The strong-field approximation (SFA) is computationally convenient and provides a clear physical picture, but it neglects the Coulomb interaction between the ionized electron and the parent ion, which may lead to inaccuracies in predicting certain details. In this work, we first introduce the Coulomb-Volkov approximation (CVA), which incorporates the effect of the Coulomb potential on the basis of the SFA. We then compare the results obtained from these two methods with those from the time-dependent Schrödinger equation (TDSE), analyzing their predictive performance for photoelectron momentum distributions in different laser fields. The results demonstrate that the CVA not only retains the computational advantages of the SFA, but also better reproduces the interference structures and angular features observed in the TDSE calculations, thereby contributing to a more accurate understanding of the role of the Coulomb potential in the ionization process under strong laser fields.