Microscopic Eyepiece

The image magnified by the objective lens is further magnified by the ocular lens for observation. An ocular lens consists of one to three lenses and is also provided with a mechanism, called a field stop, that removes unnecessary reflected light and aberration.

They fit most common size stereo microscopes. When you look into your eyepiece lens, the markings will always be the same but the size of the image superimposed under them will get larger with more magnification. So, as you change to a higher power objective lens, the represented value between marks will change proportionately.