Double vision and Visual defect

Double vision noun - Visual impairment in which an object is seen as two objects.

Visual defect and double vision are semantically related. In some cases you can use "Visual defect" instead a noun phrase "Double vision".

Visual defect noun - Impairment of the sense of sight.

Double vision and visual defect are semantically related. Sometimes you can replace phrase "Double vision" with "Visual defect", this phrases are similar.