Do you have any points in Elven Sight? If so, use
iZakaroN's SaveEditor to remove them (or give yourself skill points, if required). Re-load the save and put the skill points into Elven Sight (and maybe Ranger Sight, if you have enough). Save, and repeat if necessary. Someone else found that the sight boost when learning Elven/Ranger Sight was added right away, not calculated each time you load the game (for example), so adding and removing points to these skills can get your sight back to normal (removing the skill points does not drop your sight range and you can learn these skills multiple times, if necessary).
See also;
please help with my blind hero
