The aim of this study is to calculate the minimum effective volume of local anesthetic for peribulbar block in patients undergoing cataract extraction surgery.

The main goal of this study is to estimate the minimum effective volume(MEV90) of local anesthetic and hyaluronic acid given for local anesthesia of the eye for 2 different axial length groups of patients undergoing eye surgery. Volume assignment was carried out using a biased coin design (BCD) up-and-down sequential method (UDM), where the volume given to each patient depends on the response of the previous one. The MEV90 was calculated using isotonic regression with bias-corrected 95% confidence interval (CI) derived by boots trapping. The mean value of the estimate was obtained from 3000 bootstrap samples.

Inclusion Criteria:

• we allocated adult patients aged 40-70 years, of both gender, American Society of Anesthesiologists (ASA) II - III, listed for elective cataract extraction using phaco emulsification technique with intraocular lens implantation surgery.

Exclusion Criteria:

• Patients known to have any systemic contraindications (as severe hypertension) or allergy to the local anesthetic, those who refused local anesthesia, high myopes (axial length > 26 mm), patients with a single eye, those with complicated vitreous hemorrhage, ocular infection, or associated glaucoma have been excluded.