Prefilled syringes and usability of ophthalmic viscosurgical devices

PURPOSE To examine the influence of the configuration of prefilled syringes on the usability of ophthalmic viscosurgical devices (OVDs). SETTING Department of Ophthalmology, Jikei University School of Medicine, Tokyo, Japan. DESIGN Experimental study. METHODS The maximum force needed to extrude the whole OVD (extrusion force) was compared among viscous cohesive OVDs (OPEGAN Hi(®) 0.85 mL and Healon(®) 0.85 mL) and very low viscosity dispersive OVDs (OPEGAN(®) 0.6 mL and OPEGAN(®) 1.1 mL). Additionally, to exclude the influence of any differences between syringes of viscous cohesive OVDs on the extrusion force, empty syringes of the same configuration were refilled with the same products. In addition, the syringe inner surface and that of the piston attached to the tip of the plunger were measured. RESULTS The extrusion force of Healon 0.85 mL (3.28±0.19 kgf) was significantly (P<0.01) higher than that of OPEGAN Hi 0.85 mL (2.54±0.23 kgf). The inner syringe chamber for Healon 0.85 mL was vial shaped and had a built-in needle in the Luer tip, which was clearly different from OPEGAN Hi 0.85 mL. There were no significant differences in the extrusion force between refilled syringes. The extrusion force of OPEGAN 1.1 mL (3.44±0.12 kgf) was significantly (P<0.01) higher than that of OPEGAN 0.6 mL (1.63±0.06 kgf). The syringe of OPEGAN 1.1 mL was obviously bigger than that of OPEGAN 0.6 mL. CONCLUSION It was confirmed that the configuration of the syringes is another determinant of the extrusion force and a factor related to the difference in usability among products that meet the same cohesive class.