Comparison of gonioscopy and ultrasound biomicroscopy for evaluating the iridocorneal angle in dogs.

OBJECTIVE

To compare iridocorneal angle grading systems on the basis of gonioscopy and ultrasound biomicroscopy (UBM).

DESIGN

Original cross-sectional observational study.

ANIMALS

22 dogs.

PROCEDURE

Gonioscopy, goniophotography, and UBM were performed on 38 eyes from dogs without clinical evidence of glaucoma in the eyes examined.

RESULTS

Predominant gonioscopic grades derived from goniophotographs were considered normal (n = 26) and mild (12). Ultrasound biomicroscopy angle measurements ranged from 16 to 38 degrees (mean +/- SD, 26.2 +/- 4.5 degrees). Ciliary clefts depicted on UBM images were graded as open (n = 4), compact/narrow (23), and closed (11). Significant differences were not found between UBM-derived ciliary cleft grades and goniophotography-derived dysgenesis grades, nor between UBM-derived ciliary cleft grades and subjective gonioscopic grades.

CLINICAL IMPLICATIONS

Because gonioscopy allows evaluation of the anterior face of the ciliary cleft, whereas UBM provides cross-sectional information of the iridocorneal filtration angle, UBM may yield more information regarding pathogenesis and prognosis of, and preferred management approaches to, glaucoma. Ultrasound biomicroscopy may also be useful as a predictor of glaucoma or to diagnose early stages of glaucoma.