الفهرس 
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Abstract
Ultrasound is the ideal method for imaging the intraocular and orbital
structures even when the media are clear
Ultrasound is high frequency sonic energy above the human audible range
of 20.000 cycles per second. It is described by parameters such as propagation
speed, Frequency, and wave length.
According to these parameters beside the density of media in which the
ultrasound waves travel, ultrasound face many phenomena SUchas reflection,
refraction, and absorption.
There are many ultrasonic systems available for ophthalmic eXamination.
These system are Named A-scan, B-scan (with its modification like color coded
system-Vector control- Ultrasound biOmicroscopy), C-scan, D-scan, and Mscan.
Ultrasonic examination is done by immersion or contact method and there
are specific eXamination techniques that have been carefully designed to allow
through evaluation of the globe and orbit.
Conventional techniques remain quite accurate and reliable in their ability
to characterize ocular tumors, this ability of ultrasound was increased by using:
I-The power spectrum techniques which provide truly acoustic tissue
characterization
2-The high frequency (50-100 MHz ) ultrasound biomicroscopy which is
a modem method of imaging the anterior segment of the eye at microscopic
resolution.
The ultrasonographic differentiation of ocular tumors IS Commonly
separated into tow categories:
1- Malignant melanoma with its differential diagnosis .
2- Retinoblastoma with its differential diagnosis.
Uveal melanoma is the most common primary intraocular malignancy and
the main primary intraocular disease that can be fatal in adult.
The echographic criteria of malignant melanoma are its shape (Dome
shaped, or mushroom shape), sold consistency, regular internal structure, low to
medium reflectivity, and choroidal excavation.
Retinoblastoma is the most common intraocular tumor in children.
Retinoblastoma often appear on ultrasonography as irregular shaped mass
in the vitreous. The calcium precipitates both reflected and absorbed sound,
resulting in bright reflectivity even at low gain and shadowing of the orbital fat.
Ultrasound also aids greatly in diagnosis of orbital tumor,
By ultrasound. Orbital tumor can be classified into :
I - Cystic tumors,
2- Solid tumors,
3- Angiomatous tumors,
4- Infiltrative tumors,
This classification based on echographic criteria of transmission and
morphology.
Computed tomography and Magnetic resonance imaging are considered as
oilier advanced imaging techniques in ophilialmology. We are trying to discuss
indications, advantages, and disadvantages of them inproportion to