A glazing element (12) for an opening defined by opaque boundaries (13) has an edge region (E) shaped to divert light passing through it in a sense such as to enlarge the field of view through the opening. For this purpose the bounding surfaces (33, 34) of the element (12) diverge towards the edge thereof in the edge region (E). The same effect can be achieved by an element (25) adhered to or otherwise held in position to the surface of the element (12) in the edge region (E).