Transpupillary thermotherapy threshold parameters: effect of indocyanine green pretreatment.
OBJECTIVE
To evaluate the effect of combined treatment with systemic indocyanine green (ICG) on threshold fluence levels of transpupillary thermotherapy (TTT) in rabbits.


METHODS
Four pigmented rabbits and 13 nonpigmented rabbits were studied. TTT was performed on normal rabbit choriocapillaris using an 810-nm diode laser via slit-lamp biomicroscope delivery through a Goldmann macular lens. Laser spot size, power, and duration of laser exposure were varied to achieve a range of TTT fluences for threshold testing in both albino and pigmented rabbit fundi. Intravenous ICG pretreatment at doses of 0.41 to 10 mg/kg was initiated at varying times before TTT treatment. After the experiment, the eyes were enucleated under deep anesthesia, the animals were killed, and the eyes were prepared for light microscopy.


RESULTS
When intravenous ICG pretreatment was employed, there was a dose-dependent decrease in the TTT fluence threshold as compared with known threshold values. At threshold fluences, histopathologic sections revealed damage to all layers of the retina in addition to choriocapillaris damage.


CONCLUSIONS
Intravenous ICG pretreatment can be used to lower the TTT threshold fluence and irradiance required to create angiographically visible lesions in the normal rabbit choriocapillaris. Damage was seen in all layers of the retina and choriocapillaris at threshold levels when TTT was used alone or in combination with ICG pretreatment.
Peyman
Gholam A
GA
Department of Ophthalmology, Tulane University Health Sciences Center, New Orleans, Louisiana 70112-2699, USA. mchiass1@tulane.edu
Genaidy
Mahmoud
M
Yoneya
Shin
S
Men
Gamze
G
Ghahramani
Fatemah
F
Kuo
Po-Cheng
PC
Bezerra
Yanno
Y
Nishiyama-Ito
Yoko
Y
Moshfeghi
Andrew A
AA
D000818:Animals; D004396:Coloring Agents / Q000627:therapeutic use; D003131:Combined Modality Therapy; D005131:Eye Injuries / Q000473:pathology / Q000517:prevention & control*; D006979:Hyperthermia, Induced; D007208:Indocyanine Green / Q000627:therapeutic use*; D017075:Laser Coagulation / Q000379:methods; D023421:Models, Animal; D010778:Photochemotherapy / Q000379:methods*; D010857:Pigment Epithelium of Eye / Q000502:physiology; D011680:Pupil; D011817:Rabbits; D011836:Radiation Tolerance; D012160:Retina / Q000293:injuries* / Q000473:pathology; D012164:Retinal Diseases / Q000473:pathology / Q000517:prevention & control*; D012684:Sensory Thresholds
D004396:Coloring Agents; D007208:Indocyanine Green