Sudden Loss of Vision

Sudden loss of vision is a genuine GP emergency. Most causes require an urgent ophthalmological opinion as there is little that the GP can do. This particular symptom is not often encountered in general practice – a prompt appointment or visit and a careful examination are necessary to assess the situation and exclude the causes not requiring urgent specialist treatment. Blurring, such as that found in some cases of the acute red and painful eye, is not covered here.

Published: 2nd August 2022 | Updated: 15th August 2022

Differential diagnosis

Common Diagnoses

  • Acute Glaucoma (May Cause Blurring but Can Rapidly Progress to Complete Loss of Vision)
  • Vitreous Haemorrhage
  • Central Retinal Artery Occlusion
  • Migraine
  • CVA or TIA

Occasional Diagnoses

  • Central Retinal Vein Occlusion
  • Retrobulbar (Optic) Neuritis
  • Retinal Detachment
  • Temporal Arteritis
  • Posterior Uveitis

Rare Diagnoses

  • Functional Neurological Disorder
  • Cortical Blindness (Non-Vascular)
  • Optic Nerve Injury
  • Quinine Poisoning

Ready reckoner

Key distinguishing features of the most common diagnoses

Acute GlaucomaVitreous HaemorrhageRetinal Artery OcclusionMigraineTIA/CVA
Preceded by Spots and Flashing LightsNoPossibleNoYesPossible
Followed by HeadachePossibleNoNoYesPossible
Painful EyeYesNoNoNoNo
Absent Red ReflexNoYesNoNoNo
Affected Pupil Dilated and FixedYesNoYesNoNo

Possible investigations

  • In practice, there are none worth doing at the time, as the vast majority of cases will be referred urgently. Virtually all tests will therefore be arranged by the specialist, usually after the event, to look for underlying causes. Such investigations include the following.
  • Screening for diabetes: Undetected retinopathy may have preceded vitreous haemorrhage.
  • FBC: PCV may be raised in central retinal vein occlusion.
  • ESR: Raised in temporal arteritis.
  • Multiple microbiological investigations are needed for posterior uveitis.
  • Posterior pole ultrasound may be useful in vitreous haemorrhage to identify treatable causes.
  • CT scan only useful to investigate cerebral causes (CVA or cortical blindness).

Top Tips

  • Acute visual disturbance is often difficult to diagnose accurately and very alarming for the patient. If in doubt, refer urgently, or, at the very least, review in a few hours.
  • The patient’s assessment of visual loss, and its severity, is highly subjective – if at all possible, test it with a Snellen chart.
  • Always keep spare batteries handy for your ophthalmoscope!

Red Flags

  • Don’t forget that the visual disturbance may be the presenting symptom of some other pathology, such as hypertension, temporal arteritis or diabetes.
  • Don’t miss a heart murmur or carotid bruit. These may be present in retinal artery occlusion and TIA/CVA.
  • A cherry red spot on the fovea is pathognomic of retinal artery occlusion.
  • Never use mydriatics to aid examination at the bedside – these will cloud the clinical picture and may even precipitate acute glaucoma.
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Website disclaimer

Pulse Reference is based on the best-selling book Symptom Sorter.

The experts behind Pulse Reference are Dr Keith Hopcroft who is the co-author of Symptom Sorter, a GP in Essex and Pulse’s editorial advisor and Dr Poppy Freeman, a GP in Camden and also a clinical advisor to Pulse.

This website is for clinical guidance only and cannot give definitive diagnostic information. Practitioners should work within the limits of their individual professional practice, seek guidance when necessary and refer appropriately.