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M. H. Lundqvist, S. Nilsson, B. Lundgren; Expulsion Force Measurements of Ophthalmic Viscosurgical Devices (OVD). Invest. Ophthalmol. Vis. Sci. 2010;51(13):5398.
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In cataract surgery the OVD is an important tool. The OVD maintains the anterior chamber depth, protects the corneal endothelium, and facilitates implantation of the IOL. Differences in concentration and molecular mass of the viscoelastic components of OVDs lead to different physico-chemical characteristics, which are reflected in anterior chamber maintenance and retention capacity. This study was designed to measure the result in force required to deliver marketed OVDs as OVSs that require high or uneven expulsion forces could result in less control when used in clinical practice.
The expulsion force was measured for several commercial OVDs. The expulsion force tests were performed on a Lloyd LRX Plus pull tester set at compression mode. The measurements were performed with a 50 N loading cell and speed was set to expel 3 ml/min. For all products tested its own delivery system was used. Settings used for speed were between 52-171 mm/min and the length of piston movement set between 12-20 mm. Zero shear has been measured for all of the mentioned commercial products.
The results were on average between 16 and 24 N. For most products the expulsion force was the same during emptying the syringe. However, one product, Dispersive OVD 1, showed an early peak before going back to lower forces. Dispersive OVD 2 showed an increasing force throughout the test.
There are significant differences in force required to expel OVDs from their delivery system including maximum force required and changes in force over the entire delivery.
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