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Published byRandolph Robbins Modified over 9 years ago
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OCT:BASIC CONSEPT F.FAZEL.MD
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Optical Coherence Tomography 1995-1996 introduced in to clinical practice Retina,glaucoma,anterior segment Rapid,easy,non- contatc,noninvasive,sensitive,highly reproducible and repeatable Qualitative and quantitative
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How the OCT work The OCT uses an interferometer that measures the time it takes for light to be reflected back from structures in the retina, as compared to the time it takes for light to be reflected back from a reference mirror at specific distances. The process is similar to that of ultrasonography, except that light is used instead of sound waves.
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Retinal layer scanning
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Differences of OCT and sonography Light(830nm) vs.. Ultrasound Speed Resolution(10 micron vs100) Noncontact vs. contact
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OCT vs SONO
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Scan protocol
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Line scan
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Circle scan
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Radial line scan
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Reflectivity Qualitative analysis of the OCT scan includes observation of the reflective qualities of the retinal structures. The OCT software assigns "cooler" colors (green, blue) to structures with lower reflectivity. It assigns "warmer" colors (yellow, orange, red) to more highly reflective structures. White represents the most highly reflective structures, and black represents the least reflective structures. On the OCT scan of a normal retina, the NFL and RPE are highly reflective, the middle retinal layers are medium reflective, and the photoreceptors (just above the RPE layer) are low reflective.
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Normal retinal layers in OCT
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Anterior segment OCT Angle assessment ■ Pachymetry ■ Glaucoma surgery evaluation ■ Evaluation of corneal transplant ■ Visualization of the sclera/suprachoroidal space ■ Identification of iris lesions ■ Evaluation of crystalline lens, pseudophakic IOLs
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Visante OCT
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Top hat approach PKP
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Donor tissue depth
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Zigzag approach PKP
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Endothelial keratoplasty
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Normal AC angle
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Narrow angle
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Open PI in plateau iris
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Peripheral Anterior Synechia
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Iris cyst
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irridoschisis
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Anerior ChamberAngle tumor
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Suprachoroidal effusion
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IOL tilt
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Shallow AC needs lensectomy
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