In the last two decades, techniques to measure and correct for refractive errors have reached unsurpassed levels (spectacles, contact lenses, intraocular lenses, laser surgery) to the point where customised correction of ocular aberrations can be foreseen. In this context, aberrometers are now becoming a popular tool for assessing the optical quality of the eye. Aberrations are however only one of the two basic optical phenomena affecting our vision. Even in an aberration-free eye, there will be inhomogeneities within the eye that will scatter light (Figure 1). This scattered light will not contribute towards the ‘normal’ formation of the image and thus will degrade vision. In a young and healthy eye, ocular scatter is low, but in some circumstances (eg old age, cataract, post refractive surgery) its consequences on the quality of vision can be significant. The purpose of this article is to review what is known about intraocular scatter, its link with visual performance and the information that can be extracted from scatter and glare measurements.