Back Lit What?

Been a struggle today, very tired ( blamed washing the horse box and car) , but later checked blood pressure and found it very low for me. Watched Olympics  and after lunch went and did some shopping before going to do a secret commission that I can't use on here (at least for now ). Checked BP again and it was back up to more acceptable level ( though that's still low for me ) . Had an early meal in readiness to go and view another horse, but the owner kept putting back the time until it was going to be dark when we got there so didn't go, very annoying!!
Some might know what the abstract glass is from ! Do you?