W3 Measure and Development of Vision

What is amblyopia?

Lazy eye

What is visual development at birth like?

Incomplete- maturation of the visual system is influenced by factors such as prenatal and postnatal nutrition and postnatal visual stimulation

How are abnormalities in visual development caused?

Abnormal visual input such as amblyopia or ocular misalignment leads to abnormalities including abnormal eye growth and neurological changes- if left untreated can lead to long term or permanent visual impairment

How does nutrition play a role in visual development?

Formula containing nutrients like omega-3 and omega-6 may protect non breastfed infants

What do infants see at birth?

Acuity at birth is 6/300, this rapidly improves over the first 6-8 months of age

Why is it important to know what infants see?

To understand medical implications (critical period, amblyopia) and to further understand how the visual system works

What is critical period?

During early childhood and the visual system is highly sensitive to visual experience and can only develop normally if it receives clear, balanced and focused input from both eyes- if not, permanent visual deficits can occur

What may happen if visual deprivation occurs during the critical period?

Amblyopia- lazy eye- factors influencing this include optical errors of the eye, muscle imbalance (strabismus) or other (drooping lids)

When is the critical period for humans?

From shortly after birth and ends around 8 years of age

What is the most well known critical period in infant visual development?

Development of stereopsis- depth perception. The brains learns to integrate and process vision from both eyes, enabling perception of depth and 3D space?

What happens if the development of stereopsis is missed or disrupted?

It can lead to visual impairments such as amblyopia

When does the development of visual acuity occur?

That critical period begins shortly after birth and continues into the first few years of life where infants gradually refine their ability to see fine detail

What are modifications to visual input they may lead to reduced vision?

Optical errors- leading to refractive amblyopia

Eye muscle errors- leading to strabismic amblyopia

Light deprivation- leading to deprivation amblyopia

How do you assess infant vision?

Preferential looking- behavioural measure

Visual evoked response (VEP’S)- electrophysiological measure

OR response to light/tracking object movement

How does preferential looking work?

By recording how an infants eye fixations vary for different stimuli, a researcher can infer what an infant may be able to see

What are the 4 methods of preferential looking?

Visual stimuli- 2 varying stimuli are presented simultaneously with one blank one side by side

Eye tracking- Infants eye/head movements are observed and recording when observing stimuli

Preference measurement- researcher analyses head movement of stimuli- they are unaware of which side of the stimulus is presented

Assessment- if an infant consistently looks at a high contrast striped pattern, researcher can infer the infant has the ability to perceive the pattern