The fact that the (C-quant) Straylight Meter measures the straylight as the subject actually sees it (and is disturbed by it) may be considered as a limitation of the technique, when used in a clinical environment. Because it is a psychophysical technique, reliability of individual measurements needs to be checked (as with visual field measurents). We decided to evaluate the objectivity and reliability in patients with cataract in a regular clinical environment. For this very purpose, we studied the reliability parameter (ESD), designed to predict the accuracy of an individual measurement. We also tried to simulate frauds.