Purpose
To evaluate the feasibility of retinal thermal damage assessment in a rabbi
t eye model by using laser-induced release of liposome-encapsulated dye.
Methods
After anesthesia, thermosensitive liposomes (DSPC) loaded with 5,6-Carboxyf
luorescein were injected intravenously to pigmented rabbits. Retinal photoc
oagulations were performed with a 810 nm diode laser (p = 100 to 400 mW, ph
i = 500 mu m, 1s) (OcuLight(R), IRIS Medical Instruments Inc., USA). Fluore
scence measurements in the area of the laser exposures were then made with
a digitized angiograph (CF-60UVi(R), Canon-Europe, The Netherlands; OcuLab(
R), Life Science Resources Ltd(R), England).
Results
Fluorescent spots were observed for power ranging from 100 +/- 5 m W to 400
+/- 5 mW. The fluorescence intensity increased linearly with the power and
reached a plateau at 300 +/- 5 mW. The fluorescence intensity, was correla
ted to the maximum temperature at the center of the laser spot with a linen
s increase from 42 +/- 3 degrees C to 65 +/- 3 degrees C. These results are
consistent with our two previous studies with DSPC liposomes for temperatu
re measurements in a tissue model and then in a vascular model.
Conclusion
This preliminary study demonstrates the possibility of a laser-induced rele
ase of liposome-encapsulated dye for a quantification of diode laser induce
d thermal damage in ophthalmology. Such a method could be useful for al rea
l-rime monitoring of laser photocoagulation for conditions such as choroida
l neovascular membranes when a precise thermal damage is required near the
foveolar area.