Listening with a cochlear implant remains difficult and most listeners will report high levels of listening effort.The present study is a "pilot" aiming to evaluate listening effort for cochlear implant users. The listening effort is measured with pupillometry, by monitoring the variations of pupil size in response to different stimuli. The size of the pupil is known to increase with the listening effort. The listening effort is evaluated in two different situation: speech perception in quiet and speech perception in noise. The pupillometry measures will be compared for the two listening conditions. Moreover, the study will evaluate the relationship between objective (pupil dilatation) and subjective measures (auto evaluation) of listening effort, and between speech comprehension, cognitive abilities and listening effort.