Flashcards in Emmetropization Mechanism Deck (22)
what are some risk vision-threatening conditions to myopia?
RD, macular holes, cataract surgery complications
what kind of eye turn are hyperopes at risk for
what are some associated eye disease w/ hyperopia
1. narrow angle glaucoma
2. higher incidence AMD
3. higher incidence diabetic retinopathy
4. higher incidence non-arteritic ant ischemic optic neuropathy
what is emmetropization
mechanism whereby eye grows to match its optical components to end in emmetropia
early premature infants are usually myopic or hyperopic?
what about full--term babies? why?
premature infants usually MYOPIC
full term birth lens is flatter and vitreous chamber is longer so neonates tend to be HYPEROPIC
what curve supports emmetropization as an active process?
what are children distributed towards? what about young adults?
in the study with rhesus monkey, they sutured one eyelid. what happened to the normally reared eye? what about when an eye was covered?
normally-reared eye: perfect focus
covered eye-grows too long, myopia
what are the 2 different animal models
1. form-deprivation: lid suture, frosted/translucent lenses
in the animal models...model of eye compensation for lens-induced Rx:
the eye compensates for + and - lenses. what happened for each lens
+: slow growth rate and thickening choroid
-: increasing rate of elongation and thinning choroid, pulling retina back towards image plane
what are some ways that myopia can be induced in infants by continuous visual deprivatoin or blur during critical period?
1. mechanical ptosis ...ex from hemangioma
2. congenital catarcts
waht is the default condition to a visually deprived eye?
to grow too long=> myopia
-lacks control mech to slow eye growth
-disruption of visual feedback causes myopia
in epidemiological studies, what suggests environmental etiology?
rapid increase prevalence over one generation
ex. myopic epidemic in east asia
if there is not adequate visual input, what happens to the eye
eye grows too much
what are risk factors for myopia
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
6. oculomotor factors (accomdation inaccuracies)
what is the blur hypothesis
continuous blur at retina, or inability to appropriately use blue cues, signal that disrupts normal emmetropization process and leads to myopia
what aspect of image structure are relevant to the blur hypothesis
energy at mid/high spatial frequencies
what are the implications for treatment: "blur hypothesis"
focus of eye destined to develop myopia-significant LAG at near
what is the correction of myopia evaluation trial (COMET)
Do PALs slow rate of myopia progression compared to conventional single vision lenses?
large, multicenter, randomized, double-masked clinical trial
results: children w/ near esophoria and high AC/A benefited most from PALs
signaling cascades link retinal image processing to scleral growth in myopia through...
astigmatism increaes more in children who....
-are becoming myopic
-had more astig during infancy
-had ATR astig during infancy
astig is ____ in infants
_____ in childhood
______ in teenagers who are becoming mypia
-associted w/ _____
-_____ in older adults