Choriocapillaris photodynamic therapy using indocyanine green.
OBJECTIVE
To evaluate the potential of photodynamic therapy using indocyanine green for occlusion of choroidal neovascularization, the authors studied efficiency and collateral damage of photodynamic therapy-induced photothrombosis in the rabbit choriocapillary layer.


METHODS
Fundus photography, fluorescein angiography, and light and transmission electron microscopy were used to study the efficiency of photodynamic therapy-induced photothrombosis using indocyanine green as the photosensitizer, and to assess the resultant collateral damage. The delivery system consisted of a modified infrared diode laser tuned to 810 nm, near the maximum absorption peak of indocyanine green.


RESULTS
Choriocapillary occlusion was achieved at indocyanine green doses of 10 and 20 mg/kg and a radiant as low as 6.3 J/cm(2). When photodynamic therapy was performed with indocyanine green doses of 10 mg/kg, damage to the neural retina was minimal. Only inner photoreceptor segments showed degeneration, probably secondary to choroidal ischemia. Bruch membrane remained intact. Retinal pigment epithelium was invariably damaged, as seen with other photosensitizers. Temporary occlusion of large choroidal vessels occurred at both dye doses.


CONCLUSIONS
In this experimental study, photodynamic therapy using indocyanine green and 810-nm light irradiation produced endothelium-bound intraluminal photothrombosis, with preservation of the retinal architecture and minimal loss of visual cells. Membrane targetability, hydrophilic and fluorescent properties, and activation at 805 nm suggest indocyanine green as a potential photosensitizer for choroidal neovascularization. These combined considerations point toward further study of photodynamic therapy using indocyanine green for the treatment of choroidal vascular disease.
Costa
R A
RA
Department of Ophthalmology, Paulista School of Medicine, Federal University of São Paulo, São Paulo, SP-Brazil 04524-020. roger.retina@globo.com
Farah
M E
ME
Freymüller
E
E
Morales
P H
PH
Smith
R
R
Cardillo
J A
JA
D000818:Animals; D001813:Blood-Retinal Barrier; D002829:Choroid / Q000098:blood supply* / Q000648:ultrastructure; D020256:Choroidal Neovascularization / Q000188:drug therapy* / Q000473:pathology; D005451:Fluorescein Angiography; D005654:Fundus Oculi; D007208:Indocyanine Green / Q000627:therapeutic use*; D008027:Light; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D011817:Rabbits; D012160:Retina / Q000293:injuries / Q000648:ultrastructure
D017319:Photosensitizing Agents; D007208:Indocyanine Green