To protect against the sun's rays from the front of the car, simply fold the visors down.
If the sun's rays are blinding you from the side of the car, remove the inner side of the visor from the support and turn the visor towards the side window.
Mirror in sun visors
Pull down the sun visor and open the cover from the inside of the visor. This will turn on the light in the visor.
Article text obtained from the website (mercedesman)