Optics of the Visual System

Question 1

Describe the phenomenon of refraction

Answer 1

When light travels through one medium to another it changes velocity causing the ray to refract, this makes it appear to bend

Question 2

Where is the angle of incidence found?

Answer 2

Between the normal and the ray of incidence

Question 3

Where is the angle of refraction found?

Answer 3

Between the normal and the ray of refraction

Question 4

What is the equation for calculating index of refraction?

Answer 4

Speed of light in a vacuum/speed of light in a medium

Question 5

What should the index of refraction always be?

Answer 5

Greater than 1 because the denominator is always smaller than the numerator

Question 6

When the light goes from less dense to more dense where does it bend?

Answer 6

Towards the normal

Question 7

How many types of lens are there? What are they called?

Answer 7

2 types:
Concave
Convex

Question 8

Describe the properties of a convex lens

Answer 8

Converging lens that causes light rays to come together at a point

Question 9

Describe the properties of a concave lens

Answer 9

A diverging lens that causes light rays to spread away from each other

Question 10

What type of lens is converging?

Answer 10

Convex

Question 11

What type of lens is diverging?

Answer 11

Concave

Question 12

What type of lens causes light rays to come together?

Answer 12

Convex

Question 13

What type of lens causes light rays to spread apart?

Answer 13

Concave

Question 14

What is ametropia?

Answer 14

Refractive error, there is a mismatch between axial length and refractive power which means parallel rays don’t fall on the retina and theres no accomodation

Question 15

What is the medical name for near sightedness?

Answer 15

Myopia

Question 16

What is the medical name for far sightedness?

Answer 16

Hyperopia

Question 17

What are the types of ametropia?

Answer 17

Myopia
Hyperopia
Astigmatism
Presbyopia

Question 18

What happens to light rays in those with myopia?

Answer 18

Light rays converge at a point anterior to the retina

Question 19

What are the types of myopia? Describe them

Answer 19

Axial myopia= excessively long globe, more common

Refractive myopia= excessive refractive power

Question 20

What type of myopia is more common?

Answer 20

Axial myopia

Question 21

What are symptoms of myopia?

Answer 21

Blurred vision, squinting to help overcome this, headache as a result

Question 22

How is myopia corrected?

Answer 22

Diverging lens (negative power), contact lens, removal of lens to reduce refractive power

Question 23

What happens to light rays in those with hyperopia?

Answer 23

Light rays converge at a point posterior to the retina

Question 24

What are the types of hyperopia? Describe them

Answer 24

Axial hyperopia= excessively short globe (more common)

Refractive hyperopia= excessive refractive power

Question 25

What type of hyperopia is more common?

Answer 25

Axial

Question 26

Do those with near sightedness struggle to see near or far objects?

Answer 26

Far

Question 27

Do those with far sightedness struggle to see near or far objects?

Answer 27

Near

Question 28

Do those with myopia struggle to see near or far objects?

Answer 28

Far

Question 29

Do those with hyperopia struggle to see near or far objects?

Answer 29

Near

Question 30

What are symptoms of hyperopia?

Answer 30

Blurred vision when looking at things up close eg reading, worse if there is reduced light, burning in eyes, eye pain, headache in frontal region

Question 31

Where do those with hyperopia commonly get a headache?

Answer 31

In the frontal region

Question 32

How is hyperopia corrected?

Answer 32

Converging lens (positive power), contact lens, correction intraocular lens

Question 33

What happens to light rays in astigmatism?

Answer 33

Parallel rays focus in 2 focal lines instead of at a singular focal point because the refractive media is not spherical

Question 34

How many focal points are there in someone with asrigmatism?

Answer 34

2

Question 35

What are symptoms of astigmatism?

Answer 35

Headache, eye pain, blurred or distorted vision, head tilting/turning

Question 36

How is astigmatism treated?

Answer 36

Cylinder lens

Question 37

What is the near response triad? Describe it

Answer 37

Its how the eye adapts to look at close objects 1) pupillary miosis to increase depth of field 2) convergence to align both eyes towards a near object 3) accomodation to increase the refractive power of the lens

Question 38

In the near response triad what structure allows pupillary miosis?

Answer 38

Sphincter pupillae

Question 39

In the near response triad what structure allows convergence?

Answer 39

Medial recti of both eyes

Question 40

In the near response triad what structure allows accomodation?

Answer 40

Circular cilliary muscle

Question 41

What is presbyopia?

Answer 41

Naturally occuring loss of accomodation

Question 42

What is accomodation?

Answer 42

Focus on near objects

Question 43

At what age is there usually onset of presbyopia?

Answer 43

40 years

Question 44

How is presbyopia corrected?

Answer 44

Via reading glasses that have a convex lens so they increase refractive power or by contact lens

Question 45

What are the 3 main types of optical correction?

Answer 45

Contact lens Intraocular lens Surgical correction

Question 46

What are some advantages of contact lens?

Answer 46

Higher quality of optical image, influences the size of the image less than spectacles

Question 47

What are some disadvantages of contact lens?

Answer 47

They need careful daily cleaning and disinfection, they're expensive

Question 48

What is the best use of intraocular lens?

Answer 48

Optical correction of aphakia as they avoid significant magnification and distortion via spectacles

Question 49

What happens when the lens is cleared surgically?

Answer 49

Patients loose the ability to accomodate and require reading glasses

Question 50

What happens to the zonules and lens in accomodation?

Answer 50

Zonules relax | Lens thickens and increase in their refractive power