Vision Screening Amblyopia Investigation - Miriam Flashcards
When are ocular health screenings carried out?
- Before baby leaves hospital
- 6 week check
- 1-2.5 years old (when this happens is postcode dependent)
What two things does an ocular health screening consist of?
Making sure there is a red reflex and eye is structurally normal
Name five different groups of children which should be closely monitored
1) Children with systemic disease (diabetes, sickle cell)
2) Premature/low birth weight
3) FH of stab, amb or refractive error
4) Children with hearing loss
5) Children with learning disability
How many times more like are children with a learning disability likely to have an eye condition or require glasses?
28 times
What are premature babies/ low birth weight at risk of?
Retinopathy
What aged children undergo the pre-school vision screening?
4-5 year olds
What is the aim of pre-school vision screening?
Identify children with impaired sight so they are able to intervene in a timely manner
Who are allowed to carry out the pre-school vision screening?
Orthoptists or professionals trained by orthoptists
Why are 3 year olds not part of the pre-school vision screening programme?
- Younger children= more false positive—> unnecessary referrals
- Poor attendance rate when parents and children are invited
- Delaying treatment to 5 years old will not adversely affect the child
What is the gold standard screening test to measure vision and why?
Linear LogMAR
It includes crowding and does not use singles which helps to detect amblyopia (treating at this age is vital to treat the amb)
Describe the procedure of vision screening tests
- Explain test to child
- Get consent from both parent and child
- Ensure the child is able to match the letters at near for understanding
-Test each eye separately (RE first unless they are struggling/ have strab) - Ensure other eye is occluded
- Measure vision using Keeler logMAR
What age group is the crowded keeler LogMAR designed for?
3.5-5 year olds
What distance should keeler LogMAR be used for ?
3m
What six letters does the keeler LogMAR consist of?
XVOHUY
How many letters are on each line of the keeler LogMAR ?
4 letter each scoring 0.025 and each line scores up to 0.100
How is the keeler LogMAR carried out?
- Occlude one eye
- Start with s2 screener plate
- If they cannot identify the biggest letter then move onto S1
- Present the line of the last correct letter
- 4 letters must be attempted before moving on to a small liner
- Note line which error occurred and measure
- Test other eye and use other test
What is the LogMAR pass criteria?
Children need to see at least 0.200 in both RE and LE
What is the main condition that the vision screening test is trying to detect?
Amblyopia
What conditions may you detect with the vision screening test?
(*hint there are 9)
- Amblyopia
- Cataract
- Refractive error
- Strabismus
- Nystagmus
- Ptosis
- Muscle problem
- Anisocoria
- Rare pathologies (Coloboma and leuocoria)
What is amblyopia?
Visual impairment which results in reduced vision in one or two eyes causes by interruption of normal visual development
What can cause abnormal visual development?
- Refractive error
- Pathology
- Strabismus
- OCCURS DURING CRITICAL PERIOD
What age is the critical period?
7-8 years old (where vision is susceptible to abnormal visual input)
What age is the sensitive period?
From time of deprecation to teen/adult years (basc when treatment is effective)
-BUT poorer prognosis
What is development period?
Birth- 3/5 years old (when vision is developing)
What can amblyopia effect?
- vision
- CS
- Depth perception
- Difficulty with crowding
- Motion perception
- Visual distortion
Why would you treat amblyopia?
Better quality of life
What struggles may someone with amblyopia face?
Driving, navigation around obstacles, threading beads, reaching and grasping
Reading (slower speed), cautious behaviour
How many more times likely is someone with amblyopia at risk of a binocular visual impairment?
X2
What are the five classifications of amblyopia?
- Strabismic amblyopia
- Stimulus deprivation amblyopia
- Anisometropic amblyopia
- Meridonal amblyopia
- Ametropic amblyopia
What type of strabismus is a child more likely to have related to strabismic amblyopia?
Constant manifest deviation- esotropia
*occurs monocularly
What are the three most likely causes of stimulus deprivation?
Cataract and ptosis and nystagmus
An image cannot be clearly formed; occurs monocularly AND binocularly
Make sure to note how much the pathology prevents the macula
Does anisometropic amblyopia occur monocularly or binocularly?
Monocularly
What is anisometropic amblyopia?
Difference in refractive error where one eye receives better visual input than the other (can be sph and/or astigmatic difference)
*will occur in the eye with larger rx
Does meridonal (astigmatic) amblyopia occur monocularly or binocularly ?
(*hint this is a trick question ish)
MONOCULARLY with anisometropic amblyopia
BINOCULARLY with ametropic amblyopia
This is because a burred image is formed along more ametropic axis
Does ametropic amblyopia occur bilaterally?
Yes
What are causes of ametropic amblyopia?
- High hyperopia (accom can not compensate for this)
- High astigmatic error
- High myopia (make sure to look for pathology)
What are three things you must do when investigating amblyopia?
History
Refraction (cyclo in children)
Ophthalmoscopy
VA
CS (optional)
CT
OM
Accom.
Convergence
Binocular status (PFR, stereopsis, CT)
What should history include when investigating amblyopia?
What is the problem, what age did problem Start, how long has it been there for, with strabismus is it Constant/intermittent/alternating
Do you know which refractions you should prescribe to which children?
No?
Look at the American academy of Ophthamology 2012 table as a guide line
What is the average LogMAR for a 4-5 year old for crowded LogMAR test?
0.087
What is the average LogMAR for a 4-5 year old for an uncrowded LogMAR test?
-0.010
When measuring VA should you measure near or distance or both?
Both
What may you want to use if the child has manifest latent nystagmus to occlude the eyes?
Spielman occluder
Should you measure VA with CHP?
Yes- you should measure VA with compensatory head posture AND without
In what instance would you measure CS?
If you have time and they are not losing concentration- not practical in younger children
Wit a child who has alternating unilateral deviation, would you expect them to have unequal vision?
No- there vision should be equal ish
What observations should you look out for if VA is not possible?
When doing CT:
- Note whether there is an unilateral deviation
- If the amblyopic eye holds fixation after blink
- Central fixation or eccentric fixation through corneal reflections
- Constant or intermittent deviation
If the amblyopic eye holds fixation after blink, what does this show?
They are trying to use this eye and treatment may be working/ vision is improving
What would you see if the px looks through eccentric fixation and why is this problematic?
The px turned eye does not move to take up fixation, therefore is viewing eccentrically and not using the macular so the vision will be very reduced
What should you be looking out for when carrying out OM and the px is on amblyopia treatment/ thinking of starting this?
Look out for incomitancy as pxs with incomitancy are more likely to decompensated when you start occlusion which could lead to retractable diplopia
What are three things you should do to check binocular status to ensure that occultation will not cause the child to decompensate?
-PFR (motor fusion range)
- Stereopsis
- Cover test (recovery)
- OM - look for incomitancy
If a 4 year old had RE 0.200 and LE -0.100, would you refer them?
Yes due to the large difference in rx
-also more than 2 lines which makes it clinically significant
Does a reduced VA mean this px has amblyopia?
No if there is no amblyopic RF then probably no amblyopia
- Reduced VA may be due to incorrect VA measured/ incorrect refraction done —> REPEAT TESTS
