PSSAO works off of SSAO, but also includes how much a depth difference matters in the end result.
Let's say a is our depth/distance value.
This distance is: (in pseudocode)
a = (dot(centerPixelNormal, neighboringPixel3DPos) - dot(centerPixelNormal, centerPixel3DPos)) / distance( neighboringPixelPos * cameraDimensions, centerPixelPos * cameraDimensions)
Now put it in this formula: