sco·to·ma 
(skə-tōmə)
(skə-tōmə)n. pl. sco·to·mas or sco·to·ma·ta (-mə-tə)
An area of diminished vision within the visual field.
[New Latin scotōma, from Late Latin, dim sight, from Greek skotōma, dizziness, from skotoun, to darken, from skotos, darkness.]
sco·toma·tous adj.