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Describe the causes and assessment of sudden loss of vision.

Ophthalmology · 3rd Professional

Sudden Painless Loss of Vision

The approach rests on three questions: is it monocular or binocular? Is it transient or persistent? And is it painful or painless? Those three answers narrow the diagnosis before the eye is examined
Monocular loss indicates a lesion anterior to the chiasm; binocular loss with a field defect respecting the vertical midline indicates a lesion AT or behind the chiasm

Cause	Distinguishing features
Central retinal artery occlusion	Instantaneous, profound, painless loss with a relative afferent pupillary defect, a pale oedematous retina and a cherry-red spot. A stroke equivalent: exclude giant cell arteritis in anyone over 50 and refer for urgent carotid and cardiac assessment
Central retinal vein occlusion	Loss over hours to days; the "blood and thunder" fundus with haemorrhages in all four quadrants, dilated tortuous veins and disc swelling
Vitreous haemorrhage	Sudden floaters, a red haze then loss; loss of the red reflex with no view of the fundus. B-scan is mandatory to exclude a detachment
Retinal detachment	Flashes and floaters preceding a curtain advancing across the field; the field defect is opposite the detachment
Neovascular AMD	Sudden central distortion (metamorphopsia) and a central scotoma in an elderly patient, with subretinal fluid, haemorrhage and exudate
Ischaemic optic neuropathy	Painless altitudinal loss on waking with a swollen disc. Arteritic disease gives a chalky-white swollen disc, very poor vision and systemic symptoms — and demands immediate steroid
Optic neuritis	The exception to painlessness: subacute loss over days in a young adult with pain ON eye movement, red desaturation and an afferent defect
Occipital stroke	Binocular homonymous field loss with normal pupils and normal discs; the patient may describe it as one-sided
Functional (non-organic) visual loss	Normal pupils, normal discs, inconsistent responses and normal electrophysiology; a diagnosis of exclusion made positively rather than by default

Transient Visual Loss and Immediate Priorities

The duration of a transient episode is highly discriminating:
Seconds, on standing or bending, in both eyes — transient visual obscurations of papilloedema. Look at the discs
Minutes, monocular, described as a curtain descending and lifting — amaurosis fugax, an embolic transient ischaemic attack of the eye. It demands the same urgent carotid, cardiac and vascular work-up as a cerebral transient ischaemic attack, and antiplatelet therapy. It is a warning that should not be wasted
20 to 30 minutes, binocular, with positive phenomena — scintillations, zigzags and a spreading fortification spectrum — migraine aura, which characteristically marches across the field and may occur without headache

All questions in Ocular Trauma and Emergencies

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