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methods BLOCK 2 > Incidence and distribution of refractive anomolies > Flashcards

Incidence and distribution of refractive anomolies Flashcards

1
Q

refractive error at birth

A

-skews towards hyperopia

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2
Q

What is the percentage of newborsn with myopia?

A

0-25%

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3
Q

why do infants shift towards emmetropia as they grow?

A
  • due to eye growth
  • skew towards myopia
  • mostly within 1st year of life
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4
Q

emmetropization

A

the process in which refractive error shifts towards emmetropia

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5
Q

When does ocular development slow?

A

Ages 5-15

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6
Q

How much does the anterior chamber depth increase by?

A

0.10 to 0.20mm, slows by Aggies 5-15

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7
Q

How much does the vitreous chamber depth increase by?

A
  • 1mm
  • about 3D change for every 1mm
  • slows by ages 5-15
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8
Q

How much does the axial length increase by?

A
  • 1mm
  • about 3D change
  • slows by ages 5 to 15
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9
Q

What happens to the cornea throughout growth

A

Pretty much stable

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10
Q

What does the lens power do throughout growth?

A
  • decreases by 2D
  • lens thins but still grows new fibers
  • slows by ages 5 to 15
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11
Q

What does hyperopia do with ocular growth?

A
  • decrease about 1D

- slows by ages 5-15

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12
Q

When does emmetropization occur?

A

Age 5-15

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13
Q

Prevalence of myopia increases by how much during emmetropization

A

Increases by over 7 times to 15%

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14
Q

Juvenile-onset myopia increase

A
  • About -0.50D per year during early teens

- from reduced ability of lens to compensate for the growth in axial length

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15
Q

When does myopia progression stop?

A

Around 14.6-15.3 years for females
Around 15-16.7 for males
-from eye not growing beyond age 13-14

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16
Q

Adult onset myopia

A

10% of population is myopic after teen years

-total myopic prevalence in adult population is about 25%

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17
Q

Both hyperopia and axial length increase…

A

Slow down at 5

Stops at 13-14

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18
Q

Factors that affect refractive error distribution

A
  • age
  • gender
  • ethnicity
  • geography
  • diet
  • time
  • personality
  • systemic conditions
  • ocular diseases
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19
Q

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

A

Age

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20
Q

infants with myopia at birth

A

Very small portion

  • neonatal myopia associated with prematurity
  • astigmatism 1.00D cyl
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21
Q

When is low to moderate myopia first observed and progresses?

A
  • age 6-8

- astigmatism decreases, ATR shift (from decrease in WTR corneal toricity> ATR lenticular toricity

22
Q

Juvenile-onset myopia progression and cessation

A
  • progression is 0.40D
  • Cessation at age 14-15 females and 15-16 males
  • lens can’t compensate for growing eye
23
Q

About when does refractive error become stable?

A

High school

24
Q

Adult onset of myopia and progression of pre-existing myopia

A
  • prevalence is 25%

- decrease in prevalence of myopia in older age

25
Q

Gender

A

-inconclusive

26
Q

Ethnicity

A
  • not enough data
  • prevalence of myopia in Caucasian group twice as much as African American group
  • across all groups: myopia develops primarily from excessive axial length
  • different ocular component profiles for groups with low prevalence of myopia vs groups with high prevalence of myopia
27
Q

Geography

A
  • study results are confounded by other factors (diet, education)
  • similar trends found in US ethnicity studies
28
Q

Diet

A
  • unclear
  • ethical dilemma to alter nutritional needs of children
  • Eskimos showed no difference in eating a regional diet vs 1 American meal per day
29
Q

Time

A
  • inconclusive

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

30
Q

Personality

A

-no strong data

31
Q

What is myopia associated with (personality-wise)

A
  • introversion
  • inhibited disposition
  • disinclination for motor activity and social leadership
32
Q

What is hyperopia associated with (personality-wise)

A
  • carefree
  • impulsive
  • hyperactive
  • socially passive
33
Q

Systemic conditions

A
  • homocystinuria

- diabetes

34
Q

Homocystinuria and refractive error distributions

A
  • metabolism issue with the excretion of homocysteine in the urine and excesses of homocysteine and methionine in the blood
  • fair hair and skin
  • mental retardation
  • Lens dislocation
  • myopia
  • light iridies
  • hypotony (not enough eye pressure)
  • retinal elevation
  • cataract
35
Q

Diabetes and refractive error distributions

A

-higher prevalence of myopia

-

36
Q

Ocular diseases and refractive error distributions

A
  • majority are associated with myopia
  • clear visual input needed for normal emmetropization to occur and some diseases obscure clear vision
  • congenital cataracts
  • posterior polar and nuclear cataracts
  • congenital ptosis ( astir increases after surgical correction)
  • retrolental fibroplasia
  • corneal opacification
  • vitreous hemorrhage
  • hemangioma (astir and myopia)
  • Phylctenular keratitis (alters corneal curvature)
37
Q

Ocular diseases associated with hyperopia

A
  • involves fovea like development
  • albinism (OCULAR!, systemic is myopic)
  • maculopathies
  • rod monochromacy (color defect)
38
Q

Hereditary conditions associated with myopia

A
  • achromatopsia
  • nystagmus
  • microcornea
  • keratoconus
  • Fabry’s disease (corneal and lenticular accumulation of glycosphingolipid)
  • microphakia
  • ectopia lentis
  • coloboma
  • choroideremia
  • Gyrate atrophy
  • fundus flavimaculatus
  • retinitis pigmentosa
  • progressive bifocal chorioretinal atrophy
  • extensive myelination of the nerve fibers
  • Wagner’s disease (membranous vitreous, arteriolar sheathing, choroidal sclerosis, cataract)
  • vitreoretinopathy
  • familial external ophthalmoplegia
39
Q

Hereditary conditions associated with hyperopia

A
  • Achromatopsia
  • Nystagmus
  • microphthalmia
40
Q

Glaucoma and refractive error

A

-connected with myopia

41
Q

Near-work theory of myopia

A
  • prolonged reading (accommodation) increases IOP, driving the expansion of the eye by mechanical force
  • related to glaucoma
42
Q

Associated conditions with glaucoma and myopia

A
  • genetics link- high prevalence of positive steroid response among myopia and glaucoma patients
  • risk of OHTN appears to be higher in myopia than in emmetropes
  • risk of open angle glaucoma and conversions of OHTN to glaucoma is higher in myopes than in emmetropes
43
Q

ATR astigmatism and refractive error distribution

A
  • pellucid marginal degeneration

- thins the inferior cornea and flattens the vertical corneal meridians

44
Q

Based on consistent study results, these factors have a known affect on refractive error distributions

A
  • age
  • systemic conditions
  • ocular diseases
45
Q

These factors are found to be inconclusive on having a known refractive error association

A
  • gender
  • ethnicity
  • geography
  • diet
  • time
  • personality
46
Q

Heredity and refractive error

A
  • modes of inheritance: vary by study

- higher hertibilites in axial length and corneal power

47
Q

Studies of twins show high heritability in:

A
  • axial length
  • corneal power
  • refractive error
48
Q

Near Work Theory

A
  • Excessive reading during childhood causes abnormal eye growth , leading to myopia
  • increase in myopia prevalence in first school-educated Eskimos
  • decrease in myopia prevalence during WWII in Japan
  • adult onset myopia in college populations
  • excessive axial elongation and myopia is linked to schooling, studying, reading, and other near work
49
Q

Intelligence

A
  • myopes trend to have higher scores on tests of intelligence and cognitive ability and get better grades than other refractive error groups (even after factoring age trends)
  • hyperopes tend to show poorer reading skills and other perceptual anomalies more frequently
50
Q

Socioeconomic status

A
  • myopes tend to be over represented among the higher socioeconomic strata and underrepresented among the lower income levels
  • possibly due to connection between myopia, intelligence and education
51
Q

What percentage of adults are myopic?

A

25%

52
Q

Factors associated with refractive error

A
  • hereditary
  • near work
  • intelligence
  • socioeconomic

methods BLOCK 2 (8 decks)

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