Fig. 10 Gonioscopic classification systems. A. Scheie system. The basis for this system is posterior angle structures visualized. A grade IV angle is completely closed and a grade I is slightly narrow. No comment is made on the approach of the iris or its peripheral configuration. B. Schaffer system. The basis for this system is width of the angular recess. A grade I Shaffer angle is worrisome for closure and a grade IV approach typically implies the angle is open. An open angle however does not always imply an unobstructed trabecular meshwork. A deep angle does not always imply trabecular protection or the lack of pupil block, as is seen with reverse pupil block in pigmentary glaucoma. C. Spaeth system (see Table 3). The basis for this system is threefold. The alphanumeric designation permits a three-dimensional reconstruction of the chamber angle. The gonioprism of choice for this system is a Zeiss-type lens that facilitates indentation gonioscopy. 1. Site of insertion of iris onto the inner wall of eye in (D). 2. Angular approach in degrees (E). 3. peripheral configuration of iris (F).