L45. Vision Pt.1

Question 1

What is the longest wavelength of light?

Answer 1

Red

Question 2

What is the shortest wavelength of light?

Answer 2

Blue

Question 3

What is the visible spectrum of light?

Answer 3

400-750nm

Question 4

What is the purpose of the eye?

Answer 4

The eye is the organ that detects light and processes visual information to create visual perceptions

Question 5

What are the two basic components of the eye?

Answer 5

Optical –> collecting and focusing light into the plane of the retina

Neural –> converts energy of light into patterned changes of membrane potential

Question 6

What is the function of the lens?

Answer 6

Is the optical component: Collecting and focusing light into the plane of the retina

The lens is a transparent, fibrous and elastic structure, held in place by zonule fibres (ligaments)

Question 7

What is the function of the retina?

Answer 7

Is the neural component: Converts energy of light into patterned changes of membrane potential that other parts of the brain can decode to generate visual perceptions

The retina forms the inner posterior wall

Question 8

What is the function of the fovea?

Answer 8

Is the part of the retina that we use to look at things we want to see in great detail

The fovea is the part of the retina where we have highest visual acuity

Question 9

What is the sclera?

Answer 9

It is the fibrous covering of the spherical eyeball

The sclera is a fibrous connective tissue forming outer layer of eyeball - the whites of the eye

Question 10

What is the pupil?

Answer 10

A black centre aperture - appears black due to light absorption into the eye

Question 11

What is the cornea?

Answer 11

A transparent avascular capsule in front of iris

Question 12

What is the ciliary body?

Answer 12

Smooth circular muscle surrounding the lens

Question 13

What is the optic disc?

Answer 13

Head of the optic nerve where the axons exit the eye - contains no light sensitive neural components

Question 14

How does refraction in the eye occur?

Answer 14

Refraction occurs when light travels from a medium of one refractive index to a medium of a different index (e.g. air to water) - results in change in direction of light which is dependent on:
- Refractive indices of the two media
- Curvature of the refractive surface

Question 15

What is the refractive index of air?

Answer 15

1

Question 16

What is the refractive index of water?

Answer 16

1.3

Question 17

What is refractive power?

Answer 17

Ability of a lens to “bend” light - is measured in diopters

1 diopter: a lens that converges light to a focal point 1 metre away
–> (as you increase the diopter, divide that number by 1 to determine how far away the focal point is)

Question 18

What is the refractive power of the human eye at rest?

Answer 18

60 diopters = focal point of ~1.7cm beyond the lens

Question 19

What are the 3 elements of the ‘near response’ as you shift your gaze from distant to near objects?

Answer 19

1. Accomodation
2. Constriction of pupils
3. Convergence of eyes

Question 20

What happens during accomodation?

Answer 20

Contraction of ciliary muscle to alter lens shape and change refractive power (60 –> 75 diopters)

Question 21

What happens during constriction of the pupil?

Answer 21

Improved depth of focus, fewer optical aberrations by excluding edges of the lens

Question 22

What happens during convergence of the eye?

Answer 22

Objective remain in register on corresponding parts of the two retinae

Question 23

What is Emmetropia?

Answer 23

Normal vision
- Parallel and diverging light rays are in focus on the retina
- All distant objects are clearly visible with ciliary muscles relaxed
- Near objects are clearly visible with ciliary muscles contracted

Question 24

What is Hyperopia?

Answer 24

Farsightedness

Question 25

What is Myopia = Mila?

Answer 25

Nearsightedness - Parallel light rays from distant objects focus in front of the retina - Eyeball too long - No mechanism to decrease refractive power of lens further from rest. Therefore, distant objects remain out of focus. Image can be focused as object moves closer Correction: concave/diverging lens to decrease refractive power

Question 26

How can you correct Myopia = Mila?

Answer 26

Need a concave/diverging lens to decrease refractive power --> Push back focal point

Question 27

What is the cornea responsible for?

Answer 27

The cornea is responsible for the greatest amount of refraction in the eye; fine tuning of refraction is achieved by the lens

Question 28

What is the iris?

Answer 28

Pigmented contractile disc that regulates pupil diameter

Question 29

What is the choroid?

Answer 29

Black pigmented layer behind the eye which absorbs stray light and prevents reflection

Question 30

Examples of electromagnetic waves that are present but invisible to the human eye?

Answer 30

Radio and wifi