Hi, and thank you for requesting my help.
The three disorders that are not DID in the category of dissociative disorders are Depersonalization disorder, Amnesia and it's four subtypes, and Dissociative Fugue. None of those disorders is treatable with EMDR unless a major trauma was associated with any of them. However, in this case, the diagnosis would be PTSD or ASD, and not a Dissociative disorder.
If you are receiving EMDR for Dissociative disorder, I would be curious as to the reasons why. This is not the protocol for treating these disorders. Treatment with EMDR is limited to PTSD and ASD.
As a result, there is no pre therapy to EMDR in your situation. Nor is there any pre therapy for any disorder. There is a therapy called PFA- Psychological First Aid, that is used by first responders in crisis situations and was designed by the United States Veterans Administration Psychologists. But all other disorders are treated with regular therapy.
EMDR is based on Cognative Behavioral therapy (CBT) principles and in some research is the reason why EMDR works, and not the eye movement itself.
I hope this helps you,