The purpose of this study was to compare the effect of adding different doses of dexmedetomidine to local anesthetic mixture for peribulbar block in vitreoretinal surgeries as regards duration, efficacy and pain relief. Materials and methods: In this prospective randomized double blind clinical study, 160 patients were equally divided into four groups: Group C (the control group) (n = 40) received 10 ml mixture of lidocaine 2% and bupivacaine 0.5% with 120 IU of hyaluronidase, group D15 (n = 40) received a 10 ml mixture of lidocaine 2% and bupivacaine 0.5% with 120 IU of hyaluronidase + 15 lg dexmedetomidine, group D20 (n = 40) received a 10 ml mixture of lidocaine 2% and bupivacaine 0.5% with 120 IU of hyaluronidase + 20 lg dexmedetomidine and group D25 (n = 40) also received a 10 ml mixture of lidocaine 2% and bupivacaine 0.5% with 120 IU of hyaluronidase + 25 lg dexmedetomidine. The onset of globe anesthesia and akinesia and their duration, the intraocular pressure (IOP), patient comfort and surgeon satisfaction were all assessed. Data were analyzed and the results were presented as mean ±SD (Standard Deviation) and Ranges, number (%) and median (IQR) (Inter quartile range). Chi-square test (x2) was used to compare nonparametric variables. Comparison between groups was done using Analysis of Variance (ANOVA-One Way) as a parametric test and Kruskal Wallis Analysis of Variance by ranks as a nonparametric test. P values less than 0.05 (p < 0.05) was considered to be significant. Results: The onset of globe anesthesia was shorter in dexmedetomidine groups in comparison with control group. The difference was statistically significant in group D25 and group D20 in comparison with the control group (p > 0.05). Regarding the duration of globe analgesia, adding dexmedetomidine to the local anesthetic mixture prolonged the duration of globe analgesia, and this difference was statistically significant in group D25 in comparison with the control group (p > 0.05). Regarding the duration of globe akinesia although there was prolongation of the

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