OCT-C flashcards
OCT-C · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Low-coherence interferometry
- Technique in which broadband light is split into sample and reference paths; interference occurs only when the path-length difference is within the coherence length, giving axial depth resolution.
- Axial resolution formula
- Axial resolution is approximately 0.44 λ²/Δλ for a broadband source; increasing bandwidth or decreasing center wavelength improves axial resolution.
- Spectral-domain OCT
- OCT design using a fixed reference mirror and a spectrometer to record the interference spectrum; Fourier transformation yields the A-scan without moving parts.
- Swept-source OCT
- OCT design using a rapidly tunable laser and a single photodetector; longer wavelengths improve choroidal penetration and reduce sensitivity roll-off.
- A-scan, B-scan, en face
- An A-scan is a depth reflectivity profile; a B-scan is a two-dimensional cross-section; an en face image is a coronal slice parallel to the retinal surface.
- Circumpapillary circle scan
- A circular scan around the optic nerve head used to measure peripapillary retinal nerve fiber layer thickness for glaucoma detection and monitoring.
- Foveal pit anatomy
- At the foveola the retinal nerve fiber layer, ganglion cell layer, and inner plexiform layer are absent; the outer nuclear layer is thickened and Henle fibers are present.
- Ellipsoid zone
- A hyperreflective band formerly called the IS/OS junction; it represents photoreceptor inner-segment ellipsoids and is a marker of photoreceptor integrity.
- Interdigitation zone
- The hyperreflective band between the ellipsoid zone and retinal pigment epithelium, representing photoreceptor outer-segment tips interdigitating with retinal pigment epithelium microvilli; also called COST.
- Choroidal layers
- From inner to outer: choriocapillaris, Sattler's medium-vessel layer, and Haller's large-vessel layer, bounded by Bruch's membrane and the sclera.
- Lamina cribrosa
- A sievelike collagenous structure in the optic nerve head through which retinal ganglion cell axons pass; it appears as alternating hyperreflective and hyporeflective bands on OCT.
- Peripapillary RNFL pattern
- Retinal nerve fiber layer thickness is greatest superiorly and inferiorly and least temporally, producing a double-hump pattern used in glaucoma analysis.
- Internal fixation target
- A fixation light inside the OCT instrument that the patient looks at to stabilize the eye and center the macula during scanning.
- Z-offset adjustment
- Adjustment of the reference-arm path length or image display to place the retina within the imaging window and eliminate mirror artifact.
- Signal strength
- A quality metric indicating the amount of detected light; values below the manufacturer threshold reduce segmentation accuracy and require repeat scanning.
- Macular cube protocol
- A raster scan pattern covering the macula with multiple parallel B-scans; used to generate retinal thickness maps and detect macular edema or atrophy.
- Anterior segment adapter
- An attachment or lens used with an OCT instrument to focus on the cornea and anterior chamber instead of the retina.
- Motion artifact
- Misalignment or stepping of B-scans caused by eye movement during acquisition; it is reduced by faster scanning, eye tracking, and patient fixation.
- Mirror artifact
- A duplicate image reflected across the zero-delay line caused by incorrect Z-offset or reference-arm position; corrected by adjusting the offset.
- Segmentation error
- Incorrect automatic boundary detection, common at drusen, epiretinal membranes, or severe edema; automated lines must be verified and corrected manually.
- Shadowing artifact
- Vertical dark bands beneath dense structures such as hemorrhage, thick vessels, or media opacity; they obscure deeper layers and can mimic thinning.
- Decentration artifact
- The fovea is not centered in the scan, which invalidates thickness maps and normative comparisons; corrected by recentering fixation and scan.
- Epiretinal membrane
- A hyperreflective layer on the internal limiting membrane with underlying retinal wrinkling; it may cause macular edema and visual distortion.
- Vitreomacular traction
- Focal attachment of the posterior vitreous cortex to the macula with traction on the retina, often with cystic changes and a partial posterior vitreous detachment.
- Full-thickness macular hole
- A complete defect through all retinal layers at the fovea with elevated cystic edges; staged by size and presence of vitreomacular traction.
- Pigment epithelial detachment
- An elevation of the retinal pigment epithelium away from Bruch's membrane, seen as a dome-shaped hyporeflective space with overlying retinal pigment epithelium.
- Subretinal fluid
- A hyporeflective space between the neurosensory retina and the retinal pigment epithelium; seen in central serous chorioretinopathy and choroidal neovascularization.
- Corneal layers on AS-OCT
- Epithelium, Bowman's layer, stroma, Descemet's membrane, and endothelium; Bowman's and Descemet's are hyperreflective, and the stroma is relatively hyporeflective.
- Pachymetry
- Measurement of corneal thickness; anterior segment OCT pachymetry is used in LASIK screening, keratoconus evaluation, and monitoring corneal edema.
- Keratoconus on AS-OCT
- Corneal thinning, epithelial thinning over the cone, Bowman's layer disruption, and posterior surface elevation; it helps grade severity and plan crosslinking.
- ANSI Z136.1
- The U.S. standard for safe use of lasers; OCT output must remain within manufacturer and standard exposure limits for ocular safety.
- OCT infection control
- Clean chin rest, forehead rest, and contact surfaces between patients per manufacturer instructions; use approved covers or disinfection for contact probes.