If tear had progressed to retinal detachment would it become a constant loss?

It can: Retinal detachment causes loss of vision in the area corresponding to the detachment, which will not improve without surgery or some other re-attachment procedure. With treatment, often the vision can be salvaged, although it may not be as good as before the detachment.

Yes: Signs of rd are those seen by examining eye doctor: subretinal fluid, retinal tear, pigment cells in vitreous, and pvd. The symptoms that a patient experiences are painless, progressive loss or greying; of vision which may involve the central vision. This may be proceeded by flashes and floaters. Sometimes an rd can by asymptomatic, and therefore it is important to get checked.