Visual System 1.5 Flashcards
What is the retina?
Very thin layer of tissue that lines the inner part of the eye
What is the retina responsible for?
- capturing the light rays that enter the eye
2. these light impulses are then sent to the brain for processing, via the optic nerve.
What does the optic nerve do?
transmits electrical impulses from the retina to the brain
Where does the optic nerve connect?
to the back of the eye near the macula
What is the visible portion of the optic nerve called?
optic disc (corresponding anatomic landmark for physiological blind spot)
Where is the blind spot?
Where the optic nerve meets the retina there are no light sensitive cells
Where is the macula?
roughly in the centre of the retina, temporal to the optic nerve
What is the macula?
- small and highly sensitive part of the retina responsible for detailed central vision
- allows us to appreciate detail and perform tasks that require central vision such reading
What is the fovea?
the very centre of the macula and most sensitive part of retina
What is the concentration of rods and cones in the fovea?
- Highest conc of cones
- Lowest conc of rods
What is central vision?
- Detail day vision, colour vision
- Reading, facial recognition
How do you asses central visions?
visual acuity assessment
What does loss of foveal vision lead to?
Poor visual acuity
What is perisperhal vision?
- Shape, movement, night vision
- Navigation vision
How is peripheral vision assessed?
by visual field assessment
What happens if there is is extensive loss of visual field?
unable to navigate in environment, patient may need white stick even with perfect visual acuity
What is the outer layers of the retinal structure?
- Photoreceptors (1st order neuron)
- Detection of Light
What is the middle layer of retinal structure?
- Bipolar Cells (2nd order neuron)
- Local signal processing to improve contrast sensitivity, regulate sensitivity
What is the inner layer of retinal structure?
- Retinal ganglion cells (3rd order neuron)
- Transmission of signal from the eye to the brain
What does the retina form?
the innermost layer of the coat of eye in the posterior segment
What does the retina consist of?
- an outer thin layer of Retinal Pigment Epithelium, situated right in front of the Choroid,
- inner thicker layer called the Neuroretina.
What does the retinal pigment epithelium do?
transports nutrient from the choroid to the photo-receptor cells,
and removes metabolic waste from the retina
What is the neuroretina made up of?
photo-receptors and neurons
What are the layers of retina?
- Outer Layer consisting of photo-receptors,
- middle layer of intermediate neurons
- inner layer of ganglion nerve cells
- axon running along the optic nerve into the brain
