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BRS Y2 > Optics of the Visual System > Flashcards

Optics of the Visual System Flashcards

1
Q

Describe the phenomenon of refraction

A

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

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2
Q

Where is the angle of incidence found?

A

Between the normal and the ray of incidence

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3
Q

Where is the angle of refraction found?

A

Between the normal and the ray of refraction

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4
Q

What is the equation for calculating index of refraction?

A

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

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5
Q

What should the index of refraction always be?

A

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

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6
Q

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

A

Towards the normal

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7
Q

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

A

2 types:
Concave
Convex

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8
Q

Describe the properties of a convex lens

A

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

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9
Q

Describe the properties of a concave lens

A

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

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10
Q

What type of lens is converging?

A

Convex

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11
Q

What type of lens is diverging?

A

Concave

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12
Q

What type of lens causes light rays to come together?

A

Convex

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13
Q

What type of lens causes light rays to spread apart?

A

Concave

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14
Q

What is ametropia?

A

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

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15
Q

What is the medical name for near sightedness?

A

Myopia

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16
Q

What is the medical name for far sightedness?

A

Hyperopia

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17
Q

What are the types of ametropia?

A

Myopia
Hyperopia
Astigmatism
Presbyopia

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18
Q

What happens to light rays in those with myopia?

A

Light rays converge at a point anterior to the retina

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19
Q

What are the types of myopia? Describe them

A

Axial myopia= excessively long globe, more common

Refractive myopia= excessive refractive power

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20
Q

What type of myopia is more common?

A

Axial myopia

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21
Q

What are symptoms of myopia?

A

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

22
Q

How is myopia corrected?

A

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

23
Q

What happens to light rays in those with hyperopia?

A

Light rays converge at a point posterior to the retina

24
Q

What are the types of hyperopia? Describe them

A

Axial hyperopia= excessively short globe (more common)

Refractive hyperopia= excessive refractive power

25
Q

What type of hyperopia is more common?

A

Axial

26
Q

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

A

Far

27
Q

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

A

Near

28
Q

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

A

Far

29
Q

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

A

Near

30
Q

What are symptoms of hyperopia?

A

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

31
Q

Where do those with hyperopia commonly get a headache?

A

In the frontal region

32
Q

How is hyperopia corrected?

A

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

33
Q

What happens to light rays in astigmatism?

A

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

34
Q

How many focal points are there in someone with asrigmatism?

A

2

35
Q

What are symptoms of astigmatism?

A

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

36
Q

How is astigmatism treated?

A

Cylinder lens

37
Q

What is the near response triad? Describe it

A

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

38
Q

In the near response triad what structure allows pupillary miosis?

A

Sphincter pupillae

39
Q

In the near response triad what structure allows convergence?

A

Medial recti of both eyes

40
Q

In the near response triad what structure allows accomodation?

A

Circular cilliary muscle

41
Q

What is presbyopia?

A

Naturally occuring loss of accomodation

42
Q

What is accomodation?

A

Focus on near objects

43
Q

At what age is there usually onset of presbyopia?

A

40 years

44
Q

How is presbyopia corrected?

A

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

45
Q

What are the 3 main types of optical correction?

A

Contact lens
Intraocular lens
Surgical correction

46
Q

What are some advantages of contact lens?

A

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

47
Q

What are some disadvantages of contact lens?

A

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

48
Q

What is the best use of intraocular lens?

A

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

49
Q

What happens when the lens is cleared surgically?

A

Patients loose the ability to accomodate and require reading glasses

50
Q

What happens to the zonules and lens in accomodation?

A

Zonules relax

Lens thickens and increase in their refractive power

BRS Y2 (85 decks)

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