Humphrey field analyser (HFA) is a tool for measuring visual field and is used for detecting monocular visual field but can be used for screening, monitoring and assisting in the diagnosis and monitoring of certain conditions such as glaucoma and brain lesions.
Visual fields are frequently evaluated by simply covering one eye and asking the patient to look straight ahead while using peripheral vision to identified an object, identified and indicate the variety of light size & shape. The field is often tested at only four locations, which is sensitive only for large field defects.