Fig. 2c Continued. I. The escape of a light ray from the anterior chamber angle with a gonioprism is simpler than a goniolens (Koeppe). Note that table one divides the gonioscopic methods into refractive and reflective. A Goldmann or Zeiss equivalent gonioprism reflects light to the examiner; the goniolens refracts light towards the examiner. The problem of the critical angle is overcome with this system by allowing the light to reach a mirror with the proper inclination. The ray is simply reflected to the examiner. The majority of the mirrors are inclined at 59 degrees to 62 degrees for viewing the chamber angle.