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Retina Pt 1
Terms in this set (90)
What is the Ligament of Wieger
A condensation of collagen fibers that attach to the posterior lens capsule
What is the patellar fossa?
The retrolental indentation of the anterior vitreous
What is the Berger Space?
A potential space btw the lens and anterior cortical gel bordered by the Wieger Ligament
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 annular gap?
Area btw vitreous and aqueous compartments. There is no true basement membrane separation thus allowing diffusion
What is the precortical vitreous pocket (premacular bursa)?
A prominent liquefaction of the premacular vitreous gel
What is the area of Martegiani?
The attachment of the collagenous vitreous to the disc
What is the ciliobursal canal?
A canal in the vitreous connecting the ciliary body and macula and possibly important in CME
What two carotenoids contribute to the yellow color of the macula?
Lutein and Zeaxanthin
What is the macula defined histologically and its diameter?
The area of retina featuring two or more layers of ganglion cells
Diameter of 5.5mm
What is the fovea and diameter?
A 1.5mm depression in the inner retina which is entirely made of cones
What is the foveola and diameter?
A 0.35mm diameter floor of the fovea where the INL and ganglion cell layer are laterally displaced
What is the umbo?
A 150um in diameter depression in the center of the fovea (fixation light reflex)
What is the near periphery?
A 1.5mm ring peripheral to the temporal major vascular arcades
What is the equatorial retina?
The retinal zone around the equator
What is the peripheral retina?
The retinal zone anterior to the equator
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
What is a meridional complex?
A meridional fold that is aligned with a ciliary process
What are the layers of the retina?
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)
What types of photoreceptors are in the fovea?
Red and green sensitive cones reaching a density of 140,000 cones/mm^2
Where are rods the most dens?
A zone lying about 20 degrees from fixation
What is the IS/OS junction?
A layer on OCT forms by mitochondria, cilia, and inner discs
What is a midget bipolar cell?
A bipolar cell that forms a 1-1 synapse with a cone
What forms the Internal Limiting Membrane?
The footplates of Muller cells.
It is attached to the posterior cortical gel of the vitreous.
What is the External Limiting Membrane?
Not a true membrane, formed by zonular attachments btw the photocreceptors and Muller cells
What is the Middle Limiting Membrane?
Not a true membrane, formed by connections btw photoreceprots and bipolar cells
What are the capillary networks that supply the retina?
Radial Peripapillary Network (NFL), superficial and deep capillary plexus (on either side of the INL), and the choriocapillaris
Where are RPE cells taller and denser?
In the macula (compared to the periphery)
Functions of the RPE
Absorb light, phagocytose cone/rod segments, form blood/retinal barrier, maintain subretinal space, regen of 11-cis-retinaldehyde
What are the layers of the Bruch Membrane?
Basement membrane of RPE
inner collagenous layer
outer collagenous layer
basement membrane of choriocapillaris
What is the Haller Layer of the Choroid?
The outer layer of large caliber choroidal vessels
What is the Sattler Layer of the Choroid?
Smaller diameter vessels in the choroid
How is fluorescein eliminated from the body?
Via liver and kidneys in 24-36 hours
What wavelength does Sodium Fluorescein fluoresce at?
520-530 nm (green) after excitation by blue light (465-490 nm)
What are the phases of an FA?
Transit phase, Choroidal Phase, arterial phase, ateriovenous phase, late phases
What is the Transit Phase of an FA?
Initial phase when retinal and choroidal vessels fill, lasting 10-15 seconds
What is the Arterial Phase of an FA
Dye fills retinal arteries
What is the Arteriovenous Phase of an FA?
Begins after complete filling of the retinal arteries/capillaries and concludes with laminar filling of the retinal veins (1 min after injection)
What is autofluorescence?
Appears before the fluorescein dye is injected can caused by highly reflective substances (such as drusen)
What are the two types of HYPOfluorescence?
Vascular filling defect (vessel does not fil)
Blocked fluorescence (fibrous tissue/blood blocking fluorescence)
What are the 5 types of HYPERfluorescence?
Leakage, staining, pooling, transmission/window defect, autofluorescence
Define leakage on an FA?
Gradual, marked increase in fluorescence throughout the study (borders become blurred, greatest during late phase)?
What conditions cause leakage on an FA?
CNV, CME, neovascularization of the disc
Define Staining on an FA?
Fluorescence increases in intensity during transit views and persists in late views with FIXED borders. Results from entry into solid material
What conditions cause staining on an FA?
Entrance of fluorescein into solid tissue such as a scar, drusen, optic nerve tissue, or sclera
Define pooling on an FA?
The accumulation of fluorescein in a fluid filled space in the retina/choroid.
What conditions cause pooling on an FA?
Define a transmission or window defect on an FA?
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)
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 is Indocyanine Green Angiography used for?
Choroidal vessel imaging since it is not very permeabile and highly protein bound
What wavelength does ICG fluoresce at?
Near-infrared range (790-805 nm) thus can be injected before or after FA
Indications for ICG:
CNV, PED, RAP, polypoidal choroidal vasculopathy, central serous chorioretinopathy, intraocular tumors, choroidal inflammation
How is ICG matabolized?
By the liver and excreted into bile
Contraindications to ICG:
Liver disease, metformin use.
Overall has lower rate of side effects compared to FA, caution w/ shellfish allergy (as dye is 5% iodine)
What is fundus autofluorescence used for?
To evaluate RPE function
Areas of RPE loss appear dark
What eye structures exhibit autofluorescence?
Corneal epithelium/endothelium, lens, macular and RPE pigments
What is Near Infrared OCT used for?
Better imaging of out retinal abnormalities, RPE, Bruch membrane, and presence of subretinal fluid
What is a major difference btw Near-Infrared Autofluorescence and Autofluorescence imaging imaging?
Subretinal fluid causes much greater signal attenuation in NIA than AF
What is the rod response of an ERG?
Dark adapt pt then stim w/ dim light. Prominent b-wave with almost no a-wave
What is the Maximal Combined Response of an ERC?
Dark adapt then stim w/ bright light. Prominent a and b-wave amplitudes
What are the Oscillatory Potentials of an ERG?
Dark adapted, can be isolated by filtering out the slower ERG components.
Believed to represent integrative cells of retina, are reduced in ischemic states and in some forms of CSNB
What is the single-flash cone response of an ERG?
Light adapt pt then stim with bright light.
What is the 30-hz flicker response of an ERG?
Light adapted, obtained with flickering stimulus light.
Flicker is faster than rods can respond and represents cones.
What is a pattern ERG?
An alternating checkerboard stimulus which correlates with the integrity of the optic nerve
Not that useful clinically
What does the a wave on an ERG represent?
Response of photoreceptors
What is the early receptor potential (ERP)?
A small response that occurs with no detectable latency before the a-wave. Correlated w/ electrical changes in the cell membrane
What does the b wave on an ERG represent?
Response of Muller/bipolar cells
What is the c wave of an ERG?
A late response 2-4 seconds after stimulus generated by the RPE
What is the implicit time on an ERG?
The time to reach a peak, measured from the onset of the stimulus to the trough of the a-wave or b-wave
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
What is a bright flash ERG?
Brighter than normal stimulus used to assess retinal function with opaque media (VH, trauma) which could suggest retina is salvagable in surgical consideration
Describe how focal retinal disease affects the ERG waveform
It decreases amplitude only
Describe how diffuse retinal disease affects the ERG waveform
It decreases amplitude and causes a delayed waveform
Describe how inner retinal disease affects the ERG waveform
May selectively diminish the B-wave
What is an omnious sign on ERG in eyes with CRVO?
Inversion of the b-wave:a-wave ratio or delay in the 30-Hz cone flicker response
What is the standing potential of an ERG and its polarity?
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
What does an EOG measure?
Used to measure the standing potential
Dominated by the rod system. Most useful for involvement of the rpe when other studies have shown the retina to be normal.
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 disease is an EOG best used for?
Best vitelliform dystrophy
What is a Visually Evoked Cortical Potential (VECP)?
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
What are Visually Evoked Cortical Potentials (VECPs) best used to diagnose?
Demyelinating disease, optic neuropathy, malingering
What is an electrically evoked response and its use?
Similar to VECP but stimuli is electricity rather than light
Used for evaluation of traumatized eyes unresponsive to VECPs
What is dark adaptation useful for?
Evaluating night blindness
Dark Adaptation Curve (image)
What response is seen on VECPs w/ optic neuritis?
A temporal (delayed) response, which is more reliable than decreased amplitude
What is the anomaloscope?
The most accurate way to assess red-green color deficiency.
Pt mixes red/green to match a yellow
What are Ishihara and Farnsworth Panel color tests useful for?
Ishihara: Screening for color deficiency
Farnsworth: Classifying the color deficiency. Can differentiate congenital vs acquired deficiencies.
What is the Pelli-Robson Test?
A chart that tests for contrast sensitivity
THIS SET IS OFTEN IN FOLDERS WITH...
Retina Pt 2 Ch 4-7
Retina Pt 2 Ch 8-11
Retina Pt 2 Ch 12-15
Retina Pt 3
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