With age the clear gel inside the eye shrinks and peels off the retina — usually harmless; most people over eighty have been through it ¹. Sometimes it is stuck and rips a piece of retina off with it. Fluid then lifts that retina off the wall like wet wallpaper; the cells behind start dying within hours.

Three symptoms are that process felt from inside. Flashes are the gel tugging the retina, brief lightning to one side. New floaters are debris shaken loose, a sudden cobweb or drifting specks. A curtain from one edge is the retina already lifting; once it reaches the centre, the damage gets much worse ².

These signs are one of the best-measured rules in medicine. Two features raise the tear odds beyond the baseline one in seven: worse vision, about five-fold; blood in the gel, about ten-fold ³. The other six in seven have a harmless peel and no tear — not a wasted trip, since you ruled out the eye-ending version.

What waiting costs is specific. The clock runs out when the curtain reaches the macula, the central patch you read and see faces with. Repaired before then, most central vision returns. Repaired after, the eye stays permanently dimmer, straight lines bowing inward, even after textbook surgery ⁴; each extra day before surgery costs final vision ⁵.

Any new flashes, sudden change in floaters, or curtain in one eye means a dilated exam by an ophthalmologist today. Only that look reaches the far edge of the retina, where most tears hide.

Do not call primary care first: they cannot do the exam, and the lag is what costs the eye. Sudden total painless vision loss, no flashes, is a possible eye stroke — emergency services now.

Some people should treat the threshold as reflexive: anyone strongly nearsighted (past about -6, "high myopia"), post-cataract-surgery, with a family history, or a recent blow to the eye. A detachment in one eye leaves the other with a roughly one-in-ten lifetime risk of its own ⁷.