The biologically available concentration of gentamicin sulfate in eight ocular tissues of 140 rabbits and 96 humans was measured by a modified disc diffusion technique. If enough topically administered gentamicin was applied, this bioassay detected it in all ocular tissues tested except the lens nucleus. The decay of antibiotic activity was faster in some tissues, eg, aqueous, than in others. A higher level of antibiotic was found in corneas altered by sutures than in virgin tissue. The degree of inflammation, the frequency of application, and the interval between the drops are directly proportional to the antibiotic level in the tissues. The antibiotic free vehicle of commercial 0.3% gentamicin drops possesses an antibacterial potential.
Ellerhorst B, Golden B, Jarudi N. Ocular Penetration of Topically Applied Gentamicin. Arch Ophthalmol. 1975;93(5):371-378. doi:10.1001/archopht.1975.01010020383014