Every set of eyes tells a different story.

How the filters are organized

Everything here is a way of seeing that differs from typical daytime human vision — that’s the thread that ties an owl’s night vision to a person’s cataracts. But those are very different kinds of difference, so we sort them into three families:

• Animals — how other creatures’ eyes, evolved for their own lives, receive a scene.
• Vision conditions — how some human eye and vision conditions can affect sight. These are approximations for empathy, never medical simulations.
• Color vision — differences in how color is perceived. We keep these separate from the conditions above on purpose: color-vision differences are extremely common and are variations, not impairments or disease.

As we add more ways of seeing — like near- and far-sightedness — you may see this map grow. Refractive differences (like needing glasses) are so common and so correctable that, when they arrive, they’ll likely sit in their own family too, rather than among the conditions.