Effects of intravitreal injection of botulinum toxin on the electroretinogram of rats

The retinal toxicity of botulinum toxin A (BTA) was electroretinographicall y studied in rats. Sixteen rats were injected intravitreally with 10 ng of BTA. A response-amplitude series was recorded before and 1, 6, 13 and 21 da ys after the injection of BTA. BTA did not alter the amplitude and the peak latency of the a-wave. The amplitude of the b-wave was not changed except for 2 rats, in which the b-wave was diminished. The peak latency of the b-w ave was significantly prolonged after injection of 10 ng BTA (p < 0.05). Ex cept for these latter 2 rats, the results indicated that the dosage used th erapeutically appears to have no deleterious effect on retinal integrity or function at least in the short term, but multiple injections or higher dos es of BTA could alter retinal function.