Toxicity of an intravitreal injection of gentamicin sulfate, disodium sulbenicillin and cefazolin sodium on the retina was investigated by electroretinogram in albino and pigmented rabbits. Recordings were made before injection and 2 hours and 3, 7, 14, and 21 days after injection. Significant differences were found in the susceptibility of the electroretinogram components to various antibiotics as follows. Gentamicin 0.24 mg/0.1 ml irreversibly abolished all the components examined. Sulbenicillin 4.0, 8.0, or 12 mg/0.1 ml transiently suppressed the b-wave and the oscillatory potentials incrementally with increasing dose. Cefazolin 0.5, 2.0, or 5.0 mg/0.1 ml selectively reduced the oscillatory potentials, leaving the a- and b-waves almost unattenuated. The cefazolin-suppressed oscillatory potentials recovered within 14 days after injection. Judging from the most susceptible electroretinogram components to each antibiotic, we recommend intravitreal doses of these antibiotics for clinical use as follows: gentamicin 0.1 mg/0.1 ml, sulbenicillin 2 mg/0.1 ml, and cefazolin 0.25 mg/0.1 ml.

We studied the nontoxic intravitreal concentration of ofloxacin, a new quinolone antibacterial agent, by evaluating its effects on in vitro and in vivo electroretinograms (ERGs) in albino and pigmented rabbits. After perfusion with a 36 μg/ml solution of ofloxacin, the in vitro ERG remained unchanged. The in vivo ERG and the visually evoked potential remained unchanged 4 weeks after vitrectomy with 50 μg/ml ofloxacin, and the retina was within normal limits both ophthalmoscopically and histologically. Therefore, the retinal toxicity of ofloxacin is low and within safe limits at clinical dosage.

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The concentration of ceftazidime was determined in the aqueous humor and the vitreous body of normal, vitrectomized and aphakic/vitrectomized eyes and in the serum of albino rabbits 1 h after intravenous injection of l00mg/kg ceftazidime. The intravitreal ceftazidime concentration was low (0.1–0.2 µg/ml) in normal eyes 1 h after intravenous injection, and high (8.7 ± 8.5 µg/ml) in vitrectomized and aphakic/vitrectomized eyes when injected immediately after surgery. The ceftazidime concentration was also determined in the aqueous humor and the vitreous body of normal eyes and in the serum of albino rabbits 3, 6, 12, 24 and 48 h after intravitreal injection of 200 µg. The intravitreal ceftazidime concentration after intravitreal injection decreased exponentially for 12 h (half-life about 7.4 h). It decreased more slowly thereafter and remained at 13.0 µg/ml (mean) even 48 h after injection. This concentration exceeded the minimum inhibitory concentrations against common gram-positive and gram-negative organisms causing endophthalmitis.