OK. It is your salat. You do whatever you feel like. 
What I understand I will mention.
It is not recommended. It was never done by the prophet SAW.
As far as I know, there is not hadith that he did it.
He SAW asked for plain sheet (without a design) so he could concentrate.
One is supposed to look at the place of sajdah (Qayam), between feet (rukoo) and between knees when sitting.
If concentration is lost maybe for short time it is permissible. I am not sure.
Concentrating on words and its meaning helps.
Some hadiths forbid it since people in past used to pray with eyes closed.
One hadith says the person will be given blind Hoor?
Praying in complete darkness is also not allowed. (Looking upward also is not allowed by hadith)
At best it is controversial and different people these days give different recommendations.