An ophthalmic ultrasound scanner uses high-frequency sound waves to create images and measurements of the eye's internal structures, essential for diagnosing conditions like cataracts, retinal detachments, or optic nerve issues, with A-scans providing axial length for IOL power calculation and B-scans offering 2D cross-sections, often combined with UBM (Ultrasound Biomicroscopy) for detailed anterior segment views, aiding in pre-operative planning and monitoring eye health.