Effects of Subretinal Injection of Hyposmolar Solutions of Indocyanine Green 0.05%, Trypan Blue 0.15% and Glucose 5% in Rabbits

Abstract

Abstract: : Purpose: To evaluate the effects of subretinal injection of hyposmolar solutions of indocyanine green (ICG) 0.05%, trypan blue (TB) 0.15% and glucose (SG) 5% in rabbits. Methods: Eight pigmented rabbits underwent three–port vitrectomy in the right eye followed by subretinal injection of hyposmolar ICG (0,05% and 251 mOsm), hyposmolar TB (0.15% and 263 mOsm) and hyposmolar SG (5% and 253 mOsm). The subretinal injections were performed just inferior to the optic disc. Balanced Salt Solution (BSS) (300 mOsm) was also injected subretinally as a control solution. The subretinal blebs of the four substances were separated by two reference laser marks which were made using a red diode laser in order to facilitate histological sections after subretinal blebs reabsorption. The animals were examined at 6 hours, 12 hours, 24 hours and 14 days after surgery. The eyes were studied by fluorescein angiography, light and electron microscopy. Results: All the subretinal blebs were flat 24 hours following the surgical procedures. Subretinal injection of BSS caused minimal photoreceptor outer segments (POS) edema at 6, 12, 24 hours and 14 days after surgery. Subretinal SG injection showed POS edema, photoreceptor inner segments (PIS) edema, outer nuclear layer (ONL) edema and also ganglion cells (GGC) edema; Minimal ONL pyknosis was observed 24 hours and 14 days following subretinal hyposmolar SG injection. Subretinal TB injection caused not only POS, PIS and GGC edema but also pyknosis of the ONL during all follow–up; this damage was more important 24 hours and 14 days following subretinal TB injection, when the RPE was also affected. Additionally, subretinal ICG injection caused a severe damage of the PIS, POS, ONL, RPE and also GGC edema that was observed during the entire follow–up. Conclusions: Subretinal delivery of hyposmolar ICG (0.5 mg/ml) and hyposmolar TB (1.5 mg/ml) induced damage of the RPE, PIS/POS and ONL during all follow–up. The damage induced by ICG was more severe than the damage induced by TB. Subretinal delivery of hyposmolar SG caused PIS/POS damage during all follow–up and ONL minimal damage 24 hours and 14 days following subretinal injection. These findings may explain the RPE changes sometimes observed after macular hole surgery in human subjects and emphasizes that care must be taken not only regarding the dye and solution concentration but also the solution osmolarity used in macular hole surgery .

Keywords: retina • drug toxicity/drug effects • microscopy: electron microscopy