Retinal Topography And Vasculature Flashcards
Neural tunic of the eye?
Retina
The retina is important to optometrists because it’s the window into the…
CNS and cardiovascular system
Light energy being transformed into a neural signal
Phototransduction
Where is the neural signal modified from light energy?
Within the retina
What are the 1st 3 cells of the visual pathway within the retina?
1st - photoreceptors
2nd - bipolar cells
3rd - ganglion cells
What is the importance of neuroglial cells in the retina?
To maintain and buffer the environment
How many layers are there of the retina?
It’s divided into 2 categories, what are they?
10 layers.
Inner 9 are the Sensory/Neural Retina
Outermost 10th is the RPE
___________________ span the Outer Retina. What layers are in the Outer retina?
Photoreceptors
Photoreceptor layer, external limiting membrane, outer nuclear layer, and outer plexiform layer
What is the role of photoreceptors?
To absorb light photons and convert them into an electrochemical even (nerve signal)
Phototransduction!
What are the 2 kinds of photoreceptors in the retina?
Rods and cones
How many cones are there? What type of illumination are they used for?
5-6 million, 10% in fovea
Bright! And color.
What are the 3 photopigments stored in the disc membrane that are sensitive to different wavelengths?
Conopsins:
- S-cones (blue) 420 nm
- M-cones (green) 531 nm
- L-cones (red) 588 nm
What type of photoreceptors are only found in the Fovea?
Cones!
What type of conopsins are not found in the center of the fovea?
S-cones
Only M and L cones
What is the test used to tell a normal eye from a dichromat eye? What Photoreceptor are you testing?
Ishihara plate
Cones
How many rods are there? What type of illumination do they sense?
92-120 million
Dim vision, scotopic.
What type of photopigment is located in the disc membrane of the rods? What wavelength do they sense?
Rhodopsin
498 nm
Where is the peak density of cones on the retina?
A ring about 4.5 mm outside the fovea. Where macular degeneration usually occurs
Are there rods in the fovea?
No! Just CONES
The 2nd neuron cells are the..
Cone/rod bipolar cells
The 3rd neurons are the…
Retinal ganglion cell layers (they’re the major output cells)
What layer of the retina starts to die off in Glaucoma?
Retinal ganglion cell layer
Retinal thickness ranges from __ microns to ___ microns. Where is it the thinnest and thickest?
80 to 320 microns.
Thinnest- ora serrata (80)
Thickest - foveal rim (320) (fovea is only 150-200 microns)
What is the central retina?
Posterior Pole or Macula or Area Centralis
Dense population of cone photoreceptors
Color vision and fine detail
Where is color vision and fine detail discriminated?
Central retina/macula/posterior pole/area centralis
CONES
What is the peripheral retina?
Dense population of rod photoreceptors outside of the macula.
For night vision and motion detection
What part of the retina is for night vision and motion detection?
Peripheral retina
What is the only area of the retina to contain more than 1 layer of retinal ganglion cells?
Macula
The macula contains high levels of…
Carotenoids
In the fovea, the walls slope giving rise to the light reflex known as…
Foveal reflex
In the fovea, the sloping is known as:
The center is the:
Clivus
Foveola
Part of the fovea where there is dense packing of cones that makes them appear rod-like in structure
Foveola
Where can you find the high accumulation of bipolar and retinal ganglion cells?
Parafovea. Extends 0.5 mm rom foveal rim
Cone inner fibers that are oriented within the fovea are called:
The OPL in the fovea is often referred to as:
Henle fibers.
Henle’ fiber layer.
Nice.
Where does the peripheral retina terminate?
Ora serrata
The retina has a high demand for _________ .
The outer retina is supplied by the ___________. Then inner retina is supplied by __________ ________.
Oxygen
Choroid
Retinal vessels
Are artery supplies the macula?
Cilioretinal artery
What artery enters the eye through an aperture in the lamina cribrosa of the optic disc?
This artery is position slightly _________ in the nerve.
Central Retinal Artery
Nasal
What is the artery:vein ration in the eye?
2:3
The Central Retinal Artery loses its __________ ____________ as it enters they eye, and is replaced with a _________ _________.
Tunica elasticum. (Internal elastic shell)
This is what’s distinguishes it from other muscular arteries in the body
Tunica media (smooth muscle to enhance constriction of vessel)
What is the outermost later of blood vessels?
Is it thicker/thinner in veins?
Tunica adventitia. (Connective tissue)
Thicker in veins
Control of vasomotor tone is ________________ in the retina, unlike the choroid, where it is _______________.
Autoregulated
Neuroregulated
3 parts of retinal capillaries
- Endothelium
- Basal lamina
- Pericytes
These structures expand and contract on the capillaries in the retina and are sensitive to Aldose Reductase.
What problems are prevalent here due to sugar?
Pericytes
Diabetes!
Macular edema can lead to a ____________ shift
Hyperopic
