Vision Flashcards
Retina
Nerve cells and glia forming a thin, layered structure that lines the back of the eye, including: photoreceptors, interneurons and retinal ganglion cells
Photoreceptors
Light-sensitive sensory cells (rods for low light levels, cones for daylight vision)
Interneurons
A circuit formed that extracts salient information from the pattern of photoreceptor responses
Retinal ganglion cells
Retinal afferents
Lateral Geniculate Nucleus (LGN)
The thalamic nucleus that relays visual information from the retina to the primary visual cortex, in the pathway that perceives perception.
Primary visual cortex
Receives input from the retina via the LGN and distributes it to many “higher” visual areas for further and more specific processing.
Binocular cell
Receives input from both eyes, and can hence contribute to depth perception
Fovea
A tiny region in the centre of the retina, where the point in visual space that you are directly looking at is focussed, that is structurally adapted for fine detailed vision. Often used as synonymous with “macula”, a more extensive region distinguished by yellow pigmentation.
Photopigment
The molecule that captures a photon of light and triggers a change in a photoreceptor’s membrane potential. Consists of a protein, “opsin”, and a light-sensitive chromophore, “11-cis retinal”.
Receptive field
A region of the visual image that affects the responses of a given cell.
Describe the structure of the eye
- Horizontal section of the head taken with an MRI. - - The two eyes with the optic nerves leading back to the optic chiasm.
- There is a temporal half and a nasal half.
- Towards the nose is the nasal visual field.
- The temporal visual field is focusing on the nasal part of the retina and visa versa. This is because the optics of the eye will innervate the image.
- The upper part is focusing on the bottom part of the retina.
Which part of the retina focuses on the temporal visual field?
Nasal Retina
Which part of the retina focuses on the nasual visual field?
Temporal Retina
What is the sclera?
The white part of the eye that creates an anchoring point for the extra-ocular eye muscles. It is flexible and is needed to be held ridged.
Why does the eye need a solid body?
A solid body is needed to create a non-stretch layer which creates a ridge outside.
What holds the sclera ridge?
Intra-ocular pressure
How is the cornea made transparent?
The collagen fibres align in a way that makes the cornea transparent
How is pressure created in the eye?
By the production of aqueous humour. It flows out of the ciliary body and reabsorbed at the angle of the eye. It is a slow flow. The production and drainage needs to be balanced to produce enough pressure to hold the eye ridge.
Where is aqueous humour made?
It is produced by the ciliary body at the front of the eye supporting the lens.
What is the vitreous humour?
It is behind the lens - a jelly-like structure. It is hydrated by the aqueous humour.
How are floaters created in vision?
In older people, the proteins in the vitreous clumps leaving watery patches and pulls away the back of the eye shrinking down.
What is the cornea?
The curved structure at the front of the eye that bends light rays. As the light passes from the air to the water via this curved interface, the light rays are bent inwards. This is part of the optics of the eye. Responsible for focussing light rays
What is the lens?
Behind the cornea. It changes shape which can change the focus of the eye. It is suspended by a ring of suspensory ligaments from the ciliary body. Provides additional variable “fine” focus
What is the ciliary body?
Contains a ring of muscle that can change the shape of the lens.