Vision

Question 1

Hypermetropia

Answer 1

Long sightedness
Eyeball too short
Lens system too weak

Treatment- converging corrective lens

Question 2

Myotopia

Answer 2

Eyeball too long
Lens system too short

Treatment- diverging correcting lens

Question 3

Focus of the eye

Answer 3

Carried out by changing shape of the lens (1/3 ray bending)

Question 4

What is the function of the iris?

Answer 4

it can vary its diameter and therefore retinal intensity

Question 5

Where is the pigment layer? What is its functions?

Answer 5

Behind retina

absorbs unwanted light

Question 6

Fovea

What is its function?

Answer 6

small yellow spot on opthalmoscope
-densely packed with cones

-small region in retina that gives the clearest image

Question 7

What types of photoreceptors exist

Answer 7

Rods- dim light
-A lot more present

Cons- bright light and colour
-fewer

Question 8

Processing layers of retina

Answer 8

3 direct layers

• receptors
• bipolars
• ganglion cells

2 transverse layers

• horizontal
• amacrine cells

Question 9

Rhodopsin

• Location
• receptor type
• Mechanism

Answer 9

• rods of the retina -G-protein-coupled receptor (GPCR)
• sensitive to light
• vision in low-light conditions.

Mechanism

• Photon from light hits molecule
• change from cis to trans
• triggers intracellular events
• hyperpolarisation in membrane

Question 10

Peak spectral sensitivities of human cones

• red cones
• green cones
• blue cones
• rods

Answer 10

Red cones: 560 nm [most]

Green cones: 530
nm

Blue cones: 420 nm [least]

Rods: 500 nm

Question 11

Red/green colour blindness

Answer 11

X linked

mutation in gene

Question 12

Blue colour blindness

Answer 12

mutation on blue cone gene
chromosome 7
paired in both sexes
so rarer

Question 13

Central Achromatopsia

Answer 13

Damage to cortical colour processing areas (V4)

Question 14

Central Visual Pathway

Answer 14

Left Retina

• temporal field- R LGN
• nasal field- L LGN

Right Retina

• temporal field - L LGN
• nasal field - R LGN
• Optic nerve
• optic chiasma
• optic tract
• LGN
• Optic radiation
• visual cortex in occipital lobe (aka striate cortex)

Question 15

The Visual Association Cortex is associated with which Broadmann area?

Answer 15

Broadmann Area 18 & 19

Question 16

The Striate Cortex/Primary Visual Cortex is associated with which Broadmann area?

Answer 16

Broadmann area 17

Question 17

Name causes of scotoma [3]

Answer 17

1. retinal damage
2. Lesions in visual cortex
3. pressures from tumours restricting structures

Question 18

Describe the dorsal stream in the cortex. What is it concerned with?

Answer 18

occipital to parietal

• location
• motion
• action

Question 19

Describe the ventral stream in the cortex. What is it concerned with?

Answer 19

occipital to temporal

• object (and face identity)
• conscious perception

Question 20

Visual agnosia.

Answer 20

• Pt can’t recognise

- Lesion in ventral stream

Question 21

Prosopagnosia

Answer 21

Inability to recognise faces

-fusiform gyrus located in temporal lobe

Question 22

Vestibulo-ocular reflex

Answer 22

stabilizes gaze by countering movement of the head

Question 23

Optokinetic reflex

Answer 23

stabilizes the image of a moving object on the retina

Question 24

Pupillary reflex (example of shining light on left eye)

Answer 24

when you shine a light on one way, it will constrict (directly) and so will the other eye (consensual response)

• info travels down optic tract and synapses onto pretectal nuclei projecting to both edinger-westphal nuclei on both sides
• this stimulates the occulomotor nerve to synapse on ciliary ganglion with short ciliary nerve
• causing constriction of iris

Question 25

In short, why do both eyes constrict when you shine a light onto left retina?

Answer 25

because the information travels down and synapses onto pretectal nuclei which projects to Edinger-Westphal nuclei on both sides. this activates CN3 which synapses with ciliary nerve on ciliary ganglion.