To me eye adaption 1 or 0 in usercfg.opt, means the same as in sim general option settings camera
Section to set home cockpit on or off as is 0 = off and 1 = on
Related to this when 0 eye adaption is off and when panning up or down all overal bright stays at the same.
When 1 eye adaption is on and panning up or down all overal bright get to affect the darkening effect then when look up gets brighter and looking down gets darker.
Also to me with gamma and saturation settings on my monitor i can set to darker or brighter
But the thing i find in this sim that everything works with or in percentage of max and minus.