Author: Daniel Horner / Editors: Jonathan D Whittaker, Tajek B Hassan / Reviewer: Martin Dore, Emma Everitt / Code: NeuC10, NeuC12, NeuP7, OptC1, OptC6, OptP5, SLO1, SLO2Published: 09/05/2024


Eye problems contribute to a substantial proportion of the emergency physician’s (EP’s) workload. Even in regions with dedicated ophthalmic casualty units, more than 30% of patients with eye problems will continue to seek help via non-specialist local emergency departments (EDs). [1] Roughly 50% of attendances with eye problems are atraumatic and sudden visual disturbance amounts to over 10% of these cases. [2, 3]

Most cases of sudden visual loss are caused by serious underlying pathology and need prompt diagnosis and early treatment if vision is to be salvaged. Although specialist ophthalmological assessment is usually needed, it is important that the EP takes a thorough history and performs a comprehensive examination to make an accurate diagnosis. Treatment can often then be instigated as a matter of urgency, potentially preserving the patient’s sight.

Learning bite

More than 30% patients with acute eye problems will self refer to non-specialist EDs, and a significant proportion of them will have a sudden visual loss. Prompt diagnosis via comprehensive assessment and early treatment is essential for the majority of pathological causes.

General Aetiology

Previous authors [4] have divided the causes of sudden visual loss into three separate categories:

Pathology of the ocular media

Fig.1 Pathology of the ocular media adapted from Smart Servier


Ocular media describes the transparent structures through which light must pass in order to contact the retina. This media can be subdivided into:


  • Anterior chamber
  • Posterior vitreous

Common corneal problems include trauma (e.g. hyphaema) and infection (e.g. keratitis, corneal ulcer), whereas acute angle closure glaucoma affects the anterior chamber. Sudden visual loss due to posterior vitreous pathology occurs with haemorrhage, inflammation or structural change in this area.

Pathology involving the retina

Fig.2 Pathology involving the retina adapted from Smart Servier


For the retina to process light signals efficiently, it must be structurally intact in all layers, with a patent arterial supply and venous drainage.

Diseases of the sensory retina such as traumatic detachment or infection can cause a marked deterioration in vision, but problems with the vascular supply to the retina itself remain the most likely cause of an acute complete visual disturbance.

Neurovisual pathology

Fig.3 Neurovisual pathology adapted from Smart Servier


Neurovisual pathology includes the optic nerve, chiasm and retrochiasmal problems.

Inflammation, infection or ischaemia can affect the neural optic pathway at any step. The area of visual loss will often help in identifying the location of pathology. Both persistent and transient (e.g. TIA, migraine) lesions may occur.

Vascular Supply of the Eye

Fig.4 Vascular Supply of the Eye


The majority of the inner retina is supplied by the central retinal artery (CRA) which enters the eye at the optic disc and bifurcates into a superior and inferior branch (Fig 4).

Occlusion of the CRA causes complete ischaemia to the entire inner retina, except in 15-30% of patients with an anatomical variant, the cilioretinal artery, who will retain some central vision. [5]

The outer retina, including the macula, is supplied by the choriocapillaris, a separate capillary network originating from the ciliary arteries.

Retinal veins run posteriorly to form superior and inferior branches that converge at the optic disc.

The central retinal vein then leaves the substance of the optic nerve to drain into the cavernous sinus or the superior ophthalmic vein.

Learning bite

15-30% patients have a patent cilioretinal artery, so may retain some visual acuity even in the context of complete occlusion of the central retinal artery.

Ocular Media Problems

Fig.5 Vitreous haemorrhage adapted from Smart Servier


The clear, gelatinous vitreous humour functions to maintain the structural integrity of the eyeball and transparency of the eye.

It is anchored to the globe by three main attachments:

  • Anteriorly adjacent to the ciliary body
  • Posteriorly at the surround of the optic nerve head
  • To the retina along the course of the major vessels

Traction along any of these attachments secondary to trauma, neovascularisation or degenerative change with age can result in adjacent vessel wall damage and haemorrhage into or behind the vitreous (Fig 5). This results in painless visual loss ranging from floaters or black spots across the field to light perception only.

Pathology Involving the Retina

Central retinal artery occlusion

Fig.6 Central retinal artery occlusion – image by Dr. Gopal Bisht, via Wikimedia Commons


Central retinal artery occlusion (CRAO) can occur as a thrombotic, embolic or arteritic phenomenon.

The majority of CRAOs are caused by platelet fibrin thrombi and emboli as a result of atherosclerotic disease and account for over two-third of all CRAO cases.

Central retinal vein occlusion

Fig.7 Central retinal vein occlusion – image by Werner JU et al. via Wikimedia Commons


Venous occlusion may occur either in a branch or in the central retinal vein itself and is more common in those over 65 years. [6]

Retinal vein occlusion is due to thrombosis within retinal veins. The main associations can be defined as risk factors for atherosclerosis, and the remainder are conditions that cause hyperviscosity or slow or turbulent flow through retinal veins.

It is most common where arteries and veins cross in the retina, and in the head of the optic nerve. Progressive thickening of the arterial wall can lead to venous occlusion within the sheath (see Fig.8 below).

Fig.8 Retinal vein occlusion adapted from Smart Servier


Retinal Detachment: Overview

True retinal detachment is defined as the separation of the neurosensory retina from the underlying retinal pigment epithelium, [7] causing a lack of stimulation to the photoreceptor layer (fig 1, below).

Posterior vitreous detachment can cause very similar symptoms but has a slightly different pathological cause.

In this image, the innermost retinal layers are at the bottom.

Fig.9 Schematic representation of retinal layers adapted from Smart Servier


Retinal Detachment: Posterior Vitreous Detachment

Posterior vitreous detachment is caused by collapse of the posterior vitreous with increasing age. Eventually the vitreous detaches from the retina causing flashes of light and the appearance of floaters if haemorrhage occurs at the site of traction. Persistent traction can lead to retinal breaks and subsequent rhegmatogenous retinal detachment.

Retinal Detachment: Rhegmatogenous Detachment

Rhegmatogenous retinal detachment describes the leak of vitreous fluid through a break (rhegma = rent) in the retinal pigment epithelium and its collection in the subretinal space.

Blunt ocular trauma is the cause of between 4-10% of rhegmatogenous retinal detachments. [8]

Other conditions that predispose to atraumatic retinal breaks are:

  • Myopia
  • Previous cataract surgery
  • Peripheral vitreoretinal lesions

Neurovisual Pathology

Optic neuritis

Optic neuritis is predominately an autoimmune condition most common in middle-aged females producing demyelination of the optic nerve. Swelling of the optic nerve head ensues and may be visible on fundoscopy as papillitis. An acute and often progressive visual loss results.

Optic neuritis is a common presentation (approximately 15-20% of cases) in multiple sclerosis. [9]

Monocular optic neuritis is the presenting finding in up to 20% of patients with multiple sclerosis.

Acute ischaemic optic neuropathy

Acute ischaemic optic neuropathy is most commonly caused by giant cell arteritis, but can also be seen with other conditions such as polyarteritis nodosa and systemic lupus erythematosus (SLE).

In giant cell arteritis, vascular wall inflammation leads to lumen narrowing and eventual occlusion, resulting in ischaemia and infarction of the optic nerve. [10] The underlying cause of this inflammation remains uncertain, with autoimmune and infective mechanisms thought to be the main contributors.


In addition to the history of presenting complaint, previous ophthalmic history and underlying systemic disease with potential to affect the eye, the clinician should enquire about a history of thromboembolic risk factors and conditions predisposing to retinal detachment, i.e. myopia, cataract surgery, increasing age. In sudden visual loss, certain discriminating questions may narrow the differential diagnosis:

Is there a history of trauma?

Blunt trauma to the orbit followed by flashes of light and visual loss may suggest traumatic retinal detachment.

How quickly did the disturbance appear?

A rapid onset suggests a vascular problem or retinal detachment.

A slower onset suggests a more chronic process such as optic neuritis or glaucoma.

Is the eye red?

A red eye is suggestive of inflammatory pathology, such as keratitis, uveitis or acute angle closure glaucoma.

A poorly functioning eye, which appears normal externally, should arouse suspicion of pathology in the posterior vitreous, retinal or neurovisual structure.

Is the eye painful?

CRAO/CRVO are characteristically painless, as is posterior vitreous detachment.

However, optic neuritis is associated with pain on ocular movement.

Giant cell arteritis commonly causes a temporal headache and/or pain on mastication (jaw claudication).

Are there any extraocular symptoms?

Acute angle closure glaucoma may present with headache and autonomic features such as nausea and vomiting.

Ischaemic optic neuropathy is commonly associated with headache and jaw claudication.

Dysphasia and other neurological deficits suggest an intracerebral problem.

Is the disturbance a partial or complete loss of vision?

Complete loss of vision in one eye localises pathology to that eye or optic nerve, e.g. CRAO/CRVO.

If the disturbance is partial, what form did it take?

Partial loss of vision must be differentiated between:

  • Loss of part of the visual field – for example, quadrantopia, hemianopia or central scotoma
  • A ‘curtain coming down’ across the vision – a typical description of a retinal detachment or amaurosis fugax in a transient ischaemic attack
  • Flashes – usually due to retinal ischaemia/detachment
  • Floaters – due to opacities in the vitreous which may be normal. However, a sudden increase in floaters may be caused by vitreous haemorrhage or posterior vitreous detachment
  • ‘Haloes’ around bright objects with blurred vision – seen often in acute angle closure glaucoma

Learning bite

Discriminating questions early in the history can focus the differential diagnosis and allow investigation/exclusion of the most likely causes as a priority.


In addition to a general and standard eye examination, particular features to look for in a patient with a sudden visual loss include:

Visual acuity

Examination of the patient’s visual acuity should be undertaken using a Snellen chart.

If the patient is unable to see the top line of the chart then the assessments should be undertaken, moving to the next step if failure occurs.

Visual acuity assessment steps

Step 1: Move the patient to three metres from the chart and recheck (recorded as 3/x)

Step 2: Assess ability to count fingers (recorded as CF)

Step 3: Assess ability to perceive hand motion (recorded as HM)

Step 4: Assess ability to perceive light and dark (recorded as LP)

Pupillary reactions

When examining pupillary reactions the clinician should be looking for:

  • Appearance – is it regular and is there a red reflex?
  • Reaction to direct and consensual light
  • Reaction to accommodation
  • Presence of a relative afferent pupillary defect

Ophthalmoscopy, slit lamp and tonometry

The patient should undergo ophthalmoscopy, slit lamp examination and tonometry if available. Remember to visualise the retina adequately, the pupils must be dilated with a topical mydriatic such as tropicamide. This carries a negligible risk of precipitating acute angle closure glaucoma. [11]

Learning bite

Particular attention should be paid to bilateral accurate assessment and documentation of visual acuity for cases of sudden visual loss. The eye may well look macroscopically normal, even on fundoscopy. Visual acuity assessment then proves the only objective marker of pathology.

Fundoscopic Appearances Found in Sudden Visual Loss

Find out more about each of the fundoscopic appearances shown below.


Fig.10 Central retinal artery occlusion – image by Dr. Gopal Bisht, via Wikimedia Commons


Central retinal artery occlusion (CRAO) typically produces a very pale optic disc and retina, together with the classic ‘cherry red spot’ of the macula. This is due to the separate supply of the outer retina by the choriocapillaris.


Fig.11 Central retinal vein occlusion – image by Werner JU et al. via Wikimedia Commons


The appearance of central retinal vein occlsion (CRVO) is more dramatic; diffuse retinal haemorrhage and venous dilatation are seen in all four quadrants often referred to as a ‘blood and thunder’ or ‘stormy sky’ appearance.


In papillitis, fundoscopic changes are only seen with direct involvement of the optic nerve head resulting in a papillitis, visible as hyperaemia, blurred disc margins and occasionally haemorrhages.

This occurs in approximately one third of cases of optic neuritis, [12] the remainder causing a retrobulbar neuritis and a fundoscopically normal optic disc. Ischaemic optic neuropathy may also cause this appearance.

Retinal detachment

Fig.12 Retinal detachment via LITFL


Retinal detachment may be difficult to visualise as it often originates peripherally.

Minimal changes are usually seen with posterior vitreous detachment, but can include vitreous, retinal and optic nerve head haemorrhages. [13] Oedema of the optic nerve head and macula are also possible.


It is vital that all patients presenting to the ED with an acute change in vision must, at the very least, be discussed with a senior emergency physician or ophthalmologist and assessed as a matter of urgency.

Acute Angle Closure Glaucoma (AACG)

The management of acute angle closure glaucoma (AACG) centres around early identification and definitive surgical treatment.

Medical therapy may be initiated to reduce pain and clear corneal oedema, [14] particularly if a delay to specialist ophthalmological assessment of more than one hour is anticipated.

Acetazolamide and topical miotics or antihypertensives should be considered.

For further information see the session: Management of the Atraumatic Red Eye.

Learning bite

Definitive surgical treatment is the recommended gold standard intervention for acute angle closure glaucoma. Medical treatment exists to control symptoms and prepare the eye for intervention.

Fig.13 This image shows AACG. Note the mid sized pupil, which was nonreactive to light, and conjunctivitis. [The image by James Heilman via Wikimedia Commons]


Central Retinal Artery Occlusion

There is ongoing debate about the survival time of an ischaemic retina. A study on rhesus monkeys reported a retinal survival time of 105 minutes, [15] but other authors have suggested a beneficial effect from treatments given up to 24 hours after the onset of symptoms. [16]

Although in vivo animal experiments have suggested irreparable retinal damage after approx. 100 minutes, human studies have shown benefit of treatment up to 24 hours after the onset of retinal ischaemia.


There is weak evidence for definitive treatment of this potentially catastrophic condition. A Cochrane review looking at all interventions for acute non arteritic CRAO found no high quality evidence to support routine use of any particular therapy. [17] However, expert opinion [5] suggests the following may be used in the ED.

Digital massage in the supine position

Ocular massage has been shown to cause retinal vasodilatation and large fluctuations in intraocular pressure, which have the potential to dislodge or disrupt an embolus in the central retinal artery. This is best performed by the patient if possible, to avoid iatrogenic injury through over-exuberant pressure. One suggested method is unilateral gentle palpation of one side of the affected eye, then the other side through closed lids. [18]

Increasing retinal perfusion pressure by reduction of intraocular pressure

Intravenous acetazolamide or mannitol are preferred for this treatment in the ED.

Selective intra arterial fibrinolysis

A meta-analysis has suggested some benefit, but specialist neuroradiological support is required.

Learning bite

Although definitive evidence is lacking, treatment for CRAO in the ED primarily consists of digital globe massage and pharmacological reduction of intraocular pressure.

Central Retinal Vein Occlusion

There is no current evidence that any type of early treatment will alter the visual prognosis in established retinal vein occlusion (CRVO). Non-ischaemic CRVO may resolve without symptoms. However, all patients with suspected CRVO should be urgently referred to ophthalmology for assessment. They may consider starting anti-VEGF (vascular endothelial growth factor) as this can improve vision in patients with macular oedema secondary to CRVO. [19]

Retinal Detachment

Fig.14 Retinal Detachment adapted from Smart Servier


Given that over 95% of rhegmatogenous retinal breaks can be repaired successfully and that re-attachment rates are higher with early diagnosis and intervention, [20] ED care is primarily aimed at accurate diagnosis and prompt referral.

Optic Neuritis

Despite the fact that it would seem logical to treat acute optic neuritis with high dose steroids in the same way as exacerbations of multiple sclerosis, trial data in this area has shown little success.

A meta-analysis has shown no overall benefit from corticosteroids in improving visual acuity, contrast sensitivity or visual field deficit. [21]

Learning bite

In patients with optic neuritis, there is no conclusive evidence of benefit with corticosteroids in terms of return to normal visual acuity, visual field or contrast sensitivity.

Anterior Ischaemic Optic Neuropathy (AION)

Suspected anterior ischaemic optic neuropathy (AION) should always be reviewed by an ophthalmologist, even if the visual acuity is currently normal, to ensure aggressive treatment and continual monitoring.

If giant cell arteritis is the suspected cause of AION, the use of high dose steroids is thought to reduce inflammation and preserve blood supply to the optic nerve head.

However, there is a void of evidence regarding this well recognised and routine therapy. This is due to the unethical nature of conducting controlled trials in light of the multiple case report and cohort studies suggesting benefit from the mid-twentieth century.


Two reviews [22, 23] have found no good evidence to support the use of intravenous over high dose oral steroids in AION.

Therefore, emergency treatment in the ED should comprise of early identification, prompt referral for temporal artery biopsy and immediate initiation of high dose oral prednisolone.

Although there is no direct consensus regarding the optimum regimen for oral steroid dosing, a pragmatic regime would be 1 mg/kg/day oral prednisolone aiming to taper after four weeks.

Learning bite

Although debate is ongoing, current evidence is not of sufficient quality to routinely recommend IV over high dose oral corticosteroid preparations in the treatment of arteritic AION.

  • Failure to consider temporal arteritis in the differential diagnosis of acute headache, with resultant potentially avoidable permanent visual loss
  • Failure to document formal visual acuity at the initial presentation of the patient with sudden visual loss
  • Failure to commence appropriate high dose corticosteroid treatment for the patient with symptoms suggesting arteritic AION
  • Failure to consider acute glaucoma in the unwell patient with headache and vomiting
  • Failure to instigate prompt management and urgent ophthalmic opinion in the patient presenting with signs and symptoms of CRAO
  • Failure to consider occipital lobe pathology and thromboembolic risk factors as the cause for visual impairment and perceived ocular pathology.
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