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OT > Myopia OT #12 > Flashcards

Myopia OT #12 Flashcards

1
Q

Where are light rays focused in myopia? Which type of image is produced?

A

Parallel light rays are focused in front of the retina which results in a blurred retinal image.

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2
Q

How does a minus lens work in regard to the focal points?

A

The second focal point of the correcting lens should coincide with the far point of the eye

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3
Q

What are possible effects of a high myopic refractive error?

A

Glaucoma, Cataracts, retinal detachment, maculopathy

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4
Q

How many adults are myopic in the US from 1999-2004?

A

41.6%

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5
Q

What will happen by 2050?

A

Half the word will my myopic with 1 billion having high myopia (>6D)

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6
Q

What percentage of high myopia will develop retinal disease?

A

70%

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7
Q

What are the global economic burdens of myopia and what will it increase to in 2050?

A

$478 billion by 2050 it will be $1.2 Trillion

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8
Q

What is emmetropization?

A

Newborns are hyperopic but this refractive error decreases during infancy and early childhood

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9
Q

What is a leptokurtotic distribution?

A

Emmetropization with a high peak from -2 -> +4
This occurs in 6-8 years old

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10
Q

Which type of curve do newborns have?

A

Normal Distribution from -7 -> +11

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11
Q

What grows during the first three years of life?

A

Cornea, Ant. Chamber depth, crystalline lens, axial length

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12
Q

What needs to happen if you have a long axial length in order to be an emmetrope?

A

You need less corneal or crystalline lens power (flatter curvature)

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13
Q

What is the anomalous component of myopia?

A

Axial length especially increased vitreous chamber depth

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14
Q

How many chromosomes have been identified for high myopia?

A

4

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15
Q

What is the heritability index of myopia for twins?

A

80%

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16
Q

What is the greatest risk factor of myopia?

A

Two myopic parents

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17
Q

What are possible risk factors for myopia?

A
  1. Environment
  2. Diet
  3. Near work
  4. Intelligence
  5. Stress
  6. Lack of outdoor activities
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18
Q

What is accommodation?

A

Change in the shape of the crystalline lens which increases the refractive power of the eye thus bringing near object into focus

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19
Q

What happens if the increase in power of the eye is maintained when viewing a distant target?

A

The image of the distant target will lie in front of the retina but far point is the point conjugate with the retina of the UNACCOMMODATED eye

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20
Q

What is associated with a 1D increase in myopia?

A

67% increase in myopic maculopathy

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21
Q

What happens if you slow myopia by 1D?

A

Reduces the risk of the patient having maculopathy by 40%

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22
Q

Why does each diopter of myopia matter?

A
  1. Less visual disability when uncorrected
  2. Better option for surgical myopia correcting
  3. Reduced risk of blindness associated with lower levels of myopia
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23
Q

What is the greatest myopia related risk?

A

Myopic Maculopathy which is irreversible vision loss AKA Myopic Macular Degeneration

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24
Q

What do individuals with high myopia have increased risks of?

A
  1. Posterior Staphyloma
  2. Chorioretinal and RPE atrophy
  3. Lacquer Cracks
  4. Macular Hemorrhage
  5. Choroidal neovascularization
  6. Myopic Macular Hole
25
Q

Do 6-7 year olds or 11-12 year olds progress faster for myopia?

A

6-7yo are 2x faster for refraction and axial elongation

26
Q

Do girls or boys progress faster for myopia?

A

Girls are 10% faster

27
Q

How much faster are children with 2 myopic parents likely to get myopia?

A

30-40% faster than kids with no myopic parents

28
Q

How much quicker do Asian children in Asian progress for myopia than US children?

A

50% faster

29
Q

What are myopia treatments?

A
  1. Lenses ( SV, bifocal, PALs, myopia control lenses)
  2. Contacts (SV, multifocal, Ortho-K)
  3. Refractive Surgery
  4. Atropine
30
Q

Can environment influence the axial length of the eye and if so, how?

A

Yes, via “Hyperopia retinal defocus”

31
Q

Which type of defocus do minus lens create?

A

Hyperopic Retinal Defocus -> Increased axial growth

32
Q

Which type of defocus do plus lens create?

A

Myopia retinal defocus -> reducing axial growth

33
Q

Do bifocals slow myopia progression? What if prisms are added to them?

A

Yes, they help in 2014 the were 31% effective and prism bifocals were 34% effective

  • The lenses slowed the refractive change and slowed axial length growth more than single vision
34
Q

Do PALs slow myopia progression?

A

The difference between single vision and PALs was 0.20D

They help but bifocals are better

35
Q

Which type of patient would PALs work best with? What is their approximate reduction in myopia?

A

In patients with larger lags of accommodation and esophoria at near

  • 0.8D reduction in myopia
36
Q

What are the effects of a large dose of atropine?

A

They slow myopia the most but have large “rebound” effects

37
Q

Is there a significant difference in axial length between a placebo and 0.01% atropine?

A

NO

38
Q

Is there a difference in spherical equivalent between a placebo and 0.01% atropine?

A

YES

39
Q

What are the effects of a peripheral refraction?

A

Visual signals from the peripheral retina can impact emmetropization at the fovea and possibly the development of refractive error

It is best to eliminate hyperopia retina defocus in the periphery than centrally

40
Q

What is the ideal myopia correction?

A

PERIPHERY

41
Q

What are Essilor Stellest Lens? And how much do they slow myopia progression?

A

Aspherical Lenslets for myopia control
SAL - Slightly Aspherical Lenslets
HAL (best)- Highly aspherical Lenslets

67% slower

42
Q

What does a Hoya DIMS lens do? And how much do they slow myopia progression?

A

Add more plus in the periphery to causes peripheral myopic defocus

52% slower

43
Q

What does ortho K do?

A

Central Flattening via peripheral steepening -> leads to relative peripheral myopia

44
Q

What does LASIK do?

A

Refractive surgery that flattens the central corneal making it less myopia and slows myopic progression

Corneal reshaping and peripheral refraction

45
Q

What do multifocal CLs do?

A

Plus power in the near that way rays passing through that zone are focused in front of the retina for myopia retinal defocus

46
Q

Which are the top 2 methods for myopia control?

A

Atropine and Ortho-K

47
Q

What does sunlight exposure do for myopia?

A

54% lower risk of myopia progression if >11hrs outdoors/ week

40mins outdoor time/ day lead to 23% reduction in incidence of myopia

48
Q

What are the possible mechanisms of sunlight’s effect on myopia?

A

Less accommodation outdoors
Pupil constriction outdoors
Dopamine is released which inhibits eye growth

49
Q

What is the leading cause of visual loss throughout the world?

A

Myopia

50
Q

Has there been proof that near work is associated with increased risk of myopia?

A

NO

51
Q

What are risks that are associated with higher risks of myopia?

A

Myopic parents and higher IQ

52
Q

What are the types of refractive surgery?

A

Radial Keratometry
Photorefractive Keratometry
LASEK- Laser assisted epithelial keratomileusis
LASIK- Laser in situ keratomileusis

53
Q

Problems with RK?

A

> 12D corneal astigmatism

54
Q

What happens in PRK?

A

Laser is used to reshape the cornea
- The corneal epithelium is removed with a blade or rotary brush -> new epithelium grows back over the corneal surface

55
Q

What happens in LASEK?

A

Similar to PRK except tissue is moved aside to allow the laser to reshape the stromal bed and the replaced

56
Q

What happens in LASIK?

A

Laser is used to create an epithelial flap which is then retracted -> exposed stromal bed is removed -> flap repositioned

57
Q

What are complications of refractive surgery?

A

Reduced BCVA
Reduced contrast sensitivity
Reduced corneal sensitivity
Need reading glasses
Increased Dry Eye
Reduced Night vision
Starbursts and halos around lights
Thinner cornea

58
Q

What percentage of nerves remain after refractive surgery (years later)?

A

<60%

59
Q
A

OT (13 decks)

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