Lecture 36 DA

Question 1

What forms the optic nerve?

Answer 1

Formed by the output of the axons of ganglion cells of the retina.

Question 2

How does the optic nerve pass through the sclera?

Answer 2

Outer 2/3rds of the sclera run down the side of the optic nerve. The remaining inner 1/3rd continues across through the optic nerve.

Question 3

What is the intersection of the inner 1/3rd scelera with the optic nerve called?

Answer 3

Lamina cribosa.

Question 4

What is the structure of the lamina cribosa?

Answer 4

A band of dense connective tissue, forms a sieve-like mesh of collagen fibres.

Question 5

How many sheets make up the lamina cribosa, and what is its purpose?

Answer 5

3-10 sheets of collagen, anchors the optic nerve and gives it structure.
Makes sure the axons are in the right spot. Can be bent & impact vision.

Question 6

What happens to the lamina cribosa in glaucoma?

Answer 6

Gets distended, affecting vision.

Question 7

Where does the ophthalmic artery originate?

Answer 7

From the internal carotid artery.

Question 8

What are the four main arteries of the eye?

Answer 8

Central retinal artery
Long posterior clilliary artery
Short posterior cilliary artery
Anterior cilliary artery

Question 9

Where does the short posterior cilliary artery pierce the eye?

Answer 9

Posteriorly, just around the optic nerve.

Question 10

Where does the long posterior cilliary artery pierce the eye?

Answer 10

Similar to the short posterior, but further up, and away from the optic nerve, and is longer as a result, hence its name.

Question 11

Does the anterior cilliary artery pierce the globe?

Answer 11

No, it doesn’t.

Question 12

Where does the anterior cilliary artery run?

Answer 12

It runs anterior to the globe without piercing, and supplies the anterior eye.

Question 13

Which artery do all arteries within the choroid originate from?

Answer 13

One of the posterior arteries, including central retinal.

Question 14

What is the blood supply to the retina?

Answer 14

It has a dual supply.
The central retinal artery supples the inner retina, while the outer retina is supplied by the posterior cilliary arteries

Question 15

What is the optic nerve supplied by?

Answer 15

Short posterior cilliary artery.

Question 16

What supplies the iris?

Answer 16

Long posterior cilliary artery.

Question 17

What supplies the cilliary bodies?

Answer 17

Long posterior cilliary artery.

Question 18

What are photoreceptors aside from the inner and outer retina supplied by?

Answer 18

Long posterior cilliary artery.

Question 19

Where do the long posterior and anterior cilliary arteries anastamose?

Answer 19

At the junction between the sclera and corna, via a major perforating artery.

Question 20

What does inflammation within the eye cause?

Answer 20

Localised redness.

Question 21

What are 4 factors affecting visual acuity?

Answer 21

Pupil size
Clarity of optic media (cornea, lens)
Refrective errors
Diseases (myopia, astigmatism)

Question 22

What bends light as it enters the eye?

Answer 22

60% of whats required bent by the cornea.

40% by the lens

Question 23

What is myopia? Where is the focus?

Answer 23

Eyeball too long, focus is in front of the retina. Minus lenses needed.

Question 24

What is hypermetropia? Where is the focus?

Answer 24

Eyeball is too short, focus is behind the retina. Positive lenses needed.

Question 25

Is the fovea avascular? Why?

Answer 25

Yes, so give visual acuity.

Question 26

What is astigmatism? Where is the focus?

Answer 26

The eyeball is football shaped rather than circular. Focus is steeper in one meridian/axis than the other, light hits one side better than the other.
Cylindrical lenses needed.

Question 27

What is keratoconus?

Answer 27

Non inflammatory condition of the cornea, cone shaped cornea. Thinning of the central cornea.
Irregular astigmatism.

Question 28

What is the incidence rate of keratoconus?

Answer 28

1/2000, 70% female.

Question 29

What is keratoconus associated with and how is it treated?

Answer 29

Associated with allergic conditions.
Treated by hard contact lenses.
10% need corneal transplant.

Question 30

What is wet form macular degeneration?

Answer 30

Blood vessels grow into the fovea and destroy it.

Question 31

What is dry form macular degeneration?

Answer 31

Cellular debris (drusen) accumulates between the choroid and retina.

Question 32

What are the causes of macular degeneration?

Answer 32

Age, smoking, diet.

Many genetic, relating to lipid transport and immune function.

Question 33

Can macular degeneration be treated?

Answer 33

Yes, but requires a monthly injection into the eye. Only works for wet form.

Question 34

Which form of macular degeneration is more serious?

Answer 34

Wet form (10% of cases).

Question 35

What is a theory on the cause of macular degeneration?

Answer 35

Fovea metabolic demands aren’t being met, stimulating blood vessel growth.

Question 36

What is Bruch’s membrane? How is it believed to be involved in macular degeneration?

Answer 36

Boundary between vessels and fovea. Believed to thicken in macular degeneration and impinges on nutrient transfer.

Question 37

What age does macular degeneration usually start and what does it look like?

Answer 37

50 years and over. Begins as a white blob on the retina.

Question 38

How can Bruch’s membrane be thinned?

Answer 38

Use of a nanosecond laser.