Vision Flashcards
How does the optic nerve travel through the eye?
Travels Nasally
What is the structure of the eye?
Has an outer fibrous layer containing
- Sclera: Quite flexible
- Cornea: The transparent bit of the eye
How is the sclera flexible?
- To do this, it need an element which holds it rigid
- This is done by providing a certain amount of intraocular pressure
- Pressure generated through the production of aqueous humor
How is the flexibility of the sclera maintained?
As long as the production and drainage in balance properly, it will produce just enough pressure in your eye to keep it rigid
What are the optics of the eye?
- Cornea
- Lens
- Both bend light
What is one feature about the Cornea and the lens?
- The Cornea bends the light rays inwards to the eye
- The lens can change shape in order to change the focus of the eye
What supports the lens to help keep it in place?
The lens is held in place by a ring of suspenseful ligaments from the ciliary body
What can the ciliary body do to the lens?
Can change the shape of the lens as it’s a ring of muscle, when it contracts, it’s diameter becomes smaller causing the lens to become fatter.
When relaxed, it becomes wider, diameter becomes larger flattening the lens for distance vision
What is the iris part of the eye?
The ring of muscle which Creates the colour part of the eye
- Function: Produces an Aperture in the middle known as the pupil
- Maintains the smallest aperture it can for the illumination conditions
- The smaller the aperture, the better the focus conditions
What happens with the retina indifferent lights
Adjusts the eye based on brightness
- Becomes larger in a dim lighted area
- Becomes narrower in bright sunlight
Describe what happens when light touches the eye?
- Some photons strike the cornea and pass through
- Some are stopped by the iris
- Those which pass through the pupil will be bought to a single point for focus by the cornea and the lens
What are the key elements of the eye when under the sunlight?
- The cornea is the most powerful refractive surface of our eye
- The lens provides additional variable fine focus
- The iris controls how much light enters the eye via the pupil
Where is the retina found?
Found at the back of the eye
What are the two parts of the retina?
- Neural retina
- Retinal pigment epithelium: Provides a lot of support for photoreceptors. Also holds the retina in place
Where was the retinal pigment epithelium developed
- Developed embryonically from the neural tube
- This means because they both came from the neural tube, they’re both CNS structures
What is special about the retina?
- Holds basically the whole massive surface of the eye
- Technically apart of the brain
- Has photoreceptors
- Also has Afferens which are retinal ganglion cells
What do the retinal ganglion cells have?
- Have axons which run across the surface of the retina which form the optic nerve
Describe the Primary visual pathway (PART 1)
- The ganglion cell axons project down the optic nerve to the optic chiasm
- One on the nasal part of the retina swap sides however those from the temporal sides stay on the same side
Describe the Primary visual pathway (PART 2)
They then project back to the lateral geniculate nucleus which serves the visual system
- Cells in this region then send their axons through a region of white matter known as optic radiation
- Back to the opsiticsl cortex where you find the primary visual area
What are the two forms which photoreceptors come in?
- Rod photoreceptors: Night vision
- Cone Photoreceptors: Day vision
What is the similarities & difference between rods and cones?
- They use the same neural circuitry
- But at the retina, you’ve either got rods and their circuitry or cones and their circuitry
How do the rods become react to the level of light overtime?
- They become super sensitive since they’ve had a lot of time to react
- This allows you to see a lot more clearly in the dark