Practical clinical approaches to functional visual loss.

Functional visual loss (FVL) refers to subnormal vision or altered visual fields where no underlying pathology of the visual system can be found. It may be seen in a continuum from frank malingering to hysteria. FVL may first present to the general practitioner or physician and the financial burden of evaluation and potential disability-related claims may be substantial. Diagnosis relies on a high index of suspicion and demonstration with a few simple tests that the patient has better vision than alleged. The aim of this review is to provide a practical approach to examination of patients with suspected functional visual loss. An accurate and early diagnosis of FVL starts with a high index of suspicion. Only a few of the tests need to be learned well, performed smoothly and confidently. These clinical tests obviate the need to perform expensive imaging such as magnetic resonance imaging and if used in the correct setting have the potential to reduce further the cost of diagnosis. Management requires an understanding approach and confrontation is seldom helpful. It is important to stress to the patient that FVL has a good prognosis, thereby providing "a way out" and giving the patient the opportunity to recover.