Gentamicin sulfate was injected into the anterior chamber and vitreous body of rabbit eyes to evaluate its suitability for intraocular injection and its toxicity on intraocular tissues. No permanent toxic sequelae were produced when 250μg to 8,000μg of gentamicin sulfate were injected into the anterior chamber. Retinal toxicity was noted when 1,000μg of gentamicin sulfate or more were injected into the vitreous body. When 2,000μg to 10,000μg of gentamicin sulfate were injected into the vitreous, cataracts developed. Doses greater than 8,000μg caused keratopathy. In addition, it has been shown that a single intravitreal injection of 500μg of gentamicin sulfate will maintain levels of 4μg/ml or greater inside the vitreous body for 96 hours.
Peyman GA, May DR, Ericson ES, Apple D. Intraocular Injection of GentamicinToxic Effects and Clearance. Arch Ophthalmol. 1974;92(1):42-47. doi:10.1001/archopht.1974.01010010046011