Eye Care Services

Ophthalmic Ultrasonography

Introduction:

Ophthalmic ultrasonography is the main diagnostic imaging modality of the eye. It is a safe, noninvasive diagnostic tool that provides instant feedback for the evaluation of various ophthalmic disorders. Diagnostic ophthalmic ultrasonography is most useful in the presence of opaque ocular media caused by corneal opacities, anterior chamber opacities, cataracts, vitreous hemorrhage, or inflammatory opacities. Ophthalmic ultrasonography is also valuable in the presence of clear media and for evaluation of the iris, lens, ciliary body, and orbital structures. Ultrasonography of the eye is the best modality to evaluate the posterior segment in presence of an opaque media. The anechoic vitreous acts as a natural contrast for ultrasonography of the posterior segment. Ophthalmic ultrasonography is broadly divided into A-Scan and B-Scan. A-Scan can be used for biometric calculation and for quantifying the reflectivity of lesions in the eye and orbit. Ophthalmic ultrasonography is ideally done on a dedicated eye scanner. An ideal ophthalmic ultrasound scanner should have a dedicated 10 MHz B-Scan probe, synchonised vector A-Scan, log, linear & S-shaped amplifications. It is advisable to have a separate diagnostic A-Scan module. It is now possible to use a 20 MHz probe for better resolution especially in the posterior segment. 20 MHz probe is ideally suited for ultrasonographic evaluation of the lens and anterior vitreous. A 50 MHz probe is used for anterior segment ultrasonography which is called as Ultrasound Biomicroscopy. The resolution of this probe is 30 microns and has a depth of 4 mm.