Follow the light
The cornea and lens bend light towards the retina. See what happens when the focus and the back of the eye do not line up.
Why can the same eye see a book and a distant building differently?
Try the idea
The cornea and lens focus light onto the retina. A focusing problem is different from damage to the light-sensitive cells or the optic nerve.
Compare near and distant targets in the focus model. Notice where the light meets, compared with the retina.
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NEI: refractive errors