Mansions of Madness - Loss of Vision
The wording of the card is: 


  Whenever you explore, treat the room as if it were in darkness.


(Empahsis mine)

Normally, darkness forces you to spend a movement step in addition to the regular action step to explore and to also receive -2 to attribute tests in combat. This card just makes it so that whenever you explore, you apply the penalty of spending an additional movement step.

This trauma doesn't affect combat. If the player with the trauma is not exploring, penalty doesnt apply. 

Either way, the room is technically not in darkness.  

Based on this, I would rule it as invalid as playing a card that required a room to be in darkness.