Peribulbar anaesthesia is widely used in ophthalmic anaesthesia and is a suitable technique for vitreoretinal (VR) surgery. VR surgery is more painful due to the traction on the ocular muscles or sclera, increased intra-ocular pressure due to insertion of gas bubble or secondary to encirclement procedures. Good akinesia is an essential requisite for VR procedures.  Longer acting local anaesthetic agents and adjuvants have been used to prolong the duration of anaesthesia, hasten onset of akinesia, reduce LA toxicity and offer greater patient satisfaction. In this study we aim to study the efficacy of adding dexmedetomidine to 0.75% ropivacaine in PBB for VR surgery. The primary outcome is the requirement of supplementation of peribulbar block prior to or during the surgery.The secondary outcome is the pos-operative analgesic requirement. 100 adult patients undergoing VR surgery will be randomized using a computer generated random number table into one of the three groups. The composition of the study drug used for peribulbar anaesthesia in each of the 3 groups is Group R (8 ml of 0.75% Ropivacaine + 0.5 ml normal saline), Group D25 (8 ml of 0.75% Ropivacaine+ 0.25 ml Dexmedetomidine [100µg/ml] + 0.25 ml normal saline) and Group D50 (8 ml of 0.75% Ropivacaine+ 0.5 ml Dexmedetomidine[100µg/ml]). The time to onset of corneal anaesthesia and akinesia as well as the requirement for block supplementation will be recorded. The heart rate, blood pressure, saturation and sedation level will be monitored during the surgery. The duration of surgery and surgeon satiosfaction will be noted at the end of surgery.  The pain relief will be assessed at 1h, 2h, 6h and 24 h post-operatively as well as the total analgesic medication used in 24 hours. The expected outcome is superior quality block without additional supplementation and improvement in post-operative analgesia in the dexmedetomidine group.