Loss of vision, also known as visual failure is a common presenting complaint.

It is an important presentation, but left untreated, many causes of sudden visual loss can rapidly result in permanent blindness.

The most common cause of a visual dysfunction is a refractive error. Sudden onset visual disturbance almost always requires acute intervention to prevent loss of sight.

The only exception is migraine.

Red eye vs white eye

  • “White eye” – i.e. normal looking eye –more likely to result in blindness
  • Red eye” – acutely inflamed eye – often conditions are less serious

Definition of blindness

  • Best visual acuity less than 3/60 (WHO)
  • Less than 6/60 OR severe visual field loss (Australian definition of blindness)
    • Therefore scenarios exist where a patient can have 6/6 vision, but severely reduced visual fields and be declared blind
  • Minimum driving requirement in Australia – 6/12

Common Causes of Blindness Worldwide

  • Trachoma – caused by chlamydia trachomatis. The chlamydia infection leads to roughening of the inner surface of the eyelid, which over time causes corneal damage. The eyelid can also become scarred and misshapen which also prevents it from protecting the eye. These two effects in combination can cause eventual blindness. Most commonly affects children
  • Onchocerciasis – aka river blindness. Caused by the parasitic worm onchocerca volvulus. Transmitted by black flies. Once infected, the larvae migrate to the skin (and eye), waiting for the next black fly bite – to infect the black fly. The larva are toxic, and, over many years, cause blindness. The toxicity of the larva also makes them very itchy!
  • Vitamin A deficiency

Common Causes of Blindness in Developed Countries

  • Senile cataracts
  • Glaucoma
  • Age related macular degeneration
  • Trauma
  • Diabetic retinopathy
  • Causes of sudden visual loss
    • Migraine
    • Retinal artery occlusion
    • Vitreous haemorrhage
    • Retinal detachment
    • Central retinal artery occlusion
    • Central retinal vein occlusion
    • Papilloedema
    • Optic neuritis

History taking

Important features in the history:

  • Unilateral or bilateral?
  • Acute, gradual or progressive?
  • Central or peripheral?
  • Drug history – many drugs are associated with visual impairment

Specific History Questions

  • Floaters
    • Commonly seen with vitreous haemorrhage and vitreous detachment
    • Posterior vitreous detachment is the commonest cause of floaters – is a normal physiological ageing process happening is most people in middle age. It is often asymptomatic, but may present with floaters and flashing lights
    • Retinal detachment has a tendency to occur in myopia (short sightedness)
  • Flashing lights
    • Migraine
    • Posterior vitreous detachment
    • Retinal detachment
  • “Haloes”
    • Coloured haloes around lights
    • Indicative of glaucoma
  • Aura / zig zag lines – indicative of migraine
  • Associated headache
  • Central scotoma
    • Vision disrupted in centre
    • Macular disease
    • Optic neuritis
  • Pain on moving eyes
    • Retro-bulbar neuritis
  • Distortion
    • Macular degeneration
  • Visual field loss
    • Central – macular cause
    • Total loss – retinal arterial occlusion
    • Peripheral loss – see visual field defects

Underlying Systemic Diseases that can cause visual loss

References

Murtagh’s General Practice. 6th Ed. (2015) John Murtagh, Jill Rosenblatt

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