Blind spot

Wiktionary Word definitions in Wiktionary
n. an area of impaired or lost vision within a field of vision otherwise in a good (or at least healthy) state

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
(plural scotomata ), 1540s, from Late Latin scotoma , from Greek skotoma "dizziness," from skotoun "to darken," from skotos "darkness" (see shade ).

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Scotoma \Sco*to"ma\, n. [L.] (Med.) Scotomy.

WordNet Word definitions in WordNet
n. an isolated area of diminished vision within the visual field [also: scotomata (pl)]

Wikipedia Word definitions in Wikipedia
A scotoma ( Greek σκότος/ skótos , darkness ; plural: scotomas or scotomata ) is an area of partial alteration in the field of vision consisting of a partially diminished or entirely degenerated visual acuity that is surrounded by a field of normal – or ...