Bokeh distortion near image border

[kosso_olli]

Hey guys,
maybe somebody has had this problem before, so I ask here: We got a photo reference, where the bokeh in the DOF is starting to distort in a circular fashion near the image borders on the lower left and right. Is there a way to emulate this in V-Ray?

[hermit.crab]

VRayCamera's optical vignetting (Bokeh effects rollout) may do the trick - play around with it.