DEVELOPMENT OF THE AMETROPIAS Flashcards
Higher degrees of _____ in premature infants (especially with very low birth weights
myopia
5 or 6 year old children with +1.50 D or more ______ will still be that at age 13 or 14
hyperopia
Majority of 5 or 6 year olds with refractive error of +0.50 to +1.24 D will be _____(-0.49 to +0.99 D) at age 13 or 14
emmetropic
Most children entering school with refractive errors of 0 to +0.49 D will be _____ at age 13 or 14
myopic
Children who are myopic at age 5 or 6 will become _____ myopic
more
Changes in Hyperopes Compared with Myopes
Among school-aged children, greatest changes in refractive error occurred in
myopes
Changes in Hyperopes Compared with Myopes
Refractive change is _____ when a child crosses from hyperopia into myopia.
faster
Four types of myopia
Congenital
Youth-onset
Early adult-onset
Late adult-onset
Axial Elongation of _____ chamber is responsible for myopia progression
vitreous chamber
Emmetropic children between age 6 and 14 years old show:
Increase in axial length
Decrease in crystalline lens thickness
Decrease in crystalline lens power
Myopic Young Adults:
Greater _____ depth
_____ corneal power
Greater posterior crystalline lens _____
Greater vitreous depth
Greater corneal power
Greater posterior crystalline lens radius
School-aged and Young Adult Females
Shorter eyes
Steeper corneas
More powerful crystalline lenses
The earlier in life the onset of myopia occurs, the ____ the amount of myopia developed by late teens to young adulthood
greater
Higher rate of childhood myopia _______ is associated with earlier onset of myopia
PROGRESSION
How does astigmatism effect the rate of myopia progression?
Children with ATR at 5 or 6 years of age developed myopia by 13 or 14 years of age vs. those without astigmatism or WTR (not found in other studies)
Once myopic, ATR astigmats do not have greater rates of childhood myopia progression
What are factors associated with higher rates of childhood myopia progression?
Earlier onset age and/or higher initial amount of myopia
Near-point esophoria
Temporal crescents and other myopic fundus changes
Higher intraocular pressure
Greater amount of time spent reading and doing near work
Less time spent on outdoor activities
What are drops for myopia to slow down its progression?
Atropine and Pirenzepine
What type of contact lens can control myopia?
Rigid contact lenses
Bifocal spectacle lenses can help control myopia. How?
These lenses provide different refractive correction for distance and near.
What is most effective in lowering myopia progression rates for children with esophoria at near?
Bifocal spectacle lenses
Want a near addition power to shift near phoria to ortho / low exo range.
What is another type of lens used for myopia control?
Progressive-addition Spectacle Lenses (PALs)
5 to 6 year olds with _____ more likely to become myopic than those with ______.
5 to 6 year olds with ATR more likely to become myopic than those with WTR
General Trends (Late teens or early 20s to ~40 years old)
Refractive error stabilizes
Some have:
Onset of myopia
Progression of myopia
Small shift in the hyperopic direction
What is adult stabilization?
Adult Stabilization: childhood myopia progression is followed by stabilization of refractive error in young adulthood
What is adult continuation?
Adult Continuation: childhood myopia progression followed by a general slower progression of myopia in young adulthood
What is adult acceleration?
Adult Acceleration: refractive change in the myopic direction accelerates in young adulthood
Adults with increases in myopia tend to have _____ in corneal power
Adults with increases in myopia tend to have increases in corneal power.
What is it when Refractive Power Decreases (from decrease in crystalline lens power and decrease in corneal power)?
Hyperopia
It is unlikely for entering college student with ≥ +1.00 D (_________) in either principal meridian will be myopic after 4 years of school
noncycloplegic refraction
After Age 45:
Shift in ______ direction
Some myopes increase in myopia
Age-related Nuclear Cataracts shift towards myopia
hyperopic
Trend Toward Hyperopia
After 40, there is a trend of what kind of astigmatism?
Trend Toward Against-the-Rule Astigmatism
Axial Length greater in:
neonatal eyelid closure
juvenile corneal opacification
congenital cataracts
What are some causes of high myopia?
- lid hemangiomas
- ptosis
- neonatal eyelid closure
- retrolental fibroplasia associated with retinopathy of prematurity, vitreous hemorrhage In infants and children
Prevailing Theories of Myopia Development:
- Mechanical forces on the sclera
- Retinal Defocus
- Retinal Biochemistry
What are mechanical forces on the sclera?
Tension from Extraocular Muscles and Intraocular Pressure –> axial elongation
Could possibly be a cause of myopia.
What is retinal defocus?
Defocus itself alters axial length (not the mechanism of accommodation)
Could possibly be a cause of myopia.
What is retinal biochemistry?
Biochemical agents affect the function of retinal synapses.
Some studies show that this stops myopia, others show that these molecules induce myopia
What is a possible cause of astigmatism?
Eyelid tension steepens the vertical corneal meridian and causes WTR.
- Corneal WTR astigmatism decreases when eyelids lifted from eye
- Corneal WTR astigmatism increases when palpebral aperture (conjunctiva) is narrowed
- Shift towards ATR in over 40 years of age is due to decreased lid tension
