Evaluation of anterior segment changes after botulinum neurotoxin-a injection in patients with blefarospasm or hemifacial spasm with corneal topography and optical biometry

Objective: We aimed to investigate the effect of botulinum toxin-A (BTX-A) treatment on dry eye, corneal topography, ocular biometry and keratometry in patients with benign essential blepharospasm (BEB) and hemifacial spasm (HFS) Methods: This retrospective study comprised of 66 eyes of 33 patients with BEB and 5 eyes of 5 patients with HFS who underwent BTX-A injections consecutively. Refractive errors values, tear break-up time (TBUT), corneal topography [corneal power of flat axis (K1), corneal power of steep axis (K2), mean corneal power (Km), corneal astigmatism (K2-K1) and astigmatism axis] and ocular optical biometry [axial length (AL), anterior chamber depth (ACD)] were recorded before BTX-A treatment and 1 month after BTX-A treatment. The researchers calculated the expected emmetropic intraocular lens power (emm-IOL) by SRK-T, Holliday, Hoffer-Q and Haigis formulas at each examination with the AL, ACD, K1, K1-axis, K2 and K2-axis of patients. Results: K1 (43.48±2.02 vs. 43.57±2.08, p=0.036), Km (43.91±1.99 vs. 43.99±2.06, p=0.024) and ACD (3.22(2.77-3.76) vs 3.41(2.99-4.02) p<0.001) values were found significantly higher. The expected emm-IOL according to the SRK-T (21.04±1.6 vs 20.93±1.6 p=0.048), Holliday (21.05±1.6 vs 20.91±1.62 p=0.037) and Hoffer-Q (21.08±1.65 vs 20.94±1.68 p=0.038) decreased significantly. The expected emm-IOL according to the Haigis slightly decreased, but it was not significant (p=0.386). Also TBUT was found significantly lower (p<0.001) after BTX-A injection. Other parameters are not statistically significant (p>0.05). Conclusion: Present study is the first in the literature to compare optic biometry data and intraocular lens power calculation formulas before and after BTX-A injection in eyes with BEB and HFS. Furthermore, a decrease in TBUT values was also noted after BTX-A. BTX-A injection could effect an important role in changing the keratometric and ACD values. It should be taken into account the IOL power calculations that might be unpredictable due to blepharospasm, so repeated measurements and especially measurements after relasing the spasm with BTX-A injections are necessary in eyes with spasm.