ERG changes after an injection of corticosteroid into the vitreous

We injected a high dose (5 mg) of pure betamethasone acetate (a water-insoluble corticosteroid) into the vitreous space of aphakic rabbit eyes after and without closed vitrectomy, and followed ERG b-wave amplitude changes over 36 days. The ERG b-wave amplitude decreased immediately after vitrectomy, but recovered in one day. Administration of betamethasone increased the ERG amplitude in both eyes to abnormally high levels. The highest amplitude appeared on the 3-4th day and this enhancement continued for 7-20 days. In conclusion, administration of betamethasone into the vitreous induced no depressing effect on retinal function reflected by the ERG b-wave, even in doses as high as 5 mg.