Gentamicin toxicity in the primate retina
B. P. Conway, C. A. Tabatabay, P. A. Campochiaro, D. J. D'Amico, L. A. Hanninen and K. R. Kenyon
Department of Ophthalmology, University of Virginia School of Medicine, Charlottesville 22908.
To study the toxic effect of aminoglycoside antibiotics in the primate
retina, gentamicin sulfate was injected into the center of the vitreous
cavity of Cebus navrigatus monkeys. At a dose of 1000 to 3000 microgram, a
picture consistent with apparent macular infarction appeared on fundus
examination and fluorescein angiography by three days and gradually faded
by 21 days. While light and electron microscopic examination of the retina
showed no primary vascular lesions, striking damage to the inner retinal
layers, mainly the nerve fiber layer, ganglion cell layer, and the inner
plexiform and nuclear layer, was seen. Less severe effects in the outer
retinal layers and the retinal pigment epithelium occurred. These
observations suggest that the neurotoxic effect of intravitreal gentamicin
was sufficient to cause a complete shutdown of the regional blood flow,
perhaps by the mechanism of granulocytic plugging of the capillary bed.
Although this toxic effect occurred at doses considerably in excess of what
has been recommended for clinical use in humans, the "safe" dose of
intravitreal gentamicin, nevertheless, remains to be established
unequivocally.
