Direct extract from the section EU Ops:
OPS 1.405
Commencement and continuation of approach
(a) The commander or the pilot to whom conduct of the flight has been delegat ed may commence an instrument approach regardless of the reported RVR/Visibility but the approach shall not be continued beyond the outer marker, or equivalent position, if the reported RVR/visibility is less than the applicable minima.
(b) Where RVR is not available, RVR values may be derived by converting the r eported visibility in accordance with Appendix 1 t o O PS 1.430, subparagraph (h).
(c) If, after passing the outer marker or equivalent position in accordanc e with (a) above, the reported RVR/visibility falls below the applicable minimum, the approach may b e continued to DA/H or MDA/ H.
(d) Where no outer marker or equivalent position exists, the commander or t he pilot to whom conduct of the flight has been delegated shall make the decision to continue or abandon the approach before descending below 1 000 ft above the aerodrome o n the final approach segment. If the MDA/H is at or above 1 000 ft above the aerodrome, the operator shall establish a height, for each approach procedure, below which the app roach shall not be continued if RVR/visibility is less than applicable minima.
(e) The approach may b e continued below DA/H or MDA/H and the landing may b e c ompleted provided that the required visual reference is established at the DA/H or MDA/H and is maintained.
(f) The touch-down zone RVR is always controlling. If reported and relevan t, the mid point and stop end RVR are also controlling. The minimum RVR value for the mid-point is 125 m o r the RVR requ ired for the touch-down zone if less, and 75 m for the stop-end. For aeroplanes equipped with a roll-out guidance or control system, the minimum RVR value for the mid-point is 75 m.
Note: ‘Relevant’, in this context, means t hat p art of the runway used during t he h igh speed phase of the landing d own to a s peed of approximately 60 knots.