Toxicity of antibiotic combinations for vitrectomy infusion fluid

We have found that gentamicin 8 microgram/ml in various combinations with methicillin 25 microgram/ml, oxacillin 10 microgram/ml, clindamycin 10 microgram/ml and penicillin 80 microgram/ml to be nontoxic to the retina when used in vitreous replacement fluid.