strabismus and paediatrics Flashcards
which muscle has the closest and furthest insertion to the limbus and their distance
medial rectus closest 5.5
superior rectus furthest 7.7
movement of superior rectus
intorsion and adduction
movement of inferior rectus
depression
extorsion and adduction
movement of superior oblique
intorsion
abduction and depression
movement of inferior oblique
extorsion
abduction and elevation
what is hering’s law
yolk muscles involved in a particular direction of gaze receive equal and simultaneous flow of innervations.
sherrington’s law
increase in innervation of a muscle is accompanied by a decrease in innervation of its antagonist.
define ambylopia
characterized by a reduction in VA in the early years of life (<8 years of age) due to a developmental failure of the visual pathway between the eye and the visual cortex in the occipital lobe
aeitologies of ambylopia
Strabismus
refractive error
stimulus deprivation (e.g. cataract).
Mx of ambylopia
1) Treat underlying cause.
2) Occlusion therapy: The good eye is patched to allow visual connections between the amblyopic eye and the brain to develop properly.
3) Pharmacologic penalisation of the good eye using atropine. (Note: Atropine may cause photophobia and reverse amblyopia.)
characterisitcs of binocular single vision
simultaneous perception
fusion
stereopsis
define simultaneous perception
An image formed simultaneously on each retina.
define sensory fusion
ability to unite the two images from each retina to form a single image.
define motor fusion
The ability to align the eyes to maintain sensory fusion.
Motor fusion occurs via version (conjugate movements) and vergence (disconjugate movements) in order to achieve binocular vision.
define steropsis
perception of depth
tests for simultaneous perception and fusion
Worth 4-dot test, Bagolini glasses and synoptophore.
tests for motor fusion
Base-out or base-in prism bar or Risley prism tests. Applying a base-out prism moves the image to the temporal retina so the eye has to converge to achieve binocular single vision. The opposite is true for a base-in prism.
tests for stereopsis
Titmus, Lang, TNO, Frisby and synoptophore.
what is heterophoria
Deviation of the eye that is hidden by fusion and revealed when fusion is broken, for example, with an alternating cover test.
define esophoria
inward deviation of the eye
define exophoria
outward deviation of the eye
what is heterotropia
diagnosis
Abnormal alignment of the eye, also known as a manifest squint.
Can be tested using the cover test.
what is the normal accommodative convergence to accommodation
In the normal eye, one diopter of accommodation is accompanied by 3–5 PD of accommodative convergence.
the most common form of childhood squint
esotropia
possible causes of esotropia
nerve palsies, thyroid eye disease, trauma
what is fully accommodative esotropia
esotropia that resolves with correction of hypermetropia. Normal AC/A ratio.
Mx of fully accommodative esotropia
full cycloplegic hypermetropic correction
what is partially accommodative esotropia
partially resolves with correction of hypermetropia but needs treatment of ambylopia. Normal AC/A
Mx of partially accomoodative esotropia
fully cycloplegic hypermtropic correction and treatment of ambylopia
what is convergence excess esotropia
Esotropia for near vision only due to high convergence. High AC/A ratio.
Mx of convergence excess esotropia
bifocal glasses or surgery (e.g. bilateral MR recession).
when does infantile esotropia develop
within the first 6 months of life
what is infantile esotropia
- Large-angle (>30PD) deviation
- Cross-fixation (carries low risk of amblyopia)
- Latent horizontal nystagmus
normally develops in first 6 months
what is near versus distance esotropia
Distance: Esophoria for near vision and esotropia for distance
Near: Esotropia for near only but with normal AC/A ratio
most common type of exotropia
intermittent exotropia
Mx for intermittent exotropia
myopic correction, orthoptic exercises or surgery (e.g. unilateral or bilateral LR recession).
what is distance exotropiia
classification
TRUE - exotropia made worse looking at a distance with normal AC/A ratio.
SIMULATED - there is a larger exotropia for distance with high AC/A ratio; however, the near exotropia is increased when looking through a +3D lens or after occlusion of the normal eye.
what is near exotropia
Defined as a worse exotropia for near vision, it is common in young myopic adults or teenagers.
what is constant exotropia
A constant large-angle exotropia, typically occurring within the first 6 months of life. It is usually associated with neurological anomalies
Mx of constant exotropia
surgical with bilateral LR recession and MR resection.
what is microtropia
A small angle squint <10PD (5°), most commonly an esotropia associated with anisometropia. Patients have subnormal binocular single vision with sensory and motor fusion and reduced stereopsis
what is microtropia w identity
no manifest deviation on cover test but deviation can occur on 4PD test
what is microtropia wo identity
manifest deviation on cover test
what is duane retraction syndrome
innervation of the LR muscle by CN3 rather than CN6 with associated CN6 nucleus hypoplasia.
characteristics of duane retraction syndrome
retraction of the globe on aDDuction. Associated with deafness or Goldenhar syndrome. Three types exist
I (most common) II III Esotropia with limited abduction Exotropia with limited adduction Esotropia with limited abduction and adduction
what is brown syndrome and causes
This unilateral syndrome is caused by mechanical restriction of the SO tendon at the trochlea. It can be congenital or arise post-trauma/surgery
characteristics of brown syndrome
limited elevation in adduction or on upgaze with an
- associated click sensation.
- pts can’t look up and in
what is resection
process of shortening the muscle (strengthening procedure).
what is recession
process of loosening the muscle by moving it away from its insertion (weakening procedure).
what surgery would be done in constant exotropia
bilateral LR recession (loosening) and MR resection (strengthening) corrects the eye misalignment.
what is tucking procedure
augment the SO muscle. Indication is for congenital fourth nerve palsy.
what is advancement procedure
bringing the muscle closer to the limbus. This is done to a previously recessed EOM.
strengthening procedures
resection
tucking
advancement
what is disinsertion
primarily used for a highly active Inferior Oblique. It separates the tendon at its insertion, making it weaker.
innervation
primary function
secondary function superior rectus
CNIII
Elevation
intorsion & ADduction
innervation
primary function
secondary function inferior rectus
CN3
depression
extorsion and ADDuction
innervation
primary function
secondary function
superior oblique
CN6
intorsion
abduction & depression
innervation
primary function
secondary function
inferior oblique
CN3
extorsion
ABduction & elevation
antagonist-agonist muscles
muscles in same eye that move the eye in different directions
synergist muscles
muscles in the same eye direction (right IR & right SO)
Newborn baby VA test
fix and follow
infants upto 3 years (pre verbal) VA test
Cardiff acuity test/ cardiff cards
18m - 4 years (verbal) VA test
kay picture tests
4-5 years test VA
Keeler crowded LogMAR test
what is leucoria
white pupil - urgent referral to opthamology
what is retinoblastoma
malignant tumour of the retina - most common intraocular tumor of childhood and most sinister cause
autosomal dominant (bilateral usually) or sporadic (usually unilateral)
loss of function of retinoblastoma tumour suppressor gene on chromosome 13
Mx
- radioactive plaque or enucleation + adjuvant chemo
what is congenital cataract
features
Mx
leukocoria, dull red reflex, squint or nystagmus
commonly idiopathic but alos hereditary linked w rubella
Mx
surgery - lensectomy
— contact lens, aphakic glasses or lens implant
what is retinopathy of prematurity
screen pre term babies (<30 weeks) + low birth weight (<1.5Kg)
retinal periphery is only fully vascularised close to term
incomplete retinal vascularisation causes hypoxia
leukocoria seen in advanced cases due to a retinal detachment
Mx- ablation of avascular retina + laser
what is coloboma
- keyhole pupil
- present at birth
- failure of choroidal fissure to close during embryological development - mutation of PAX2 gene + also linked with fetal alcohol syndrome
- degree of visual impairment ranges from asymptomatic to significant visual loss
- white retinal reflex + severe amblyopia
what is ptosis
Mx
- more likely t have weak LPS
- more pronounced when tired or unwell
Mx
- require urgent frontalis suspension surgery (within 2-4 weeks)
- take part of fascia lata and insert it onto tarsal plate and frontalise muscle
what is congenital glaucoma/ buphthalmos
buphthalmos is an enlargement of the eye acd in children is a feature of the congenital glaucoma
- consanguity
- corneal diameter >12mm before 1 year
- cloudy cornea
- excessive tearing
- photophobia
mX
- > Medical: drops
- > surgical: goniotomy
Pathogens of chlamydial conjunctivitis
Sx
Ix
Mx
chlamydia trachomatis
unilateral red eye
white follicules
periauricular lympahdenopathy
mucopurulent/’stringy’ discharge
Ix - giemsa stain
Mx
erythromycin drops
Pathogens
Sx
Ix
Mx
Gram -ve diplococci Neiserriae Gonnorhoea
- severe infection can cause corneal ulceration and perforation
- severe discharge
- early presentation
- may co-exist with chlamydia
Ix - swab gram stain
Mx
- IM/IV ceftriaxone
what is capillary haemangioma
swelling commonly superonasally from borth which increases in size for 6 months
- benign tumour
- risk of refractive error
- can causes mechanical ptosis which risks ambylopia if the lid covers the visual acis
Mx - oral beta blockers
what is limbal dermoid
benign congenital tumour often ass w eyelid coloboma or goldenhar’s syndrome
what is dermoid cyst
smooth round non-tneder immobile lump on orbital rim
- gradually grows with risk of rupture
