Home

Ultrasonography

Ultrasonography

With ultrasonography, high-frequency, inaudible sound waves are emitted into the eye. These waves bounce off any tissue surface back towards the probe, which measures the ‘loudness’ of the reflected sound and the time taken for the sound to travel into the eye and back again. The intensity of the reflected signal gives an idea of the ‘hardness’ of the reflecting tissue. The time taken for the reflected signal to be received gives an indication of the distance travelled by the sound.

 

 

Fig4-5

 

A-scan ultrasonography produces a linear signal, with a series of waves, which reveal the consistency of the tumour. In the image above, the A-scan is the jagged line near the lower border of the photograph.

 

With B-scan ultrasonography, the beam sweeps the eye from side to side, producing a visual slice of the eye and a good idea of the size and shape of any tumour in the eye. This scan shows a choroidal tumour adjacent to the optic nerve.


Ultrasonography has several applications in assessing an eye with a tumour:

  • If the media are opaque, it enables the tumour to be detected.
  • Ultrasonography can also reveal tumour extension outside the eye.
  • By demonstrating a collar-stud shape, ultrasonography can help establish the diagnosis.
  • With calipers, it is possible to measure tumour thickness and basal diameter. These measurements are useful when selecting treatment and measuring how a tumour is growing or regressing over time.


The front of the eye is assessed with a special high-frequency probe, which requires the use of a small eye-bath or a sheath filled a clear jelly-like fluid.