paediatric optometry - lecture 5 , visual development

What can hinder visual development in a child?

- deprivation

- amblyopia

- congenital cataract

- strabismus etc.

Von Hofsten et al. (2014) and vision

Suggested that

newborns were able to

discriminate facial

expressions from 30

cm.

• More difficult when

distance was greater

than 120 cm

How can we tell if infants can see?

- forced preferential looking( can be quantitative as recording sine gratings seen )

- electrophysiology

- ocular following movements

What is preferential looking?

AKA forced preferential looking (FPL)

- visual fixation responds to certain stimuli more readily than others

- FPL can be used as a quantitative measure (different sine gratings)

What is electrophysiology?

- electronic brain responses triggered by visual stimuli

What are the different measurements that you can get from electrophysiology?

- electroretinograms (ERG's): retinal components

- Electrooculograms (EOG's): retinal pigment epithelium

- Visual evoked potentials (VEP's): cortical measurement

how does visual electrodiagnostic work

-sensory accessory at the front of the eye ( cornea) or back of head

- EOG front of eye

- VEP back of the head

- goes to amplifier

- then to analyser

- present stimulus

- can see where in the retina and vc is working

downside of elecrophysiology

more invasive method

What is electrophysiology used for?

- to assess visual function in infants as young as 1 week old

What are the limitations of using an optokinetic drum?

- depends on the mood and attention of the child

- stimulates a larger area of the retina so not as sensitive as a snellen letter

How is ocular following movements measured?

- using an optokinetic drum

- both infants and adults make reflexive eye movements following the presentation of a moving target

-optokinetic nystagmus

- change the grating

- involuntary response

Limitations of ocular movement

- depends on mood and attention

- stimulates larger area of retina so less sensitive than stellen

mayer et al and VA

used FPL to measure VA in 460 children ages 1 month-4years

- can be used to determine norm

Norm data VA children

What method shows higher acuities?

- VEPs tends to show higher acuities compared to FPL

VEP vs FPL

subjective vs objective

VEP

What is emmetropisation?

The rapid reduction in RE over first few years of life towards emmetropia.

-axial length

- refracting power of the cornea

- refractive power of the lens

- depth of the AC

How long does infant hyperopia last?

- subsides within the first 3 years of life with the most significant decrease occurring in the first year

What is the axial length of a childs eye?

- On average, the childs eye grows from 18mm at birth to 23mm by the age of 3.

What is the average adult eye axial length?

24mm

What did atchison et al suggest regarding axial length and refraction?

- an increase of 0.35mm increases myopic Rx by 1D

- This is NOt seen in normal development

What are some ocular components which can compensate for axial length?

- lens

- cornea

- AC depth

How does cornea effect Rx?

data is equvolm

How does anterior chamber depth change as you grow?

- it increases by 0.9 to 1mm from birth to 1.5 years

- 0.3mm to 0.4mm from 1 to 7 years

- 0.1mm from 8 to 13 years

- AC depth growth normally stops by the age of 15 years.

How does anterior chamber depth effect Rx?

0.1mm = 0.2D

- not a big effect

what does research suggest about a lens when growing?

- as the eye gets bigger and expands, it stretches the lens, making it thinner and reduces its dioptric power

- this tends to stop at the age 9 to 10

children rx normal data (1 month -4 years)

younger age, larger variarion of RE

With ranges below age norm values , RE remains more stable

With ranges of RE higher than normal values there is a steep decrease of RE as we age

it is okay of child is at lower 95 and upper 95 ( emmetropisation is likely to occur)

What is contrast sensitivity?

the ability to differentiate an object and its background

At what parts is contrast sensitivity particularly reduced in children?

- at mid and high spatial frequencies

Contrast Sensitivity• Westell et al. (1992)

Used FPL to assesscontrast sensitivity in 30 infants and children ranging in age from 3months to 5 yrs

westerly peak cs

Peak Contrast Sensitivities

• 3 months

  • 5 at 1 cpd

• 6-8 months

  • 10 at 3 cpd

• ->30 months

  • Close to 100 at 5-6 cpd