The clinical<unk>  is seen when viewed from the pupil, as in ophthalmoscopy or<unk> l photography. Whereas loss of peripheral vision may go unnoticed for some time, damage to the<unk>  will result in loss of central vision, which is usually immediately obvious. The progressive destruction of the<unk>  is a disease known as<unk> r degeneration and can sometimes lead to the creation of a<unk> r hole.<unk> r holes are rarely caused by trauma, but if a severe blow is delivered it can burst the blood vessels going to the<unk> , destroying it. Visual input from the<unk>  occupies a substantial portion of the brain's visual capacity. As a result, some forms of visual field loss that occur without involving the<unk>  are termed<unk> r sparing. (For example, visual field testing might demonstrate homonymous hemianopsia with<unk> r sparing.) In the case of occipitoparietal ischemia owing to occlusion of elements of either posterior cerebral artery, patients may display cortical blindness (which, rarely, can involve blindness that the patient denies having, as seen in Anton's Syndrome), yet display sparing of the<unk> . This selective sparing is due to the collateral circulation offered to<unk> r tracts by the middle cerebral artery. Neurological examination that confirms<unk> r sparing can go far in representing the type of damage mediated by an infarct, in this case, indicating that the caudal visual cortex (which is the principal recipient of<unk> r projections of the optic nerve) has been spared. Further, it indicates that cortical damage rostral to, and including, lateral geniculate nucleus is an unlikely outcome of the infarction, as too much of the lateral geniculate nucleus is, proportionally, devoted to<unk> r-stream processing.
Macula of retina
Retinal nerve fiber layer
Scleral lens
Optic pit
Iris pigment epithelium
Optic cup 
Optic vesicle
Foveal avascular zone