Vision - Eye and Retina Flashcards
Which range of vision is the human eye sensitive to
The visible range 400-700nm
Examples of long vs short wavelength
Long: Radiowaves
Short: Gamma Rays
Where is the visual cortex
Occipital Lobe
What is the visual path
Eye>Optic Nerve> Optic Chiasm>Optic Tract>Lateral Geniculate body(Thalamus)>Primary visual cortex
What are the retinal targets
- Lateral geniculate nucleus (thalamus)
- Superior colliculous
- Pretecum-Edinger Westphal nucleus
- Hypothalamus
What is the definition of visual acuity
The capacity of the visual system to resolve fine spatial detail
What are the 3 factors of visual acuity
- Stimulus
- Eye
- Central visual pathways
What is Snellen acuity
When you view the letter chart at 20ft
What is 20/20 vision
at 20ft a viewer can detect 1 degree critical features
What is lower visual actuity
at 20ft, you can see like normal people at 40ft. (20/40)
What is higher visual acuity
at 20ft you can see like normal people at 15ft (20/15)
What does it mean to be legally blind
When a persons best corrected vision is 20/200 or worse
What is the sclera
The white part of the eye (90%)
What is the orbit?
The boney captivity that protects the orbit
What is the cornea
A clear sheet in front of the pupil and iris
What is the conjunctiva
Little space inside of the eyelid
What is the lens
The inside of the pupil. the disk being pulled in and out of focus by the zone fibers and ciliary muscles
What is the Aqueous Humor of the eye
It is between the cornea and the lens
What is the Vitreous Humor of the eye
Between the lens and the retina
What is the retina
A wall of photoreceptors at the back of the eye
What is the fovea
A spot in the retina where there are no rod cells
What are the 5 cell types of the retina
- Ganglion
- Amacrine
- Bipolar
- Horizontal
- Photoreceptors
What are the 2 retinal layers
- Nuclear layer - Where the cell bodies are
2. Plexiform layer - where the synapse and axons are
What is the order of the retinal layers?
Ganglion cell layer Inner plexiform layer Inner nuclear layer Outer plexiform layer Outer nuclear layer Photoreceptor outer segments
How many layers of cells lines the back of the retina
3
What lines the back of the retinal wall
The epithelium wall is after the photoreceptors and is black
What are the 2 main parts of a photoreceptor
Outer segment - photosensitive part
inner segment - contains the cell body
What are the 2 types of photoreceptors
Rod and cone
What are cone cells
Colour sensitive
Used during daylight conditions
5 million in each retina
Fovea only consists of cones
What are rod cells
Light sensitive
Used during dim lighting conditions
120 million per retina
Which retinal contains the blind spot
Nasal retina
-usually bigger
What is the distribution of rods to cones like in the retina
Rods are more likely to be on the periphery (except on the fovea and blind spot)
Cones are concentrated in our central vision (fovea)
What is the optic disk
The blind spot in which no photoreceptors are present, there all the ganglion cell axons gather to form the optic nerve
What is the fovea
A pit in the back of the retina where ganglion and bipolar cells are pushed to the side. This allows for the light to have an easier time striking the photoreceptors
What is the blind spot
Area without receptors
-1 million ganglion cell axons leave the eye from the optic nerve
What is phototransduction
converting light into electricity
-photoreceptor segment is where this occurs
