Twenty-four consecutive patients with Hemifacial spasm and 25 age and gender-matched randomly selected eyes of healthy volunteers underwent corneal pachymetry and intraocular pressure measurements using Goldmann Applanation Tonometer and non-contact tonometer. An interval of 15 minutes was maintained between Goldmann Applanation Tonometer and non-contact tonometer measurements. Intraocular pressure measurements were performed before (during hemifacial spasm) and 2 weeks after Botox injections in Hemifacial spasm patients and in healthy volunteers without Botox injections. All the measurements with Goldmann Applanation Tonometer were carried out by a single physician while those with the non-contact tonometer were done by another physician who was masked to the results of the Goldmann Applanation Tonometer. All measurements were taken between 10:00 and 11:00 a.m.

Inclusion Criteria:

• patients with hemifacial spasm

Exclusion Criteria:

• Subjects will be excluded if they have allergies to botulinum toxin or any component of the drug, previous eyelid, refractive or intraocular surgery, any abnormality preventing reliable tonometry in either eye, strabismus, contact lens wear, pregnancy, glaucoma, ocular hypertension and patients using agents that could interfere with neuromuscular transmission.

Twenty-four consecutive patients with Hemifacial spasm (study group) and twenty-five age-matched and gender-matched healthy volunteers (control group) will be prospectively included in the study. Intraocular pressure measurements will be performed before and 2 weeks after Botox injections in patients with HFS (involved and uninvolved eyes of HFS both) and in healthy volunteers without Botox injections.