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PPO 1b > Epidemiology > Flashcards

Epidemiology Flashcards

1
Q

what is refractive error determined by

A
  1. optical components of the eye
    - cornea
    - lens
  2. axial length
    - determined primarily by the post chamber
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2
Q

what is too long in the eye that causes myopia

A

post. chamber

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3
Q

what is with the rule

  • for K’s?
  • for Rx’s?
A

K: more power in the vertical meridian
Rx: axis 180 + or - 30 (if minus cyl)

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4
Q

for against the rule

  • for K’s?
  • for Rx’s?
A

K: more power in the horizontal meridian
R: axis 90 + or - 30 (if minus cyl)

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5
Q

what is oblique (least comon)

  • K’s?
  • Rx’s?
A

K: meridians > 30 away from 90 or 180
Rx: axis 30-60 or 120-150

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6
Q

what is anisometropia

A

different refractive error btwn the two eyes

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7
Q

what is presbyopia, what changes?

-onset at what age

A

changes in the crystalline lens occur w/ again => lose ability to accomodate
-onset around 40 years

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8
Q

what is primary refractive error

A
  • etiology is multifactoria (visual input, genes, environment)
  • more refractive errors are primary
  • we focus on today
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9
Q

what is secondary refractive error

A
  • we can identify a specific cause
  • often deviate from what is predicted by epidemiology and natural history
  • disease, pharmacological, mechanical process that changes axial length or refracting power of cornea or lens
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10
Q

what is epidemiology

A

the study of the patterns, cuases, and effects of health and disease conditoins in defined populations
-natural history, changes or progression of conditoin over time

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11
Q

uncorrected refractive error is a leading cause of what?

  • how many indiv affected worldwide
  • how many children
  • accounts for how many % visual impairments
A

correctable visual impairment worldwide

  • 98-200 million indiv affected worldwide
  • ~13 million children 5-15 y/o are affected worldwide
  • accounts for 5.3% of visual impariments in the US
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12
Q

myopia has high increasing prevalence

  • in the US
  • pop of East Asia
  • differences in prevalence with what?
A

> 25% in US
80% some populations of East Asia
-w/ race, gender, age, geographic location, rural/cities

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13
Q

what are the risk factors for vision-threatening conditions

myopic degeneration is what cause of vision impairment?

A

glaucoma, retinal detachment, maculopathy, retinoapthy

-2nd cause of vision impairment in HK

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14
Q

hyperopia affects how many % of children at 1 year old?

A

4%

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15
Q

infants w/ high hyperopia are up to how many times more likely to develop strabismus by 4 years of age?

  • how many times more likely to have reduced visual acuity
  • what is the leading cause of amblyopia
A

13x
6x
anisometropic hyperopia (~2/3 of children w/ strabismus or amblyopia have > 1.00D of anisometropia)

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16
Q

what is needed for emmetropization

A

ability of the eye to adjust its growth during development to acheive emmetropia
-optical componenets balance axial length

visually guided, active process that uses visual feedback to regulate eye growth (genetic and environmental factors)

17
Q

what is the mean refraction for normal full term infants

A

+2.00D

18
Q

when is astigmatism greatest

A

during first 6 mos and decreases thereafter
>1.00 of astig is common in infants and toddlers
axis is quite variable

19
Q

mild anisometropia of what is common in infants?

likely to presisnt into childhood if anisometropia is what?

A

1.00D

3D

20
Q

in premature infants, what are they more liekely to have

A

retinopathy of prematurity and myopia (high), astig and anisometropia
-emme tends to be disrupted if low birth birth weight

21
Q

what is the mean for toddlers and preschoolers (3-5 yrs)

A

mean is slightly hyperopic

22
Q

when does astig decrease most significantly

A

during the first 2 years and stabilizes by 3-4 years

-shifts in axis are common

23
Q

at age 5-6:
around 80% have how much of astig?
transition to waht?

A
  1. 25D of astig
    - transition to mostly emmetropic (+-.75)
    - 80% btwn 0.50 and 3.00
24
Q

at age 6-20

  • what do some develop
  • what stablizes or decreases
  • if < 0.75 hyperopic at 6 eras, what happens
  • if > 1.0 hyperopic at 6 years, what happens
A 
childhood myopia
hyperopia 
myopic 
remian hyperopic for life
-astig stable in hyperopes 
-may revert to infantile astig in myopes; asit stabilizes when myopia stabilizes
25
Q

what does myopia typically progress by each year in childhood myopia
-the earlier the onset…..

A
  • 0.50D per year
  • progession more rapid during school months

the higher amount of myopic reached

26
Q

when is refractive error usually stable

A

~20+ years

27
Q

what are the two forms that young adult (18-20 years) onsent myopia progression can take

A
  1. further progression of juvenile onset myopia

2. new incidence of low myopia

28
Q

around 25-60 years rx is stable w/ the following exceptions…

A

age ~25 years: hyperopia stable, but more becomes ‘absolute’ or ‘manifest’ due to decreasing ability to acommodate
-pseudomyopia will decrease

age 40+ years

  • prebyopia begins
  • absolute presbyopia by ~65 years
29
Q

at ~ 60 years of age you may have stable refractive error or …

A

changes in refractive error that are secondary to nuclear sclerosis of the crystallin lens

  • seondary refractive errors: myopic shift-second sight bc pt can see at near more easily (senile myopia)
  • increase in ATR astig in some indiv
30
Q

what are teh 3 different kinds of amblyopia

A
  1. refractive
  2. strabismic - constant unilateral strabismus
  3. deprivation-lack of visual input to one or both eyes
31
Q

amblyopia develops only if when?

A

risk factors are present and uncorrected during the critical period (first 5-6 years of life)

32
Q

what is isoametropia

for astig, hyperopia, and myopia

A

same refractive error in both eyes
astig > 2.5D
hyperopia > 5.00D
myopia > 8.00D

33
Q

what is anisometropia

for astig, hyperopia, and myopia

A

different refractive error btwn eyes
astig > 1.5
hyperopia > 1.00D
myopia > 3.00

PPO 1b (11 decks)

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