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Clinical Skills > INCIDENCE AND DISTRIBUTION OF REFRACTIVE ANOMOLIES > Flashcards

INCIDENCE AND DISTRIBUTION OF REFRACTIVE ANOMOLIES Flashcards

1
Q

What is the refractive error like at birth?

A
  1. Normal distribution 
  2. Skew towards hyperopia 
  3. Myopia: 0-25% of newborns
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2
Q

As an infant grows, refractive error shift towards 1. ______. However, by the time the child is about a year old, the refractive error skews towards 2. ____.

A
  1. emmetropia due to eye growth

2. myopia

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3
Q

What is emmetropization?

A

The process in which refractive error shifts towards emmetropia.

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4
Q

When does ocular development slow down?

A

Ages 5-15

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5
Q

Ages 5-15

Anterior chamber depth increases by only _____ mm

A

0.10 to 0.20 mm

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6
Q

Ages 5-15

Vitreous chamber depth increases by

A

~1 mm

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7
Q

Ages 5-15

Axial length increases by

A

~1 mm

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8
Q

Ages 5-15

Cornea is stable or unstable?

A

STABLE

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9
Q

Ages 5-15

Lens power decreases by ____ (lens thins, but still grows new fibers) 

A

2 D

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10
Q

Ages 5-15

Hyperopia decreases by

A

~1 D

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11
Q

Emmetropization: Age 5-15 

Prevalence of myopia increases by over___times to __%

A

7 times to 15%

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12
Q

Juvenile-onset myopia: increase _____/ year during early teens

A

~ -0.50 D

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13
Q

Adult-onset myopia: ___% of population is myopic after teen years

A

10%

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14
Q

Total myopic prevalence in adult population is ~__%

A

~25%

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15
Q

9 possible factors that affect refractive error distributions:

A
  1. Age 
  2. Gender 
  3. Ethnicity 
  4. Geography 
  5. Diet 
  6. Time 
  7. Personality 
  8. Systemic Conditions 
  9. Ocular Diseases
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16
Q

What is the single most important determinant of distribution of refractive error in a given group?

A

Age

17
Q

What do studies show about how gender effects refractive error distribution?

A

Gender 
Trends in refractive error distribution are inconclusive  Studies have shown: no significant differences, shift towards males, shift towards females

18
Q

What do studies show about how ethnicity effects refractive error distribution?

A

Not enough data

Prevalence of Myopia: Asians > Caucasians > African-Americans

19
Q

What do studies show about how geography effects refractive error distribution?

A

Study results are confounded by other factors (ex. diet, education) 

Similar to trends found in US ethnicity studies
Alaska/Eskimo has most myopia at 44.7%

20
Q

What do studies show about how diet effects refractive error distribution?

A

Diet 
Effects on refractive error is unclear, due to confounding factors (ethical dilemma to alter nutritional needs of children)

21
Q

What do studies show about how time effects refractive error distribution? What is it’s overall trend?

A

Inconclusive, as studies are done in different decades with different research methods and different refractive error criteria 

Overall trend: decrease in prevalence of myopia with increasing age in elderly range

22
Q

What do studies show about how personality effects refractive error distribution?

A 
No strong data!
Myopia is associated with:  
Introversion  
Inhibited disposition  
Disinclination for motor activity and social leadership  
Hyperopia is associated with:  
Carefree  
Impulsive  
Hyperactive  
Socially passive
23
Q

What do studies show about how systemic conditions effects refractive error distribution?

A

Effect the development of the eye  affects its refractive state

Examples: Albinism, Down Syndrome, Connective Tissue Disorders, Diabetes, Homocystinuria (metabolism issue with excretion of homocystine in the urine and excesses of homocystine and methionine in the blood)

24
Q

What do studies show about how ocular disease effects refractive error distribution?

A

Clear visual input needed for normal emmetropization to occur 

Majority of conditions are associated with myopia

Conditions associated with hyperopia; involves foveal development: Albinism, Maculopathies, and Rod monochromacy

25
Q

What are the factors have a known affect on refractive error distributions?

A

Age
Systemic Conditions
Ocular Diseases

26
Q

Studies of Parents & Children show higher heritabilities in:

A

Axial Length 

Corneal Power

27
Q

Studies of twins show higher heritabilities in:

A

Axial Length 
Corneal Power 
Refractive Error

Differences between twins is smaller for Monozygotic (identical) than Dizygotic twins

28
Q

Near Work Theory 

Excessive reading during childhood causes abnormal eye growth leading to myopia. What are studies that support this?

A

Studies supporting this: 

  1. Increase in myopia prevalence in first school-educated Eskimos 
  2. Decrease in myopia prevalence during WWII in Japan 
  3. Adult-onset myopia in college populations
29
Q

Excessive Axial Elongation and Myopia is linked to:

A

schooling, studying, reading, and other near work

30
Q

How does intelligence seem to trend with myopia?

A

Myopes tend to have higher scores on tests of intelligence & cognitive ability and get better grades than other refractive error groups.

31
Q

How might socioeconomic status effect myopia?

A

Myopes tend to be overrepresented among the higher socioeconomic strata and underrepresented among the lower income levels 

Possibly due to connection between Myopia, Intelligence, and Educatio

Clinical Skills (7 decks)

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