The campimeter is an instrument for examining the visual field

Visual field

The term visual field is sometimes used as a synonym to field of view, though they do not designate the same thing. The visual field is the "spatial array of visual sensations available to observation in introspectionist psychological experiments", while 'field of view' "refers to the physical...

. Campimeters have been in clinical use since the mid-nineteenth century. Initially, examination of the visual field was concerned only with the outer limits, or 'perimeter' of the visual field, hence the term 'perimetry

Perimetry

Perimetry or campimetry is the systematic measurement of differential light sensitivity in the visual field by the detection of the presence of test targets on a defined background. Visual field testing can be performed clinically with confrontational field testing keeping the subject's gaze fixed...

', which tends to be used inter-changeably with 'campimetry'.