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A-scan ultrasonography

Eye Care estimated about CNY 150-350

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Description

A diagnostic ultrasound technique used to measure ocular dimensions, including axial length and anterior chamber depth, primarily for intraocular lens power calculation prior to cataract surgery.

Main Uses

Primary uses include preoperative intraocular lens (IOL) power calculation for cataract surgery, diagnosis and monitoring of myopia progression and pathological myopia, assessment of microphthalmia/nanophthalmos, evaluation of suspected globe size abnormalities, and biometric confirmation when optical biometry (e.g., IOLMaster) is contraindicated (e.g., dense cataracts, corneal opacities, or small pupils).

Normal Range

A-scan ultrasonography for ocular biometry measures axial length (AL), anterior chamber depth (ACD), lens thickness (LT), and vitreous depth (VD). Normal adult axial length: 22.0–24.5 mm; ACD: 2.5–3.5 mm; LT: 3.6–4.5 mm; VD: 15.0–17.5 mm. Values vary by age, ethnicity, and refractive status (e.g., children have shorter AL; myopes often >24.5 mm; hyperopes often <22.5 mm).

Low Values - Possible Causes

Congenital microphthalmia, nanophthalmos, high hyperopia, posterior scleral staphyloma (rare, atypical presentation), measurement error due to dense cataract or corneal opacity, or operator inexperience.

High Values - Possible Causes

Axial myopia (most common), pathological myopia with posterior staphyloma, vitreous hemorrhage or detachment causing overestimation, silicone oil tamponade post-vitrectomy, and erroneous calibration (e.g., incorrect sound velocity setting for aphakic or pseudophakic eyes).

A-scan ultrasound ocular biometry axial length measurement

estimated about CNY 150-350