Fig. 56. Classification of flat anterior chamber. A. There is contact between the peripheral iris and the cornea in grade 1 flat anterior chamber. B. In grade 2 flat anterior chamber, the chamber remains only over the pupillary portion of the iris and over the pupil. C. There is contact between the corneal endothelium and the lens, intraocular lens, or vitreous in grade 3 flat anterior chamber. Virtually all cases of grade 3 flat anterior chamber require immediate correction. (Spaeth GL. Glaucoma surgery. In Spaeth GL (ed). Ophthalmic Surgery: Principles and Practice. Philadelphia: WB Saunders, 1990.)