Visual Defects

Question 1

Define: Glare. What often causes it?

Answer 1

Difficulty seeing in bright light.

Corneal/lens problem - usually cataracts. “Cloudy when its not cloudy outside”

Question 2

What is often damaged to cause distortion?

Answer 2

Retina
> Wet macular degeneration
> Macula hole
> Macula pucker
> Retinal detachment

Question 3

What is damaged to cause colour change?

Answer 3

Retina or optic nerve

Question 4

Field defects are caused by damage to what?

Answer 4

Homonymous = visual pathway 
Non-homonymous = Retina or nerve.

Question 5

What causes a floater?

Answer 5

Vitreous humour opacity

Question 6

How is a cataract examined?

Answer 6

Red reflex or slit lamp

Question 7

What causes drusen?

Answer 7

Impairment of the retinal pigment epithelium to remove waste products of the rods and cones

Question 8

Drusen, RPE pigmentation and RPE atrophy are the signs of what disease?

Answer 8

Dry Age Related Macular Degeneration - small area loss = severe visual loss

Question 9

What is the most common cause for Central retinal artery occlusion?

Answer 9

Carotid artery disease

Question 10

How does Giant cell arteritis cause visual loss?

Answer 10

Anterior Ischaemic Optic neuropathy or Central retinal artery occlusion

Question 11

What is Wet ARMD?

Answer 11

When the choroidal neovascular membrane grows towards macula, new blood vessels can break –> damage macula –> loss of vision.

Question 12

Why is Anti-VEGF the treatment for Wet ARMD?

Answer 12

Inhibits VEGF which causes the choroidal neovascular membrane to growth towards the macula.

Question 13

What are some of the features of Rods?

Answer 13

> Sensitive to scattered light
Capture more light than cones
High sensitivity to light (night vision)
Low temporal resolution (slower response)
Higher amplification

Question 14

What are the receptor proteins in rods and cones called?

Answer 14

Opsin’s
Rhodopsin in Rods
Cone opsin - Red, Bluee and green.

Question 15

What determines colour perception?

Answer 15

Contribution of R, B and G opsins to the retinal signal.

Question 16

When all the three cone types are active, according to the Young-Helmholtz trichromatic theory, what colour is made?

Answer 16

White

Question 17

Being trichromatic gives you what vision?

Answer 17

Normal

Question 18

What is anomalous trichomat?

Answer 18

When one pigment absorbs slightly different wavelength to most normal trichomats.

Question 19

What condition arises due to being a dichromat?

Answer 19

Colour blindness

Question 20

What do ON bipolar neurones depolarise in response to?

Answer 20

Light

Vice versa…

Question 21

Direct input from photoreceptor to bipolar cell is from the….?

Answer 21

Receptive field CENTRE

Question 22

Indirect input from the photoreceptor to horizontal cell to bipolar cell is from the…..?

Answer 22

Receptive field SURROUND

Question 23

What is the process of an ON bipolar cell becoming depolarised from the receptive field centre?

Answer 23

1) Light onto centre photoreceptor
2) Photoreceptor becomes HYPERPOLARISED
3) Bipolar cell depolarises

AND VICE VERSA

Question 24

What is the process of an ON bipolar cell becoming hyper polarised from the receptive field surround?

Answer 24

1) Light onto surround
2) Photoreceptor HYPERPOLARISED
3) Horizontal cell HYPERPOLARISED
4) Makes central photoreceptor more Depolarised
5) So bipolar cell –> more hyper polarised