Visual System anatomy (pt1) Flashcards
What is the afferent nerve for the lacrimal system?
Cornea, cranial nerve V1 (ophthalmic trigeminal).
What is the efferent nerve for the lacrimal system?
Parasympathetic
What’s the neurotransmitter used?
ACh
What is the tear film
Most superficial layer of the eye
What are the 3 layers it’s made up of and what do they each do?
-Superficial lipid layer
-Aqueous layer
-Mucinous layer
What is the conjunctiva?
-Thin, transparent tissue that covers the outer surface of the eye.
-It’s nourished by tiny blood vessels
What are the 3 layers of the coat of the eye?
Sclera- Hard, tough and opaque. High water content, responsible for protecting the eye and maintaining its shape. (White of the eye)
Choroid- Pigmented and vascular, provides circulation and shields out unwanted scattered light.
Retina- Neurosensory tissue, converts light into neurological impulses to be transmitted to brain via optic nerve.
What is the white of the eye also known as?
Sclera.
What is the cornea?
Transparent, dome-shaped window on the front of the eye.
Cornea purpose?
Protection and refracting power.
What are the 5 layers of the cornea (superficial-deep).
1)Epithilium
2)Bowman’s membrane
3)Stroma
4)Descemet’s membrane
5)Endothelium
Which of the layers of the cornea contribute most to transparency?
The stroma and its regularity
What happens if you hydrate the cornea.
It becomes white
What is the uvea?
The Vascular coat of the eyeball. Lies between the sclera and retina.
What are the 3 parts of the uvea
-Iris
-Ciliary body
-Choroid
What is the choroid and where is it
Its composed of layers of blood vessels that nourish the back of the eye.
Lies between the retina and sclera.
What does the iris do?
Controls Light levels inside the eye.
What is the retina?
Very thin layer of tissue lining the inner part of the eye.
Captures light and sends impulses to brain optic nerve for processing.
What does the optic nerve do and where is it?
Transmits signals from the retina to the brain,
Connects to the back of the eye near the maculla
Visible portion is called the optic disc
What is the blind spot?
Where the optic nerve meets the retina, there are no light sensitive cells.
Where is the maculla and what does it do?
Located roughly on the centre of the retina, near optic nerve.
Responsible for detailed central vision.
What is the very centre of the maculla called?
The fovea
What are the properties of the fovea?
It is the most sensitive part of the retina.
Highest conc of CONES, low conc of RODS.
What is central vision?
Detailed day vision, colour vision.
How do you assess central vision?
Visual acuity assessment.
What does loss of foveal vision lead to?
Poor visual acuity.
What is peripheral vision responsible for
-Shape
-Movement
-Navigation
-Night vision
How do you assess peripheral vision
Visual field assessment
What would extensive loss of visual field cause?
Unable to navigate in environment, may need walking stick even with perfect visual acuity.
Describe the retinal structure.
2 layers
Outermost thin layer of retinal pigment epithelium.
Inner thicker layer called neuroretina
What is the purpose of the thin and thick layers of the retina
Thin layer- Transports nutrients from the choroid to photoreceptor cells.
Removes metabolic waste.
Thick layer- light detection and signal processing.
How is the neuroretina made up.
Made of three layers.
Outer layer-1st order neurons.
middle layer- 2nd order neurons.
inner layer- 3rd order neurons.
What are the two types of photoreceptors?
Rods and cones
What is the purpose and properties of Rods?
Used for night vision high light sensitivity.
Longer outer segment with photosensitive pigment.
What is the distribution of rods in the eye?
Highest concentration of rods in the periphery of the eye.
What is the purpose and properties of cones?
Responsible for daylight fine vision and colour vision (photopic vision)
Less sensitive to light but faster response
Where are cones mainly concentrated in the eye
The centre of the eye.
What is the most common colour vision deficiency and what’s the mechanism?
-DEUTERANOMALY,
-Due to shifting of M cone sensitivity peak towards L cone curve, causing red-green confusion.
What is full colour blindness called?
Achromatopsia
What does monochromatism refer to?
complete absence of colour vision.
What are the different types of monochromatism?
Blue cone monochromatism- Presence of only blue L cones, Normal daylight visual acuity.
Rod monochromatism- Total absence of all cone photoreceptors
What is the colour blindness test called?
Isihara test.
