When in use, the surface of the concave lens was pressed against the cornea and observed with a slit lamp microscope. In the picture:

1 To view the light path in the center of the retina;
2 To view the light path from the area around the center to the equator;
3 To view the light path from the equator to the front of the surrounding area;
4 Look at the rear of the perimeter.

After using a trinocular lens, the slit lamp microscope will be able to observe more parts of the human eye, but the eye to be examined should be dilated and anesthetized during use.

Anterior angle mirror. The shape and structure of the anterior angle mirror is similar to that of a three-sided mirror, except that its reflector only has a tilt angle (62 °), so it is only used to view the anterior angle. The reflecting surface of the anterior angle mirror can be one, Can be made into multiple (3), usually the latter is appropriate. Because it does not need to rotate after being applied to the cornea, you can see the state of the anterior chamber angle in all directions. The eye being examined should be anesthetized during use.