An optical occluder 10 is in the form of a sleeve 16 formed of a polymer material. The occluder comprises an inner 22 and outer 18 side, the inner side 22 of the sleeve comprises an opening (36, Fig. 6). The sleeve 16 is configured to receive a lens 12 of a pair of glasses (14, Fig. 1) such that in use the lens is at least partially covered by the sleeve and the user's vision in one eye is at least partially occluded. The inner 22 and outer 18 sides of the sleeve may be connected at a top end by an upper part (28, Fig. 4) and bottom end by a lower part (34, Fig. 4), said upper and lower parts may be configured to receive a lens or spectacle frame. The occulder may comprise a side section (48, Fig. 6) attached to the occulder by a hinge (50, Fig. 6). The occluder may be retained on the glasses via anti-slip properties of the material, gravity or a combination thereof. The occulder may be made from an antimicrobial silicone elastomer. The occulder may vary in thickness from 0.1-2mm. The occluder may be used to treat amblyopia (lazy eye syndrome) or aid in sporting practice.
