Tag: octagon

– Optical Coherence Tomography (OCT) is a non-invasive diagnostic technique that provides a cross-sectional view of the retina.
– OCT was introduced in 1991 and has been used in ophthalmology and other fields.
– Time domain OCT acquires approximately 400 A-scans per second.
– Spectral domain technology scans 20,000-40,000 A-scans per second.
– Spectral domain systems have higher resolution and diminish the chance of missing lesions.
– Swept-source technology uses a wavelength-sweeping laser and can acquire 100,000-400,000 A-scans per second.
– OCT angiography is a recent development that uses motion contrast to detect blood flow.
– The term “band” refers to the three-dimensional structure of the retinal layers anatomically.
– The term “zone” describes regions on OCT where the anatomical correlation is not clearly delineated.
– The RPE (retinal pigment epithelium)/Bruch’s complex is one of the layers considered a zone because they are inseparable due to cellular interdigitation.
– Mirror artifacts in OCT occur when the area of interest crosses the zero delay line and result in an inverted image.
– Vignetting or cut edge artifact occurs when part of the OCT beam is blocked by structures like the iris, resulting in a loss of signal on one side of the image.
– Misalignment or off-center artifact occurs when the fovea is not properly aligned during a volumetric scan, leading to incorrect measurements.
– Out of Range Error or out of register artifact happens when the area of interest is not at the center of the image, leading to cutoff or improper positioning of structures.
– Blink artifacts result in partial loss of data due to momentary blockage of OCT image acquisition during blinking.
– Motion artifact occurs when there is movement of the eye during OCT scanning, leading to distortion or double scanning of the same area.
– Segmentation error can occur in horizontal scans when the software of the OCT machine automatically detects the border of the inner retina.
– Cystoid macular edema appears as multiple circular hyporeflective spaces in the retina.
– Senile retinoschisis involves a splitting of retinal layers at the outer plexiform layer.
– The “pearl necklace sign” is seen in exudative macular diseases and appears as hyperreflective dots arranged in a ring around the inner wall of cystoid spaces in the retina.
– Paracentral acute middle maculopathy (PAMM) is characterized by a hyperreflective band at the level of the inner nuclear layer in OCT scans.
– Disruption of the ISOS line (separating the inner and outer segments of photoreceptor cells) is correlated with retinal function loss in various retinal disorders.
– The ILM drape sign is seen in macular telangiectasia 2 and occurs when a thin membrane overhangs a cystoid lesion at the base of the fovea