What it is
The cornea is the clear window at the front of the eye that lets light in. To stay clear, its cells constantly move fluid out of the tissue. In dystrophy this work falters: fluid or other substances build up in the cornea, and it slowly turns cloudy, like looking through a misted pane.
The condition is inherited and can show already in a young cat. The cornea may swell, and small blisters sometimes form on its surface; when they burst they leave a painful sore.
Day to day, a cat adapts well to dimming sight, especially in a familiar home. The key thing to watch is whether the eye hurts: squinting, watering or rubbing means it should be shown to a vet.
Signs you may notice
A grey or bluish haze appears on the surface of the eye and can spread over time. If small blisters form on the cornea, the eye waters and the cat squints or rubs it with a paw.
When to see a vet
Book a visit if you notice cloudiness in the eye. If the eye waters, or your cat squints or rubs it, contact a vet as soon as you can.
This is general information, not veterinary advice. For your own cat's health, tests and treatment, see a vet.