الفهرس 
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Abstract
White cataracts and intumescent cataracts are challenging cases
for almost all surgeons. In these eyes, during capsulorhexis creation,
the pressure created by the hyper-hydration of lens fibers can cause
spontaneous tears in the capsulorhexis that extend to the periphery.
This has been termed the Argentinean Flag Sign. Once this occurs, the
cataract surgery may become extremely difficult due to poor
construction of the capsulorhexis, and possible rupture of posterior
capsule.
OCT is a non-invasive method that have the ability of in situ
visualization of tissue, It became of particular importance in
ophthalmology because of the key information provided by them
regarding the physiology and the diseases related to the eye .The
structures of the anterior segment can be analyzed using OCT .It
became used increasingly due to its ability for providing a non -
contact scans to the anterior segment of the eye. This makes the
examination comfortable, safe and fast.
The anterior segment optical coherence tomography (AS-OCT)
act as a guide in determining the presence or absence of fluid pockets
under the anterior capsule for stable and easy removal of subcapsular
fluid pockets.
The eye is a superficial fluid filled structure; ultrasound is an
easy to use modality for visualization of ocular pathology and
anatomy. The principles of ocular ultrasound are the same as other
applications of this technology. Sound waves are generated at a
frequency greater than 20,000Hz (20 kHz), and reflected back to the
transducer by tissue in its path. When the sound wave returns, a
Summary
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piezoelectric crystal in the transducer vibrates, resulting in electrical
impulses that are translate in to an image or other data.
There are two main types of ultrasound used in ophthalmologic
practice currently, A-Scan and B-scan. In A-scan or time-amplitude
scan and In B-scan, or brightness amplitude scan, sound waves are
generated at 10 MHz and converted into spikes that correspond with
tissue interface zones.
Biometry enables the measurement of the various dimensions of
the eye, including axial length (AL), anterior chamber depth (ACD),
lens thickness (LT) or central corneal thickness (CCT). These values,
together with the keratometry are essential for the IOL power
calculation.
Precision of measurements is crucial, as a 0.1 mm error in AL
results in a refractive error of about 0.27 diopter (D). B scan
ultrasonography is the most commonly used modality for the
assessment of posterior segment pathologies.
Cataract is a degenerative disease of the lens. Ophthalmoscopy
shows a white reflection with an opaque lens (leukocoria). In
immature cataracts, scattered opacities are separated by clear zones.
In a complete cataract, the lens has a completely opaque cortex;
on US it is seen as a hyperechoic structure. Although cataract
detection is not the primary aim of US, this technique is often
routinely performed before mature cataract extraction in order to rule
out possible contraindications to surgery, such as retinal or vitreous,
and choroidal detachments, tumors, and other that cannot be seen on
the ophthalmoscopic examination because of the cataract and could
influence the choice of treatment and prognosis.