Loss of VF is detected and quantified using automated perimetry. It is vital that this test be performed at least 1-2 times a year and that the frequency be adapted to the aggressiveness of the disease and how accurately the patient responds. If the disease progresses, more field tests must be done to detect the disease quickly before it is too late. If the disease advances slowly, VF tests are required less frequently. That is why the ophthalmologist decides how many and how often to perform visual field tests at each appointment in order to monitor each patient accordingly.