Visual Acuity Test

Visual acuity is the sharpness of your vision — how well your eyes resolve fine detail at a distance. The classic way to measure it is the Snellen chart, the wall of shrinking letters hanging in every optometrist’s office since the 1860s: you read down the rows until the letters become too small to identify, and the smallest row you can read defines your acuity.

This screening follows the same idea in your browser. Letters are drawn at progressively smaller sizes, and how far you get gives an educational estimate of how sharp your distance vision is — enough to notice that something might be worth a professional look.

The fraction compares you to a typical eye. 20/20 means that at 20 feet you can read what a typical eye reads at 20 feet — normal sharpness, not “perfect vision”. 20/40 means you need to be at 20 feet to read what a typical eye can read from 40 feet away — the detail has to be twice as close (or twice as large) before you resolve it. In metric countries the same idea is written 6/6 and 6/12.

Acuity is only one dimension of eyesight. Contrast sensitivity, peripheral vision, depth perception and color vision are separate abilities — you can be 20/20 and still have a color vision deficiency, which is why screenings test them separately.

Treat this test as a prompt, never as an answer. A real eye exam controls the two things a browser cannot: a fixed viewing distance and a calibrated letter size — and it examines eye health, not just sharpness. Book a professional exam if you struggle to read street signs or subtitles, find yourself squinting or getting headaches after screen time, notice a sudden change in either eye, or simply have not had your eyes checked in the last two years.

If your result here was worse than you expected, do not panic — screen glare, display scaling and sitting too close all skew the outcome. If it stays poor across attempts on a properly positioned screen, that is exactly the signal a quick optometrist visit is for.