Visual Systems anatomy

Question 1

What structures make up the eye?

Answer 1

Upper eyelid
Palpebral fissure
Lateral canthus
Lower eyelid
Pupil 
Iris
Sclera
Medial canthus
Caruncle
Limbus (border between cornea and sclera)

Question 2

What are the main featured of the lacrimal system?

Answer 2

Tears produced by lacrimal gland

Drain through the two puncta, openings on medial lid margin

Flow through superior and inferior canaliculi

Gather in tear sac

Exit tear sac through tear duct into nasal cavity

Question 3

What is tear film?

Answer 3

Maintains smooth cornea-air surface
Oxygen supply to Cornea – normal cornea has no blood vessels

Removal of debris (tear film and blinking)

Bactericide

Question 4

What are the three layers of tear film?

Answer 4

Lipid layer

Water layer

Mucin layer

Question 5

What is the function of the lipid layer?

Answer 5

reduce tear film evaporation - produced by a row of Meibomian Glands along the lid margins

Question 6

What is the function of the mucinous layer corneal surface?

Answer 6

maintains surface wetting

Question 7

What is the conjuctiva?

Answer 7

Thin, transparent tissue that covers the outer surface of the eye

Question 8

What is the extent of the conjuctiva?

Answer 8

It begins at the outer edge of the cornea, covers the visible part of the eye, and lines the inside of the eyelids

It is nourished by tiny blood vessels that are nearly invisible to the naked eye

Question 9

What are the three layers of the coat of the eye?

Answer 9

Sclera - hard and opaque

Choroid - pigmented and vascular

Retina - neurosensory tissue

Question 10

What is the sclera?

Answer 10

commonly known as “the white of the eye,”

the tough, opaque tissue that serves as the eye’s protective outer coat.

High water content

Question 11

What is the cornea?

Answer 11

The transparent, dome-shaped window covering the front of the eye.

Low water content

Question 12

What is the function of the cornea?

Answer 12

Powerful refracting surface, providing 2/3 of the eye’s focusing power. Like the crystal on a watch, it gives us a clear window to look through

Question 13

What are the 5 layers of the cornea?

Answer 13

1 – Epithelium
2 – Bowman’s membrane
3 – Stroma – its regularity contributes towards transparency
4- Descemet’s membrane
5- Endothelium – pumps fluid out of corneal and prevents corneal oedema, glucose supply

Question 14

What happens if you hydrate the cornea?

Answer 14

Becomes white

Question 15

What is the Uvea?

Answer 15

Vascular coat of eyeball and lies between the sclera and retina.

Question 16

What are the three parts of the uvea?

Answer 16

iris, ciliary body and choroid

Intimately connected and a disease of one part also affects the other portions though not necessarily to the same degree.

Question 17

What is the choroid?

Answer 17

lies between the retina and sclera. It is composed of layers of blood vessels that nourish the back of the eye.

Question 18

What is the iris?

Answer 18

Controls light levels inside the eye similar to the aperture on a camera.

Controls light levels inside the eye similar to the aperture on a camera.

Question 19

What is the pupil?

Answer 19

Round opening in the centre is the pupil.

Question 20

What is the lens structure?

Answer 20

Outer acellular capsule
Regular inner elongated cell fibres – transparency
May loose transparency with age – cataract

Question 21

What is the function of the lens?

Answer 21

Refractive Power
1/3 of the eye focusing power - higher refractive index than aqueous fluid and vitreous
Accommodation
Elasticity

Question 22

What is the retina?

Answer 22

Very thin layer of tissue that lines the inner part of the eye.

Question 23

What is the function of the retina?

Answer 23

Responsible for capturing the light rays that enter the eye. Much like the film’s role in photography.

These light impulses are then sent to the brain for processing, via the optic nerve.

Question 24

What is the optic nerve?

Answer 24

transmits electrical impulses from the retina to the brain

connects to the back of the eye near the macula

visible portion is called the optic disc

Question 25

Where is the optic blind spot?

Answer 25

Where the optic nerve meets the retina there are no light sensitive cells

Question 26

Where is the macula located?

Answer 26

Located roughly in the centre of the retina, temporal to the optic nerve

Question 27

What is the macula?

Answer 27

A small and highly sensitive part of the retina responsible for detailed central vision

Question 28

What is the fovea?

Answer 28

The fovea is the very centre of the macula.

Question 29

What is the function of the macula?

Answer 29

The macula allows us to appreciate detail and perform tasks that require central vision such reading.

Question 30

What is the most sensitive part of the retina?

Answer 30

Fovea

Question 31

What is the composition of the fovea?

Answer 31

It has the highest concentration of cones, but a low concentration of rods

Question 32

What is the anatomic landmark for the physiological blind spot?

Answer 32

Optic disc

Question 33

What are the features of central vision?

Answer 33

Detail day vision, colour vision – fovea has the highest concentration of cone photoreceptors Reading, facial recognition Assessed by visual acuity assessment Loss of foveal vision – Poor visual acuity

Question 34

What are the features of peripheral vision?

Answer 34

Shape, movement, night Vision Navigation vision Assessed by visual field assessment Extensive loss of visual field – unable to navigate in environment, patient may need white stick even with perfect visual acuity

Question 35

What comprises the outer layer of the retina?

Answer 35

Photoreceptors (1st order neuron) | Detection of Light

Question 36

What comprises the middle layer of the retina?

Answer 36

``` Bipolar Cells (2nd order neuron) Local signal processing to improve contrast sensitivity, regulate sensitivity ```

Question 37

What comprises the inner layer of the retina?

Answer 37

Retinal ganglion cells (3rd order neuron) | Transmission of signal from the eye to the brain

Question 38

What are the main features of rods?

Answer 38

Longer outer segment with photo-sensitive pigment 100 times more sensitive to light than cones Slow response to light Responsible for night vision (Scotopic Vision) 120 million rods

Question 39

What are the main features of cones?

Answer 39

Less sensitive to light, but faster response Responsible for day light fine vision and colour vision (Photopic Vision) 6 million cones

Question 40

Describe rod (scotopic) vision?

Answer 40

Peripheral and night vision More photoreceptors, more pigment, higher spatial and temporal (time) summation Recognizes motion

Question 41

Describe cone (photopic) vision?

Answer 41

Central and day vision | Recognizes colour and detail

Question 42

Describe the different cones and the colours they are responsible for?

Answer 42

S-Cones: Blue M-Cones: Green L- Cones: Red

Question 43

What is deuteranomaly?

Answer 43

also known as Daltonism is the most frequent form of colour blindness they don’t perceive the colour red

Question 44

What is full colour blindness called?

Answer 44

achromatopsia

Question 45

What is the colour blindness test called?

Answer 45

Ishihara test