Résumé : The shape of exotic even-mass Pb182-190 isotopes was probed by measurement of optical isotope shifts providing mean square charge radii (δ r2). The experiment was carried out at the isolde (cern) on-line mass separator, using in-source laser spectroscopy. Small deviations from the spherical droplet model are observed, but when compared to model calculations, those are explained by high sensitivity of δ r2 to beyond mean-field correlations and small admixtures of intruder configurations in the ground state. The data support the predominantly spherical shape of the ground state of the proton-magic Z=82 lead isotopes near neutron midshell (N=104). © 2007 The American Physical Society.