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C CLINICAL RESEARCH

• Schwalbe line:
• The most anterior angle structure is Schwalbe line (SL).

• SL is the peripheral termination of Descemet membrane and the anterior border of the TM.

• It appears as a fine opaque line with variable pigmentation, particularly inferiorly. A pigmented SL
is also known as Sampaolesi line, and is suggestive of exfoliation or pigment dispersion.

• In cases where the SL is difficult to visualize, the ‘corneal wedge’ formed by the intersection of off-axis
slit beam reflections from the anterior and posterior surfaces of the cornea can aid in its detection.

• If SL is the only visible structure, the angle is considered narrow and at risk of closure.

• A prominent and anteriorly displaced SL (posterior embryotoxon) may be a variation of normal found in as
many as one in four individuals, or associated with angle anomalies including Axenfeld-Rieger syndrome. 393

Normal iris blood vessels are more visible in eyes with less pigment, tend to be thick, and run both circumferentially
at the root of the iris and radially in the iris stroma. Normal vessels and tissue do not cross SL, which can help in
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the differential diagnosis of feathery and meandering neovascularization from normal vessels, and synechiae from
iris processes. Angle neovascularization should be suspected whenever there is posterior segment ischemia: two
common examples are proliferative diabetic retinopathy and ischemic central retinal vein occlusion. 395

Clinical Recommendation for the performance of gonioscopy:
• For an excellent resource on the principles, performance, and interpretation of indirect gonioscopy, please
visit Dr. W. Alward’s www.gonioscopy.org, a site that offers a wealth of information in video format.

60 CANADIAN JOURNAL of OPTOMETRY | REVUE CANADIENNE D’OPTOMÉTRIE VOL. 79 SUPPLEMENT 1, 2017