Anatomy of the Visual System

Question 1

How many types of tears are there? What are they called?

Answer 1

3 types
Basal
Emotional
Reflex

Question 2

What are the afferent components of the lacrimal system?

Answer 2

Cornea, cranial nerve V1 (ophthalmic division of trigeminal) supplies it

Question 3

What are the efferent components of the lacrimal system?

Answer 3

Parasympathetic

Question 4

What neurotransmitter is involved with the lacrimal system?

Answer 4

Acetylcholine

Question 5

What produces tears?

Answer 5

Lacrimal gland

Question 6

What do tears drain through?

Answer 6

The 2 puncta, these are the opening on the medial lid margin, they then flow through superior and inferior canaliculi

Question 7

Where do tears gather and then exit?

Answer 7

Gather the tear sac amd then exit through tear duct into nasal cavity

Question 8

What is the role of the tear film? (4)

Answer 8

Maintain a smooth cornea to air surface
Provide oxygen supply to the cornea
Allow removal of debris alongside blinking
Bactericide

Question 9

What is the blood supply to the cornea?

Answer 9

There is no blood supply to the cornea

Question 10

How may layers are there to the tear film? What are they called?

Answer 10

3 layers (from superficial to deep they are):
Lipid layer (reduces tear evaporation- oil produced by row of meibomian glands along lid margins)
Water layer (aqueous tear film)
Mucin layer (maintains surface wetting)

Question 11

What is the conjunctiva?

Answer 11

A thin, transparent tissue that covers the outer surface of the eye
Starts at the cornea and lines inside of the eyelid

Question 12

What is the blood supply to the conjunctiva?

Answer 12

Supplied by tiny blood vessels that we can’t see

Question 13

How many layers are there in the coat of the eye? What are they called?

Answer 13

3 layers (from outer to innermost they are):
Sclera- hard and opaque
Choroid- pigmented and vascular
Retina- has neurosensory tissue

Question 14

What is the sclera?

Answer 14

‘White of the eye’
Tough, opaque tissue that serves as eyes protective outer coat
High water content

Question 15

How many layers does the cornea have? What are they called?

Answer 15

5 layers:
Epithelium (outermost)
Bowman's membrane
Stroma
Descement's membrane
Endothelium

Question 16

What is the cornea?

Answer 16

The transparent dome shaped window covering the front of the eye

Question 17

Describe the water content of the cornea

Answer 17

Low

Question 18

What is the role of the cornea?

Answer 18

It is a powerful refracting surface (2/3 of the eyes refracting power)

Question 19

What is the significance of the endothelium of the cornea?

Answer 19

It pumps fluid out of the cornea and prevents corneal oedema

Question 20

What is the uvea?

Answer 20

It is the vascular coat of the eyeball

Question 21

What does the uvea lie between?

Answer 21

The sclera and the choroid

Question 22

How many layers are there in the uvea? What are they called?

Answer 22

3 layers
Iris
Ciliary body
Choroid

Question 23

Describe the role of the iris

Answer 23

It controls how much light is let into the eye, and has an opening in the middle which is the pupil. Muscles allow the pupil to constrict and relax

Question 24

What is the choroid composed of?

Answer 24

Tiny blood vessels that nourish the eye

Question 25

What is the role of the lens?

Answer 25

To allow transparency | Has refractive power also (1/3 of the eye)

Question 26

Describe the structure of the lens

Answer 26

Outer acellular capsule | Inner elongated cell fibres

Question 27

What is it called when lens transparency is lost with age?

Answer 27

Cataract

Question 28

Describe the retina and where its found

Answer 28

It is a very thin layer of tissue that lines the back of the eye

Question 29

What is the role of the retina?

Answer 29

To capture light rays that enter the eye

Question 30

What happens to light rays that are captured by the retina?

Answer 30

They are sent to the brain for processing via the optic nerve

Question 31

What is the optic disc?

Answer 31

The visible part of the optic nerve that connects to the retina

Question 32

Where does the optic nerve connect to the eye?

Answer 32

At the back near the macula

Question 33

What is formed where the optic nerve meets the retina?

Answer 33

A blind spot, there are no sensitive light cells here

Question 34

How many layers are there to the retina? What are they called and what are their roles?

Answer 34

3 layers Outer layer: photoreceptors, 1st order neurons, detect light Middle layer: Bipolar cells, 2nd order neurons, local signal processing to improve contrast sensitivity Inner layer: retinal ganglion cells, 3rd order neurons, transmits signals from eye to brain

Question 35

What type of cell is found in the outer layer of the retina?

Answer 35

Photoreceptors

Question 36

What type of cell is found in the middle layer of the retina?

Answer 36

Bipolar cells

Question 37

What type of cell is found in the inner layer of the retina?

Answer 37

Retinal ganglion cells

Question 38

What is the macula?

Answer 38

A small highly sensitive part of the retina that is responsible for detailed central vision and allows us to appreciate detail for tasks such as reading

Question 39

What is the fovea?

Answer 39

The centre of the macula, the most sensitive part of the retina

Question 40

What type of cells are found in the fovea?

Answer 40

Highest conc of cones (allows perception of detail) and lowest conc of rods

Question 41

What does central vision include?

Answer 41

Detailed vision during the day Colour vision Reading Facial recognition

Question 42

How is central vision assessed?

Answer 42

Visual acuity assessment

Question 43

What does peripheral vision include?

Answer 43

Shape, movement, night vision, navigation vision

Question 44

How is peripheral vision assessed?

Answer 44

Visual field assessment

Question 45

What happens if there is a loss of visual field?

Answer 45

This is an impairment in peripheral vision and so people cannot navigate May need a stick even with perfect visual acuity

Question 46

What are photoreceptors for?

Answer 46

Visual processing

Question 47

What are the 2 types of photoreceptors?

Answer 47

Rods and cones

Question 48

Describe rods

Answer 48

They have a long outer segment which is photo-sensitive They have a slow response to light but are 100x more sensitive to light than cones They are responsible for night vision 120 million rods

Question 49

What is the scientific name for night vision?

Answer 49

Scotopic vision

Question 50

Out of rods and cones which is more sensitive to light?

Answer 50

Rods

Question 51

Describe cones

Answer 51

Less sensitive to light but fast response to light Responsible for day vision and colour vision 6 million cones

Question 52

What is the scientific name for day vision?

Answer 52

Photopic vision

Question 53

How does the eye see colour?

Answer 53

Through different photoreceptors S cones= blue M cones= green L cones= red

Question 54

What colours are rods sensitive to?

Answer 54

No colours

Question 55

What is deuteranomaly?

Answer 55

Aka daltonism | Partial colour blindness (the most common form) where they don't perceive red

Question 56

What do we call full colour blindness?

Answer 56

achromatopsia

Question 57

What test is used to diagnose colour blindness?

Answer 57

Ishihara test

Question 58

What is the function of the lens?

Answer 58

``` Transparency Regular structure Refractive power 1/3 of eye focusing power- higher refractive index that aqueous fluid and vitreous Accommodation Elasticity ```