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