Retinal Topography And Vasculature Flashcards
What is the retinas job
Innermost part of eye that does transduction and sends signal to brain
What is the retina the window into
The CNS and cardiovascular system
What happens in the retina
- light energy is transformed into a neural signal (phototransduction)
- signal is modified within the retina
- contains the first three cells of the visual pathway: photoreceptors (1st), bipolar cells (2nd), and ganglion cells (3rd)
- interneurons
- neuroglia cells
What must happen for light to reach the 1st order neuron
Light must pass through all layers of the retina to reach the 1st order neuron wher it is converted into neural signal by the process of phototransduction. The signal is modified by the 2nd and 3rd order neurons and sent to the brain
How many layers of the retina
10
What are the inner 9 layers collectively referred to as
The sensory or neural retina
What is the 10th retinal layer
RPE
What are some cell types located within the retina
Many
-photoreceptors, horizontal cells, bipolar cells, amacrine cells, interplexiform cells, ganglion cells, and muller cells
Are all regions of the retina the same
No
What are the outer layers of the retina
Photoreceptor layer
External limiting membrane
Outer nuclear layer
Outer plexiform layer
All dealing with the photoreceptors
What is in the photoreceptor layer
- rod outer segment
- rod inner segment
- cone outer segment
- cone inner segment
What is within the outer nuclear layer
Row of cone nuclei
Multiple rows of rod nuclei
What is within the outer plexiform layer
Contains rod spherules and cone pedicles
What do photoreceptors span
Outer retina (photoreceptor layer, external liming membrane, outer nuclear layer, and outer plexiform layer)
Role of photoreceptors
Absorb light photons and convert them into an electrochemical event (nerve signal) through the process of phototransduction.
Rods and cones
How many cones
5-6mill
What percentage of cones are in the fovea
10%
What do cones detect
Bright illumination (photopic) and color
What are the 3 types of cones
S cones (blue, 420) M cones (green 531) L cones (red 588)
What is the only photoreceptor in the fovea
Cones
What type of cone is NOT in the center of the fovea
S cones
How many rods
92-120 mill
What do rods detect
Dim vision (scotopic)
What do rods contain
Photopgiment, rhodopsin, which is located in the disc membrane
Peak density of rods
In a ring 4.5mm outside the fovea
Are there rods in the fovea
No
Blind spot
ONH
Nasal
20 degrees
Horizontal cells
Lateral processes between the cells
What is the second cell in the chain of phototransudction
Bipolar cells
What do amacrine cells do
Processing
What do muller cells do in the retina
They are the radial glial cells of the retina
Maintain structural support/buffering environment
Where are there astrocytes in the retina
RNFL around blood vessels
What does glaucaom kill
Ganglion cells (3rd one) Stem cells wont work here
Retinitis pigmentosa affects what
Photoreceptors
Stem cells could work here
Retinal thickness
80 microns to 320
Fovea retinal thickness
150-200
What is the thinnest part of the retina
Ora serrata
80 microns
Where is the ora serrata more serrated
Nasally
Where is the ora serrata more smooth
Temporally
What is there a dense population of in the central retina
Cones
What is the central retina designed for
Color vision and fine detail discrimination
What is there a dense population of in the peripheral retina
Rods
What is the peripheral retina designed for
Night vision and motion detection
How big is macula
5.5mm to 6mm diamter
What is the only area of the retina that contains more than 1 layer of retinal ganglion cells
Macula
What is there high levels of in the macula
Carotenoids
What are the names ofhte parts of the macula from inside out
Umbo Foveola Foveal avascular zone fovea Parafovea Perifovea Macula
What causes the foveal light reflex
Umbo
Central depression of macula that is 1.5mm in diamter
Fovea
Walls of fovea
Walls slope giving rise to light reflex known as foveal light reflex
What photoreceptors are in the fovea
Cones only
How are the axons of cones oriented in the fovea
Obliquely in the outer plexiform layer of the fovea (henle fibers)
How is the inner retinal layers displaced in the fovea
Laterally
Central 350 microns of the fovea
Foveola
Dense packing of cones makes them appear rod like in structure in this area
Foveola
What is the thinnest region of the fovea
Foveola
Cone inner fibers that are oriented obliquely within the fovea are called ________
Henle fibers
Thus, the OPL in the fovea is often referred to as Henke’s fiber layer
What is Henles fiber layer
Outer plexiform layer obliquely displaced in the fovea
Extend 0.5mm from the foveal rim
Parafovea
Highes accumultion of bipolar and retinal ganglion cells
Parafovea
Rod photoreceptors reach their peak density here
Parafovea
1.5mm from the parafoveal rim
Perifovea
Axons of Henles fiber layer resume their vertical orientation here
Perifovea
Peripheral retina
Rod dominated region of central retina
Terminates at the ora serrata
What is the peripheral termination of the retina
Ora serrata
Outer Retinal vasculature
Choroid (for photoreceptors)
Vasculature for the inner retina
Retinal vessels (central retinal vasculature)
Is there an overlap between the choroidal blood supply and the central retina lblood supply
No
Cilioretinal artery
20% of population has this. It is collateral blood supply to the macula
Which is more nasal, central retinal artery or vein
Artery
Which is more temporal, central retinal artery or vein
Vein
Which is bigger, central retina artery, or vein
Vein
2:3
When does the central retinal artery loose its elastic tunic
Upon entering the eye
This distinguishes it from the muscular arteries in other parts of body
What is the tunica elasticum of the central retinal artery replaced with when it enters the eye
Prominent tunica media composed of smooth muscle
Control of retinal vasomotor tone is
Auto regulated
Control of choroidal vasomotor tone is
Neuroregulated
What does the smooth muscle in the tunica media respond to in the central retinal artery
IOP and systems pressure, and metabolic waste levels
Pericytes in the retinal caps
Helps blood flow
Pericytes in DM
Increased blood sugar converts glucose to OH which kills pericytes and weakens others, causing fluid to leak into the eye through there
Loss of pericytes and endothelial cells from retinal caps in DM patients can lead to
Microaneurysms, hemorrhages, exudates, and fluid in the macular region
What are the two layers of the retinal cap plexus
Deep cap plexus
Supercficial cap plexus
Round hemorrhages
Deep
Flame shaped hemorrhage
Superficial cap plexus
RNFL
What kind of shift do you get with macular edema
Hyperopic shift
Which branch is more likely to be occluded in bran retinal vein occlusion
Superior, just because there are more of them
Neovascularization
Will be leaky. Any vessels developed after Birth will be leaky
When is it a good time to have a cilioretinal artery
Central retinal artery occlusion
