Amblyopia Flashcards
what is amblyopia?
- loss of visual acuity in one or both eyes that cannot be improved by corrective lenses
- pathology is absent
- shows no potential of 20/20 vision
does a strabismus always indicate amblyopia?
-nope
decrease in VA for amblyopia is caused by…
- pattern vision deprivation
2. abnormal binocular interaction
can amblyopia be caused by reduced VA due to a disease?
nope
when should you be suspicious of amblyopia?
-loss of at least 2 lines of VA that is NOT caused by disease or correctable by refractive correction
amblyopia can cause (like 9 things)
- reduced VA
- dysfunction of accommodation
- poor eye alignment
- reduced contrast sensitivity
- bad spacial judgments
- poor resolution
- brain induces monovision
what percent of the population in the US has amblyopia?
2-4%
what is the critical period?
- the critical period ends around 8-10
- after this, it is really hard to correct it and you’re probably stuck
is amblyopia unilateral or bilateral?
can be either
why is it called the critical period?
- visual system is still developing so it can be molded
- neurological and sensory development of visual system is not impaired yet
during the critical period, what helps with the development of the visual system and visual potential?
- stimulation
- thats why treatment is better during the critical period
abnormal visual input result in what during and after the critical period?
during: blurred image, brain tries to fix it
after: blurred image, but not a halt to the sensory development of the visual system (brain is not moldable anymore)
what happens if you treat amblyopia TOO early?
-you can interrupt the emmetropization process and natural change their eyes can make
why does amblyopia occur? (in general with pathways and such)
-the visual pathway fails to develop properly due to inadequate stimulation, which could cause dissimilar images and binocular dysfunction
what are the two most common causes of amblyopia?
- strabismus(eyes not aligned on the target at the same time)
- anisometropia (difference in refractive error between eyes)
can a phoria cause amblyopia?
no!!!!!!!!!!!!!!!!!!!! because both eyes are working together with a phoria
what are the three types of refractive amblyopia?
- Meridional
- isoametropia
- anisometropia
what is meridional amblyopia?
-caused by uncorrected high astigmatism in one or both eyes
why can meridional amblyopia easily missed?
-because kids can squint and compensate
what is isoametropic amblyopia?
- caused by very high refractive error in BOTH eyes
- so high that a clear retinal image cannot be obtained
what change in VA is experienced with isoametropic amblyopia?
-bilateral decrease in VA (both eyes)
with a kid with high uncorrected hyperopia in both eyes, should you immediately expect him to get to 20/20 corrected vision?
-nope. initially VA will stay reduced in both eyes
high hyperopia can SOMETIMES cause what kind of deviation?
esotropia
a 4 year old with high hyperopia hasn’t started school yet, will you/ they notice an eye deviation?
- nope
- they have had no motivation to accommodate or focus, so there is not strabismus yet
what is the most common type of amblyopia?
anisometropi amblyopia
what is anisometropic amblyopia?
- normal refractive error with good VA in one eye
- high refractive error with reduced VA in the other
what are some common signals a kid can give to signify anisometropic amblyopia?
- thats my bad eye
- that eye never sees well
what are 5 things that are not good practice that can allow a doctor to miss amblyopia?
- VA with both eyes open
- not making sure each eye is properly covered when checking VA
- skipping parts of the exam
- assume kids cannot have visual impairments
- not checking history
if you suspect anisometropic amblyopia?
- VA
- Stereo
- retinoscopy
- ophthalmoscopy
- HISTORY
- pupils
in a properly functioning visual pathway, what responds to high spatial frequency stimulation?
-parvocellular layers of the lateral guniculate nucleus
the effect of blur on the visual pathway are highest when?
-critical period
what is hyperopic anisometropia?
- amblyopia resulting from a difference of hyperopia between the eyes
- common
what is the least amount of difference between the eyes that can cause amblyopia?
1 diopter
what kind of tropia can be developed as a side effect of hyperopic anisometropia?
esotropia
aside from VA, what two things are likely to be affected by hyperopic anisometropia?
- stero
- worth 4 dot (could show fusion depending on severity, could pick up scotoma)
what is myopic anisometropia?
-high UNILATERAL myopia in one eye and with lesser myopia in the other
what is staphyloma?
-out patching of the retina, eye is larger, could explain high myopia
why is amblyopia NOT likely to develop with moderate myopic anisomeptroia (OD -0.75, OS -3.25)?
- one eye can focus at near and one can focus at distance
- since both eyes have a point of pure focus, the brain does not try to change it
what is form deprivation?
- obstruction of the line of sight that prevents a clear image to form on the retina
- can occur in one or both eyes
name some physical obstructions than can lead to amblyopia?
- congenital cataracts
- ptosis
- traumatic cataracts
- corneal opacity
- vitreous hemorrhage (shaken baby syndrome)
which entrance test determines the presence of strabismus?
cover test
what is a strabismus?
-visual axes of both eyes do not intersect at fixation
what are the three types of strabismus?
- early onset
- accommodative strabismus
- trauma or systemic disease (acquired)
strabismus is classified by which eye?
-the non fixating eye
what are three things you should make sure you get covered in history when diagnosing a strabismus?
- occlusion therapy
- refractive correction
- surgeries
the ______ time there is _________________ before strabismic disruption, the _______ the chances that binocularity can be reestablished
the MORE time there is EQUAL VISUAL ACUITY AND BINOCULARITY before strabismic disruption, the BETTER the chances that binocularity can be reestablished
name 3 sensory adaptations
- amblyopia
- scotoma/supression
- anomalous correspondence
stereopsis implies what?
-better prognosis
strabismus prognosis is WORSE with what 3 things?
- ESOtropia
- anomalous correspondence
- CONSTANT unilateral strabismus
strabismic amblyopia causes what?
- spacial uncertainty and difficulty with localization WHICH CAUSES…
- monocular adaptations
- anomalous correspondence
- weird oculomotor behaviors
what are signs of spatial uncertainty?
- patients read out of order or drop letters, after likely correctly identifying the first and last ones
- poor stereo
- eccentric fixation
which eye is at risk of injury with strabismic amblyopia?
-the non amblyopic eye
what is eccentric fixation?
- an eccentric point assumes the role of the fovea and becomes the straight ahead where the visual axes starts (focus somewhere other than the fovea)
- VA is reduced with eccentric non-foveal point
what type of strabismus is MORE likely to cause amblyopia?
-constant unilateral strabismus is more likely to result in amblyopia than intermittent or alternating strabismus
the later the onset of strabismus,
the better chance of reestablishing binocularity
-because the patient already had binocularity, easier to get it back
what are the three amblyopic treatments
- optical treatment
- occlusion therapy
- vision therapy
what is the first treatment you should USUALLY do for ambyopia?
optical treatment
-treat refractive error
why should you have a patient with a deviated eye close one eye when you do ret?
-the ret will be done off axis and can give you the wrong refractive correction
what is the method of choice to determine refractive error in children?
cyclo refraction
optical correction is done with ___________
glasses or contacts
why is the amblyopic eye not able to respond well in subjective refraction?
-the amblyopic eye is insensitive to the small changes to discriminate during subjective refraction
why use cyclo?
-it completely relaxes the accommodation to help give the best objective refraction
how much correction should you prescribe?
it depends on the case and other relevant information
what is the goal of optical treatment?
- create a clear retinal image for each eye to allow binocularity
- stop the amblyogenic process
why should you start with refractive correction before other treatments?
- allow kid to adapt to Rx
- you can determine the amount of clarity gained by correction only
- allows you to see how aggressive you have to be
when should you have them come back after giving them refractive correction?
-3-4 months
when should you only issue a partial Rx?
-if hyperopic anisometropic amblyobia is present WITHOUT esotropia
when should you issue a full Rx?
-when esotropia is present
what eye should be patched in occlusion therapy?
- the good eye
- force the bad eye to work
occlusion can be done with what two methods?
- occlude good eye
- put atropine in good eye
what are side effects of anticholinergics?
- hot
- dry
- cant see
- flush skin
- mad as a hatter
what are some concerns with occulsion therapy?
- compliance
- development of strabismus
- occlusion amblyopia
what is vision therapy?
-visual tasks and procedures to improve vision
optical correctin is to improve_________ while vision therapy is to improve___________
- vision
- vision efficiency
does vision therapy replace optical correction?
NO!
-it augments it!
what are the treatment trends for treating strabismic amblyopia?
- refractive correction
- reevaulate VA and binocularity
- occlusion therapy
- vision therapy
- surgery
should you do surgery for accommodative esotropia?
-IF IT IS PURELY ACCOMMODATIVE, DO NOT DO SURGERY
