Binocular Vision: Lecture 19: Abnormal Binocular Vision Development

Question 1

1. In Monkeys, what is the Critical Period for Spectral Sensitivity (Luminosity) Functions?
   a. What about for Spatial Vision?
   b. And For Binocular Vision?

Answer 1

1. 3-6 months
   a. 25 months
   b. longer than 25 months

Question 2

Visual Deprivation

1. Deprivation is more likely to disrupt functions whose critical periods are LONG LASTING, Like what 2?
   a. It is less likely to affect functions whose critical period is short and completed early in infancy, like what?
2. Which cells develop more slowly: Small, High-spatial-frequency-specific neurons responsible for VA, or Larger, low-spatial-frequency-tuned cells?
   a. Which ones are more susceptible to the effects of Deprivation, which leads to REDUCTIONS in what?

Answer 2

1. Spatial Vision and Binocularity
   a. Color Vision
2. Small, High-spatial-frequency-specific neurons responsible for VA
   a. in Spatial Resolution

Question 3

Amblyopia

1. What is it?
2. What is it defined as?

Answer 3

1. Abnormal Visual Development of Spatial Vision

2. Reduced VA in one eye below 20/40, with at least 2 line difference in Acuity (Not a precise Definition)

Question 4

What 5 Types of Amblyopia are there?

Answer 4

1. Strabismic
2. Anisometropic
3. Refractive
4. Stimulus
5. Meridional

Question 5

Strabismic Amblyopia

1. What is it?
2. Is it Uni/Bi?
   a. Is it a Constant thing?
3. Who is at 4-6x’s Greater risk of development of Strabismus AND Amblyopia?

Answer 5

1. Amblyopia that’s associated w/the presence of Strabismus, usually either ESOtropia or EXOtropia
2. Unilateral
   a. Constant. (1 good eye and 1 Amblyopic Eye)
3. Pre-Mature and Low-Birth Weight Infants

Question 6

1. What is ANISOMETROPIC AMBLYOPIA Caused by?
   a. 1 Eye tends to be favored and takes up the role of what?
   b. What does the other eye do?
2. REFRACTIVE AMBLYOPIA
   a. the 2 eyes may have equal refractive errors, but they can have 1 of 2 things?
   b. AKA?

Answer 6

1. Significant, Unequal Refractive Errors b/w the 2 eyes.
   a. of Controlling the Degree of accommodation
   b. The other eye, because of Consensual Accommodation, has a CONSTANTLY DEFOCUSED RETINAL IMAGE
2. a. can be EXTREMELY MYOPIC (more than -6D to -9D) or HYPEROPIC (more than +4D)
   b. BILATERAL AMBLYOPIA

Question 7

Accommodative Esotropia and Amblyopia

1. If you fully correct a High refractive error during infancy may disrupt what?
2. The infant must be provided with what to prevent further form deprivation?
   a. They also have to start reversing the effects of what?
3. What reflects the severity of the Amblyopia?

Answer 7

1. the EMMETROPIZATION process cuz it removes the image blur that acts as a FEEDBACK MECHANISM for Eye Growth
2. a Sharp Retinal Image
   a. of the Deprivation and start Equalizing the function of the 2 eyes
3. The Contrast Sensitivity Function of a Strabismic or Anisometropic Amblyopic Eye.

Question 8

Accommodative Esotropia and Amlyopia

1. DEEPER Amblyopia results in Losses in Sensitivities across what frequencies?
   a. But it’s more pronounced at what Spatial frequencies?
2. In the MOST SEVERE CASES of AMBLYOPIA, what Deficit is “Marked”?
   a. The patient can barely see what with the Amblyopic Eye?

Answer 8

1. at ALL Frequencies
   a. At Higher Spatial Frequencies
2. the Contrast-Processing Deficit is Marked.
   a. can barely see Contours at all

Question 9

Strabismic vs. Anisometropic Amblyopia

1. What 2 things are affected to different degrees in strabismic and anisometropic Amblyopes?
2. Who has MORE SEVERE SPATIAL DISTORTION: Strabismic or Anisometropic Amblyopes?
   a. This is due to the DISORGANIZATION of what?

Answer 9

1. Contrast Sensitivity and Hyperacuity
2. Strabismic Amblyopes
   a. of Retinotopic Mapping

Question 10

Spatial Undersampling

1. If receptive fields are too coarsely spaced to adequately sample a HIGH-Spatial-Frequency Retinal Image (Image is undersampled by the receptive fields), then what occurs?

Answer 10

1. SPATIAL ALIASING (false low frequencies are introduced into the representation of that image) and it DISTORTS the REPRESENTATION of that image.

Question 11

Strabismic Amblyopia

1. In STRABISMIC AMBLYOPES, what is AFFECTED to a LESSER DEGREE than Snellen Acuity?
   a. Why?
2. What about in Anisometropic Amblyopia?
3. Why the difference b/w Strabismic and Anisometropic Amblyopes?

Answer 11

1. GRATING ACUITY
   a. Because as a Homogenous, repetitive stimulus pattern, the GRATING remains DETECTABLE despite the distortions that make Snellen letters indistinguishable.
2. Snellen and Grating Acuity are DEGRADED EQUALLY
3. Because Strabismic Amblyopes just don’t have problems resolving high spatial frequencies and detecting low contrast like Anisometropic Amblyopes do.

Question 12

Strabismic Amblyopia (2)

1. In strabismic amblyopia, the REDUCTION in CONTRAST SENSITIVITY is limited to what area?
   a. This is the region at which what exists?
2. What about in Anisometropic Amblyopia?
3. Spatial distortions coupled with eye movement problems in Amblyopes makes them perceive certain parts of the visual space to be doing what?

Answer 12

1. to the CENTRAL VISUAL FIELD
   a. their suppression scotoma exists
2. Contrast-Processing deficit persists thru the ENTIRE VISUAL FIELD, even in the retinal periphery
3. to be Changing Shape and Position.

Question 13

Amblyopia

1. What 6 Things ARE NOT AFFECTED by Amblyopia?
2. Is Amblyopia Retinal in origin?
   a. Critical Period for these effects (the 6 listed above) are what?

Answer 13

1. Color Vision, Dark Adaptation, Glare Recovery, Scotopic and Photopic Luminosity Functions, and Temporal Vision
2. NO.
   a. are SHORTER and HAPPEN EARLY

Question 14

Amblyopia

1. Patients with STRABISMIC AMBLYOPIA will also Experience what?
   a. This is manifested clinically by what?
2. In order to minimize crowding effects, acuity in amblyopes is also measured with what?

Answer 14

1. CROWDING EFFECT (neighboring contours interfere w/the Visibility of the Target Stimulus)
   a. by Differences in VA determined by Single-letter, Whole-line, and Whole-chart Presentations
2. with ISOLATED SINGLE LETTERS on the SNELLEN CHART

Question 15

Amblyopia

1. What type of Amblyopia happens in pts with a CONSTANT OBSTRUCTION in the image formation mechanism of the eye, like CONGENITAL or TRAUMATIC CATARACTS, Congenital ptosis, or Congenital or Traumatic Corneal Opacities that were left UNTREATED for some time?
   a. these things are known as what?
2. You may not be able to cure a given amblyope, but what can HELP stabilize their eye movements, improve their Accommodative Skills, and REDUCE spatial misperceptions, so the Pt can achieve the BEST possible acuity that the amblyopic eye can get?

Answer 15

1. STIMULUS DEPRIVATION AMBLYOPIA
   a. PATTERN DEPRIVATION
2. VISION THERAPY!

Question 16

Amblyopia

1. Different from other types of Amblyopia, what type can cause PROFOUND Loss of Acuity, Abnormalities of Light Sensitivity and Color vision?
2. What kind of Amblyopia is this: An infant w/a VERY HIGH ASTIGMATISM (1 meridian blurred and the orthogonal meridian in focus), which can produce an Amblyopia Along the BLURRED ASTIGMATIC MERIDIAN only, even with Full Astigmatic Correction Later in Life?

Answer 16

1. STIMULUS DEPRIVED AMBLYOPES

2. MERIDIONAL AMBLYOPIA

Question 17

Amblyopia

1. A Child with MERIDIONAL AMBLYOPIA will show what?
2. Amblyopes EXHIBIT what?
3. Amblyopes demonstrate what?

Answer 17

1. much lower acuities and Contrast sensitivities for targets in that orientation as compared w/other orientations (e.g.: E vs. V)
2. Eccentric Fixation
3. Abnormal Stereopsis: (either they Lack stereoscopic Vision (stereoblindness) or possess only Residual Stereopsis (due to Image Inequality)

Question 18

Amblyopia

1. Suppression Scotoma may produce Loss of what?
2. Alternating Strabismus without Amblyopia could produce what?

Answer 18

1. of Local Stereopsis

2. Binocular Stereo Deficits

Question 19

Amblyopia

1. During development of Binocular Vision, there’s a Simultaneous Development of what?
   a. The ability to see stereomotion in a direction toward or away from you develops CONCURRENTLY with the ability to make what?

Answer 19

1. of Correlated Eye Movements

a. to make BALANCED Binasal and Bitemporal Optokinetic Nystagmus (OKN) and Pursuit Eye Movements

Question 20

Amblyopia

1. Nasal Eye movements in each eye are of a higher/lower gain than their Temporal Counterparts to Equal velocities of stimulus motion?
2. Nasotemporal OKN asymmetry is a RESULT of what?

Answer 20

1. HIGHER

2. of ABNORMAL OCULOMOTOR CONTROL and MOTION PERCEPTION in strabismus rather than the disruption of Binocularity

Question 21

Animal Models of Visual Deprivation

1. Infant animals can be reared with ARTIFICIAL STRABISMUS (induced by Optical prisms or via surgical sectioning of the EOMs) which does what?
2. Stimulus deprivation amblyopia is created by doing what to kittens?
   a. This is similar to what?
3. A Kitten is reared w/one or both eyelids sutured shut for how long?
   a. Lids are then parted, and responses of what cells of the animal are recorded?

Answer 21

1. Produces the same visual perception and Oculomotor defects seen in human AMBLYOPES.
2. suturing the eyelids of kittens
   a. to a VERY DENSE CATARACT
3. from BIRTH until 4-5 MONTHS of AGE
   a. of Cortical Cells

Question 22

Dominance Column

1. What category represents Monocular Cells that can only be DRIVEN by Stimulation of the IPASILATERAL Eye?
2. What category Contains cells driven only by the CONTRALATERAL Eye?
3. What category marked by cells that respond EQUALLY to stimulation of each eye?
4. The remaining categories also respond to BOTH EYES, so they contain what?
   a. And the response is what?

Answer 22

1. Category 1
2. Category 7
3. Category 4
4. Binocular Cells
   a. Response is greater for one eye than the other

Question 23

Amblyopia

1. In a MONKEY, what % of STRIATE CORTICAL CELLS are BINOCULAR?
   a. They fall into what CATEGORIES?
   b. Category 1 and 7 cells are NOT REALLY what?
   c. What do Category 1 and 7 cells EXHIBIT?
2. The key to the development of amblyopia following Monocular Deprivation is that disrupting the formation of what?

Answer 23

1. 72%
   a. 2 through 6
   b. are not really exclusively Monocular
   c. They can exhibit BINOCULAR, subthreshold summation under some testing conditions, so the proportion of cells in V1 that are binocular may be even higher.
2. of simultaneous clear images to corresponding retinal locations in the 2 eyes leads to DEGRADATION of VISION

Question 24

Amblyopia

1. The effects of Monocular Deprivation may also be seen in what?
2. In the normal animals, Equal numbers of Monocular Cells in Layer 4C receive input from the left eye and the right eye. So, the WIDTHS of the LEFT EYE and RIGHT EYE OCULAR DOMINANCE COLUMNS are what?

Answer 24

1. in the Pattern of Ocular Dominance Columns in LAYER 4C of Striate Cortex in BOTH Kittens and Monkeys
2. EQUAL

Question 25

Amblyopia

1. With Monocular deprivation, the Visual Cortex Reorganizes itself in such a way that the WIDTH of the DEPRIVED EYE’s OCULAR DOMINANCE COLUMNS do what?
   a. This happens with a CORRESPONDING INCREASE in what?
2. With Monocular Deprivation, the neurons serving the deprived eye also show what?
   a. THE RESULT?

Answer 25

1. SHRINKS
   a. in WIDTH OF THE NONDEPRIVED EYE’s COLUMNS
2. show SMALLER and SPARSER DENDRITIC BRANCHING, as their dendrites atrophy more than do those of the nondeprived eye during development of the ocular dominance columns
   a. is a NARROWER ZONE of CELLS RECEIVING INPUT from the DEPRIVED EYE, that is, narrower ocular dominance columns for the deprived eye.

Question 26

1. The HEBBIAN MODEL states what?
   a. If 1 monocular input is compromised through deprivation, the BINOCULAR CELL FAILS to develop BINOCULAR responsiveness and is DRIVEN PRIMARILY by what?

Answer 26

1. states that Binocular Neural Development is DEPENDENT on the RECEIPT of SIMULTANEOUS STRONG MONOCULAR INPUTS
   a. by the Nondeprived Eye Alone; That is, it becomes a MONOCULARLY driven cell.

Question 27

Cortical Inhibition

1. Inputs from the two eyes compete for synapses or connectivity onto cortical binocular neurons: what is it?
2. During development, the number and strength of the synaptic connections that form on a given binocular neuron depend on what?

Answer 27

1. BINOCULAR COMPETITION

2. on the Strengths of the Monocular Inputs onto that cell.

Question 28

Photorefraction

1. Camera Flash acts as what?
   a. The camera photographing the image of the flash as it is refracted on what?
   b. Analyzing the image of the REFLEX allows for the detection of what?

Answer 28

1. as a STREAK RETINOSCOPE
   a. on entering and leaving the eye.
   b. of High Refractive Error or ANISOMETROPIA (these are 2 of the RISK FACTORS FOR AMBLYOPIA)