Squints Flashcards
What is the medical name for a squint
Strabismus
What is a squint
A misalignment of the visual axes of the eyes
How are squint’s named
If eyes turn in it’s eso-
If eyes turn out it’s exo-
If eyes go up its hyper-
Down its hypo-
Eyes may also be rotated away from each other - excyclotortsion
Towards each other - incyclotortsion
If the squint is manifest (there all the time) you add tropia to the end
If it is latent (only there on testing when binocular vision is disrupted) you add phoria
What type of squint is more common - horizontal or vertical
Horizontal
How does a squint affect the vision
Often leads to double vision
What can cause a squint in children
Most commonly due to them being long sighted (hypermetropic)
Can be congenital
Retinoblastoma
Nerve palsy due to intracranial pathology
How do squints present
Usually asymptomatic and picked up by screening
May be noticeable by looking at them but usually subtle
What is the main risk of an untreated squint
Amblyopia - loss of vision in the affected eye
The brain prioritizes the good eye to avoid double vision so the proper visual pathways don’t form from the squint eye
Squints in children can be treated up until which point
Around age 8
At this stage the vision is fully developed and won’t change
How do you treat a childhood squint
Patching of the good eye - stimulates the squinting eye to prevent amblyopia and form the visual pathways
Give them glasses - promotes binocular vision by improving occular alignment and preventing overuse of accommodation reflex
Some may need surgery for ocular alignment - alter the muscles
What can cause a squint in adulthood
Missed childhood squint presenting late Nerve palsy - 3rd, 4th or 6th Trauma - eg blowout fractures Muscle pathology - thyroid eye disease, Brown's, Resrtictive Duanes, MG
How do squints present in adulthood
Diplopia - often disabling
Eye movement testing usually reveals some reduction in
movement in one or more directions causing the size of the deviation to vary in different
positions of gaze (an incomitant squint).
How do you treat a squint in adulthood
Use a patch to eliminate double vision
Can also use a prism
Many need botox to paralyse muscle or surgery
Investigate for underlying cause
Do squints run in families
They can do!
What examinations would you do to diagnose a squint
Test eye movements
Cover test - when you cover the good eye the squint should correct itself
Cover/uncover test for latent squint -
When would a childhood squint require urgent referral
If there are unusual features such as loss of red reflex or incomitance ( worse in certain gaze positions)
How does a latent squint present
Typically asymptomatic
Only picked up on testing - interrupt binocular vision by covering one eye (cover/uncover test)
Can become symptomatic if it decompensates to a manifest squint - patient is tired or unwell
What is the medical name for a lazy eye
Amblyopia
Most convergent squints are corrected by glasses - true or false
True
Why does long-sightedness cause squints in children
They get an esotropia (eye turns in) as they try and use the accommodation reflex to correct their vision
Overaccommodation and overconvergence
Which squint patients require surgery
Large infantile squints - for aesthetic reasons
Significant residual squints
If there is a chance of restoring binocular vision
What are the main types of squint surgery
Recession –reattach muscle posterior to insertion. (weakens muscle)
Resection –Excise a segment of muscle (strengthens muscle)
What can cause an opacity in the red reflex of the eye
Cataracts
What can cause an alteration in the colour of the red relfex
Pale yellow - asymmetrical camera angle (flash hits differently), retinoblastoma or coloboma
Black/no reflex - retinoblastoma, retinal detachment
