الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
The optical coherence tomography is a new, noncontact noninvasive optical imaging technique that is capable of performing micron-scale, cross-sectional, high depth resolution imaging of internal microstructure in biological systems. It uses low-coherence interferometry to produce a two-dimensional image of optical scattering from internal tissue microstructures in a way that is analogous to ultrasonic pulse-echo imaging (B-scan) except that it uses light rather than sound and performs imaging by measuring the back-scattered intensity of light from structures in tissue. It has longitudinal and lateral spatial resolutions of a few micrometers (10 micron) and can detect reflected signals as small as 10.10 of the incident optical power (Huang et al., 1991).
Nerve fiber layer thickness can be measured using OCT. These measurements provide good structural and functional correlation with known parameters. Nerve fiber layer thickness can be reproducibly measured using OCT. Internal fixation is superior to external fixation. Each circle diameter tested provides adequate reproducibility (Schuman et al., 1995& 1996).
It appears useful for objectively monitoring retinal thickness with high resolution in patients with macular edema. It may eventually prove to be a sensitive diagnostic test for the early detection of macular thickening in patients with diabetic retinopathy. Its topographic mapping
pigment epithelial detachments. It may have potential in accurately defining the boundaries in a subset of angiographically occult choroidal neovascularization (Hee et at, 1996).
There can be significant nerve fiber layer thinning in patients with both glaucoma and optic disc drusen, despite the appearance of the optic nerve head in these patients. The cup margin may be obscured by the drusen, giving rise to a falsely full-appearing disc. In such cases, OCT may provide a useful means to quantitatively measure the nerve fiber layer thickness and to aid in the management of these patients by detecting nerve fiber layer thinning earlier than would otherwise be possible. Increased numbers of clinically visible optic nerve head drusen correlated with nerve fiber layer thinning shown by OCT measurements and both visual field defects and nerve fiber layer loss seen by red-free photography (Roh et aL, 1997 & 1998).
OCT confirms the two layer structure of optic disc pit maculopathy in which a macular detachment develops secondarily to a pre-existing schisis-like lesion consisting of severe outer retinal edema. It shows that improvement in central vision after pneumatic displacement coincides with a reattachment of the outer layer detachment in the macula and that the inner layer separation, which persists, provides a conduit for the continuous flow of fluid from the pit to the displaced retinal elevation (Lincoff and Kreissig, 1998).
Some of the polypoidal structures in eyes with idiopathic polypoidal choroidal vasculopathy are anteriorly protruding lesions in the
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