Lines look bent because the retina is being pushed out of shape. Wet AMD leaks a dome of fluid under the center of the retina. The brain still reads the lifted photoreceptors as flat, so a grid line crossing the dome looks wavy ¹. The grid sees only the central 20 degrees; anything further out it cannot detect.

It's a mediocre test that's defensible only because it's free. In dry AMD eyes it catches about seven in ten wet conversions and false-alarms on roughly a third of stable days ². Its edge is available daily between clinic visits, when the alternative is no monitoring at all.

Three groups should do this daily. Almost nobody else should. One eye already treated for wet AMD, watching the other, where conversion runs near 10% a year ³. Intermediate dry AMD an eye doctor has already seen, with roughly 18% turning wet over five years ⁴. Or a parent or sibling with AMD when you're past 60. Outside those, false alarms outnumber real catches.

New waves, gray patches, or a missing corner means a same-day call. Wet lesions grow over days, and the vision you keep is set by the lesion size when treatment starts ⁵. No slot within 48 hours means an emergency eye clinic.

The part that vanishes is the face across the table. Untreated wet AMD turns a bent line into a gray smudge into a permanent dark hole in central vision, over weeks. Injections stop the damage but can't rebuild dead photoreceptors ⁵. It is the leading cause of irreversible blindness over 60 ⁶.

ForeseeHome, a tabletop hyperacuity device, catches more and is Medicare-covered for high-risk dry AMD. The real upgrade is shorter clinic intervals with an OCT scan, which sees fluid before you see a wavy line; the grid just tells you when to ask for one off-schedule ⁷.