Many ophthalmologists are prepared to offer cataract extraction at good levels of visual acuity and do not use other tests of vision (Frost & Sparrow 2000), suggesting that vision tests have little, if any, role in deciding who should have surgery. The purpose of this review is to summarise the evidence that informs about the possible role of vision tests in clinical decision making about cataract extraction. There is no doubt that visual function tests give information about vision. Such information may be useful in a variety of settings, for example in clinical practice when correcting refractive errors, or in research studies that aim to quantify the visual impairment caused by cataract. But this review focuses on only one particular clinical problem: decision making about whether to recommend cataract surgery. It is uncertain whether vision tests provide information that is useful to the decision making process beyond that obtained by history taking and ocular examination. Cataract research has concentrated on the role of visual acuity testing, contrast sensitivity testing and glare testing. The review discusses four relevant questions about the role of these vision tests in clinical decision-making: 

• Can vision tests be used to confirm or exclude the presence of cataract? 
• Can vision tests inform about cataract symptoms, ‘disability’ or ‘handicap’? 
• Can vision tests predict the benefit of surgery? 
• Can vision tests be used to monitor the progression of cataract in order to decide when to operate?