How we see 1: refraction and accommodation

Question 1

What is refraction?

Answer 1

the bending of light rays to form a sharp image on the retina

Question 2

What is accommodation?

Answer 2

We can focus on far off or near objects by changing how much we bend light rays

Question 3

What is a refractive error?

Answer 3

mismatch between how much we bend light rays

Question 4

what are the 4 refractive media in the eyeball?

Answer 4

cornea, aqueous humor, lens and vitreous humor

Question 5

What 2 parts of the eye do light rays bend at?

Answer 5

the cornea and the lens

Question 6

How does the lens change when an object gets closer?

Answer 6

becomes thicker and more powerful

Question 7

Is the cornea or lens more powerful bender of light?

Answer 7

cornea

Question 8

Can the cornea or lens change its bending power?

Answer 8

lens

Question 9

List the 3 components of accommodation

Answer 9

lens changes shape - thicker and more spherical
pupil constricts
eyes converge

Question 10

Does the ciliary body contract via sympathetic or parasympathetic innervation?

Answer 10

parasympathetic

Question 11

Describe what happens when the ciliary body contracts to the lens

Answer 11

contracts and bulges
suspensory ligaments become loose
lens becomes thicker and more rounder

Question 12

Why does the pupil constrict during accommodation?

Answer 12

to only let a few light rays - of the object - in

Question 13

What muscles and its innervation constricts the pupil?

Answer 13

constrictor pupillae

parasympathetic via the oculomotor (CN 3) nerve

Question 14

What is the only part of accommodation you can actually see?

Answer 14

pupil constriction

Question 15

What is the process of the eyes turning in to look at the object called?

Answer 15

convergence

Question 16

What muscles and its innervation is responsible for convergence?

Answer 16

medial rectus by oculomotor nerve

Question 17

Why is the medial rectus thicker than the lateral rectus muscle?

Answer 17

close work

Question 18

Name the 4 refractive errors

Answer 18

myopia, hyperopia, presbyopia, astigmatism

Question 19

What is myopia?

Answer 19

short sighted

Question 20

What is hyperopia?

Answer 20

long sighted

Question 21

What is presbyopia?

Answer 21

age related long sighted

Question 22

What is astigmatism?

Answer 22

non spherical curvature of the cornea/lens

Question 23

What is the term for someone with perfect vision?

Answer 23

emmetrope

Question 24

What is the underlying problem in myopia?

Answer 24

eyeball a bit too long, lens a bit too powerful

Question 25

In myopia where is the image focussed?

Answer 25

in front of the retina

Question 26

Myopia symptoms

Answer 26

headache, cannot see far away objects, divergent squint in infants and loss in sports/people - more interested in books

Question 27

Correction of myopia

Answer 27

biconcave lenses - decrease bending power

Question 28

Hyperopia underlying problem

Answer 28

eyeball too short, lens not powerful enough and too flat

Question 29

Hyperopia symptoms

Answer 29

eyestrain after reading

convergent squint

Question 30

Why must a convergent squint be rectified right away to prevent?

Answer 30

lazy eye

Question 31

Correction of hyperopia

Answer 31

biconvex lens

Question 32

In astigmatism are close or far away objects hazy?

Answer 32

both - random

Question 33

What 2 special corrections of astigmatism are used?

Answer 33

cylindrical glasses curved in one axis

toric contact lenses

Question 34

What is the physiological cause of presbyopia?

Answer 34

lens becomes less mobile and less elastic to be able to change shape

Question 35

Presbyopia - age, symptoms, correction

Answer 35

50’s, strain to read newspaper, biconvex reading glasses