Papilloedema

Optic disc swelling can be caused by a number of conditions; papilloedema relates more specifically to optic disc swelling secondary to raised intracranial pressure. Disc swelling is distinct from disc atrophy which refers to a loss of nerve fibres at the optic nerve head and which results in a pale disc. Atrophy may be primary (where it occurs without prior disc swelling) or secondary (where it is preceded by disc swelling). This article provides an overview of the most common (and some less common) causes of optic disc swelling.

If you suspect a swollen disc on fundoscopy, there are several points to note that will be helpful in guiding your diagnosis and referral.

• DO NOT DILATE the patient's pupils until you have ascertained the presence or absence of a relative afferent pupillary defect. This is a very valuable sign which must not be missed.
• Look around the margin of the disc: are there any clear segments of the disc margin or is it swollen all around? An isolated area of 'swelling' may actually be myelination of nerve fibres around the nerve head.
• What colour is the disc? Pallor suggests a whole additional range of conditions (compare to the other side). If the swelling is severe, you may not be able to distinguish the disc from the background retina.
• If you have a very good view, look for the presence of a spontaneous venous pulsation: this is a pulsation seen in the veins just as they emerge from the optic nerve before radiating out. This absent in 20% of normal patients but not unilaterally.
• Don't forget to examine the fellow eye even in the absence of symptoms.

• Check visual acuity (VA) with a Snellen chart.
• Check for an afferent pupillary defect (RAPD) using the swinging flashlight test: first, make sure that you are in a dark room, use a bright light and ask the patient to gaze into the distance (such as a far wall) to avoid physiological constriction of the pupil and to maximise your chances of spotting an abnormal response. Shine the light source from one eye to the other in rapid succession. Stimulation of the normal eye should elicit a brisk constriction of both pupils but when the light is shone on the diseased eye, both pupils dilate (what happens is that the dilatation produced by withdrawing the light from the normal eye outweighs the weak constriction produced by shining light on the diseased eye - this is why it is called a relative afferent pupillary defect: an afferent pupillary defect occurs where there is a complete optic nerve lesion: the patient is then blind in that eye "it's all black when I cover my good eye" and that pupil won't constrict at all when light is directly shone on it).
• Check for colour impairment (dyschromatopsia). Ideally, this is done using an Ishihara colour test booklet: cover the good eye first and flick through the book, allowing about 5 seconds per number, then compare with the fellow eye. If the booklet is not available, ask the patient to compare the colour of a bright red object (such as a child's toy) - descriptions of things looking "washed out" should ring alarm bells.
• Assess brightness sensitivity: shine a light in each eye and ask the patients to compare the brightness. A useful measure is to suggest: "If I were to give you a pound for this brightness" (shine light in good eye), "how much would you give me for this ..." (shine light in bad eye).
• Carry out a confrontational visual field test, specifically looking for an enlarged blind spot.

Raised intracranial pressure: papilloedema²

This may be due to obstruction of the ventricular system, space-occupying lesions, imapriment of CSF absorption, disffuse cerebral oedema or idiopathic (benign / essential) intracranial hypertension.

• Presentation: headache (worse on waking and when coughing), may have nausea / vomiting and may have other neurological symptoms. VA not impaired initially but in later stages, may complain of fleeting visual loss lasting seconds, related to posture (transient visual obscurations). There may be a history of head trauma.Take note of the over-weight woman of child-bearing age on the oral contraceptive pill - they account for 90% of cases of essential intracranial hypertension.
• Ocular findings: disc swelling that is nearly always bilateral (it may be asymmetrical), normal (early) or reduced (late) visual acuity (VA), enlarged blind spot, impaired colour vision, may have a VI Cranial Nerve palsy.
• Systemic findings: neurological signs depending on the cause of the raised intracranial pressure.
• Additional notes: Patients with suspected papilloedema should be considered to have an intracranial mass until proved otherwise. Imaging of the brain and orbits is mandatory and a lumbar puncture may also be performed if imaging is normal. Not all patients with raised intracranial pressure develop papilloedema - this depends on the site and size of the tumour. Patients who have previously had papilloedema may also fail to redevelop it in the future.

Space occupying lesions of the optic nerve head

• Presentation: reduced vision, may complain of diplopia if globe movement restricted. Large lesions may also cause epiphora (tearing) and discomfort as a result of proptosis and the patient may complain of a red eye due to congested blood vessels.
• Ocular findings: may range from few or no findings to a proptosed eye which is congested (conjunctiva is red and may be oedematous) and has a limited range of movement. VA reduced in later stages and there may be a RAPD.
• Systemic findings: depends on the nature of the lesion. Look for neurological signs, any pointers towards possible malignant disease and evidence of hyperthyroidism.

Optic neuritis

This term refers to an inflammation of the optic nerve, which can occur as a result of demyelinating or infective disease processes. The optic nerve head is occasionally swollen but pallor of the disc is the norm.

Demyelinating optic neuritis³

• Presentation: subacute monocular visual impairment (bilateral symptoms can occur but are rare) and there may also be some mild globe discomfort, particularly on moving the eye. Demyelinating optic neuritis can occur in isolation but is more commonly part of a systemic problem which can include multiple sclerosis (MS), Devic disease (which is characterised by bilateral optic neuritis) and Schilder disease.
• Ocular findings: reduced VA, RAPD, optic disc pallor, dyschromatopsia and visual field defects (most frequently altitudinal or arcuate). Palsies involving the III, IV and VI cranial nerves may be present.
• Systemic findings: this depends on where else the demyelination has occurred. For example, a trigeminal or facial nerve palsy may be found in brain stem lesions.
• Additional notes:There is a close association between optic neuritis and MS. 16% of patients who have optic neuritis but a normal MRI scan will go on to develop MS within 5 years. 50% of patients presenting with optic neuritis will have demyelinating lesions on MRI scan and in 70% of established MS cases, there will be evidence of a previous episode of optic neuritis. Finally, there are a number of factors that increase the risk of a patient who presents with optic neuritis developing subsequent MS: winter onset, HLA-DR2 positivity and worsening of symptoms with increase in body temperature (exercise, hot bath - the Uhtoff phenomenon). VA often returns over the course of several weeks (in 85% of cases, to 6/12 or better) but other functions often remain abnormal and a mild RAPD may persist.

Parainfectious optic neuritis

• Presentation: severe visual loss, usually bilateral, 1-3 weeks following a viral infection (e.g.: measles, mumps, chickenpox, whooping cough, glandular fever). Children are more frequently affected than adults and this may occur after immunisations. There may have been other neurological phenomena: headaches, ataxia or seizures.
• Ocular findings: disc may be swollen or normal.
• Systemic findings: look for features of meningo-encephalitis.
• Additional notes: spontaneous complete visual recovery is the norm in the majority of patients - only a small number will need systemic steroids if the visual loss is severe.

Infectious optic neuritis

• Varicella zoster virus: primary optic neuritis uncommon unless immunocompromised. Secondary optic neuritis arises from viral spread where acute retinal necrosis has occurred. These patients will be treated with intravenous antivirals.
• Sinus infections: occasionally, direct spread of infection (possibly due to sinus wall defects) or occlusive vasculitis may occur following spheno-ethmoidal sinusitis. Patients will complain of severe headaches and recurrent episodes of unilateral visual loss.Treatment is with systemic antibiotics but surgical drainage of the sinus may also be needed.
• Cat-scratch fever: this self-limiting infection has a good prognosis with visual recovery occurring within 1-4 weeks of starting antimicrobial therapy.
• Lyme disease: optic neuritis may occasionally occur. Peripheral neurological manifestations may mimic MS. A course of intravenous ceftriaxone is the management of choice.
• Syphilis: Acute optic neuritis may occur both in the primary or secondary stages. Involvement may be unilateral or bilateral.

Ischaemic anterior optic neuropathy²

Non-arteritic

• Nature: this is a partial or total infarction of the optic nerve head due to occlusion of the posterior ciliary arteries. Patients tend to be in the 45-65 year old age group and predisposing factors include hypertension, diabetes, hypercholesterolaemia, collagen vascular disease, antiphospholipid antibody syndrome, sudden hypotensive episodes and cataract surgery.
• Presentation: sudden painless monocular visual loss (often discovered on waking).
• Findings: 70% of patients have moderate to severe reduction in VA, most will have a visual field defect (typically altitudinal), dyschromatopsia proportional to the level of visual impairment and a pale oedematous disc.
• General management following referral: fasting lipids and glucose, exclusion of autoimmune diseases. Carotid artery doppler ultrasound scans will also be valuable to rule out a source of emboli. Address other factors relating to cardiovascular diseases including advice on smoking cessation.
• Prognosis: most patients experience no further reduction in VA but 30-50% of them go on to experience the same problem in the fellow eye within months or years. Non-arteritic ischaemic optic neuropathy never occurs in the same eye twice.

Arteritic (Giant Cell arteritis)

• Nature: granulomatous inflammation of vessels involving the elastic tissues of the media and the adventitia. There is a predilection for the temporal, ophthalmic, posterior ciliary and vertebral arteries.
• Presentation: one or more of jaw claudication, scalp tenderness, neck pain, malaise, temporal artery tenderness, visual reduction or loss in the patient over 55 years of age (some argue that this condition does not occur before the age of 60 or 65). Episodes of amaurosis fugax may occur prior to infarction of the optic nerve head. Patients may also complain of flashing lights and periocular pain.
• Findings: VA may still be normal. Pale or swollen optic disc. Palpate the temporal artery: a tortuous, tender artery with no palpable pulse are worrying findings.
• Initial management on suspicion of diagnosis: this is a medical emergency - failure to diagnose and treat adequately can result in blindness of one or both eyes. Once diagnosis is suspected, take a baseline set of bloods to be processed urgently, including plasma viscosity or ESR (depending on local availability) and CRP - if the CRP is normal, this is not giant cell arteritis. It is also helpful to do a full blood count and a chest X Ray as these patients will be treated with intravenous methylprednisolone initially and oral steroids subsequently. Refer the same day: treatment will be initiated if the suspicion is strong, even before a temporal artery biopsy is performed. This may confirm the diagnosis (the disease is patchy and may not occur in the segment biopsied) and will support the decision to start the patient on high dose oral steroids (in the region of 60-80mg per day) after three pulses of intravenous steroids (1mg methylprednisolone on 3 consecutive days). A temporal artery biopsy will remain positive up to 10 days after starting treatment but should ideally be performed within three days (by the ophthalmologists or vascular surgeons). Starting patients on low doses of steroids and using a watch and wait approach in the community is inappropriate and could reasonably result in medical negligance procedures should vision be lost.
• Prognosis: good if treatment is initiated promptly. If there is visual loss, nothing can be done for that eye but the fellow eye's vision can be saved with treatment.

Accelerated (malignant) hypertension

• Presentation: decreased VA and episodes of temporary visual loss. May be asymptomatic.
• Ocular findings: attenuation of arterioles (copper wiring), arteriovenous nipping (narrowing of the veins as the arteries pass over them) and signs of vascular leakage (haemorrhages and exudates). Disc swelling occurs in the presence of very high blood pressure.
• Systemic findings: very high blood pressure (usually greater than 200 systolic and 100 diastolic).
• Additional notes: this medical emergency consitutes one of the commonest causes of optic disc swelling.⁴ Although the mainstay of treatment is clearly to lower the blood pressure, this must be done progressively as a sudden drop can precipitate vascular occlusion.

Central retinal vein occlusion⁵

• Presentation: this common condition may be ischaemic or non ischaemic and involves occlusion of the central retinal vein resulting in a backlog and stagnation of blood which leads to generalised (including disc) oedema. Presentation is with a painless reduction in VA which ranges from very mild to profound. This is monocular but the fellow eye can be affected in unfortunate patients. Rarely, patients complain of discomfort and a red eye.
• Ocular findings: mild to severe reduction in VA (if severe, RAPD may also be present), dilated, tortuous veins, diffuse retinal haemorrhages and disc oedema. Later on, there may be conjunctival congestion and disc oedema.
• Systemic findings: evidence of cardiovascular disease. Other causes include clotting disorders, blood dyscrasias, paraproteinaemias, vasculitides, systemic lupus erythematosis and the oral contraceptive pill.
• Additional notes: in the UK, these patients tend to be managed conservatively with regards to the eye but there should be efforts made to address underlying predisposing factors. Some patients will benefit from fluorescein angiography and laser treatment several months down the line - this decision will be made by the ophthalmology team based on their clinical findings. However, the prognosis for visual rehabilitation is generally poor.

Diabetic papillopathy

• Presentation: progressive monocular visual loss.
• Ocular findings: modest decrease in VA (6/12 or better), disc swelling may be unilateral or bilateral, visual field defects (general constriction or scotoma), ± RAPD and dyschromatopsia.
• Systemic findings: evidence of peripheral diabetic vasculopathy.
• Additional notes: some controversy regarding treatment (many just observe) but spontaneous resolution does frequently occur over several months. These patients will be closely monitored for evidence of other diabetic retinopathy or maculopathy.

Leber optic neuropathy

• Presentation: unilateral acute, severe but painless visual loss with similar symptoms occurring in the fellow eye within 2 months - typically in males in their twenties (rarely: females 10-60 years old). May have family history as this is an inherited disorder.
• Ocular findings: dilated capillaries on (swollen) disc surface and visual field defects (scotoma).
• Systemic findings: none.
• Additional notes: prognosis is generally poor although a small number of patients will have some degree of recovery in due course (may be years).

• Nature: this is apparent disc swelling due to an underlying benign process. This could be due to colloid bodies (drusen) buried within the optic nerve head, an unusual angulation of the disc or a small disc from which the neurones emerge with a residual myelin sheath.
• Presentation: these patients are usually asymptomatic but drusen can occasionally cause a progressive loss of peripheral vision (and rarely, central vision too).
• Ocular findings: apparent disc swelling in the absence of any other findings. Small discs may look "crowded" with the vessels sprouting out like a bunch of flowers. Residual myelin sheath is often limited to one part of the disc only.
• Additional notes: treat as true optic disc swelling until proven otherwise.

This is guided by the severity of the presenting symptoms but as a rule of thumb, these patients all need prompt referral for further assessment, particularly patients with suspected papilloedema or giant cell arteritis.