Rescued Belgian Malinois is barking all night without any reason

So my Belgian girl is 6 years old and I was told her last owner was beating her. After the rescue I am aware of not screaming,showing her love and even after 3 years with me I am really patient with her. BUT she is barking all night long and not as she barks to a cats or just walkers, I would say it´s more of the same monotone barking. Lately I´ve discovered she has a glaucoma which I am recently trying to fix with a vet. So my question is-is she barking because she doesnt see good or does she have some kind of a ritual? When I let her sleep in the house ( only when there are fireworks or it´s too cold), I dont know about her all night. We live in a very quiet neighborhood with no trafic and not too many walkers and I considered she could use me like this to let her in but I dont think she would do this every single day. I also tried to put outside a light for her so she could feel more secure but it didnt help.

Thanks for an answer.