1) The visual system develops post-natally and requires exposure to normal environmental stimuli during critical periods for proper maturation. 2) Monocular deprivation during the critical period can lead to ocular dominance and amblyopia due to abnormal cortical development and lack of binocular interaction. 3) Visual acuity develops rapidly in the first year of life, reaching adult levels of 20/20 by ages 3-5 years for spatial vision functions like grating acuity.

1. POST NATAL PERECEPTION
DEVELOPMENT
GREESHMA G
MPHIL OPTOMETRY

2. Developmental aspects
Birth – not fully matured
Proper maturation- exposure to normal environment is required

3. Ocular dominance
Most binocular cortical neurons do not receive inputs from two eyes
Closure of an eye of an immature animal results in a lack of cortical cells driven by the deprived
eye
Critical/ sensitive period
•Period in which visual system is influenced by environmental manipulation
•During critical period cortical cells of eye will compete
No binocular action- No stereopsis

4. Ocular Dominance
Numberofcells
4 5 6 7321
Contralateral Ipsilateral
OCULAR DOMINANCE HISTOGRAM

5. Ocular Dominance
Numberofcells
4 5 6 7321
Contralateral Ipsilateral
First five weeks
R L

6. Ocular Dominance
Numberofcells
4 5 6 7321
Contralateral Ipsilateral
Six week through ten weeks
R L

7. MONOCULAR DEPRIVATION DURING THE CRITICAL PERIOD CAN
LEAD TO AN ASSYMETRICAL OCULAR DOMINANCE COLUMN

8. Synopsis of critical period- Hubel’s and
weisel’s experiment
Synaptic connectivity in the in the cortex is strengthened by the neural activity and lack in the
neural activity result in weakening of this connections

9. Amblyopia
•Reduction in vision secondary to monocular deprivation during the critical period
•Amblyopia results from the abnormal cortical development, not an abnormality of eye
•It can occur secondary to
• Anisometropia
• Strabismus

10. AMBLYOPIA
Occlusion
amblyopia
-One eye occluded in
critical period
-Monocular congenital
cataract
-Lid ptosis
Anisometropic
amblyopia
-Unequal refractive
errors
Strabismic
amblyopia
-Constant unilateral
strabismus present
during critical period
-Diplopia
-Suppression
Meridional
amblyopia
-Cortical neurons are
orientation selective
-Meridional astigmatism

11. Alternating
strabismus

12. Development of refractive error in
humans
First years of life- <2.50D hyperopic

13. Age- months Average visual acuity
1 20/638
1.5 20/540
2.5 20/278
4 20/224
6 20/106
9 20/88
12 20/93
18 20/70
24 20/63
30 20/52
36 20/28
48 20/24
VISUAL ACUITY IN EARLY LIFE

14. Post natal vision
NEONATE
• 8 to 14 inches
• 20/200 - 20/600
• Mothers arm to
her eyes
1-3 MONTH
• Start gazing at
objects
• 2 months- eye’s
coordination
develop
• Hand-eye
coordination
• Color perception
4-7 MONTH
• Enjoys more
complex designs
• Till 1 meter
• Fine movement
of objects
8-12 MONTH
• Focuses on a toy,
crawl pull it and
picks it
• Grasp and throw
objects
• Can perceive
depth
1 YEAR
• Depth
perception
continues

16. Contrast
sensitivity

17. Stereopsis
•Infant- Preferential looking test
•Rapid onset between 3 and 6 months
•6 months- 1 min of arc

18. Spatial vision
Vernier acuity
•Preferential looking
•Develops more slowly in late years
•Depends on cortical processing
•Adult levels at slightly older ages (6–8 years of
age)
Grating acuity
•Preferential looking
•Forced choice
•1 month- 20/600
•1 year- 20/100
•Adult levels at 3- 5years – 20/20

19. PREFERENTIAL LOOKING TEST

20. Temporal Vision: Critical Flicker Fusion
Frequency
•40 Hz at 1 month
•55 Hz by 3 months- adult level
The retinal and cortical immaturities that slow the
development of grating and Vernier acuity apparently have
little effect on the maturation of temporal resolution

21. Scotopic Sensitivity
•Adult-like at 1 month of age
•Shape of the function- Characteristics of rhodopsin
•Does not depend on postreceptoral processing
•Scotopic sensitivity- 507 nm
•Reaches adult levels by approximately 6 months

22. Colour Vision
•Red–green discrimination arises during the second month of life
•Blue–yellow discrimination
•Adult like on the 1 year of life
•Photopic spectral sensitivity function is adult-like in young infants

24. Thank you