Choroidal and Retinal Features in PACD and POAG on OCT and OCTA

Condition(s) studied

Study summary

Glaucoma is a group of irreversible, progressive optic neuropathies that can lead to severe visual field defects and even blindness, affecting nearly 95 million people worldwide. Based on anterior chamber angle structure, glaucoma is classified into primary angle-closure glaucoma (PACG) and primary open-angle glaucoma (POAG). Although POAG is more common, PACG is more severe and more likely to cause blindness if not managed appropriately. Globally, PACG accounts for approximately 25% of all glaucoma cases but is responsible for roughly 50% of glaucoma-related blindness. Generally, the term "glaucoma" implies optic nerve damage; however, glaucomatous optic neuropathy may be absent in subacute and acute angle-closure glaucoma. Therefore, according to international consensus, primary angle-closure disease is categorized as PACD-encompassing primary angle-closure suspect (PACS), primary angle closure (PAC), and PACG-based on the extent of angle closure, intraocular pressure elevation, and optic nerve damage. With advances in ophthalmic imaging, an increasing array of diagnostic modalities has been applied to glaucoma diagnosis. Optical coherence tomography (OCT), which utilizes low-coherence light to display cross-sectional images of the retina in vivo, represents a rapid, non-invasive, and continuously evolving imaging method. Building upon OCT, OCTA has emerged as a novel imaging technique that allows non-invasive visualization and assessment of blood flow in individual retinal layers \[5\]. Existing OCT and OCTA research on glaucoma primarily focuses on the optic disc and macula of glaucoma patients, providing evidence of changes in the retinal nerve fiber layer, macular ganglion cell thickness, optic nerve head structure, and peripapillary and macular vasculature. Other studies have examined choroidal vascular architecture and thickness in glaucoma; previous findings from our research group also indicate that choroidal vascular density is significantly lower in eyes with POAG and PACG compared to normal eyes, while choroidal stromal area is significantly greater in PACG than in POAG eyes and normal controls. Further investigation into choroidal and retinal alterations in glaucoma is warranted. Consequently, the OCT and OCTA fundus characteristics of patients with PACD and POAG remain an area with unexplored unknowns. This study utilizes OCT and OCTA to observe the choroidal and retinal tissue structure and vascular hemodynamics in patients with PACD and POAG, aiming to comprehensively investigate structural changes in the glaucomatous fundus, broaden new research directions, and explore and supplement the understanding of glaucoma pathogenesis.

Eligibility

Primary outcome measure(s)

• Subfoveal choroidal thickness (μm) — Day 1
  Subfoveal choroidal thickness (SFCT) is defined as the vertical distance between the outer border of the retinal pigment epithelium (RPE)/Bruch's membrane complex and the choroid-scleral junction directly beneath the fovea centralis. This measurement is obtained using a widefield swept-source OCT device, which enables enhanced depth imaging and high-resolution visualization of the choroid.The assessment is subsequently conducted by a masked, experienced grader using the integrated caliper tool. SFCT serves as a quantitative biomarker for choroidal structural changes associated with primary angle-closure disease (PACD) and primary open-angle glaucoma (POAG).
• Deviation of the horizontal watershed zone — Day 1
  The deviation of the horizontal watershed zone (HWZ) is assessed by determining whether the HWZ is displaced superiorly or inferiorly relative to the fovea centralis. This evaluation is performed using 24 × 20 mm en face OCTA images acquired with a widefield swept-source OCTA device. All measurements are carried out with the device's built-in caliper tool by a masked, experienced grader. The HWZ deviation serves as a quantitative indicator reflecting alterations in choroidal venous outflow patterns.

Trial sites (1)

More Zhongshan Ophthalmic Center, Sun Yat-sen University trials in China

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