Arched windows or "eyebrow/half circle windows" can be a challenge to cover especially in bedrooms. You still need the room darkening in order to sleep well but there are very few options available. Here are a few solutions...Shutters. The shutters are installed with a tilt bar on the front so you can open and close the them. They are room darkening but not black out as some light will still bleed through the louvers.
The other option is pleated or cellular blinds. A good manufacturer will offer these for specialty shape windows that still open and close. You want ones that are operable and not just closed or stationary all the time. These blinds will operate from the bottom up. They stack neatly at the bottom of the window when they are not needed and pull up to a fastener to close when you need them to be closed. They come in room darkening and light filtering.
Both of these options are great if you need to cover the window and you can coordinate the bottom of the window in the same covering.
