I'm with Chimbu. At minima in minimum vis:
CAT 1: 200' - vis 800m (550m RVR) - HIALS - you will NOT see the threshold.
If you can see that much, no counting of lights, you're OK
My interpretation of what you have just said is that you wont see the threshold at the DA and thats OK to continue.
So how do YOU judge whether YOUR visibility is enough or not in such a situation?
Do you just continue on down the slope the rest of the way because you see part of the HIALS?