RESUMO
Gentamicin, a broad spectrum antibiotic of the aminoglycoside group, is effectively used in the treatment of bacterial endophthalmitis caused by pseudomonas and staphylococcus strains [Zachary and Foster, 1979]. This antibiotic was found to be toxic for retinal structures if high concentrations are administered in the vitreous especially the retinal pigment epithelium, photoreceptor outer segment complex. [D'Amico et al., 1984]. However, the presence of significant histopathological changes on the other layers of the retina was not clearly documented with its commonly used doses. So, in this study, a group of adult albino rabbits were injected with doses 2000 micro g, 1000 micro g and 500 micro g gentamicin [one dose for each group]. The results showed severe affection of the inner retinal layers even with the smallest dose [500 micro g] used. These were in the form of cytoplasmic and nuclear vacuolation, margination of the chromatin of the cells in the inner nuclear and ganglion cell layers and fusion of processes in the nerve fiber layer. In addition, intermingling of the cells of the different layers with each other was also seen. In addition, there were severe fundus changes as evidenced by ophthalmoscopic examination. Due to the presence of these dramatic effects on the retina induced by a single injection of commonly used doses of gentamicin, we advised not to use intravitreal gentamicin except if it is highly indicated in a dose not more than 100-200 micro g