The Spaeth Grading System of gonioscopy finding.
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Spaeth System
Spaeth considered that available grading systems provided limited information and proposed a system that grades the three major features of the angle’s anatomy: the level of iris insertion, the width of the angle, and the configuration of the iris (Spaeth, 1971).
The level of iris insertion is represented by letters “A” through “E.” If the iris inserts anterior to Schwalbe’s line, it is described as grade “A” (for “anterior”). If it inserts anterior to the posterior limit of the trabecular meshwork, it is grade “B” (for “behind” Schwalbe’s line). If insertion is posterior to the scleral spur, the iris is grade “C” (for the “c” in sclera). Insertion into the ciliary body face is recorded as grade “D” (for “deep”) or grade “E” (for “extremely” deep) (6‑4).
Angular width is the estimated angle between a line tangential to the trabecular meshwork and a line tangential to the surface of the iris about one-third of the way from the periphery. The angle is expressed in degrees (6‑5).
The third characteristic that is described is the curvature of the peripheral iris: “r” for a regular or flat configuration, “s” for a steep curvature or iris bombé, and “q” for a “queer” or concave curvature (6‑6). This system was subsequently modified in order to be more descriptive, using “f ” to denote a flat configuration, “c” to describe the concave or back-bowed iris, “b” to describe the forwardly bowed iris, and “p” for a plateau iris configuration.
Spaeth graded posterior pigmented meshwork in the 12 o’clock angle on a scale of 0 to 4+. He also graded the type and number of iris processes.
The Spaeth system permits the inclusion of information obtained by indentation gonioscopy. If indentation demonstrates that the insertion is a “D” when it originally appeared to be a “C”, this would be indicated as “(C)D”. Therefore an angle is carefully defined by an alphanumeric description—such as (C)D30S—as is illustrated in 6‑7 (Spaeth, 1977).
6-4 Spaeth’s classification system includes the level of iris insertion. A, anterior to trabecular meshwork; B, behind Schwalbe’s line; C, posterior to scleral spur; D, deep, into ciliary body face; E, extremely deep. (Reprinted with permission from Macmillan Publishers Ltd. Spaeth GL. The normal development of the human anterior chamber angle: a new system of descriptive grading. Eye. 1971;91:709–739.)
6-5 In Spaeth’s classification the width of the angle is approximated by a line tangential to the iris about one-third of the way from the iris root to the pupil and a line tangential to the face of the trabecular meshwork. (Reprinted with permission from Macmillan Publishers Ltd. Spaeth GL. The normal development of the human anterior chamber angle: a new system of descriptive grading. Eye. 1971;91:709–739.)
6-6 Iris configuration in the Spaeth classification. s, steep or convex; r, regular or flat; q, queer or concave. (Reprinted with permission from Macmillan Publishers Ltd. Spaeth GL. The normal development of the human anterior chamber angle: a new system of descriptive grading. Eye. 1971;91:709–739.)
6-7 A (C)D30S angle in the Spaeth classification. The D means that iris insertion is into the ciliary body face, but the C means that the steep approach made the insertion appear to be just posterior to the scleral spur until indentation gonioscopy was performed. The number 30 is the angular width of the angle. The letter S means that the iris has a steep or convex configuration. This is an angle capable of closure. (Reprinted with permission from Macmillan Publishers Ltd. Spaeth GL. The normal development of the human anterior chamber angle: a new system of descriptive grading. Eye. 1971;91:709–739.)
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