Monocular retinal degeneration induced by intravitreal injection of sodium iodate in rabbit eyes

Abstract

Purpose Our purpose was to evaluate the anatomical and functional changes in retinae of rabbit eyes following monocular intravitreal injection of sodium iodate (SI). Methods Twenty albino rabbits were divided into four groups and underwent monocular intravitreal injection with four different doses of SI (0.1, 0.2, 0.4, and 0.8 mg). Before and for 28 days after injection, the eyes were examined using fundus photography, optical coherence tomography (OCT), and electroretinography (ERG). At postinjection days 2, 7, and 28, the eyes were enucleated and underwent histological examination. Results On fundus examination, no distinct retinal changes were seen in any group except the 0.8-mg group, which showed chorioretinal vascular attenuation. In 0.1 and 0.2-mg groups, no significant anatomical changes were found except transient hyperreflective dots over the vitreoretinal interface on OCT. In 0.4 and 0.8-mg groups, disruption of the ellipsoid zone and diffuse retinal swelling were observed in the early period on OCT. In the 0.4-mg group, the outer retina was significantly destroyed at day 28, whereas the inner retina was relatively preserved. In the 0.8-mg group, the entire retina was destroyed irreversibly. The b-wave of ERG was reduced immediately in all groups, which recovered fully (0.1- and 0.2-mg groups), partially (0.4-mg group), or never (0.8-mg group). No structural or functional abnormalities were found in the fellow control eyes. Conclusions Retinal degeneration following intravitreal injection of SI appears to be dose dependent; retinal damage is reversible at low doses but irreversible at high doses. At a certain dose, the outer retina may be preferably ablated.