The top section of the panel contains the key.. It makes iris clearer, removes red and blue shades from eyes, change a color of the iris, bright the iris and enhances the glare from the light source.
Learn it all, from lighting with flash, to the camera settings and gear, to retouching in lightroom and photoshop 2nd edition. The mua retouch panel consists of four main sections, each responsible for specific parts of your post.