A technique for the real-time visualization of material line movement during transparent gel deformation was developed based on caged photo-activated fluorophores covalently attached to the gel network. It is used to quantitatively monitor the swelling of sodium polyacrylate and poly(acrylamide-sodium acrylate) gels in quasi two-dimensional constrained geometries. The experimentally obtained profiles for the Finger deformation tensor and the polymer concentration are compared with transient simulations of a model of transport in polyelectrolyte gels.