A cassette in an injection device (21, figure 2) has a container 2 which receives an intraocular lens 4 and extends along a portion of the longitudinal axis A of the injector. The container has a front end face 6 and a rear end face 7 each containing an aperture 8,9 through which the plunger (23, figure 2) of the injection device can pass to deploy the intraocular lens. One or both of the apertures are closed by foil attached to the receiving container. The foil may be wrapped around the end faces and attached to a pull tab 14 for removal. Alternatively, it may be thermally welded to the container and have a cross of perforations to facilitate it being pierced by projections on the injection device. The foil may be a coextruded foil made from aluminium and polypropylene, having a thickness of 0.5 mm. A second container 38 holding viscoelastic material may be present (figure 12).
