<unk>  <unk>  is a medical condition involving loss of vision due to damage to the<unk>  nerve from insufficient blood supply.<unk>  is generally divided into two types: arteritic<unk>  (or AAION) and non-arteritic<unk>  (NAION or simply<unk> . This article will focus primarily on non-arteritic<unk> .
The distinction between AAION and NAION was made to highlight the different etiologies of<unk> . AAION is due to temporal arteritis (also called giant cell arteritis), an inflammatory disease of medium-sized blood vessels that occurs especially with advancing age. In contrast, NAION results from the coincidence of cardiovascular risk factors in a patient with "crowded"<unk>  discs. Non-arteritic<unk>  is more common than AAION and usually occurs in a slightly younger group than AAION. While only a few cases of NAION result in near total loss of vision, most cases of AAION involve nearly complete vision loss.
Beyond this introduction, this article will focus on non-arteritic<unk> . For a discussion on arteritic<unk>  see the separate article arteritic<unk> . Though the term "AION" can be used to describe either<unk>  in general or non-arteritic<unk>  specifically, in this article "AION" henceforth will be used to refer to non-arteritic<unk> .
Anterior ischemic optic neuropathy
Optic neuropathy
Kjer's optic neuropathy
Central serous retinopathy
Bacterial endophthalmitis
Interstitial keratitis
Endogenous endophthalmitis
Acute retinal necrosis