Visual Development Flashcards by Aayan Rafiq

What things can a newborn infant recognise and detect?

-Recognise mother’s face
(hairline and chin not fine facial features)

-Detect biological movement
(human or animal motion)

-Detect colour

NOTE : Other responses are probably also present but difficult to assess due to immaturity

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True or false
Only the red cone is present in the retina of a baby

False
All 3 cones are present in the retina

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Which type of cones is a baby more sensitive to?

Sensitivity to red and green is much better than for blue

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What do we need in order for the baby to use its blue cones?

Need higher luminosity of blue (short) wavelengths for the baby to respond

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Even though a baby can detect colour, what 2 things are poor?

Wavelength and saturation are poor

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Define Critical Flicker Fusion (CFF)

Measure of the fastest speed at which the central nervous system can detect change

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What is photopic luminosity?

A representation of the human eye’s response in daylight

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Which type of photoreceptor is photopic luminosity mediated by?

Cones

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What is scotopic luminosity?

A representation of the human eye’s response in low light levels

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Which type of photoreceptor is scotopic luminosity mediated by?

Rods

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True or false
Babies should be hyperopic at birth and hyperopia is normal in infants

True
Babies should arrive hyperopic and then should eventually become emmetropic as they grow

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What changes occur to babies that makes them emmetropic?

-Eye grows (axial length increases)
-Lens power decreases

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What is the process where a baby arrives hyperopic and then starts to become emmetropic?

Emmetropization

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What is an Optomap image?

Wide scanning laser image

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What structure does an Optomap image allow us to see to?

Ora Serrata

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In a baby, why are cones not all packed in the centre?

Cones are fatter and shorter and take up space

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How long does the foveal depression take to fully develop?

≈15 months

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True or false
Mid peripheral rods and cones are more mature at birth

True

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What does the ability to develop adult levels of acuity in each eye rely on?

-Normal development of the eye

-Visual system receiving equal signals to the two eyes

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What is amblyopia?

An uncorrectable reduction in the acuity of one or both eyes which is not exclusively associated with a structural abnormality of the eye

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Where does myelination start and where does it go to?

Starts at the ONH and goes back to the brain

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What does a lack of myelin reduce?

Reduces the speed of conduction

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What effect does a lack of myelin have on the signal from the stimuli?

Signal can’t get to the brain or the stimuli will progress more slowly through the visual pathway

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True or false
Both magnocellular and parvocellular cells are larger at birth

False
Both magnocellular and parvocellular cells are SMALLER at birth

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What are magnocellular cells involved in?

Larger cells involved in depth and motion detection

What are parvocellular cells involved in?

Smaller cells involved in contrast and colour detection

Do cells from V1 (striate cortex) receive inputs from one or both eyes?

Both eyes

What are the cells of V1 organised into?

Ocular dominance columns

When can ocular dominance columns only develop?

Normal ocular dominance columns can only develop if the signal from each eye is clear

If normal ocular dominance columns cannot be developed, what does this risk not having?

Stereopsis

What experiment was done to see if babies could determine depth perception?

Visual Cliff -Babies were placed on one side if the cliff and on the other side there was a drop -If the baby could tell that this was a drop then it would not proceed to move over the plate

What is a version/conjugate eye movement?

Where the two eyes move in parallel (looking to the left or right)

What are the 2 types of conjugate movements?

i) Saccades ii) Pursuit

What are saccades?

Short sharp version movements

What is the purpose of saccadic eye movements?

Purpose is to bring the object of regard onto the fovea

What are the 2 aspects involved in bringing the object of regard onto the fovea in saccadic eye movements?

a) The reaction time to register that the eyes need to be moved b) The accuracy of movement to place the visual axes onto the object

What is a pursuit movement?

Smooth tracking movements

What do pursuit movements require?

Requires both eye and head movements to be co-ordinated

What are vergence or disjunctive eye movements?

Where the two eyes move in opposite directions (convergence)

What is laevoversion?

Eye movement where both eyes move to the left

What is dextroversion?

Eye movement where both eyes move to the right

What is convergence?

Eye movement where both eyes look in

What is divergence?

Eye movement where both eyes look out

What are the causes of an ageing population?

-“Baby boomers” - high birth rates between 1946-1964 -Decline in infant mortality -Increased life expectancy

What are some eyelid changes that can occur with age?

-Dermatochalasis -Entropian -Ectropian -Astigmatism changes from WTR to ATR

What is Dermatochalasis?

Drooping skin on the eyelids

Why do the eyelids droop as we age?

Elasticity of the eyelids changes and they get less tensile and droop more

What happens to the eyelids as we age?

Eyelids progressively lose their tone and bulk

What happens to corneal sensitivity as we age?

Decreases as we age

What changes can occur to the cornea as we age?

-Corneal arcus -Hudson-Stahli line -Crocodile shagreen -Corneal gutatta

What is a corneal arcus?

Halo around the cornea due to lipid deposition from the limbal blood vessels

What is Hudson-Stahli line?

Iron deposition line

What is crocodile shagreen?

Peripheral corneal opacities that follow the pattern of the corneal fibres

What is corneal gutatta?

Outgrowth of basement membrane in the corneal endothelium (beaten metal appearance) accompanied by fine pigment dusting

Which corneal dystrophy can corneal gutatta lead to?

Fuch’s endothelial dystrophy

What type of surgery can Fuch’s endothelial dystrophy complicate?

Cataract surgery

What changes can occur to the conjunctiva as we age?

Pingueculae can form

What are pingueculae?

A degenerative thickening of the bulbar conjunctiva

Where are pingueculae often found?

-Adjacent to the limbus -Nasally

Which type of people do you see pingueculae in?

-Adult Px's who work outdoors and do not wear sunglasses -Elderly

What is the treatment for pingueculae?

UV blockers in spectacles and/or sunglasses

What happens to the tear film as we age?

Tear film stability (tear break up time) decreases

What is age-related pupillary miosis?

Natural reduction in pupil size

Why may presbyopic Px's need to use a supplementary light source when reading?

Pupil size is smaller so not enough/much light can enter the eye

Give an advantage of elderly Px's having a small pupil

Effect of refractive error is made a little better (blur circle size reduces)

Give a disadvantage of elderly Px's having a small pupil

Less light can get into the eye

What are lens changes that occur with age?

-Increases in thickness -Nucleus hardens -Reduced flexibility -Increased light scatter -Increased yellow pigment in the centre -Increased flurophers (fluorescent pigments) -Lens refractive index gradient changes

What causes increased flurophers (fluorescent pigments) in the lens as we age?

UV radiation

What happens to the vitreous humour as we age?

-Becomes more liquid (liquefaction) -Shrinks (syneresis) -When it shrinks it pulls on structures that it is attached to (retina, ONH, ora serrata, blood vessels etc)

What is it called when the vitreous shrinks and pulls on structures?

Vitreo-retinal traction

What does the Px experience when the vitreous humour shrinks and pulls on structures as they age?

Experience peripheral flashes of white light

What changes occur to the macula as we age?

Foveal reflex is lost

Why is the foveal reflex lost as we age?

As a result of a change in shape of the foveal pit due to ganglion cell loss

Give the optical factors that cause vision loss with age

-Increased light absorption (lens appears increasingly yellow due to blue light absorption) -Increased light scatter in the lens (pupil fluoresces under UV light) -Age-related pupillary miosis (pupil gets smaller with age; this reduces retinal illumination)

Give the neural factors that cause vision loss with age

-Rod and cone changes and loss -RPE changes -Cell and neurotransmitter degeneration and loss throughout the visual system

Why may the symptoms of dry eye disease not be as severe in older Px's compared to younger Px's?

Older Px's have a reduced corneal sensitivity

Give the risk factors for dry eye disease

-Age -Female -Computer use -CL wear -Hormone Replacement Therapy (HRT) -Medications (antidepressants/anti-histamines)

What is a Weiss ring?

A PVD from the attachment at the ONH

Visual Development Flashcards

(78 cards)