Have a look at the Manual of standards Part 139
Manual of Standards Part 139 - Aerodromes
Chapter 9 covers airfield lighting and 9.10.4 states:
9.10.4 Longitudinal Spacing of Runway Edge Lights
9.10.4.1 The longitudinal spacing of runway edge lights must be uniform and be:
(a) for an instrument runway, 60 m +0 / -5 m;
(b) for a non-instrument runway, 90 m ± 10 m, or 60 m +0 / -5 m if there is an intention to upgrade the runway to an instrument runway at some time in the future.
(c) for non-precision instrument runways intended to be used in visibility conditions of 1.5 km or greater, where existing edge lights are spaced at 90 m ±10 m, it is acceptable to retain this spacing until the next replacement or improvement of the edge lighting system. (This situation typically arises from an existing non-instrument runway being upgraded to a non-precision instrument runway, but without re-installing the runway edge lights to the 60 m +0 / -5 m standard.)
Hope this helps