My grandpa had it diagnosed and was operated on within 7 days. He couldn't read the biggest single letter "E" on the eye testing board thing.. so it was pretty bad.
Apparently it was caused because of a tear in the lining somewhere and so liquid got between the retina and wall of the eye ball... something like that...? They drained the fluid and injected a gas bubble to hold the retinal back up while it healed. Supposedly the bubble disappears within a month ( during which you should avoid looking down/hitting your head ) but it's been a little over a month now but he still sees two rings.
It's been progressively getting better though!
This is what happened to him: Rhegmatogenous retinal detachment
– A rhegmatogenous retinal detachment occurs due to a hole, tear, or break in the retina that allows fluid to pass from the vitreous space into the subretinal space between the sensory retina and the retinal pigment epithelium.
I'm not sure which of these he had done: Pneumatic retinopexy
This operation is generally performed in the doctor's office under local anesthesia. It is another method of repairing a retinal detachment in which a gas bubble (SF6 or C3F8 gas) is injected into the eye after which laser or freezing treatment is applied to the retinal hole. The patient's head is then positioned so that the bubble rests against the retinal hole. Patients may have to keep their heads tilted for several days to keep the gas bubble in contact with the retinal hole. The surface tension of the air/water interface seals the hole in the retina, and allows the retinal pigment epithelium to pump the subretinal space dry and pull the retina back into place. This strict positioning requirement makes the treatment of the retinal holes and detachments that occurs in the lower part of the eyeball impractical. This procedure is usually combined with cryopexy or laser photocoagulation. Vitrectomy
Vitrectomy is an increasingly used treatment for retinal detachment in countries with modern healthcare systems. It involves the removal of the vitreous gel and is usually combined with filling the eye with either a gas bubble (SF6 or C3F8 gas) or silicon oil. Advantages of using gas in this operation is that there is no myopic shift after the operation and gas is absorbed within a few weeks. Silicon oil (PDMS), if filled needs to removed after a period of 2–8 months depending on surgeon's preference. Silicon oil is more commonly used in cases associated with proliferative vitreo-retinopathy (PVR). A disadvantage is that a vitrectomy always leads to more rapid progression of a cataract in the operated eye. In many places vitrectomy is the most commonly performed operation for the treatment of retinal detachment.