University of Edinburgh
 

Understanding the diagnosis: Childhood visually impairing conditions

Presented on Thursday 1 November 2007

Brain causes of Visual Impairment

Dr Andrew Blaikie, Consultant Ophthalmologist, NHS Fife

Cerebral Palsy

  • Motor impairment due to some kind of brain injury
  • Often unknown
  • Often associated with other impairments
  • Not cause of visual impairment
  • It's an associated symptom

Cerebral Palsy

  • Visual Acuity
  • Visual Field
  • Eye Movements
  • CVI
  • Refractive Errors
  • Accommodation

Visual Acuity

Visual Field

area affected by CP

Eye Movement difficulty

  • Squint
  • Nystagmus
  • Dysmetric saccades
  • Deficient smooth pursuit
  • Paroxysmal deviation
  • Compensate by head movements
  • Watch TV where central character is large and stays still

Cerebral Visual Impairment

Two streams of visual information in the brain

  • The 'Where' stream
    Fast reflex unconscious information to act upon
  • The 'What' stream
    Slower conscious recognition of world

dorsal and ventral

dorsal & ventral

Simultanagnosia

  • Inability to deal with complex scenes also known as simultanagnosia
  • Functionally visual field becomes small
  • Poor attention and easily distracted
  • Sticky fixation

fixation

Accommodation

  • What is accommodation?
  • Over 40s lose it
  • Need reading glasses

accommodation

Impaired accommodation
Common in:

  • Cerebral Palsy
  • Down's Syndrome
    Absent
    Slow
    Inaccurate
    Easily fatigued
    Unstable

Accommodation - Down's Syndrome

down's syndrome

Refractive error

  • Assess whether child might benefit from glasses
  • Tolerance of wearing glasses related to developmental age
  • Related less to visual benefit for child
  • Fitting of glasses critical

refraction graph

refractive errors

Congenital Nystagmus

  • Involuntary wobbly eyes due to problem with part of brain that controls eye movements
  • Typically vision not too bad
  • Near vision usually relatively good

Hydrocephalus

  • Imbalance in the production and drainage of cerebral spinal fluid (CSF)
  • Fluid reservoirs (ventricles) in brain expand

hydrocephalus

hydrocephalus

Causes of Hydrocephalus

Multiple

  • A-C malformation
  • Brain tumour
  • Neonatal brain haemorrhage
  • Infection
  • Unknown

How does Hydrocephalus affect vision?

  • Optic Atrophy
  • Chiasmal Compression
  • Occipital Lobe Damage
  • Eye Movement Problems
    • Squint
    • Nystagmus
    • Supranuclear disorders (setting sun)

Periventricular Leucomalacia

Brain Damage in Premature Babies

  • Hypoxia
  • Hypo-perfusion
  • Leads to brain injury of Periventricular White Matter
  • Spastic Diplegia
  • Visual Impairment

brain scan

Craniopharyngioma

craniopharyngioma

Arises from stalk of pituitary

  • Presses on chiasm from behind and above
  • Young patients present with pituitary problems or hydrocephalus
  • Older complain of visual disturbance

Aicardi’s Syndrome

  • Infantile Spasms
  • Agenesis of corpus callosum
  • Abnormal optic disc
  • Overlaps with Septo-optic-dysplasia

aicardi's syndrome

Neuronal Migration Disorder

  • During 2nd, 3rd and 4th gestational months neurons migrate around brain
  • Disturbance in migration leads to abnormal brain structure and function

Neuronal Migration Disorder

  • Lissencephaly: Smooth Brain
  • Pachygyria: reduced and thickened gyri
  • Polymicrogyria: lots of small gyri
  • Schizencephaly: absence of brain
  • Combinations

NMD

Foetal Alcohol Syndrome

  • Astigmatism
  • Coloboma
  • Congenital Corneal Clouding
  • Peter’s Anomaly
  • Chorioretinal Atrophy
  • Duane’s Syndrome
  • ONH
  • Optic Atrophy

Neurofibromatosis

  • Type 1
    von Recklinghausen or Peripheral
  • Type 2
    Central
           
    Both have:
    typical marks on the skin; and
    An increased risk of developing tumours

neurofibromatosis

Causes of VI

  • Tumours
    Optic Nerve Glioma (type 1)
    Optic Nerve Mengioma (type 2)
  • Glaucoma (type 1)
  • Cataract (type 2)

optic nerve tumour

optic nerve tumour

tumour

Tuberous Sclerosis Complex (TSC)

tuberous sclerosis

tuberous sclerosis

Genetic Disease

  • 70% new mutations
  • 30% inherited dominantly
  • Genes
    TSC1 (9q34)
    TSC2 (16p13.3)
  • Incidence 1 in 6000

Products of genes

  • Important in intracellular cell signalling
  • Neurotransmission
  • Cognitive problems not necessarily due to 'tubers' or 'epilepsy' but may relate to impaired communication between cells
  • TSC2 seems to have worse cognitive outcome

Infantile Spasms

  • Fitting from early age
  • Difficult to control
  • Delays development
  • Often associated with structural brain problems

Medication

  • VIGABATRIN – anticonvulsant drug
  • Used in the treatment of generalized seizures and infantile spasms
  • Field defects noted after approx 1 year treatment
  • Prevalance of between 42% (Wohltab, G et al., 1999) and 71% reported (Russell Eggitt, IM et al 2000)

Vigabatrin

  • Atrophy of the retinal nerve fibre layer sparing macular area
  • Generalised constriction of visual field
  • May not be reversible (Hardusa P et al (2000)

Brain VI Conditions

  • Lots of different types
  • All very different
  • Mainly static
  • Often visual function improves in time
  • Or at least appears to get better
  • Often associated with additional disabilities making assessment challenging