To quantitatively compare iridocorneal angle assessments using gonioscopy and anterior segment optical coherence tomography (AS-OCT). US and Chinese patients with open-angle glaucoma (OAG) and/or ocular hypertension (OHT). Analysis was pooled from 2 multicenter, noninterventional studies conducted in the US and China. Gonioscopy Shaffer grade and an AS-OCT method that approximates the angle width relative to local morphologic variations were compared by measuring the same iridocorneal angles. A third, separate, single-center, noninterventional study was conducted to verify results observed from the pooled analysis. From the pooled studies, a total of 239 eyes were measured using Shaffer grade and AS-OCT. Of these, 6 were Shaffer grade 2, 37 in Shaffer grade 3, and 196 in Shaffer grade 4. There was a trend of increasing Shaffer grade with increasing AS-OCT angle width. Open iridocorneal angles, Shaffer grade ≥3, had a ~98% sensitivity and 88% positive predictive value for identifying AS-OCT angle width ≥300 µm, using the AS-OCT method. To verify these results, a total of 28 right eyes were imaged for the third study. A trend of increasing Shaffer grade with increasing AS-OCT angle width was observed, and angles with Shaffer grade ≤2 had AS-OCT angle width <300 µm. The AS-OCT method can determine the space in the anterior chamber and can potentially identify angles that are the appropriate size for certain glaucoma devices. Information gathered from AS-OCT can provide additional comprehensive and quantitative assessment to gonioscopy.