Amblyopia Flashcards
Broadly define amblyopia
A functional loss of vision NOT attributed to pathology.
What is the layman’s term for amblyopia?
“lazy eye”
Up to what age does amblyopia usually develop?
Up to age 6-8
Once amblyopia develops, how long may it persist?
May persist for LIFE once established.
Oversimplified mechanism of action for amblyopia:
- Brain receives ____ image(s)
- Brain wants ___ image(s)
- Eye with _____ picture ____
- Eye with _____ picture ____
Oversimplified mechanism of action for amblyopia:
- Brain receives TWO image(s)
- Brain wants ONE clear image(s)
- Eye with BEST picture WINS
- Eye with WORST picture TURNS OFF
Amblyopia leads to problems with ______ vision
binocular
Precise definition of amblyopia
Reduction in VA to 20/30 or worse in one eye or a two line difference between two eyes in the absence of pathology and with best refractive correction.
Three main causes of amblyopia
- Form deprivation
- Optical defocus/refractive
- Strabismus
(4. Any combo of the above)
Define form deprivation
Physical obstruction along the line of sight
What are three examples of form deprivation
- Congenital cataracts; congenital ptosis
- traumatic cataracts
- Corneal opacities
Results of form deprivation
Prevents a clear, sharp image from reaching the retina
For form deprivation to cause amblyopia, what age does it usually have to occur by?
Usually occurs before age 8 to cause amblyopia.
Degree to which amblyopia develops from form deprivation depends on what two things?
Depends on the
- time of onset
- extent of the form deprivation
What are the 3 main categories of refractive amblyopia?
- Anisometropia
- Meridional
- Isoametropia
Define anisometropia
An unequal refractive error between the two eyes, usually more than 1 diopter difference
The TYPE of refractive error effects the ____ of amblyopia.
severity
Characteristics of refractive amblyopia:
Myopia OU:
- Type of refractive amblyopia
- Can tolerate a ____ amount of aniso w/o reduction in VA
- Pt will use (both/one) eye(s) at all distances
- How many diopters is needed for pt to experience an amblyopia?
- anisometropia
- large
- both
ex. OD -2.50D (see fine at near)
OS -1.00D (see fine at near and OK at distance) - 5.00D
Characteristics of refractive amblyopia:
Hyperopia OU:
- Type of refractive amblyopia
- Amblyopia will occur _____
- Pt will use (both/one) eye(s) at all distances
- How many diopters is needed for pt to experience an amblyopia?
- anisometropia
- sooner
- one eye (with the least plus)
ex. OD +2.00D (blurry at D & N)
OS +1.00D (clear at D & N) - 1.00D
A general rule for amblyopia is that the more severe the ____, the more severe the ____, and the worse the ___.
- anisometropia
- ablyopia
- visual acuity
Characteristics of refractive amblyopia:
Uncorrected high astigmatism OU
- Type of refractive amblyopia
- Patient’s image will be clear at (distance, near, neither)
- How many diopters is needed for pt to experience an amblyopia?
- meridional
- Neither distance or near will be clear
ex. OD plo, -3.00 x180 (blurry D & N)
OS plo, -3.00 x180 (blurry D & N) - at least 1.50D to 2.00D of uncorrected astigmatism
Define isoametropia
High degrees of ametropia in both eyes, usually 20/40-20/50.
Isoametropia usually associated with hyperopia more than ____ diopters and myopia more than ____ diopters in ___ eye(s).
- 5.00D
- 8.00D
- both
ex. OD +6.00D (blurry D & N)
OS +6.50D (blurry D & N)
Stabismic amblyopia usually attributed to…
an early onset CONSTANT unilateral strabismus
As a result of strabismic amblyopia, what happens to the two images as they are being processed by the brain?
The two images are NOT fused
Too confusing for the brain
What does the brain do to reduce the confusion caused by strabismic amblyopia?
The brain will “switch off” one eye
Which of the 3 causes of amblyopia is the most common?
Constant eye turn is the most common cause of amblyopia
Will an intermittent eye turn lead to amblyopia?
It may lead to a less severe amblyopia or no amblyopia at all
Is it important to screen for amblyopia?
Important to diagnose it early in children because it is treatable and preventable especially if detected early
What are some tests used to diagnose amblyopia? 1. 2. 3. 4.
- Visual acuity; watch your patient carefully
- Plus lens test
- Cover test
- Stereopsis
When left untreated, amblyopia can result in 1. 2. 3. 4.
- reduced stereopsis
- occupational exclusions (pilot, police, military, etc)
- reduced visual performance (driving, eye-hand coordination, etc)
- Lack of a “reserve” or “backup” eye
If children with amblyopia are treated before age __, they may be able to recover most of their vision .
age 5
When treating amblyopia _____ alone will improve the VA in about 25% of the patients.
optical correction
