PROCEDURE OF OCT:
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• STEP-1: PATIENTS DATA
Activation of instrument & entering patients data
• STEP-2: PATIENTS PREPARATION:
Pupil dilate with mydriatics (tropicamide)
Asked to look into the internal fixation target light in the
ocular lens
• STEP-3: PROTOCOL FOR SCAN ACQUISITION:
Selected as per the case requirements
The scanning beam is placed on the target area and scans
are obtained
• STEP-4: PRODUCTION & DISPLAY IMAGE:
Several data points are integrated by the interferometer to
construct a tomogram of the target area
The tomogram is displayed in either grey scale or false color
on a high-resolution computer screen
INTERPRETATION OF OCT:
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• VITREOUS:
* Anterior to retina is non-reflecting & is seen as a dark space
• VITREORETINAL INTERFACE:
* Is well defined due to the contrast between the non-reflecting
vitreous & backscattering retina
• RETINAL LAYER:
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o ANTERIOR BOUNDARY:
* Formed by highly reflective RNFL & is seen as red layer due to bright
backscattering
o POSTERIOR BOUNDARY:
* Its also seen as red layer representing highly reflecting retinal
pigment Epithelium (RPE) & choriocapillaries.
o OUTER SEGMENTS OF RETINAL PHOTO-RECEPTOR LAYER:
* As minimally reflective are represented as dark layer just anterior to
RPE-choriocapillaries complex
o DIFFERENT LAYER OF RETINA:
* Between the dark layer of photoreceptor & red layer of RNFL are
seen an alternating layers of moderate and low reflectivity
• OCT ONH:
* Optic disc has also been shown to demonstrate useful
discrimination between normal & glaucomatous eyes.
• MACULAR OCT:
* Has demonstrated clear visualization of macular hole, macular edema & lesion associated with Age Related Macular Degeneration (ARMD).
RNFL ASSESSMENT WITH OCT:
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• Retinal nerve fiber layer (RNFL), is highly reflective and its thickness
increases from the macula to optic disc margin
• OCT-3 offers a variety of RNFL thickness measurement and analysis
protocol like: RNFL thickness scan, fast circular scan, concentric
three-ring protocol, RFNL map and proportional circles
• Circular scan of 1.34 mm radius on the Optic nerve hypoplasia has been
shown to exhibit maximum reproducibility foe RNFL measurement
• The mean RNFL thickness is calculated using age-adjusted RNFL
thickness protocol.
INDICATION OF OCT:
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A. RETINAL DISEASE:
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• PRE & POST MACULAR HOLE SURGERY:
o Helps to determine presence & grade of macular hole
o To determine whether anatomical closure has occurred or not
• MACULAR EDEMA:
o Detection & monitoring edema during treatment
• SUB-RETINAL NEOVASCULAR MEMBRANE:
o To evaluate pre & post treatment features
B. GLAUCOMA:
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o OCT scan patterns for the optic nerve head and peripapillary retinal
fiber layer
o Glaucoma follow-up to detect evidence of progresson
Optical Coherence Tomography - OCT | part-1: [ Ссылка ]
