4- Ophthalmology (Chilhood orthoptic conditions) Flashcards
Childhood orthoptic conditions
- Strabismus
- Amblyopia
orthoptic assessment in children
Vision testing
- visual acuity
- colour
- classification of squint e.g. cover tests
Cycloplegic refraction (used in children because can’t give accurate answers)
- Cyclopentolate and Tropicamide are drugs used to induce relaxation of the accommodation (focusing) system and mydriasis (pupil dilation) to allow for objective measurement of refractive error.
Fundus and media examination
- to ensure strabismus is not a result of eye pathology e.g. cataracts, retinoblastoma
Visual development
- The visual system at birth is immature.
- The eyes of a full term infant are relatively well developed compared to other organs. The axial length is less than an adult; the retina is fully differentiated but the fovea not fully developed until 4-6 months of age.
- The development of normal vision depends on normal anatomical development and on an adequate stimulus.
- The visual cortex remains plastic up to approximately age 7-9.
strabismus and amblyopia are
not the same thing
describe strabismus
Strabismus is a problem with eye alignment, in which both eyes do not look at the same place at the same time
describe amblyopia
Amblyopia is a problem with visual acuity or eyesight (usually in one eye, but can be bilateral)
how are strabismus and amblyopia related
- Strabismus is the most common cause of amblyopia
- Amblyopia caused by poor visual acuity in one eye can cause strabismus
strabismus is also known as
a squint and cross eye
strabismus background
Ophthalmic condition where the eyes do not align properly with each other when focusing to look at an object (poor fusion), which results in the eyes taking different positions, this means the images on the retina do not match and the person will experience double vision
why do children not tend to have double vision if they have congenital strabismus
when strabismus occurs in childhood, before the eyes have fully established their connections with the brain, the brain will cope with misalignment by reducing the signal from the less dominant eye
- This results in one eye they use to see (dominant eye) and one eye they ignore (lazy eye)
- If not treated this lazy eye can become progressively more disconnected from the brain
- This is called amblyiopia
onset of childhood strabismus can be caused by
1) Idiopathic
2) Congenital
- Hydrocephalus
- Cerebral palsy
- SoL
- Trauma
- Prematurity
- Family history
- Refractive error e.g. amblyopia
onset strabismus in adulthood can be caused by
- Cranial nerve palsy (extraocular muscles)
- Intracranial infection
- Intracranial, intraorbital and intraocular masses
- Orbital fracture
- Myasthenia gravis
- Thyroid eye disease
Psuedostrabismus
(false strabismus) is where the eye may appear turned, often in children- but is due to structural causes that resolve over time e.g. broad, flat nose
key definitions to think about with strabismus
- Manifest vs Latent
- Concomitant (non-paralytics) or incomitant (paralytic)
Types of heterptropia
- Esotropia/ esophoria
- Exotropia/ exophoria
- Hypertropia/ hyperphoria
- Hypotropia/ hypophoria
summary of cause and presentations of strabismus - very helpful
manifest squint
Easily discovered on inspection
- presents when the eyes are open and being used
- single- cover test used to determine heterotropia
- can be classified as vertical or horizontal
manifest squints can be classified based on whether they are
horizontal or vertical
latent strabismus (-phoria)
Hidden squint
- the eye only turns when it is covered or shut
concomitant strabismus
deviation does not vary in different direction of gaze
- most esotropias are concomitant and begin in early childhood
incomitant strabismus
deviation varies in different direction of gaze
e.g. gets worse in certain eye movements
- occur both in childhood and adulthood as a result of neurological, mechanical or myogenic problems affecting the muscles controlling eye movement
esotropia
inward positioned squint (affected eye towards the nose)
Exotropia
outward positioned squint (affected eye towards the ear)
Hypertropia
upward moving affected eye
Hypotropia
downward moving affected eye
orthotropic
where the eyes are well aligned
Risk factors for congenital strabismus
- Family history
- Low birth weight
- Premature birth
- Maternal smoking
presentation of strabismus in children
History of presenting complaint
- Onset (e.g. dependent on the direction of gaze or time of day)
- Reduced visual acuity
- Diplopia
- Asthenopia (i.e. eye strain, fatigue or pain), particularly in the afternoon or at the end of the day
- Decreased academic and/or work performance
- Decreased socialisation
- Behavioural problems
- Maladjustment at home or school
- Walking difficulties (i.e. bumping into objects, tripping over)
investigations for strabismus
- Light reflex - check that the light reflex is int he same place on both eyes
- Cover test- manifest
- Cover uncover test- latent
Light reflex test
(a.k.a. corneal reflex test or Hirschberg test)
1. Ask the patient to focus on a target approximately half a metre away whilst you shine a pen torch towards both eyes.
2. Inspect the corneal reflex on each eye:
- If the ocular alignment is normal, the light reflex will be positioned centrally and symmetrically in each pupil.
- Deflection of the corneal light reflex in one eye suggests a misalignment.
Cover test (a.k.a. single-cover test)
Manifest deviations
The cover test is used to determine if a heterotropia (i.e. manifest strabismus) is present.
1. A patient is asked to fixate on a target (e.g. light switch).
2. One of the patient’s eyes is occluded and the non-occluded eye is observed for a shift in fixation:
* If there is no shift in fixation in the contralateral eye, while covering either eye, the patient is orthotropic (i.e. normal alignment).
* If there is a shift in fixation in the contralateral eye, while covering the other eye, the patient has a heterotropia.
3. The cover test is then repeated on the other eye.
The direction of the shift in fixation determines the type of tropia; the table below describes the appropriate interpretation.
Cover–uncover test (a.k.a. alternate cover test)
Latent deviations
1. The cover–uncover test is used to differentiate if a misalignment is either a tropia or a phoria; that is, if the above cover test demonstrates no tropia, it is used to determine if a phoria (i.e. latent strabismus) is present. Large ones can be associated with asthenopia (i.e. eye strain) and diplopia. Note, small, subtly perceptible phorias are common and non-pathological.
2. The examiner occludes one eye for approximately 1-2 seconds, then quickly removes the occluder to restore binocular vision. The eye that was previously occluded is observed (rather than the unoccluded eye, as in the cover test) for refixation movement. If a phoria is present, this eye will shift back to being orthotropic (i.e. straight-looking) to re-establish sensory fusion with the other eye.
3. The speed and smoothness of refixation indicates the strength of fusion
Management of strabismus
- Observation
- Optical correction
- Overminus therapy
- Prisms
- Occlusion therapy
- Vision therapy
- Surgery
describe
may look like a right esotropia - however this is a psuedostrabismus due to flat nose
- Aniscoria (unequal pupil size)
- Right miotic (constricted pupil)
- Right ptosis
- Right horners
o Issue with sympathetic nerve supply -> pupil wont dilate
describe
- Large R esotropia
describe
Compensatory head posture (CHP)
o Face turn to the right
o Head tilt left
o Chin depression
Amblyopia also known as
- Commonly known as lazy eye
amblyopia is due to
Unilateral (bilateral less commonly) reduction in visual acuity due to an insult to the visual pathway during the critical period of visual development
pathophysiology of amblyopia
- Critical period: birth to three months of age
- Some critical development continues until 7-8 years of life
- This happens where theres a breakdown in how the brain and eye work together and the brain cant recognise sight from one eye, over time the brain relies increasingly on the stronger eye
- Cortical adaptation due to abnormal binocular environment
amblyopia is the most common cause of
- Most common cause of preventable and reversible visual disability in children
summary of cause of amblyopia
strabismus
anisometropia (interocular difference in refractive error)
high bilateral refractive error
stimulus deprivation e.g. cataracts
high astigmatism
Strabismic amblyopia:
the most common form of amblyopia which develops in the consistently deviating eye of a child with ocular misalignment.
Anisometropic amblyopia
develops when an unequal refractive error in the two eyes causes the image on one retina to be chronically defocused.
Isometropia amblyopia
bilateral reduction in acuity that results from large approximately equal uncorrected refractive errors in both eyes of a young child causing blurred retinal images on both retinas
Deprivation amblyopia:
usually caused by congenital or early acquired media opacities such as congenital cataracts or early-onset ptosis. This is the least common, but most damaging and difficult to treat amblyopia.
Presentation of amblyopia
- No outward signs
- Poor depth perception
- Difficulty catching and throwing options
- Clumsiness
- Squinting or shutting eye
- Head turn or tilt
- Eye strain
- Fatigue with near work
management of amblyopia
Management
* Eliminating, if possible, any obstacle to vision such as cataracts
* Correcting refractive error
-> This is done by correcting the full refractive error as determined by cyloplegia (search this)
* In unilateral/asymmetrical cases, forcing the use of the poorer eye by limiting the use of the better eye within the sensitive period of visual development.
-> Patching of the good eye -> to force use of the weak eye
