choriocapillaris in both WT and TG indicating that ICG is transported through caveolae. In the choroid, ICG-labeled cells co-localized with Tryptase, a mast cell marker, and ICG-labeled linear structures co-localized with TUBB3 indicating that ICG labels choroidal nerves.
After IV injection, at 1 hour, ICG localized in the RPE, homogeneously in WT, heterogeneously with vesicle-like structures in TG rats. Choroidal nerves and mast cells are stained with ICG. In TG rats, increased number of mast cells was observed. In the neural retina at 1h, ICG is localized in the vessels and in the ganglion cell layer. At 6h, ICG was observed in photoreceptors outer segments. In TG rats, outer retina staining was increased suggesting higher transport from the choroid towards photoreceptors.

Conclusions : ICG should not be considered only as a vascular dye. It is transported in the RPE and in the outer retina and stains mast cells and choroidal nerves. ICG-A images should be reconsidered taking into account these observations. In TG rats, increased transport from the choroid towards the outer retina indicates that steroids control the macromolecular gradients.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

 

Incubation of rat choroid with ICG labels mast cells and nerves.

Incubation of rat choroid with ICG labels mast cells and nerves.

 

ICG localization in the RPE and choroidal mast cells number 1 hour after IV injection in WT and TG rats.

ICG localization in the RPE and choroidal mast cells number 1 hour after IV injection in WT and TG rats.

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