See how seeingactually works

Dial in your own prescription and watch a street dissolve, look at a tiger the way a deer does, and check your own eyes in thirty seconds. No jargon, no sign-up.

What does -2.50 actually look like?

Type in the numbers off your own prescription — sphere, cylinder and axis — and see the street exactly that soft. Then put the lenses back in.

A city street shown at the selected prescription

EXIT 24 · 300m

Can you still read the sign?

-2.50 / -1.00 × 90°

Your prescription, visualised

You need glasses to drive. Clear vision ends about 33cm from your face.

Sphere is how strongly light is bent in front of your retina — at -2.50 dioptres your world stops being sharp past about 40cm. Cylinder and axis describe astigmatism: the cornea is shaped more like a rugby ball than a football, so one direction focuses before the other and edges smear along a single angle.

See through other animals' eyes

Human vision on the left, the animal's on the right — a deer that can't pick a tiger out of the grass, a cat that owns the dark, an eagle that spots a rabbit you can barely find.

A tiger standing in green jungle foliageHuman vision
A tiger standing in green jungle foliage, as it would appear to a deerDeer vision

Deer

No red cone — a tiger's orange coat reads as dull green.

The tiger is obvious to you. To a deer, it is the same green as the leaves.

Deer are dichromats: blue and green-yellow cones, no red one. Orange and green excite their remaining cones almost identically, so a tiger's coat sinks into the foliage instead of contrasting with it. Their acuity is roughly a fifth of ours, which softens the stripes further. That single missing cone is the tiger's entire hunting strategy.

A 30-second eye check

Four quick screens — contrast, sharpness, colour and astigmatism — and a summary at the end. For curiosity, not diagnosis.

  1. Contrast
  2. Sharpness
  3. Colour
  4. Astigmatism
  5. Result

Which is the faintest row you can still read?

Sit at your normal screen distance and don't lean in. Tap the last row you can make out.

How your eye focuses

Reshape the lens, open and close the pupil, and shrink your vision back to the thumbnail-sized patch that's actually sharp.

A city street used to demonstrate how the eye shifts focus and adjusts to light

Held at reading distanceYour lens has to physically change shape to bring this line into focus. After about 40 it stops managing it.

Eye diagram responding to the slider

Lens flat — focused on the street, the card is blurred

Accommodation

The lens changes shape to move your focal point.

A ring of muscle squeezes the lens rounder for close work and lets it flatten for distance. You can only ever be focused at one distance at a time — you just switch so fast you never notice. From your forties the lens stiffens and the near end of that range slides away: presbyopia.

What conditions really look like

One street, seven ways of seeing it. Pick a condition and drag the severity slider.

A city street at dusk used to demonstrate how vision conditions change what you see

Menu, held at arm's lengthGrilled sea bass, lemon butter, samphire — 18. Ask about today's specials and the small print at the bottom of the card.

Astigmatism

Edges smear in one direction, and lights grow tails.

The cornea is shaped more like a rugby ball than a football, so it focuses light along two different axes. One direction lands sharp while the other lands blurred — which is why streetlights streak.

Correction: A toric lens has different power in different meridians, cancelling out the uneven curve.

Test your own eyes

Ten short games, each built on a real visual function — colour discrimination, acuity, colour memory, smooth pursuit, saccades.