Background/aims In patients with hemifacial spasm (HFS), treatment relieves eyelid spasms on the affected side, thus changes in corneal topography and eyelid morphometry may be observed after treatment. We aimed to evaluate these parameters during a 4-month period in patients with HFS treated with botulinum toxin A (BTX-A).

Methods This prospective study evaluated eyelid morphometric and corneal topographic changes in patients with HFS before onabotulinum toxin A application, and after 15 days and 2, 3 and 4 months.

Results 24 patients were treated with BTX-A. On the normal side, the mean palpebral fissure height (PF), interpalpebral surface area (ISA), steep K and astigmatism values were 8.7±1.98 mm, 122.09±39.37 mm², 44.99±1.45 D and 0.9±0.64 D, respectively, before treatment. A statistically significant difference was not observed in these parameters after treatment (p>0.05). On the affected side, the mean PF, ISA, steep K and astigmatism were 5.5±1.77 mm, 67.68±28.49 mm², 46.91±3.57 D and 2.63±2.46 D, respectively, before treatment. We observed a statistically significant (p<0.05) increase in the mean PF and ISA on the affected side 15 days (8.36±1.91 mm and 115.92±34.44 mm², respectively), 2 months (8.18±1.80 mm and 112.22±33.57 mm², respectively) and 3 months (7.27±1.65 mm and 95.48±27.80 mm², respectively) after treatment. A statistically significant decrease in steep K and astigmatism was observed at 2 months (45.14±1.20 D and 1.01±0.58 D, respectively) and 3 months (45.64±1.77 D and 1.36±1.31 D, respectively) after treatment.

Conclusions The results suggest that treatment with BTX-A in patients with HFS leads to eyelid and corneal changes on the affected eye that are significant during the known period of action of the toxin. Thus, caution should be taken when performing ophthalmological examination in patients with HFS, since it may vary according to BTX-A period of action.