The study investigates whether add-on treatment with eyewear that blocks the short wavelengths of visible light (<500nm) reduces manic symptoms and improves sleep in patients receiving outpatient treatment as usual for bipolar disorder.

When in a hypomanic or manic phase, participants will be randomized to receive add-on treatment with either blue blocking or low filtration eyewear from 18 PM to 8 AM daily for 7 days.

After this initial intervention phase, the eyewear is used daily for 3 months in either antimanic dose (14 hours) or maintenance dose (2 hours before bedtime).

The study is a 2-arm single-blind RCT to assess the effects of blue blocking (BB) or clear glasses as an acute 7-day antimanic intervention and as a 3-month mood stabilizing maintenance intervention. BB or clear glasses will be applied in addition to outpatient TAU for BD. Participants will be recruited among patients treated for BD in specialized outpatient clinics within the Mental Health Center Copenhagen.

The active intervention is BB-glasses that eliminate 99 % of light with a wavelength below 530 nm, whereas the clear glasses filter out only 15% of short wavelength light (low filtration (LF).

Participation includes 3 months use of the designated eyewear along with daily electronic self-monitoring of mood, sleep and activity as well as participation in a 2-day baseline assessment and a total of 3 follow-up visits including clinical assessment interview, questionnaires, and actigraphic (48 hours) and pupillometric assessments at day 9, week 5 and week 15.

Participants will be included during hypomanic or manic state and begin treatment with an antimanic dosage of 14 hours (6 PM - 8 AM) for 7 consecutive days. Subsequently, during the 3-month follow-up period, the dosage (hours using the glasses) can be adjusted according to the current state, with use for 14 hours during hypomanic/manic phases and 2 hours before bedtime during euthymic and depressive states.

Outcome assessors will be blinded to the treatment assignment and patients will be informed that they are randomized to eyewear with either high or low filtration of light. Patients will be randomized on a 1:1 basis with stratification according to sex and outpatient clinic.

Inclusion Criteria:

• Diagnosis of bipolar disorder
• YMRS-score >13
• Age 18-60 years
• Speaks and writes Danish at a level equal to mother tongue

Exclusion Criteria:

• Not willing or able to adhere to the protocol
• Severe eye disorder or eye trauma
• Treatment with betablockers
• Sleep disturbances not related to BD (e.g, sleep apnea, restless legs syndrome) • • Substance abuse
• Unwilling to use the electronic self-monitoring system, the Monsenso system
• Prior/current use of BB glasses
• Current/planned pregnancy
• Night shift work
• Suicidality

Participants are instructed not to discuss the appearance of their designated eyewear with their care providers or the investigator or outcome assessor. Participants are not informed of the exact filtration level of their eyewear.