Scottish Sensory Centre

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

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

Simultanagnosia

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

Accommodation

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

Impaired accommodation
Common in:

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

Accommodation - 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

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

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 inPremature Babies

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

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

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

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

Causes of VI

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

Tuberous Sclerosis Complex (TSC)

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

• Understanding the diagnosis