الفهرس 
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Abstract
Glaucoma is a group of progressive optic neuropathies associated with characteristic visual field defects and structural changes in the optic nerve head.
Glaucoma is a worldwide leading cause of irreversible vision loss. Because it may be asymptomatic until a relatively late stage, diagnosis is frequently delayed.
The Intra ocular pressure is the most important risk factor of glaucoma and the primary modifiable risk factor.
The anterior chamber angle has a special care in diagnosis of glaucoma. The normal angle of the anterior chamber is seen as the junction between the cornea and sclera, where the iris root inserts into the ciliary body. The scleral spur is the most important landmark in angle evaluation.
Assessment of the angle is important to determine the mechanism and type of glaucoma. According to the angle of A.C glaucoma can be classified into open and closed angle.
Ultrasonic biomicroscopy (UBM) is an imaging technique that utilizes 50 MHz high-frequency sound waves to produce a high- resolution image, it has multiple applications in ophthalmology to evaluate both anterior segment structures and peripheral posterior segment anatomy. Since its inception, it has become an important method that greatly assists the clinician in the diagnosis and management of angle closure and other subtypes of glaucoma. Currently, UBM is the most widely used method for the study of ACA regardless of optical media transparency.
Ultrasound biomicroscopy systems are suitable for imaging of virtually all anterior segment anatomy and pathology, including the cornea, iridocorneal angle, anterior chamber, iris, ciliary body and lens.
It is possible to use the UBM to quantify the width of the angle. The use of this technology gives an excellent view of the pathology occurring in the anterior and posterior chambers of the eye and allows objective documentation of the anterior chamber angle and the ciliary body, thereby providing a clear insight into the cause of aqueous obstruction. It also aids in establishing the causes for failure of filtering surgery.
The most important A.C angle parameters can be measured by UBM is angle-opening distance AOD 500, Trabecular–iris angle TIA and A.C depth.
Through Studying the relationship between primary glaucoma types (primary open and closed angles) over UBM detection parameters, we could identify that there is statistically significant (p<0.001) higher mean AOD 500/mm and AC depth /mm2, among eyes with open angle than with closed angle glaucoma.
UBM technique is a good tool for glaucoma diagnosis, which remains the gold standard for the quantitative measurement of angle parameters.