Effects of Subretinal Injection 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 indocyanine green (ICG) 0.05% (279mOsm), trypan blue (TB) 0.15% (312 mOsm) and glucose (SG) 5% (280mOsm) into the subretinal space of rabbit eyes. Methods: Eight pigmented rabbits underwent three–port vitrectomy followed by subretinal injection of ICG (0,05% and 279 mOsm), TB (0.15% and 312 mOsm) and SG (5% and 280 mOsm). The subretinal injections were peformed 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 and SG caused minimal photoreceptor outer segments (POS) edema during all follow–up. Subretinal injection of TB caused POS edema at 6 and 12 hours after surgery; this damage was more important 24hours and 14 days following subretinal TB injection when not only POS and photoreceptors inner segments (PIS) were damaged but also minimal pyknosis was observed at the outer nuclear layer (ONL). The retinal pigment epithelium (RPE) was barely affected. Additionally, subretinal injection of ICG caused a severe damage on PIS and POS, ONL and RPE that was observed during all follow–up. Conclusions: Subretinal delivery of ICG (0.5 mg/ml and 279mOsm) induced damage of the RPE, PIS/POS and ONL during all the follow up. Subretinal delivery of TB (1.5 mg/ml and 312 mOsm) induced minimal damage of the ONL and RPE 24 hours and 7 days following injection. The damage induced by ICG was more severe than the damage induced by TB. No differences were seen between BSS and SG blebs. 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 to select the dye to be used during macular hole surgery but also to avoid that dye gains access to the subretinal space during the surgical procedure in humans subjects.

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