Visual evoked potential changes following Botox administration in patients with blepharospasm

Purpose To examine visual evoked potential (VEP) changes following botulinum toxin type A (BTA) administration in patients with blepharospasm. Methods Patients diagnosed with blepharospasm receiving BTA administration were included in the study. Three groups, a control group and two study groups (patients examined 14 days after BTA administration—Study Group 1, and patients examined 28 days after BTA administration—Study Group 2) were evaluated. Dilated fundus examinations were performed following detailed ophthalmological examinations and VEP tests. Keypoint (Dantec, Denmark) and ISCEV criteria were adopted for pattern VEP (PVEP) recording. BTA was applied in the form of local injections at a total 15–30 units, at 2.5–5 units per injection. Results A mean 19.4 ± 3.2 units of BTA was used for each eye. N70 (ms), P100 (ms), and P100 (uV) values were statistically significantly lower in both study groups following drug administrations compared to the control group ( p < 0.001 for all). Significant positive correlation was observed between increased P100 amplitudes and age in the control group ( p = 0.008, r = 0.200). Significant negative correlation was observed between the BTA units used and decreased P100 amplitudes in both study groups 1 and 2 following drug administrations ( p = 0.017, r = − 0.180 and p = 0.043, r = − 0.153, respectively). Conclusion VEP may be an important method in the diagnosis and follow-up of blepharospasm and in determining the success of drug administration and additional therapeutic requirements.