Techniques currently available for investigating retinal/neural function in the presence of media opacities have traditionally been assessed in terms of their ability to predict the level of Snellen acuity which will be achieved following therapy. We propose an alternative method of assessment in which techniques are evaluated in terms of their ability to pre-operatively distinguish patients with reduced retinal/neural function from normals. In order to demonstrate this method of assessment, the data from a paper comparing the predictive abilities of a white-light and a laser interferometer in patients undergoing capsulotomy [21] have been re-analysed. The approach enables fair comparison of the predictive abilities of the various techniques and will therefore help to resolve the issue of which technique provides the best means of assessing retinal/neural function in the presence of media opacities.