VD Exam 2

axial length in full term newborn

16mm (90D)

axial length in adult

24mm (60D)

When does emmetropization not occur?

for extreme refractive errors (\>5.00D or -4.50D)

How many children remain hyperopic during school years?

80-85%

How much is the human compensation range assumed to be?

+1 to +5, but it is not known for sure yet

What range do chickens compensate over?

-10D to +15D

What range to monkeys compensate over?

-2D to +8D

What gestation period is prematurity defined as?

less than 37 weeks

What are the birthweight categories for infants?

1. LBW -

2. VLBW -

3. ELBW -

What are the qualities do premature infants usually have in terms of ROP?

1. weigh

2. born before 31 weeks

What is the average refractive error of premature infants at birth?

- 0.50 D (S.D. + 2.80 D)

Average refractive error of FULL TERM infants at birth

+ 2.00 D (S.D. + 2.00 D)

Average refractive error of 1-year-old child is

+ 1.00 D (S.D. + 1.10 D)

Average refractive error of 3-year-olds is

+ 0.95 D (S.D. + 1.00 D)

when does the refractive state of children reach an emmetropic plateu?

5-7 years old

Classifications of myopia

1. Low -

2. Moderate - -3.00D to -5.75D

3. High - \>6.00D

How many newborns have astigmatism?

50% of them

What is the mean amount of astigmatism in 6 month old infants?

2.00 D (ATR)

What is the mean amount of astigmatism in 2 year olds?

0.50 D

What is the mean amount of astigmatism in 18 month olds?

1.00 D

What age do the ATR and WTR slopes intersect?

54 months

When are is the adult level of astigmatism reached?

5 years old

By school age (5 to 7 years), the prevalence of significant amounts of astigmatism is between

2% and 4%.

How much less spectral sensitivity in short wavelengths do infants have compared to adults?

1 log unit

How many times less sensitive are 1 month old infants compared to adults in terms of scotopic spectral sensitivity?

80 times less sensitive

How many times less sensitive are 3 month old infants compared to adults in terms of scotopic spectral sensitivity?

15 times less senstitive

Rod responses from Peripheral retina reach 50% of adult values by the age

about 3 months

close to the fovea (Parafovea), Rod responses only reach 50% of adult levels by

about 5 months

No age related differences between 2 and 4 months old for what test?

VEP

No differences between 3 & 4- months old for what test?

FPL

By what age can infants discriminate red, yellow, green and blue from GRAY

3 months

Rudimentary RED-GREEN discrimination arises during the

second month of life

all the test wavelengths could be discriminated by what age?

By 7 weeks

only the curve for the 645-nm TEST and 547-nm SURROUND indicates discrimination at what age?

3 months

infants between what age show that they have some ability to discriminate among chromatic stimuli across most of the visible spectrum

2 and 3 months

infants as young as __ have functional MWS and LWS cones

2 weeks of age

infants as young as __ have functional SWS cones

5 weeks of age

infants demonstrate Dichromatic color vision when?

8-10 weeks

Trichromatic vision is present by?

3 months

The FORM (SHAPE) of the Scotopic sensitivity function is adult-like at

1 month of age

The ABSOLUTE SENSITIVITY of the Scotopic system reaches adult levels by approximately

6 months

New borns can discriminate only between Red and achromatic stimuli until

3 months of age

The ability to discriminate all hues from achromatic stimuli reaches adult levels by

3-4 months (and continues to develop well into childhood)

Scotopic sensitivity curve in infants does not reach adult levels until

4-7 months of age, avg. 6 months

When is fixation developed in infants?

2 months

At 6 months, how many infants make a series of saccades instead of one large one?

30%

Normal pursuit gain (eye velocity = target velocity) is reached by

4 months of age

When do all eye movements typically reach adult levels?

by 6 months

When do infants make series of small saccades instead of smooth pursuit?

Until 8 weeks

Tonic Accommodation in adults

0.50D

Tonic accommodation in infants (3-12months)

1.59 D to 0.50 D

accommodation at 3 months

accommodation is present but not accurate

accommodation at 4 months

accommodation is well-developed, ADULT LEVELS

Vergence in 1 month old infants

consistent DIVERGENCE eye movements

vergence within first few weeks after birth

unstable and inaccurate, cannot be initiated based on image disparity alone

Vergence in 2 month old infants

consistent CONVERGENCE eye movements.

When do accommodation and convergence become linked?

after 2 months

Vergence in 6 month old infants

adult levels, can be initiated based on disparity alone

stereopsis in infants age 4 to 6 months

Adult levels of stereopsis (Clinical Test: 40 arc seconds)

stereopsis at age 24 months

Stereoacuity reaches 1 second of arc

Fusion at 12.8 weeks (mean age)

fusion present

what is limiting factor to sensory fusion &stereopsis before 3 months of age?

immaturity of visual cortex

What age do we usually use titmus housefly stereopsis test at?

3 years<

What age do we do frisby test plates?

FCPL method for children 13 months or older

What age do we use the Lang Stereo tests?

6 months to 4 years

What ages do we use for the Randot test?

4 years and older

What ages can we use the Randot E test?

3 years <

What sensory fusion test do we use for age 4 years and beyond?

Keystone visual skills card

What age can we use vectograms?

3 years <

Sensitivity to Rapid motion is adult levels

soon after birth

Sensitivity to Slow motion improves

gradually with age.

Global motion processing reaches adult levels at about

14 years

Speed discrimination for Fast Stimuli: Reaches adult levels at about

11 years

Is speed discrimination for slow stimuli matured at 11 years?

No

Cells in LGN respond to higher temporal frequencies than

60 Hz

In infants, CFF reaches adult levels by

2-4 months of age

at 1 month of age how high is CFF?

40 Hz

When does CFF reach adult levels, and what is the approximate frequency?

3 months of age; 55 Hz

Form vision at 6 months

can discriminate faces

At 4 years old, can a child perceive an object when shown only part of it?

No, must be full object

At 6 months of age, human infants are capable of discriminating between..?

2 human faces and/or 2 monkey faces

older infants (9 months old) and adults, are ____ ____ of discriminating between the two monkey faces

less capable

LID CLOSURE in response to Bright Light

30 weeks gestation

PUPILLARY REFLEX (Pre-natal): Average

32 weeks (28-35 weeks)

Blink response to visual threat

2-5 months after birth

Visual Fields Between birth and 2 months

very little development

visual fields between 2-8 months

rapid development that slows again

Binocular Superior (upper) VF (reaches adult levels) by

12 months

Horizontal & Inferior Fields adult level by

15 months

Monocular fields reach adult levels by

17 months

visible light spectrum in humans

400-700 nm

Kittens critical period

1-3 months

Monkey critical period

first 6 weeks of life

Human critical period

birth to 7-9 years

Most sensitive period of visual development in humans

6-8months to 2 years