  We present a model-independent framework to determine finite-volume
corrections of matrix elements of spatially-separated current-current
operators. We define these matrix elements in terms of Compton-like amplitudes,
i.e. amplitudes coupling single-particle states via two current insertions. We
show that the infrared behavior of these matrix elements is dominated by the
single-particle pole, which is approximated by the elastic form factors of the
lowest-lying hadron. Therefore, given lattice data on the relevant elastic form
factors, the finite-volume effects can be estimated non-perturbatively and
without recourse to effective field theories. For illustration purposes, we
investigate the implications of the proposed formalism for a class of scalar
theories in two and four dimensions.
