A concave lens is used by the people having near-sight. Your eye is a convex lens and near-sighted people focus the light too much. A concave lens is put in place to spread the light out before entering the eye, thereby getting the light to focus further back. Concave lens is thinner at the middle and thicker at the edges. It is a diverging lens and used in the spy holes in doors, in optical instruments(telescope).The image you see is upright but smaller than the original object. Concave lenses are used in a variety of technical and scientific products.Camera manufacturers use combinations of concave and convex lenses to improve the quality of photographs.Concave lenses used with lasers are made from fused silica to withstand the ultraviolet rays produced by the light source.