By one way, if you mean that shallow reflections are always strongest, then yes.

If by one way, you meant external reflections versus internal, then no - it works both ways.

For internal reflections, such as from inside glass or water, the ratio of the IOR is less than 1. In such cases, there is the phenomenon of total internal reflection (TIR).

My TrueFresnel function will implement TIR if you give it an IOR less than 1.

There is an unfortunate limitation in Poser that a shader can't tell (at least not easily and universally) if it is shading the outside or the inside of a surface. This means it is difficult to make a single fresnel shader that works correctly for things such as diamond. In a diamond, the TIR effect is very important - in fact the angles of the facets are chosen specifically to exploit TIR.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)