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COCO Course Retina Part 1
Terms in this set (31)
Where is the vitreous firmly attached to the retina?
Vitreous base (2mm anterior, 3mm posterior), lens capsule, retinal vessels, optic nerve, and macula
What is the macula defined histologically?
The area of retina featuring two or more layers of ganglion cells
Define the fovea:
A depression in the inner retina which is entirely made of cones
What are dentate processes?
Jetties of retinal tissue that extend anteriorly into the pars plana and are more prominent nasally
What are ora bays?
Posterior extensions of the pars plana toward the retinal side
What is a meridional fold?
A radially oriented, prominent thickening of retinal tissue extending into the pars plana
Does increase risk of RD
List the layers of the retina from inner to outer:
Internal Limiting Membrane
Nerve Fiber Layer
Ganglion Cell Layer
Inner Plexiform Layer
Inner Nuclear Layer
Middle Limiting Membrane
Outer Plexiform layer
Outer Nuclear Layer
External Limiting Membrane
Rod/cone inner and out segments (IS/OS)
Where are rods the most dens?
A zone lying about 20 degrees from fixation
What forms the Internal Limiting Membrane?
The footplates of Muller cells.
It is attached to the posterior cortical gel of the vitreous.
List the functions of the RPE
Absorb light, phagocytose cone/rod segments, form blood/retinal barrier, maintain subretinal space, regen of 11-cis-retinaldehyde
List the layers of the Bruch Membrane (from inner to outer)
Basement membrane of RPE
inner collagenous layer
outer collagenous layer
basement membrane of choriocapillaris
What wavelength does Sodium Fluorescein fluoresce at and what wavelength of light excites it?
520-530 nm (green) after excitation by blue light (465-490 nm)
Name the two types of HYPOfluorescence on FA?
Vascular filling defect (vessel does not fil)
Blocked fluorescence (fibrous tissue/blood blocking fluorescence)
Name the 5 types of HYPERfluorescence on FA?
Leakage, staining, pooling, transmission/window defect, autofluorescence
Define leakage on an FA and what conditions can cause it?
Gradual, marked increase in fluorescence throughout the study (borders become blurred, greatest during late phase)?
Caused by CNV, CME, neovascularization of the disc
Define Staining on an FA and what conditions can cause it?
Fluorescence increases in intensity during transit views and persists in late views with FIXED borders. Results from entry into solid material
Caused by entrance of fluorescein into solid tissue such as a scar, drusen, optic nerve tissue, or sclera
Define pooling on an FA and what conditions can cause it?
The accumulation of fluorescein in a fluid filled space in the retina/choroid.
Caused by RPE detachment
Define a transmission or window defect on an FA and what conditions can cause it?
View of normal choroidal fluorescence through a defect in the RPE pigment. Occurs early (during choroidal filling) and does not increase in intensity in late phases (usually fades due to dilution)
Caused by RPE atrophy
Wha are the side effects of fluorescein?
Yellowing of skin/conj (6-12h), yellow urine (24-26h), n/v (10%), anaphylactic (less than 1 in 100,000), rash (1%)
What wavelength does ICG fluoresce at?
Near-infrared range (790-805 nm) thus can be injected before or after FA
How is ICG matabolized and what are its condraindications?
Metabolized by the liver and excreted into bile
Contraindications: Liver disease, metformin use.
Caution w/ shellfish allergy (as dye is 5% iodine)
What does the a wave, b wave, and c wave on an ERG represent?
A wave: Response of photoreceptors
B wave: Response of Muller/bipolar cells
C Wave: A late response 2-4 seconds after stimulus generated by the RPE
Can a non-multifocal ERG distinguish between macular and peripheral lesions?
No, although the macula contains mostly cones, 90% of cones are outside of macula
Use of a multifocal ERG with good patient fixation CAN distinguish if macular dysfunction is present however
Describe how inner retinal disease affects the ERG waveform
May selectively diminish the B-wave
What does an EOG measure and what disease is it useful for?
Used to measure the standing potential
A 6-10mV generated by the polarity of the RPE (the rpe cell has different ion concentrations on its apical and basal side). Cornea is positive, posterior pole is negaive
Only useful in Best Vitelliform Dystrophy
What is the Arden Ratio?
In an EOG, the resting potential of the RPE in light divided by that in dark.
Normally > 1.85
What is a Visually Evoked Cortical Potential (VECP) and what are they best used to diagnose??
An electrical signal generated by the occipital cortex in response to stimulation of the retina by either light flashes or patterned stimuli
Primarily tests macular function as most of the visual cortex represents macula
Useful for demyelinating disease, optic neuropathy, malingering
Dark Adaptation Curve (image)
What is the anomaloscope?
The most accurate way to assess red-green color deficiency.
Pt mixes red/green to match a yellow
Of the Ishihara and Farnsworth Panel color tests, which test is a screening test and which classifies the color deficiency? Also which colors are tested by each?
Ishihara: Screening for
Farnsworth: Classifying the color deficiency. Can differentiate congenital vs acquired deficiencies.
What is the Pelli-Robson Test?
A chart that tests for contrast sensitivity
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