This is a simple non-invasive test that uses sound waves to see the internal eye structures. It is a painless, safe and short procedure, performed routinely in the OPD, without any anesthesia. It is of two types-A and B scan. A-scan is used to measure the antero-posterior length of the eyeball to calculate the IOL power in cases of cataract surgery.

B-scan is used when the clarity is not good for examining the internal structures of the eye. This is test is useful in cases like dense vitreous hemorrhage, significant cataract, corneal opacity, small pupil, trauma (to see for eyeball rupture), hazy media in endophthalmitis and retained intraocular foreign body. It is also very useful in making a diagnosis in cases of eye tumors like retinoblastoma, Choroidal melanoma, Choroidal osteoma and in inflammatory conditions like posterior scleritis. The sound waves are beamed into the eye by a vibrating crystal, which are reflected back from the various eye structures depending on their density. The image is reconstructed by the computer and the printout gives a fair idea of the status of the ocular structures like retina. This test helps in diagnosis and planning the management. It also helps us in predicting the outcome of the treatment.