Amblyopia - Visual Neurophysiology and Perception Spring 2026

functional vision loss in one or both eyes with no obvious ocular pathology

What is the definition of amblyopia?

developmental

Amblyopia is a ________ vision disorder

abnormal

Amblyopia results from a ______ visual experience

critical periods

Amblyopia is related tot he ____ for damage and treatment

-deprivation amblyopia

-refractive amblyopia

-strabismic amblyopia

What are the 3 types of amblyopia discussed in this class?

It will lose synaptic connections

If one eye is handicapped during the competition during visual development, what will happen to it?

exaggerated -- "the great land grab"

Dominance of the "good" eye becomes _____ during development, because of the successful competition over the "bad eye"

narrower

Ocular dominance columns responding to the deprived eye are (narrower/wider) because fewer cells respond to the deprived eye

by will timed reversal; "patching the good eye"

How can the non-responsiveness of the deprived eye be rescued?

vision loss d/t the visual deprivation of one or both eyes during the critical period

What is deprivation amblyopia?

-congenital cataract

-corneal opacification

-ptosis over the pupil

What are the possible causes of deprivation amblyopia in humans?

by suturing the eyelids shut or by rearing in the dark for binocular deprivation -- no signal through the eyelid

How has deprivation amblyopia been studied in animal models?

reverse suture (depriving the previously non-deprived eye)

_____ has been used as a model of patching therapy

Normal Human V1 v Deprived Human V1 (Pic)

Normal Human V1 v Deprived Human V1 (Pic)

**in the deprived human, the central retina is reduced & projection from the deprived eye is reduced. Black = good eye info. Extreme deprivation shown

Normal Ocular Dominance Columns in V1 (Pic)

Normal Ocular Dominance Columns in V1 (Pic)

**Width of black and white is symmetrical and similar

Deprivation During Critical Period v Deprivation After the Critical Period (Pic)

Deprivation During Critical Period v Deprivation After the Critical Period (Pic)

**deprivation during CP = massive land grab by the good eye; major deprivation of bad eye

After CP = less land grab; wiring not as changed

Goldilocks -- patching during the critical period is the "just right" time to create symmetrical dominance columns

Animal patching model runs into the ____ issue

Yes

Can an individual have deprivation in one or both eyes?

-surgical removal of the cataract ASAP

-effective optical correction

-aggressive patching

**use it or lose it

What is the treatment of deprivation?

true

True or False:

There is often a bad outcome from unilateral, congenital cataracts

VA Measurements after Cataract Removal in Children Born with Cataract & Who Develop Cataracts in Childhood (Pic)

VA Measurements after Cataract Removal in Children Born with Cataract & Who Develop Cataracts in Childhood (Pic)

Yes

Is the use it or lose it principle related to critical periods?

-Deprivation is most problematic if it happens early

-Early deprivation causes more issues if it is longer, but even short periods of deprivation produce damage

How is the use it or lose it principle related to critical periods?

true

True or False:

Treatment for deprivation amblyopia must occur for the right time and duration

-if too late or too brief, it is ineffective

-if too early and too long, you get reduced responses to signals arising in the fellow eye

What are the problems you can run into when trying to find the correct timing for treatment of deprivation amblyopia?

typically unequal refractive error between the eyes

In refractive amblyopes, what is typically seen?

steeper

RECALL: CSF is (steeper/flatter) with more blur

high

Loss of VA occurs at ____ spatial frequencies

high, middle

With more and more blur, the __ and ___ spatial frequencies will be affected

they pass unattenuated -- these channels develop normally

If stimuli in the visual field are blurred on the retina during the critical period, what happens to the low spatial frequencies?

reduced/eliminated -- these channels either never develop or are lost

If stimuli in the visual field are blurred on the retina during the critical period, what happens to the high spatial frequencies?

Normal Human CSF v CSF of Blurred Eye (Pic)

Normal Human CSF v CSF of Blurred Eye (Pic)

the low/middle frequencies -- the great land grab

If high spatial frequencies are lost d/t amblyopia & never develop, what will take over their synaptic connections in the striate cortex?

Yes

Will VA decrease in amblyopia d/t the loss of high spatial frequencies?

normal

Lowest spatial frequency channels are _____, because they are stimulated normally during the critical period

used

Receptive fields must be ____ if they are to be maintained

true

True or False:

If stimuli in the visual field DO NOT stimulate the receptive fields effectively, the cells tend to stop responding to the "intended" stimulus even if it is presented occasionally

anisometropic amblyopia

What is the MOST COMMON form of refractive amblyopia?

unequal refractive error between the 2 eyes

What is the problem in anisometropic amblyopia?

yes -- the 2 eyes do the same thing

Is accommodation symmetrical in anisometropic amblyopia?

generally, by the eye with smaller refractive error

Accommodation is controlled by which eye in anisometropic amblyopia?

chronic blur

Because the eye with the smaller refractive error will control the accommodation, the eye with the larger RE will experience what?

Anisometropic Amblyopia CSF (Pic)

Anisometropic Amblyopia CSF (Pic)

yes

Can you lose high AND med spatial frequencies with Anisometropic Amblyopia?

The Effect of Blur on the "Best Corrected" CSF in Monkeys (Pic)

The Effect of Blur on the "Best Corrected" CSF in Monkeys (Pic)

Drawings of Sine Waves by Patients with Refractive Amblyopia (Pic)

Drawings of Sine Waves by Patients with Refractive Amblyopia (Pic)

No -- both eyes receive low spatial frequency stimulation (blur throws away high spatial frequencies)

Is anisometropic amblyopia as severe/complete as monocular deprivation?

Hyperopes -- myopes can sometimes see in focus image depending on their refractive error.

Are myopes or hyperopes more prone to anisometropic amblyopia?

more -- the fellow eye is a strong competitor and land grabs connections that would normally be reserved to the blurred eye

Anisometropic amblyopia is (more/less) severe than binocular refractive error. Why?

-not a strong consensus on this subject

-you never want a child to experience anisometropia, at any age

-patients are more sensitive to damage under the age of 5

-critical periods for developing amblyopia and responding to treatment may be different

What is the best estimate of the "critical period" for human refractive amblyopia?

yes

Synaptic Pruning in V1 is particularly plastic and involves the loss of synapses. Is this when patching would be effective?

a vision loss in one eye caused by disordered correspondence between the distal stimulus and the cortical cells of the visual system (V1 and higher)

What is strabismic amblyopia?

abnormal visual experience d/t an eye turn that occurs during the critical period

What is strabismic amblyopia the result of?

-eye turn in infancy/early childhood

-more common for ET than XT

-concomitant anisometropia possible

What are common etiologies for strabismic amblyopia?

-eye turn of the affected eye

-reduced optotype acuity in the affected eye

-suppression of the affected eye during binocular viewing

-perceptual signs

-little or no stereo

What are common signs and symptoms of strabismic amblyopia?

Strabismic Sx During Critical Period (Pic)

Strabismic Sx During Critical Period (Pic)