B-scan Ultrasonography, often just called B-scan, gives a two-dimensional cross-sectional view of the eye and orbit. A B-scan is performed on the outside of the closed eyelid to image the eye. This tool is helpful in many situations when there is difficulty examining the eye by normal methods. This could be due to severe cataracts, eyelid problems, corneal opacities, or very small pupils. A B-scan can be helpful in diagnosing conditions such as retinal detachments, optic disc drusen, vitreous hemorrhages, as well as choroidal nevi and melanomas.
A-scan Ultrasonography is commonly used to measure the length of the eyeball, also called the “axial length.” This is useful in monitoring and managing myopia or nearsightedness. An A-scan is also used prior to cataract surgery for intraocular lens calculations. Longer axial lengths are associated with retinal disease and early formation or cataracts among other eye conditions.