In previous edition only digital imaging devices could take digital visual enhancements and magicians could not cast ranged direct spells if their vision was digitally enhanced. They had to see the actual natural light of their target.
Having said that, some digital imaging devices also came as optical devices (utilizing optical items like mirrors, prismas and lenses). Optical binoculars, for example, will still provide magnification without digitally enhancing the image as a pair of digital binoculars would. Or regular prescription contacts or glasses. Or mage sight goggles. Or endoscopes. Or an optical periscope using mirrors rather than displays and cameras. etc
The common theme of optical devices seem to be that they typically don't have capacity for digital visual enhancements (and that they also don't have wireless capability / wireless bonuses).
Now..... magicians were also allowed to cast ranged direct spells via digitally enhanced vision if they paid essence for it. A magician with a thermographic enhancement, for example, could cast ranged direct spells on targets in total darkness by using thermographic vision enhancement. And of course natural enhancement of your vision was also Ok (metatypes or qualities that provide you with low light or thermo vision, for example).
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When it comes to layering. No clear rules at all when it comes to imaging devices.
A common solution within shadowrun seem to be that only the outer layer count. For example, if you have goggles, contacts and cyberyes only the enhancements you have in your goggles would apply. If you wish to instead use the enhancements you have in your contacts you remove your goggles. If you wish to use your augmented eyes you remove your contacts as well.
Another common solution to layering within shadowrun seem to be that the user have to choose which device or layer to use at any given situation. For example, if you have goggles with low light and thermo, contacts with smarlink and cyberyes with flare compensation you had to choose in any given situation if you wanted to make use of low light/thermo but not smartlink or flare comp. Or smarlink instead of low light/thermo or flare comp. Or just comp instead of low light/thermo or smartlink.
A third solution (and perhaps the most simple) would be to allow all layers to be active at the same time at all times :-)
(edit: but note that the original intention was probably that capacity should act as a limiting factor to force you to make some hard choices / sacrifice)
