1. A rear view mirror for a vehicle with an adjustable mirror surface to prevent the effects of dazzle; said rear view mirror comprising a mirror unit including a mirror, and a drive gear for automatically tilting the mirror unit from a normal position to a tilted position when a dazzle effect is present on the mirror in said normal position, said drive gear being housed in a drive gear casing, the mirror unit being pivotally mounted on the drive gear casing for pivoting relative to the drive gear casing: the drive gear comprising a cam member rotatably mounted in the drive gear casing said cam member comprising a pair of oppositely-facing annular cam surfaces, each cam surface having a first land lying in a flat plane and defining a datum, and a second land lying in a flat plane spaced from the plane of said first land and defining a lift surface portion, said first and second lands being joined by inclined connecting surface portions, an actuator engaging each of said annular cam surfaces and connected to the mirror unit so as to tilt the mirror unit on rotation of the cam member, the lift surface portion of one cam surface being diametrically opposed to the lift surface portion of the other cam surface whereby on rotation of the cam member one cam surface serves to move the actuator outwardly relative to the drive gear casing while successively the other cam surface serves to move the actuator inwardly relative to the drive gear casing, an electric motor drivingly connected to the cam member for driving the cam member in a constant single direction, and electric circuit means connected to said motor and including light sensing means for the provision of control signals and switch means controlling the driving of the electric motor.