My blind eye has come detached it can't be fixed, it is shrinking and will need removed, it's 7.6/7.8 now what will it measure before this happens?

What are numbers?: What are these numbers? Corneal diameter? The decision to remove a blind eye should be made for pain or cosmetic reasons. Pain can be managed with retrobulbar alcohol neurolysis injection but the cosmetic results are not great-droopy eyelid are a common side effect. If you want a cosmetic result, consult an oculopastic surgeon before you decide anything. Enucleation with a prosthetic implant.

Not sure: We remove blind eyes commonly for pain or when they are at risk of spreading inflammation to the fellow eye. The fact that it is shrinking ( phthisis bulbi) is a common issue once the retina is permanently detached. Sometimes a prothesis can be fit over a phthisical eye avoiding an operation. Ask your eye care professional.