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Anterior segment OCT

Eye Care estimated about CNY 300-550

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Description

Imaging modality using optical coherence tomography to visualize and quantify structures of the anterior eye segment, including cornea, anterior chamber, iris, and lens, with high resolution and non-invasively.

Main Uses

Primary clinical uses include: (1) Objective assessment of anterior chamber angle anatomy for glaucoma screening and angle-closure risk stratification; (2) Pre- and post-operative evaluation of corneal surgeries (e.g., LASIK, DALK, DSEK); (3) Diagnosis and monitoring of corneal ectatic disorders (keratoconus, pellucid marginal degeneration); (4) Evaluation of iris morphology in pigment dispersion syndrome, plateau iris, or iris tumors; (5) Visualization of intraocular lens position, ciliary sulcus anatomy, and filtering blebs after glaucoma surgery.

Normal Range

Anterior segment OCT (AS-OCT) is a qualitative and semi-quantitative imaging modality; it does not yield universal numerical 'normal ranges' like laboratory tests. Instead, normal findings include: corneal thickness (central: 520–560 µm), anterior chamber depth (2.5–3.5 mm), angle opening distance (AOD500: 0.25–0.50 mm), trabecular-iris space area (TISA500: 0.10–0.25 mm²), iris thickness (at 750 µm from scleral spur: 0.3–0.5 mm), and clear visualization of intact corneal layers, open iridocorneal angle, and regular lens capsule contour. Values vary by age, ethnicity, and device (e.g., Visante, CASIA, SS-OCT).

Low Values - Possible Causes

1. Corneal edema or decompensation (e.g., Fuchs dystrophy), 2. Anterior chamber shallowing due to pupillary block or plateau iris configuration, 3. Angle closure (primary or secondary), 4. Post-surgical anatomical distortion (e.g., after penetrating keratoplasty or phakic IOL implantation), 5. Severe uveitis with inflammatory exudates obscuring structures.

High Values - Possible Causes

1. Corneal ectasia (e.g., keratoconus — increased central corneal curvature & thinning, though thickness itself may be low; high asymmetry indices), 2. Deep anterior chamber (e.g., high myopia, aphakia), 3. Wide-open iridocorneal angle (e.g., in hypermetropes with shallow angles? No — correction: wide angles are typical in younger, non-angle-closure subjects; 'high' AOD/TISA values reflect openness but are not pathological unless contextually atypical), 4. Iris stromal atrophy (e.g., ICE syndrome — apparent 'increased' posterior chamber depth due to transillumination defects), 5. Artifact from excessive tear film or poor fixation causing segmentation errors mimicking thickening.

anterior segment OCT corneal thickness measurement angle-closure glaucoma assessment AS-OCT imaging iridocorneal angle analysis

estimated about CNY 300-550