Giant cell arteritis (GCA) is an ophthalmic emergency because, if undetected or managed inadequately, there is a high risk of developing a painless, permanent blindness in one or both eyes; however, if it is quickly identified and treated urgently and aggressively, blindness is almost entirely preventable. The ocular manifestations of GCA are essentially ischaemic in nature, with blindness as the most dreaded complication. Blindness is usually due to anterior ischaemic optic neuropathy (AION) and occasionally to other causes, e.g. posterior ischaemic optic neuropathy or central retinal or cilioretinal artery occlusion, although extremely rarely it may be cortical in origin. Diplopia and other types of ophthalmoplegias are seen in some cases but are usually transient in nature. Ischaemic lesions of the anterior segment of the eye are also seen in a few cases. Diagnosis of arteritic AION is discussed at length. Finally, management of GCA from the point of view of visual loss is discussed in detail.