Adult patients requiring surgery for esotropia will be randomized to surgery under topical anesthesia or sub-Tenon's anesthesia. Amount of surgery required with the two anesthetic procedures will be compared. Motor and sensory outcome of the two treatment groups will also be compared.

Inclusion Criteria:

• Esotropia deviation angle equal to or lower than 45 prism dioptres (requiring one or two-muscle surgery)
• Visual acuity at least 20/40 in each eye
• Cooperation for topical anesthesia

Exclusion Criteria:

• Paretic or restrictive strabismus
• Previous eye muscle surgery
• Significant eye disease other than strabismus