lecture 25 - vision

Question 1

What is the term for the ‘white of the eye’?

Answer 1

Sclera

Question 2

What muscle controls lens shape for accomodation?

Answer 2

Ciliary muscle

Question 3

What structure in the eye defines pupil diameter?

Answer 3

Iris

Question 4

What is the function of the ciliary body?

Answer 4

Secretes aqueous humor

Question 5

What fluid is found within the anterior chamber of the eye?

Answer 5

Aqueous humor

Question 6

What fluid is found within the posterior chamber of the eye?

Answer 6

vitreous humor

Question 7

Why does the retina need a good blood supply?

Answer 7

Relies on oxidative metabolism, so relies on a good supply of oxygen and gluocse

Question 8

What is the function of the choroid of the eye?

Answer 8

Contains lots of blood vessels that provides blood to the deep retina

Question 9

Where is the location of the deep retina?

Answer 9

At the back of the eye, on the outer part of the eyeball, but is deep to the light source that comes from the anterior

Question 10

What condition arises when there is damage from raised intraocular pressure?

Answer 10

Glaucoma

Question 11

What are the findings on ophthalmoscopy in diabetes?

Answer 11

Increased vascularisation

Question 12

What are the findings on ophthalmoscopy in papilloedema?

Answer 12

Optic disc bulges

Question 13

What are the 6 extraocular muscles that control eye movement?

Answer 13

Superior oblique, Inferior oblique, Lateral rectus, medial rectus, superior rectus, inferior rectus

Question 14

Which cranial nerves control eye movement?

Answer 14

Oculomotor (III), trochelar (IV), abducens (VI)

Question 15

Which extraocular muscles are controlled by the oculomotor nerve?

Answer 15

Superior rectus, Inferior rectus, medial rectus, inferior oblique

Question 16

Which extraocular muscles are controlled by the trochlear nerve?

Answer 16

Superior oblique

Question 17

Which extraocular muscles are controlled by the abducens nerve?

Answer 17

Lateral rectus

Question 18

What is the relationship between the contraction state of the ciliary muscles and the shape of the lens?

Answer 18

Contracted muscles = lower tension and more rounded lens
Relaxed muscles = higher tension and more flattened lens

Question 19

What is the action of the ciliary muscles during near vision?

Answer 19

They contract to relax the zonular fibres and relax the lens so it becomes thicker and more spherical

Question 20

What is the pathophysiology of glaucoma?

Answer 20

There is build of aqueous humor in the front of the eye due to excessive production or blocked drainage. This increases pressure which damages eye blood vessels and the optic nerve.

Question 21

What are the steps in the pathway of visual information from the retina to the optic nerve?

Answer 21

Photoreceptor cells (rods/cones), bipolar cells, ganglion cells, axons of ganglion cells converge to form optic nerve

Question 22

What are the basic steps in the pathway of visual information from the optic nerve to the visual cortex?

Answer 22

optic nerve, optic chiasm, optic tract, lateral geniculate body, optic raditation

Question 23

What visual field defect occurs when there is a single optic nerve lesion?

Answer 23

mononuclear blindness (loss of vision in the ispilateral eye)

Question 24

What visual field defect occurs when there is an optic chiasm lesion?

Answer 24

Bitemporal hemianopia

Question 25

What type of visual field defect will often arise in patients with a pituitary tumor?

Answer 25

Bitemporal hemianopia (loss of peripheral vision) due to pressure on the optic chiasm

Question 26

What visual field defect occurs when there is a lesion to the optic tract?

Answer 26

Homonymous hemianopia (loss of vision on half of each each eye on the side opposite to the lesion)

Question 27

What visual field defect occurs when there is a lesion affecting Meyer’s loop?

Answer 27

Upper quadrantic anopia

Question 28

What visual field defect occurs when there is a partial lesion of the optic radiation?

Answer 28

Lower quadrantic anopia

Question 29

What visual field defect occurs when there is a PCA infarct?

Answer 29

Homoonymous hemianopia with macular sparing (vision in the centre of each eye is intact)

Question 30

What is the purpose of the retino-hypothalamic tract?

Answer 30

Convey information about light for circadian rhythm, body clock, sleep-wake cycles

Question 31

What is the function of the superior collicullus-visual pathway?

Answer 31

Role in unconscious automatic control of orientation to visual stimuli

Question 32

What are the 2 types of light-sensitive receptors in the retina?

Answer 32

Cones, rods

Question 33

What is the function of cones in the eye?

Answer 33

Colour vision - each cone can absorb different wavelengths of light

Question 34

What is the function of rods in the retina?

Answer 34

Grey-scale vision - vision in low light levels

Question 35

Which type of light receptor cell operates in higher light intensity?

Answer 35

Cones - can only see colour at high light density

Question 36

Which type of light receptor cell is more sensitive?

Answer 36

Rods

Question 37

Where in the retina is the highest density of cones?

Answer 37

Fovea

Question 38

How are cones adapted to see different wavelengths of light?

Answer 38

There are 3 different types of cones, with 3 different cone opsins that have sensitivity to red, blue and green