Technology "dielectric constant" information
The effect whereby the dielectric constant of a material changes with frequency is called 'dispersion'.

To be useful in RF design, any substrate material needs to have low dispersion over the RF band of interest, as well as low loss, and will have been measured over those frequencies. If it's also been measured at optical, then maybe people expect it might be integrated with LEDs at some point, or the physicists were curious. Either way, the constants specified at your operating frequency are the right ones to use for your operating frequency.

There is no universal relation between dielectric constant at RF and optical frequencies. Pure water (for example) is 2(ish) at optical and 80(ish) at RF.