Double images
One scene, more than one outline.
These demonstrations illustrate ideas about vision. They do not reproduce another person's experience, measure your eyesight or diagnose an eye condition. Real vision varies with the person, the lighting, the task and the surroundings.
Double images
Double vision can affect one eye or both and has many causes. Orthoptists assess how the eyes work together, including alignment and eye movements.
Sudden double vision, or double vision with eye pain, needs urgent medical advice. Go to the urgent help page and read the NHS guidance.
Two offset images do not reproduce every form of double vision. Do not use these controls as an eye exercise, a treatment or a self-test.
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Read the original sourceWhen the light changes, sight needs time
A change in the light can bring several difficulties at once. Cones handle detail and colour in brighter light. Rods handle dim light. Cone-rod dystrophy often affects cones first, with rod difficulties developing later, and the balance differs from person to person. Slow adjustment and a lasting problem in dim light are two separate things. Extra time helps with one but does not remove the other.
Think of walking into a hallway from a sunny street, or leaving a dim cafe. The difficulty changes while you stand in the same spot. Tell your eye-care team about both directions: what is hard straight away, what gets easier with time, and what stays hard.
This is a designed teaching sequence, not a measured adaptation curve. A 15 or 60 second playback is a demonstration length, not a prediction of how long anyone takes to adjust. A washed-out screen cannot reproduce light sensitivity or pain. Nothing flashes, and the rest of the page stays unchanged.
Sources checked 5 October 2026: RNIB: inherited retinal conditions, MedlinePlus: cone-rod dystrophy, Macular Society: cone dystrophy.
Beyond the picture
A change in sight can affect reading, getting around, work and recognising people. Choose a condition above for everyday examples and ideas to raise with your eye-care team.