During A-scan ultrasonography biometry, a measurement artifact shows multiple spikes within the vitreous cavity that do not correspond to any anatomical structure. This occurs because the ultrasound beam is not perpendicular to the interface. This phenomenon is best described as:
- A Acoustic shadowing
- B Refractive error artifact
- C Oblique scanning artifact (pseudo-membrane) ✓
- D Reverberation artifact
Correct answer: C. Oblique scanning artifact (pseudo-membrane)
Explanation
When the A-scan beam strikes a membrane (vitreous interface) at an oblique angle, a false low-amplitude spike appears, mimicking a vitreous membrane. Proper technique requires the beam to be perpendicular to the fovea, confirmed by the tallest retinal spike. Reverberation produces equidistant repeated spikes; acoustic shadowing blocks posterior structures.
Reference: Ophthalmic Ultrasound, 3rd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.