1. 1Test each eye separately with habitual correction; occlude the other eye fully (palm or occluder, no peeking through fingers).
2. 2Start at the top line and descend; record the smallest line with more than half the letters correct (e.g. 20/40−2).
3. 3If worse than 20/40, retest with pinhole — improvement implies refractive error.
4. 4If the patient cannot read 20/400: count fingers (with distance), hand motion, light perception (with projection), no light perception.
5. 5Near: test at 40 cm with near card; record in Jaeger, N-point or M-units.

Children: use LEA symbols or HOTV from age 3; fix-and-follow and CSM (central, steady, maintained) in pre-verbal children.