Lecture 3 vision screening and amblyopia investigation Flashcards
What ages is vision screening done?
before newborn leaves hospital (check eye is structurally normal and for red reflex)
6 week GP check (red reflex)
1 year to 2.5 years depending on location
vision screening 4-5 years
Which children should be more closely monitored than screening tests?
children with systemic disease
premature/low birth weight children
FH of strab, refractive error, amblyopia
children with hearing loss
children with learning disability
what are the features of crowded keeler logMAR test?
designed to use for 3.5-5 year olds
3m test distance
4 letters on each line (each letter worth 0.025 and each line worth 0.1)
2 flip books incase child memories letters (one for each eye)
What is the testing procedure for crowded keeler logMAR test?
what is the pass criteria in the UK?
screening plates give an estimate of acuity so you can start with testing from that acuity line
don’t point to letters or cover crowding bars
ensure child head is still and observe for nystagmus, ptosis, AHP, excessive blinking, screwing eyes up
What conditions are vision screening trying to detect?
amblyopia
refractive error
mainfest strabismus
muscle palsy
pathology
nystagmus
What is Amblyopia?
What causes it?
When does it occur?
a form of cerebral visual impairment
usually occurs in one eye
interruption of normal visual development e.g., refractive error, pathology, strab
critical period where visual pathway is still developing (birth to 8 years old)
What are the three periods of visual acuity?
developmental period: period from birth to where vision is developing
critical period: period where vision is susceptible to abnormal visual input
sensitivity period: period where treatment is effective
What does amblyopia effect?
vision, contrast sensitivity, depth perception, difficulty with crowding, motion perception, visual; distortion, binocular vision
What are the different types of amblyopia?
Strabismic amblyopia
stimulus deprivation amblyopia
anisometropic amblyopia
meridional amblyopia
ametropic amblyopia
What causes strabismic amblyopia?
constant manifest deviation (more likely in esotropia as its more likely to be constant)
usually only monocular
What causes stimulus deprivation amblyopia?
happens due to pathology
there is an obstruction to the clear passage of light which prevents clear formation of an image.
this can be cataracts, significant corneal scarring, ptosis etc
can be monocular or binocular
if pathology affects the macula, more likely for amblyopia to develop.
bilateral amblyopia may be caused by congenital nystagmus.
What causes anisometropic amblyopia?
there is a difference in refractive error between the two eyes
one eye receives better visual input at all distances
amblyopia occurs in eye with larger refractive error.
What causes meridional amblyopia?
occurs monocularly with anisometropic amblyopia
occurs binocularly with ametropic amblyopia
eye with the largest amount of astigmatism will be the most amblyopic.
What causes ametropic amblyopia?
high degree of uncorrected bilateral refractive error (hyperopia, myopia, astigmatism)
occurs bilaterally
What refractive errors in children will require glasses to reduce risk of amblyopia developing?
age 2-3:
Isometropia: hyperopia +4.50
myopia -3.00
Anisometropia: hyperopia +1.50
myopia -2.00
astigmatism -2.00
