The Eye in Health and Disease

Question 1

What are the basic components of the eye?

Answer 1

bony orbit, contents, eyeball, eyelids, lacrimal apparatus, muscles

Question 2

What is the ‘tear-drop sign’ indicative of?

Answer 2

An orbital floor fracture which has herniated into the maxillary sinus

Question 3

What is the role of orbital fat?

Answer 3

Cushioning the globe. Key for support

Question 4

What components make up the outer fibrous coat of the eye?

Answer 4

The sclera and cornea

Question 5

What components make up to middle vascular coat of the eye?

Answer 5

The iris, ciliary body, choroid

Question 6

What makes up the outer sensory coat of the eye?

Answer 6

Retina

Question 7

What liquid like substance resides in the anterior portion of the eye?

Answer 7

Aqueous humour

Question 8

What gel like substance is contained in the posterior portion of the eye?

Answer 8

Vitreous humour

Question 9

Describe the cornea

Answer 9

The anterior 1/6 of the fibrous outer coat, transparent window that will allow light rays to enter the eyeball

Question 10

Describe the sclera

Answer 10

The posterior 5/6 of the fibrous outer coat, gives attachment to the muscles moving the eyeball

Question 11

Describe the histology of the cornea

Answer 11

Stratified squamous non-keritanized epithelium

Question 12

What is Bowman’s membrane?

Answer 12

The basement membrane of the corneal epithelium

Question 13

What are the stroma of the corneal epithelium?

Answer 13

Regularly arranged collagen deposits with no blood vessels

Question 14

What are the three factors which maintain the transparency of the cornea?

Answer 14

Histologically - regular arrangement of collagen in the stroma
No blood vessels
Endothelium cell layer has a pump that actively keeps the aqueous humour out

Question 15

What are the two categories of corneal pathology?

Answer 15

Inflammatory - e.g. corneal ulcers

Non-inflammatory - e.g. dystrophies

Question 16

What is a common result of corneal pathology?

Answer 16

Opacification. May need to be treated by corneal transplant - Keratoplasty

Question 17

Why is avascularity important to surgeons performing a corneal graft?

Answer 17

The lack of blood supply results in a lesser chance of foreign antigens from a donor graft being detected by the host immune system and therefore less chance of subsequent rejection. Cornea is “immune-privileged’

Question 18

Describe the function of the iris

Answer 18

Controls the diameter of the pupils and therefore the amount of light rays entering the eyeball

Question 19

Describe the function of the ciliary body

Answer 19

Suspends the lens and produces Aqueous Humour

Question 20

Describe the function of the choroid

Answer 20

Supplies the blood to the outer layers of the retina

Question 21

What are the key histological layers of the retina?

Answer 21

9, the nerve fibre layer
2, the layer of rods and cones
1, the pigment epithelial layer

Question 22

What are the four quadrants of the retina?

Answer 22

Clockwise from top-left of the left eye; superonasal, superotemporal, inferotemporal, inferonasal

Question 23

What is the optic disc?

Answer 23

The start of the optic nerve, a physiological blind spot

Question 24

What is the fovea centralis?

Answer 24

A small, central pit composed of closely packed cones in the eye. It is located in the center of the retina. The high number of cones gives high visual acuity

Question 25

Describe the lens

Answer 25

A transparent, crystalline biconvex structure which is suspended by zones from the ciliary body. It can change shape

Question 26

What feature allows the lens to be transparent?

Answer 26

Avascularity

Question 27

What is another name for lens opacification?

Answer 27

Cataract

Question 28

What is a function of aqueous humour?

Answer 28

To maintain intraocular pressure

Question 29

What is a function of vitreous humour?

Answer 29

To cushion the retina

Question 30

Where is aqueous humour produced?

Answer 30

By the ciliary body, in the posterior chamber - the space behind the iris and in front of the lens

Question 31

What can an obstruction along the pathway of aqueous humour cause?

Answer 31

Damming up of AH and therefore increased intraocular pressure i.e. Glaucoma

Question 32

Describe the conjunctiva

Answer 32

Thin vascular membranes that cover the the inner surface of eyelids and loop back over the sclera. It does not cover the cornea

Question 33

What are the two conjunctiva?

Answer 33

Bulbar - over the sclera

Palpebral - covering the innner surface of the eyelid

Question 34

Where is the lacrimal gland situated?

Answer 34

Laterally in the orbit

Question 35

How do tears reach the surface of the eye?

Answer 35

Through punctae on the medial side if each eyelid

Question 36

Where do tears drain to from the eyelid?

Answer 36

The lacrimal sac which sits over the lacrimal bone, then draining through the nasolacrimal duct into the inferior meatus of the nasal cavity

Question 37

What are the four functions of the tear film?

Answer 37

Keeps the cornea moist
Washes away particulate foreign bodies
Contains antibodies and lysosomes to kill microbes
Smooths outer surface the cornea providing smooth surface for refraction

Question 38

What dye can be used to visualise the tear film?

Answer 38

Fluorescein

Question 39

Describe the first (deepest) layer of the tear film

Answer 39

Mucinous layer which makes up around 30% of the tear film. Overlies the corneal epithelium

Question 40

Describe the second (middle) layer of the tear film

Answer 40

The aqueous layer which makes up around 69% of the film. Overlies the mucinous layer

Question 41

Describe the third (superficial) layer of the tear film

Answer 41

The oily layer (~1%)

Question 42

How is aqueous humour filtered out of the anterior portion of the eye?

Answer 42

When it reaches the angle of the AC it is filtered out through a meshwork called the trabecular meshwork