The focus of this review is the role of endocannabinoid system in ocular and systemic circulation. By critically examining preclinical and clinical research, we explore the cannabinoid receptors localization and vascular implications as well as their interaction with other anti-inflammatory drugs. The objective is to transfer knowledge on the use of cannabinoids, specifically their effect on ocular circulation and intraocular pressure, and provide a better understanding of the endocannabinoid system complexity in modulating local and systemic circulations in order to identify potential uses and limitations of cannabinoid-based therapeutics.

Introduction: The iris vascular supply originates in the anterior and long posterior ciliary arteries. The endothelium influences local blood flow by releasing endothelium relaxing and contracting substances. From a functional perspective, the ocular vascular tonus adjustment is humoral and neural dependent. Objectives: The present article aims to evaluate the possible implications of topical administration of selective COX2 and nonselective COX inhibitors generically named nonsteroidal anti-inflammatory drugs (NSAIDs) and their possible interactions with the endocannabinoid system and the way they could interfere with the vascular tone at the level of ocular iris territory in Wistar rats. Materials and methods: Experimental protocol on Wistar rats was performed in accordance with present laws regarding animal welfare and ethics in animal experiments (Directive 86/ 609EEC/ 1986; Romanian Law 205/ 2004; Romanian Laws 206/ 2004, 471/ 2002 and 9/ 2008; Romanian Order 143/ 400). The studied substances were instilled topically under general anesthesia, and images of the rat iris vessels were captured over a period of 10 minutes. The obtained images were further analyzed using an appropriate hardware and software program. Results: The nonselective NSAIDs induced vascular dilation in the iris vessels, while the selective COX2 inhibitors determined a variable degree of vasoconstriction. Conclusion: In view of the results of this experiment and the added evidence found in literature, we consider that further research will show the potential benefits for the additional use of NSAIDs in ocular pathology, otherwise unaffected by this medication until the present time (for example, glaucoma treatment).

Background/Purpose: Perfluorocarbon heavy liquid (PFCL) is used in vitreoretinal surgery to flatten the unsupported detached retina before insertion of silicone oil in cases of giant retinal tear or relaxing retinectomy. Direct exchange of PFCL for silicone oil is recommended to reduce retinal slippage when compared with fluid-air exchange, but it is commonly regarded as a difficult procedure. We describe our technique for direct PFCLsilicone oil exchange using a 20-gauge drainage cannula, reliably avoiding the complications of retinal slippage and high intraoperative intraocular pressure.Methods: We present a consecutive case series of patients undergoing PFCL-oil exchange and explain, using Poiseuille's equation for laminar fluid flow through a cannula, the rationale for using a 20-gauge drainage cannula rather than smaller gauges to avoid high intraocular pressure.Results: Twenty-six patients underwent PFCL-oil exchange from February 1, 2019, to September 30, 2019. There was no intraoperative retinal slippage or pressure-related complications. Postoperatively 20 patients underwent oil removal. Six suffered retinal redetachment, and 14 remained attached. The vision postoil removal ranged from 6/6 to hand movements. Conclusion:We are confident that the PFCL-oil exchange technique described here is reliable and safe. The use of a 20-gauge drainage cannula is recommended regardless of vitrectomy gauge.