Chamber angle of average width. In most eyes the inferior quadrant is widest, the lateral quadrants narrower, and the superior narrowest. In eyes with narrow angles, the temporal quadrant may be narrowest.

Fig. 5-6  Parallelepiped method of identifying the boundary between cornea (thick light beam) and anterior trabecular meshwork (thin strip of light). (From Palmberg P: Gonioscopy. In Ritch R, Shields MB, Krupin T, editors: The glaucomas, 2nd edn, St Louis, Mosby, 1996.)

changes to the larger radius of the sclera.This change in curvature and the beginning roughness of the trabecular surface provide a lodging place for the pigment granules that may be carried into the inferior angle by the aqueous convection currents (Sampaolesi’s line). Such pigmentation is rare in healthy young eyes but becomes increasingly common in older or diseased eyes.

Trabecular meshwork and trabecular pigment band

Between Schwalbe’s line and the scleral spur lies the trabecular meshwork, through which aqueous humor flows to Schlemm’s canal.The internal layer of the trabecular meshwork is a syncytium

of fibers called the uveal meshwork. The outer portion of the trabecular meshwork is composed of corneoscleral trabecular sheets that insert into the scleral sulcus and the spur.These sheets are not visible gonioscopically.

Gonioscopic appearance

Gonioscopically, the trabecular meshwork has an irregularly roughened surface, which in childhood appears as a glistening, translucent-like semitransparent gelatin with a stippled surface. With increasing age its transparency decreases.33 The roughness of its surface is caused by the large openings of the uveal meshwork. It should be stressed that the examiner’s gaze should parallel the iris as nearly as possible when looking at the trabecular surface. With indirect gonioscopy, such as with the Zeiss lens, having the patient look away from the viewing mirror gives an optimal view of the meshwork in wide-angle eyes. In the narrow-angled eye, the convex plane of the iris forces a more oblique visualization (optimized with the patient looking toward the viewing mirror), which allows the angle recess to be seen, but which may give a somewhat foreshortened and distorted appearance to the meshwork.

Just anterior to the scleral spur is the effective filtering portion of the meshwork, lying in front of Schlemm’s canal. In aging and disease processes, the aqueous flow carries pigment from the iris and deposits it in varying amounts and depths in the meshwork, giving rise to the trabecular pigment band, which tends to be denser in the lower angle. Such pigmentation can be homogenous in appearance (as in the pigment dispersion syndrome) or variegated (as seen after anterior segment trauma).The presence and extent of trabecular pigmentation may provide valuable clinical information, such as suggesting an occult case of pseudoexfoliative syndrome or being indicative of a favorable response to laser trabeculoplasty.

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