I wish to add a bit more reference on this question.
For dimension 1, it can be found in Malgrange's book "equations differentielles a coefficients polynomiaux" P60 Theorem (3.1), that (honomic D module on curve) is equivalencet to the category of (local system outside of singularities, stokes structures on the singularities, some compactibility condition desribed by vanishing cycles). Part I of Sabbah's book "an introduction to stokes structre" gives a detailed introduction.
For higher dimension, Part II of Sabbah's book discusses the case of "good" meromorphic connections.