Comparison of the configuration of the human anterior chamber angle, as determined by the Spaeth gonioscopic grading system and ultrasound biomicroscopy.

Abstract PURPOSE: The primary purpose of this investigation was to validate anatomically, if possible, the Spaeth gonioscopic grading system. METHODS: The gonioscopic appearance of the anterior chamber angle of 22 patients was described, using a Zeiss 4-mirror gonioscopic lens; the angle was graded according to the Spaeth gonioscopic grading system (SGGS) previously described elsewhere. This system provides a more comprehensive characterization of the angle than other methods, including the site of iris insertion, the angular approach to the recess and the curvature of the peripheral iris. The same patients were then evaluated with biomicroscopic ultrasound examination of the anterior segment; the nature of the anterior chamber angle was described independently by two observers. The two methods of characterizing the anterior chamber angle were then compared. RESULTS: There was a high correlation between the two different methods of characterizing the anterior chamber angle. Ultrasound biomicroscopy had limitations relating to inability to distinguish between iris-cornea apposition and iris-cornea adhesion, and to exact location of the posterior trabecular meshwork. The angularity of the approach to the anterior chamber angle using the SGGS tended to be underestimated by about 5 degrees. Other aspects showed high correlation. CONCLUSION: The SGGS appears to be an accurate method of characterizing the anatomic appearance of the anterior chamber angle in patients. It also provides a more comprehensive description of the angle that other grading systems.