Visual field test: A test that measures the extent and distribution of the field of vision. A visual field test may be done via a number of methods, including termed confrontation, tangent screen exam, and automated perimetry. These tests are not painful or uncomfortable. Many diseases can adversely affect the visual field, including glaucoma, strokes, high blood pressure (hypertension), diabetes, multiple sclerosis, and overactivity of the thyroid gland (hyperthyroidism). Medications, including the antimalarial drugs chloroquine (brand name: Atabrine) and hydroxychloroquine (brand name: Plaquenil), can also affect the visual field.