ERG and electron microscopic findings after intravitreal use of aminoglycosides

The electroretinographic (ERG) changes and the retinal lesions shown by electron microscopy were studied in rabbits after intravitreal use of amikacin and tobramycin. We studied 40 eyes of 20 rabbits in which different doses ranging from 250 micrograms to 1000 micrograms of aminoglycosides were injected into the vitreous cavity. Tobramycin, and to some extent amikacin, were toxic to the retina even in doses of 500 micrograms as shown by ERG changes. The pathologic retinal lesions shown by electron microscopy were characterized by membranous inclusions in the retinal pigment epithelium, tumefaction of the photoreceptors, and partial disorganization of the inner layers. In doses of 250 micrograms or less, these two antibiotics seem to be nontoxic after a follow-up of three months.