The Effect of Intravetious ICG Pretreatment on Threshold Energy Values of Transpupillary 810-nm Diode Laser Retinal Photocoagulation

Purpose: To study the effect of intravenous indocyanine green (IV ICG) pretreatment, on threshold energy values of transpupillary 810-nm diode laser photo coagulation-induced, ophthalmoscopically visible lesions of the rabbits' retina. Materials and Methods: Fourteen eyes of 4 albino and 3 pigmented, New Zeland rabbits were studied. The right eyes of 4 albino and 3 pigmented rabbits underwent, transpupillary 810nm diode laser photocoagulation, using 600 and 1000 pm spot sizes, and 0.1, 0.2 exposure times. Clinically defined grade 3 (30) photocoagulation lesions were produced, with all laser parameters. IV ICG was injected, and diode laser photocoagulation was repeated in the fellow eyes using same parameters, after 5 minutes from the injection. After 40 minutes from the IV ICG injection, the procedures were repeated in the different areas of the retina of the same 3 rabbits' left eyes. Threshold values obtained before and after IV ICG injection, were compared statistically. Results: Intravenous ICG pretreatment reduced threshold values (mW) necessary to produce, ophthalmoscopically visible lesions, with 810-nm diode laser photocoagulation, on 4 albino and 3 pigmented rabbits' retinas, significantly. For all laser parameters, comparisons made by " Wilcoxon Signed Ranks" test were statistically significant (p<0.05) for values obtained 5 minutes after IV ICG injection. Conclusion: In this experimental study, IV ICG pretreatment reduced the power necessary to produce clinically defined retinal photocoagulation lesions with 810-nm diode laser retinal photocoagulation, both in albino and pigmented rabbits' retinas. Especially in hypopigmented retinas, threshold values necessary to produce clinically visible retinal lesions with diode laser increase and for that reason, IV ICG and transpupillary 810 nm-diode laser photocoagulation combination can be a useful method in hypopigmented retinas.