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.
- Acute Glaucoma (May Cause Blurring but Can Rapidly Progress to Complete Loss of Vision)
- Vitreous Haemorrhage
- Central Retinal Artery Occlusion
- CVA or TIA
- Central Retinal Vein Occlusion
- Retrobulbar (Optic) Neuritis
- Retinal Detachment
- Temporal Arteritis
- Posterior Uveitis
- Functional Neurological Disorder
- Cortical Blindness (Non-Vascular)
- Optic Nerve Injury
- Quinine Poisoning
Key distinguishing features of the most common diagnoses
|Acute Glaucoma||Vitreous Haemorrhage||Retinal Artery Occlusion||Migraine||TIA/CVA|
|Preceded by Spots and Flashing Lights||No||Possible||No||Yes||Possible|
|Followed by Headache||Possible||No||No||Yes||Possible|
|Absent Red Reflex||No||Yes||No||No||No|
|Affected Pupil Dilated and Fixed||Yes||No||Yes||No||No|
- 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).
- 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!
- 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.