Indocyanine green as useful guide for retinal vein cannulation and injection of tissue plasminogen activator in rabbits

Abstract

Central retinal vein occlusion (CRVO) is caused by a fibrin clot in central retinal vein and is one of the intractable diseases that deteriorate visual acuities. Tissue plasminogen activator (TPA) is a thrombolytic agent that has a high affinity for fibrin and that activates plasminogen into plasmin. Injection of TPA into the retinal vein was helpful to treat CRVO. But TPA injection into retinal vein was difficult for clinical use, because TPA solution was transparent and confirmation of its injection was not easy. Indocyanine green (ICG) has been used as an angiographic agent and a tissue-marking agent in ocular surgeries. We studied the effectiveness and safety of ICG assisted injection of TPA into the retinal vein in rabbits. The major retinal vein was punctured using a micropipette fabricated from a glass tube, then TPA/ICG was injected. Total of 12 eyes and 5 eyes were enucleated 7 days and 1 month after injection of TPA/ICG for histological observations including immunostaining of glial fibrillary acidic protein (GFAP) and TUNEL staining, respectively. GFAP is expressed in Müller cells under pathologic conditions and indicates retinal damages. TUNEL indicates apoptosis of sensory retina cells. Retinal vein cannulation was easily performed, as retinal vein became green following injection of TPA/ICG. Histologically, no retinal damages, due to the TPA/ICG solution, were observed. GFAP and TUNEL staining were negative. TPA/ICG causes no disturbance in retinal circulation when performed correctly. Because of its safety, ICG is a useful agent as a guide for retinal vein injection of TPA.