Structure and Function of the Eye

Question 1

Label the anterior view of the eye

Answer 1

Upper eyelid
Palpebral fissure
Lateral canthus
Medial canthus
Lower eyelid 
Pupil
Iris
Sclera
Caruncle
Limbus

Question 2

What are the types of tears

Answer 2

Basal tears
Reflex tears
Crying/emotional tears

Question 3

Describe the reflex pathway for tears

Answer 3

Afferent - corner CN V1 (ophthalmic branch of the trigeminal)
Efferent - parasympathetic
NT - acetylcholine

Question 4

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Answer 4

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Question 5

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Answer 5

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Question 6

What are the functions of the tear film

Answer 6

Maintains smooth cornea-air surface
Provides oxygen supply
Removal of debris
Bactericide

Question 7

Describe the structure of the tear film

Answer 7

Superficial oily
Aqueous tear film
Mucinous later on the corneal surface

Question 8

Describe the conjunctiva

Answer 8

Thin, transparent tissue that covers the outer surface of the eye
Begins at the outer edge of the cornea, covers the visible part of the eye and lines the inside of the eyelids
Nourished by tiny blood vessels (invisible to the eye)

Question 9

In which conditions may the vessels of the eye become visible

Answer 9

Conjunctivitis

Uveitis

Question 10

Label a sagittal section of the eye

Answer 10

Cornea 
Iris 
Ciliary body 
Rectus muscle 
Retina 
Choroid 
Sclera
Optic nerve
Optic disc 
Vitreous
Lens

Question 11

Describe the coat of the eye

Answer 11

Anterio-posterior diameter - 24mm 
3 layers
Sclera - hard and opaque 
Choroid - pigmented and vascular 
Retina - neurosensory tissue

Question 12

Describe the sclera

Answer 12

Tough, opaque tissues that serves as the eye’s protective outer coat
High water content

Question 13

Describe the cornea

Answer 13

Transparent, dome-shaped window covering the from
Refractive surface, providing 2/3 eye focusing power
Low water content

Question 14

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Answer 14

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Question 15

Describe the layers of the cornea

Answer 15

1 - epithelium 
2 - Bowman's membrane
3 - stroma
4 - Descemet's membrane
5 - endothelium

Question 16

Describe the storm layer of the cornea

Answer 16

Regularity contributes to transparency
Corneal nerve endings provides sensation and nutrients for healthy tissue
No blood vessels in normal cornea

Question 17

Describe the endothelial layer o the cornea

Answer 17

Pumps fluid put of the cornea and prevents

Question 18

Describe the uvea

Answer 18

Vascular coat of the eye ball
Lies between sclera and retina
Composed of iris, ciliary body and choroid
They are connected and a disease of one part will affect the others

Question 19

Describe the choroid

Answer 19

Lies between retina and sclera

composed of layers of blood vessels that nourish the back of the eye

Question 20

Describe the iris

Answer 20

Coloured part of the eye
Controls light levels in the eye
Embedded with tiny muscles that dilate and constrict the pupil size

Question 21

Describe the structure of the lens

Answer 21

Outer acellular capsule
Regular inner elongated cell fibres - transparency
May lose transparency with age e.g. cataracts

Question 22

Descriebe the function of the lens

Answer 22

Transparency (regular structure)
Refractive power (1.3 power, higher refractive index than aqueous fluid and vitreous)
Accommodation (elasticity)

Question 23

What are lens zonules

Answer 23

Lens is suspended by a fibrous ring (lens zonules) consisting of passive connective tissue

Question 24

Describe the retina

Answer 24

Thin layer of tissue lining the inner part of the eye
Responsible for capturing light rays that enter the eye
Light impulses are then sent to the brain via the optic nerve

Question 25

Describe the optic nerve

Answer 25

Transmits electrical impulses from the retina to brain Connects to the back of the eye near the macula Visible portin = optic disc

Question 26

Describe the macula

Answer 26

Located roughly in the centre of the retina. temporal to the optic nerve Small and highly sensitive part of the retina - central vision Fovea is the centre of the macula Allows for appreciating detail (reading)

Question 27

Describe the anterior chamber

Answer 27

Froms the lens forwards Between cornea and lens Filled with clear aqueous fluid Supplies nutrients

Question 28

What is the ciliary body made up of

Answer 28

Ciliar muscle Ciliary epithelium Dilator Sphincter

Question 29

What are the functions of the ciliary body

Answer 29

Secretes aqueous fluid into the eye | Aqueous fluid supplies nutrients

Question 30

Describe the ciliary body

Answer 30

Intraocular fluid flow anteriorly into the anterior chamber along Normal pressure = 12-21

Question 31

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Answer 31

Canal of scheme - 80-90% | Uveal -sclera outlaw

Question 32

What is glaucoma

Answer 32

Medical condition of sustained raised intraocular pressure | Retinal ganglion cell death and enlarged optic disc cupping

Question 33

What can glaucoma lead to

Answer 33

Visual field loss | Blindness

Question 34

What are the types of glaucoma

Answer 34

Primary open angle glaucoma | Closed angle glaucoma

Question 35

What is the blind spot

Answer 35

Where the optic nerve meets the retina there are no light sensitive cells. It is a blind spot.

Question 36

Describe primary open angle glaucoma

Answer 36

Trabecular Meshwork Dysfunction

Question 37

Describe closed angle glaucoma

Answer 37

Increased pressure pushing the iris/lens complex forwards, blocking the trabecular meshwork – vicious cycle Risk factors - small eye (hypermetropia), narrow angle at trabecular meshwork May present with sudden painful red eye with acute drop in vision Can be treated with peripheral laser iridotomy to create a drainage hole on the iris

Question 38

Describe the fovea

Answer 38

most sensitive part of the retina. | Has the highest concentration of cones, but a low concentration of rods.

Question 39

Describe central vision

Answer 39

Detail Day Vision, Colour Vision – Fovea has the highest concentration of cone photoreceptors to navigate in environment, patient may need white stick even with perfect visual acuity

Question 40

Describe peripheral vision

Answer 40

``` Shape, Movement, Night Vision – Navigation Vision – Assessed by Visual Field Assessment – Extensive loss of Visual Field – unable Central and Peripheral Vision – ```

Question 41

Describe the structure of the retina

Answer 41

Outer Layer – Photoreceptors (1st Order Neuron) – Detection of Light Middle Layer – Bipolar Cells (2nd Order Neurons) – Local Signal Processing to improve contrast sensitivity, regulate sensitivity Inner Layer – Retinal Ganglion Cells (3rd Order Neurons) – Transmission of Signal from the Eye to the Brain

Question 42

macula and fovea

Answer 42

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Question 43

Describe the rod receptor

Answer 43

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Question 44

Describe the cone receptor

Answer 44

-

Question 45

Whichisthe commonest form of colour vision deficiency in humans

Answer 45

Red-green confusion