A 37-year old German woman who survived an accident 17 years ago, is slowly regaining her vision – sometimes. The woman, known as “B.T” also suffers from dissociative identity disorder, and her doctors believe she has over 10 personalities. While being treated for her disorder, the woman’s teenage boy persona could eventually see.

Brain activity tests actually confirm that BT is telling the truth. In some personalities, she can see. In others, B.T. is blind. According to a report in the PsyCh Journal, BT’s ability to see turns on and off “within seconds.”

Dissociative identity disorder (DID) is a controversial diagnosis, believed by some to be the result of years of abuse, while others believe DID to be a cultural invention driven by therapists. It’s not clear if B.T.’s vision-impairing accident occurred at the same time as her 9 other personalities.

Doctors now believe that the accident that BT suffered when she was 20-years-old did nothing to damage her eyes but rather caused so much psychological damage that she became unable to see.

“These presumably serve as a possibility for retreat,” German psychologist Dr. Hans Strasburger told Braindecoder. “In situations that are particularly emotionally intense, the patient occasionally feels the wish to become blind, and thus not ‘need to see’.”

Basically, B.T. is able to see when she’s not experiencing her own, original self – presumably the self that suffered the trauma.

B.T. is not the first person to go “blind” after suffering a trauma. Doctors describe this type of vision impairment as, “a legitimate psychophysiologically based syndrome of psychological distress.”

There is a documented case of a German soldier ordered to kill Jews in 1941. Before he was able to murder his intended targets, the soldier went blind overnight.