الفهرس 
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Abstract
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SUMMARY
Diagnostic ultrasound is an offspring of
sonar. A-scan and B-scan are the most popular techniques
of ophthalmic ulrasonic examination. In both
techniques, a short pulse sound is transmitted and
the returning echoes are received and examined.
Diagnostic ophthalmic ultrasound requires a
frequency of about 5 _ 25 M-I Z. The length of time it
akes for ultrasound to travel from the transmitter to
the back. of the eye and return to the receiver is
approximately 30 million ths of a second.
In the A-scan technique, the transdlucer is
held against the cornea or sclera and the sound is
sent in the direction in which the transducer points.
The returning ech DeS are shown as upward deffections
from a base line with the horizantal axis indicating
distance. Any structure in the eye is an acoustic
discontinuity and will return an echo, some obviously
stronger than others We can see echoes returned
from the cornea, the anterior lens capule, the posterir
lens capsule and the p osteriar wall followed by
multiple echoes from the orbital fat.
In the B-scan technique, the transducer is
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moved from side to side and the echoes, instead of
appearing as upward spikes, are depicted as dats. The
dats, when put together, make an anatomical picutre
of the eye, with the intensity of the echo appearing
as brightness.
Ul trason ography has proved to be of grdat
value in ophthalmology. Important informaticn has
been obtained by ’correlating echo patterns, primarily
on the basis of their lOcatian and appearance, with a
variety of eye disorders. Ul trasono graphy provides a
valuable means of evaluating opaque media where no
other technique can provide sufficient information to
determine adequately the diagnostic and rationale for
treatment.
Ultrasound offers an additional means of
studing suspected ocular tumours. Ultrasound is as
reliable as optical techniques in showing structural
changes wi thin the eye. The location of intraocular
foreign bodies can be found accurately with ultrasonog.
Utrasound is even more helpful in the assessment of
the associated dainage caused by a foreign body.
Orbital ultrasonography provides a reliable,
safe and Btraumatic method of examining th~ orbit for
tumour, inflammatory change or foreign body, because
ultrasonic tomograms can demonstrate the tissue
outlines of the
Orbital walls of
globe, optic
the normal
nerve,muscles and
orbit. In pathologic
conditions abnormal mass outlines can be seen and
their shape, position and acoustic character can be
reliably used to differentiate orbital lesions.