Description Ophthalmic Viscosurgical Devices (OVDs) are complex fluids, which exhibit viscoelastic and shear thinning properties, and have helped to revolutionise the way cataract surgeries are performed. Their main functions during surgery are to protect the corneal endothelium, maintain pressure in the anterior chamber, and create space for the procedure to be performed with ease. There are different types of OVDs , whichdiffer in their composition and molecular weight of the polymer. As a consequence they exhibit different rheological behaviours and interfacial properties for enhanced functionality. Guidelines from manufacturers indicate OVDS should be stored in the fridge and used at ambient temperature. A clinical observation of the medical collaborator (Dr. Lockington) and his team is that often a second OVD is required in cataract surgery and it is often delivered from the fridge, ensuing a number of difficulties in the delivery and function of the OVD during the surgery, with important implications during the surgery process and the safety of delivery. Although it is known that the viscosity decreases with increasing temperature, detailed information on the rheological and interfacial properties under different conditions is not readily available.The aim of the project is to characterise the rheological properties of different OVDs as well as its surface tension under different conditions. There are various avenues to explore:

• characterisation and comparison of different types of OVDs
• effect of temperature on the rheological and other physical properties of OVDs - impact of the heating/cooling cycles on the OVD properties An increased knowledge on how these fluids act will improve the success rate of the surgeries, make it easier for surgeons to use them, and will allow for the methods and technologies to be updated to further increase the safety and efficiency of their use.  Key Objectives
• Literature review on OVDs
• Learn the fundamentals of rheology and rheometer operation
• Perform measurements to meaure the properties such as viscosity, storage and loss modulus, etc using a rotational rheometer and when possible using the capillary breakupextension rheometer (CaBER).
• Perform measurements to characterise surface tension and /or thermal behaviour.
• Assess the effects of various parameters on the properties and compare the behaviour of different OVDs.