Emmetropization Mechanism

Question 1

what are some risk vision-threatening conditions to myopia?

Answer 1

POAG, CNV

RD, macular holes, cataract surgery complications

Question 2

what kind of eye turn are hyperopes at risk for

Answer 2

ET

Question 3

what are some associated eye disease w/ hyperopia

Answer 3

1. narrow angle glaucoma
2. higher incidence AMD
3. higher incidence diabetic retinopathy
4. higher incidence non-arteritic ant ischemic optic neuropathy

Question 4

what is emmetropization

Answer 4

mechanism whereby eye grows to match its optical components to end in emmetropia

Question 5

early premature infants are usually myopic or hyperopic?

what about full–term babies? why?

Answer 5

premature infants usually MYOPIC

full term birth lens is flatter and vitreous chamber is longer so neonates tend to be HYPEROPIC

Question 6

what curve supports emmetropization as an active process?

what are children distributed towards? what about young adults?

Answer 6

leptokurtic curves

children-hyperopia
young adults-myopia

Question 7

in the study with rhesus monkey, they sutured one eyelid. what happened to the normally reared eye? what about when an eye was covered?

Answer 7

normally-reared eye: perfect focus

covered eye-grows too long, myopia

Question 8

what are the 2 different animal models

Answer 8

1. form-deprivation: lid suture, frosted/translucent lenses

2. lens-induced

Question 9

in the animal models…model of eye compensation for lens-induced Rx:
the eye compensates for + and - lenses. what happened for each lens

Answer 9

+: slow growth rate and thickening choroid

-: increasing rate of elongation and thinning choroid, pulling retina back towards image plane

Question 10

what are some ways that myopia can be induced in infants by continuous visual deprivatoin or blur during critical period?

Answer 10

1. mechanical ptosis …ex from hemangioma

2. congenital catarcts

Question 11

waht is the default condition to a visually deprived eye?

Answer 11

to grow too long=> myopia

• lacks control mech to slow eye growth
• disruption of visual feedback causes myopia

Question 12

in epidemiological studies, what suggests environmental etiology?

Answer 12

rapid increase prevalence over one generation

ex. myopic epidemic in east asia

Question 13

if there is not adequate visual input, what happens to the eye

Answer 13

eye grows too much

Question 14

what are risk factors for myopia

Answer 14

1. age of onset: amount and progression of myopia. refraction at age 6 years
2. parental myopia: 2 vs 1 parent
3. race (asian > europ> african american > hispanic
4. environment (near work: blur hypothesis, outdoor time, light exposure, urban/rural, educatoin
5. oculomotor factors (accomdation inaccuracies)

Question 15

what is the blur hypothesis

Answer 15

continuous blur at retina, or inability to appropriately use blue cues, signal that disrupts normal emmetropization process and leads to myopia

Question 16

what aspect of image structure are relevant to the blur hypothesis

Answer 16

energy at mid/high spatial frequencies

Question 17

what are the implications for treatment: “blur hypothesis”

Answer 17

focus of eye destined to develop myopia-significant LAG at near

Question 18

what is the correction of myopia evaluation trial (COMET)

Do PALs slow rate of myopia progression compared to conventional single vision lenses?

Answer 18

large, multicenter, randomized, double-masked clinical trial

results: children w/ near esophoria and high AC/A benefited most from PALs

Question 19

signaling cascades link retinal image processing to scleral growth in myopia through…

Answer 19

dopamine pathway

Question 20

astigmatism increaes more in children who….

Answer 20

• are becoming myopic
• had more astig during infancy
• had ATR astig during infancy

Question 21

astig is \_\_\_\_ in infants
\_\_\_\_\_ in childhood
\_\_\_\_\_\_ in teenagers who are becoming mypia
-associted w/ \_\_\_\_\_
-\_\_\_\_\_ in older adults

Answer 21

higher
decreaes
increases
myopia
increaes

Question 22

what is the primary consequence of changes in protein content crystalline lens

Answer 22

lack of flexibility