An optical module for a motor vehicle headlight comprising a reflector having an optical axis and at least one focus, a light source placed in the vicinity of the focus to be reflected, and a transparent optical deviation element placed in front of part of the reflector and comprising a lens referred to as a "square lens", the reflector being placed at the rear of the lens, the optical deviation element being able to provide an essentially horizontal spread of the light. The exit face of the "square lens"is tangent to a plane disposed obliquely with respect to the optical axis.