Strabismus Flashcards
(36 cards)
A child is brought in whose eyes are misaligned/ “one eye is turned in”. What are 10 questions you should ask?
- Have you noticed any problems with child’s vision? e.g. being clumsy, bumping into things?
- Has the eye always been like this?
- Has the child had any injury to the head?
- Has the child had any other problems with eyes or surgery on them?
- Were there any problems during pregnancy or was child premature?
- Has child’s development been normal?
- Is child fully up to date with immunisations?
- Is there family history of eye problems?
- Is child on any medication?
- Has child spent time in hospital in past?
Who will first see a child with strabismus in the eye clinic?
Orthoptist
What is the role of the orthoptist generally?
- Crucial member of NHS eye care team, work closely with ophthalmologists, optometrists and vision scientists.
- Involved in diagnosis and management of conditions e.g. glaucoma, cataract, stroke, retinal disease, neurological disorders.
- Examine patients with eye problems, such as ocular motility problems, binocular vision, amblyopia (lazy eye) or strabismus (squint)
- some screen vision of children in schools and community health centres
What are 7 examinations performed by the orthoptist in a child with strabismus?
- Visual acuity: don’t know their alphabet in this age group, so checked with Cardiff Acuity Cards (Kay Pictures) + preferental looking
- Deviations of the eyes
- Hirschberg (corneal light reflex) test
- Cover test
- Prism cover test
- Ocular movements
- Binocular signle vision
What are Cardiff Acuity Cards (Kay Pictures) and how are they used?
- Use familiar pictures and preferential looking; observer notes child’s eye movements to determine if they can see pictures. Use pictures of house/car/duck etc. at top or bottom of otherwise grey card.
- 11 visual acuity levels with three cards at each level
What is the Hirschberg (corneal light reflex) test?
- Shine a light on the eyes with a pen torch, look to see where corneal light reflex is (reflection of light off cornea, a pinpoint white light) in relation to the pupil.
- If eyes are straight, corneal light reflex will be in the middle of each pupil
- If, e.g., left eye turned in (esotropia) then for the right eye, corneal light reflex will be in the middle of the pupil but for left eye it will beon the outside of (lateral to) the pupil
What is the cover test?
can identify if strabismus is present constantly (tropia) or if there is a tendency for there to be a squint when unaffected eye is covered (phoria)
What is a phoria in strabismus?
A phoria is a misalignment of the eyes that only appears when binocular viewing is broken and the two eyes are no longer looking at the same object (i.e. by covering one eye), can also appear when patient is tired
What is a tropia in strabismus?
Misalignment of the eyes that is present constantly, rather than just when one eye is covered (phoria)
What 6 things will an ophthalmologist perform in a child with strabismus, after they have seen the orthoptist?
- Confirm the findings of the orthoptist
- RAPD: swinging light test to check for optic nerve or gross retinal pathology
- Pupils dilated with cyclopentolate 1% and phenylephrine 2.5% drops to allow next three steps
- Red reflex check - detect cataract
- Cycloplegic refraction (testing for glasses) - see if there’s an accommodative element to the strabismus
- Fundus check - look for optic nerve and retinal pathology such as retinoblastoma
Why would the ophthalmologist perform the swinging light test to check for RAPD in a child with strabismus?
check for optic nerve or gross retinal pathology
What is used to dilate the pupils of a child with strabismus when seeing the ophthalmologist, and why?
- Cyclopentolate 1%
- Phenylephrine 2.5% drops
This is to ensure child will be unable to accommodate, to allow red reflex check, cycloplegic refraction, & fundus check to be performed
Why is cycloplegic refraction performed by the ophthalmologist in a child with strabismus?
To see if there is an accommodative elemtn to the strabismus i.e. child may be very hypermetropic (long-sighted) and a pair of glasses may completely correct (accommodative esotropia) or partly correct the deviation (partially accommodative esotropia), plus it will improve the vision in the deviated eye
Why is a fundus check i.e. ophthalmoscopy performed by the ophthalmologist in a child with strabismus?
To look for any optic nerve and retinal pathology, such as retinoblastoma
What is the prism cover test, performed by an orthoptist in a child with strabismus?
An objective measurement and gold standard in measuring strabismus; bar containing prisms of different strengths is used to overcome the deviation of the eye. Amount eye is deviated (in or out) meausred in prism dioptres (the higher the number, the larger the deviation)
How is a tropia revealed by the cover test?
- One eye is covered while fixating on a point
- Observe uncovered eye for corrective movement
- When normal eye covered, abnormal eye will move from deviated position to take up correct fixation position → indicates abnormal eye is uncovered, normal eye covered
How is a phoria revelealed by the cover test?
- Is actually revealed by the “uncover” test
- one eye covered for 5 seconds while child fixates on target
- cover is quickly removed, newly uncovered eye observed for corrective movement (i.e. if it was deviated behind the cover)
- if corrective movement occurs after uncovering, a latent phoria is present in newly uncovered eye
- defect is in eye that was covered/ newly uncovered
Why are tests of ocular movements performed by the orthoptist in a child with strabismus?
To exclude III, IV or VI cranial nerve palsy
What is the binocular single vision test performed by the orthoptist a test of?
ability to view the world with two eyes; requires clear image to stimulate fovea in each eye
What are 4 different types of strabismus?
Estotropia/phoria
Exotropia/phoria
Hypertropia/phoria
Hypotropia/phoria
What is amblyopia (lazy eye)?
- Developmental defect of central vision processing, leading to reduced form sense and reduced vision.
- In a young child, unless there is a perfect foveal image the brain will switch off/ignore the image, leading to a reduction in vision
When should amblyopia be treated?
ALWAYS needs treatment even after it’s unlikely to be effective (7-8 years of age)
After which age is treatment of amblyopia unlikely to be effective?
7-8 years of age
What are 2 options for the treatment of amblyopia?
- Occlusion/ “patching”: patching of the good eye for a few hours a day OR
- Penalisation: atropic drops used in good eye to dilate the pupil and blur the vision
