The pupil

Question 1

What are the reflexes that affect pupil size?

Answer 1

Light reflex
Near reflex
Psychosensory reflex

Question 2

What is dilation also known as?

Answer 2

Mydriasis

Question 3

What is constriction also known as?

Answer 3

Miosis

Question 4

What is pupil size a trade off between?

Answer 4

Diffraction
Abberations
Acuity
Light entering the eye

Question 5

What are the functions of the pupil?

Answer 5

Increase the depth of focus (during near reflex)
Protect - from UV damage
Reduction of abberations
Reduction of diffraction
Optimising VA

Question 6

How many log units of light can the eye operate over?

Answer 6

13

Question 7

How many log units of light does the change in the size of the pupil affect?

Answer 7

~1.2

Question 8

What nervous system controls the pupil under pleasant conditions, and how does the pupil change?

Answer 8

Sympathetic NS
Dilates

Question 9

What nervous system controls the pupil under unpleasant conditions, and how does the pupil change?

Answer 9

Parasympathetic NS
Constricts

Question 10

When else can dilation occur?

Answer 10

Sexual stimulation
Mental strain
Seconds before decision making

Question 11

How does pupil constriction in bright light help with subsequent dark adaptation?

Answer 11

The area which is light-adapted is reduced, so fewer photoreceptors have to readjust to the dark

Question 12

What is the Stiles-Crawford effect?

Answer 12

Cones only respond to light from straight on (angled towards the centre of the pupil) and the brightest light is in the centre of the pupil
Blur circle is reduced bc aberrations are ‘ignored’ due to only responding to central light
Foveal cones act as a ‘secondary pupil’

Question 13

When does the Stiles-Crawford effect help?

Answer 13

During psychosensory reflex pupil dilation