Differential Diagnosis
Papilloedema is the third most common causes of optic disc swelling ( 14 %). The most common are non-arteritic anterior ischaemic optic neuropathy ( 35 %) and optic neuritis ( papillitis ) ( 31 %). Optic discs may also become oedematous secondary to vascular conditions such as occlusions of the central retinal artery vein , hypertension and diabetes . 21
Figure 2 - Non Arteritic Anterior Ischaemic Optic Neuropathy or near-normal visual acuity , normal colour vision and normal pupil reactions .
Pseudopapilloedema is an apparent swelling of an otherwise healthy optic disc and can be due to congenitally anomalous discs , optic nerve head drusen or a combination of the two . Congenitally anomalous discs are often small optic discs that lack a physiological cup ( Figure 4 ). All healthy optic nerves , even small ones , carry between 1 and 1.2 million nerve fibres . If the disc is small these fibres are packed tightly together , leaving no space for cupping and sometimes giving the optic disc a swollen appearance .
Optic nerve head drusen ( Figure 5 ) are not real drusen . They are globular hyaline bodies , which may be calcified . They are often seen incidentally during routine eye tests and up to 2 % of the general Caucasian population are thought to have them . 22 In adults , they are usually obvious . However , in children and teenagers they can be buried .
Figure 4 - An anatomically small optic disc
Anterior ischaemic optic neuropathy ( Figure 2 ) and retinal artery occlusion are associated with unilateral optic disc swelling . Both cause sudden , and usually permanent , loss of vision . Initial swelling of the optic disc due to hypoxic oedema is quickly followed by atrophy of the optic disc .
Figure 5a - Optic disc drusen visible Figure 5b - Optic disc drusen hidden
Figure 3 - Optic Neuritis
Optic neuritis ( papillitis ) ( Figure 3 ) is almost always bilateral but usually asymmetrical so that one optic disc looks more swollen than the other . Swelling of the optic nerve caused by inflammation is more likely to obscure the disc vessels and may also be associated with haemorrhaging . Patients with optic neuritis usually have poor visual acuity in the affected eye , a desaturation of colour vision , a relative afferent pupil defect and may complain of pain or discomfort on eye movement due to the inflammation of the optic nerve .
Papilloedema normally presents as a bilateral swelling of the optic discs . Patients usually have normal
Figure 5 shows optic disc drusen in both eyes of the same patient . The drusen are just visible in the right eye but largely hidden in the left eye .
They migrate forward with age and eventually erupt onto the disc surface . Ultrasound and OCT can be used to confirm their presence and optic disc drusen will also autofluoresce ( Figure 6 ). Large optic disc drusen can cause arcuate field defects but vision is usually unaffected .
Figure 6 - Optic disc drusen autofluorescing
16 etCETera | November 2016