Quantitative Anterior Segment SD-OCT Assessment of the Iridocorneal Angle in Chinese Patients with Open-Angle Glaucoma or Ocular Hypertension: An Observational Study

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Purpose: We evaluated iridocorneal angle biometrics using anterior segment spectral-domain optical coherence tomography (SD-OCT) compared with Shaffer grade clinical assessments in Chinese patients with open-angle glaucoma (OAG) or ocular hypertension (OHT) to determine which method is most suitable for preoperative angle assessment. Methods: This noninterventional, prospective study enrolled 206 patients with OAG or OHT in both eyes and Shaffer grade >1 iridocorneal angles at 3 sites in China. Shaffer grades and SD-OCT 5-line raster scans (Zeiss Cirrus HD-OCT 4000) of the inferior angle were obtained under dark conditions. Images were evaluated for visualization of Schwalbe's line, the superior iris surface, and angle recess. ImageJ software was used to measure the angle-opening distance at Schwalbe's line (SL-AOD) in gradable images. Results: Almost all study eyes had Shaffer grade 4 (91.0%) or grade 3 (8.3%) angles. Mean (standard deviation) SL-AOD was 0.75 (0.33) mm (median 0.73, range 0.051-1.9, n=322). The SL-AOD was <0.635 mm (the tube outer diameter of the Ahmed glaucoma valve and Baerveldt glaucoma implant) in 37.6% of the eyes. SL-AOD values did not differ significantly between OAG and OHT diagnoses or between phakic and pseudophakic eyes. Conclusion: Iridocorneal angle biometrics derived from SD-OCT images in Chinese patients with OAG or OHT showed large variation in the SL-AOD in eyes with open angles on gonioscopy. Over one-third of patients had SL-AOD too small to safely accommodate commonly used glaucoma tube shunts. Expanded preoperative use of SD-OCT could potentially be beneficial to detect angles at risk for corneal complications and inform device selection.

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