Studies have been performed with pseudophakic eyes to determine which factors influence quality of vision postoperatively. However, straylight-dependent symptoms occur separately from VA-associated symptoms.2,3,8 Statistically, some relation between VA and straylight may occur in the population because media disturbances can be expected to affect both VA and straylight, although probably not to the same degree. In our population the relation did not reach statistical significance, in correspondence with earlier research that shows a weak relationship.2 This information stresses that straylight results from different processes than VA. Because straylight measurement rests on an equalization test, VA cannot in a causative sense influence the result of a straylight test. During straylight measurement, the patient observes which of 2 test fields shows more flicker. The point of identity between these 2 test fields is not influenced by VA. Identity remains the same, independent of VA. This has been verified in laboratory experiments (van den Berg, September 1990, unpublished data). It must be stressed that straylight is an aspect of visual function, although the term straylight might suggest it to be a purely optical entity. Straylight assesses the strength of the hindering spreading of light as seen by the person. However, it is the spreading at relatively large angles (typically >1°) as opposed to the spreading of light that governs VA and contrast sensitivity (in the range of minutes of arc). It governs disability glare and in general the quality of vision in most visual scenes because of the general prevalence of large luminosity differences in that type of scene.32 Both VA and contrast sensitivity do not take that factor into account. In extreme cases of media turbidity both domains of light spreading may overlap, and the distinction gets lost. Normally, straylight is an independent aspect of visual function. A study33 of 2422 drivers investigated the ways that straylight measurements relate to lens opacity grading (Lens Opacities Classification System III), VA, contrast sensitivity, and self-reported impairments of visual function. From correlation analysis, it was found that straylight is a vision impairment not directly related to VA and contrast sensitivity, and, moreover, that if VA is known, contrast sensitivity has limited added value.33 As mentioned previously, this independence of straylight and VA may be understood from the underlying processes that govern both aspects of visual function. A VA assessment is not sufficient to assess the visual disability of a person and visual problems caused by straylight2,3,5,8,15,34: additional vision measures are required to understand the impact of vision loss on everyday life.34 The results of the large study33 of European drivers support this assertion. Straylight measurements are necessary to fully understand the subjective concerns of the patient.2 With the straylight meter it is possible to capture functional concerns, such as straylight and disability glare, in an objective parameter (s).13 In this study, a functional model was developed that shows the effect of capsulorrhexis size and anterior capsule opacity on the parameter s. Figure 3 is a graphic representation of this functional model, as explained in the “Methods” section of the Abstract.