Clinical signs and symptoms

The loss of vision in ischaemic optic neuropathy is usually painless, although some patients (approximately 8%) report discomfort behind and around the eye at the time of visual loss.65 Visual acuity (VA) data for the initial loss of vision indicate that 31-52% of patients have a VA better than 20/64, whereas 35-54% have a VA worse than 20/200.57,65,66 Altitudinal field defects comprise the most common pattern of visual field loss in 58-80% of cases.56 65-68

In acute AION, the optic disc is swollen with the swelling being either diffuse (75% of cases) or focal (25% of cases57). The disc may be pale or hyperaemic. Single or multiple flame shaped haemorrhages are present in the peripapillary region and a few soft exudates (Figure 12.3). As disc oedema begins to subside, optic atrophy develops and optic disc cupping similar to that seen in glaucoma may occur.

Some cases of AION may be associated with other signs of ocular ischaemia, such as choroidal infarction, retinal emboli, or iris or anterior chamber neovascularisation. The finding of iris neovascularisation in conjunction with AION in the absence of diabetic retinopathy or evidence of giant cell arteritis strongly suggests concomitant and causative ipsilateral carotid occlusive disease.

Posterior ischaemic optic neuropathy (PION) due to ischaemia of the retrobulbar portion of the optic nerve occurs in many settings, both arteritic and non-arteritic.56,69-75 This results in clinical signs and symptoms of ischaemic optic neuropathy with acute visual loss, a field defect, a relative afferent pupillary defect but with, initially, a normal appearing optic disc. In such cases, optic disc pallor usually develops within four to six weeks. Thus, PION is distinguishable from AION by signs of optic nerve dysfunction unassociated with optic disc swelling or retinal haemorrhages.

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