Subfield is defined as the part of the room, which is visually perceived, while the eye straight fixed a fixed point.
The visual field is a functional analysis in measuring whether any failures or limitations in the field exist. The investigation will take several minutes. The patient lies for most in a separate quiet, dark room, not to be distracted by the noise practice. Only one eye is always examined, the other, meanwhile, covered with an eye patch. The result of the visual field is very much dependent on the cooperation and concentration of the patient. For the patient, this test is often somewhat tedious and time consuming, however, the only method is to measure visual function active.
