This cross-section shows the anatomical structure of the eye:

Normal sightedness – Emmetropia.

Normal (emmetropic) eye, looking into the near distance and into far distance

The state of the eyes without refractice errors is called emmetropia or the eye is being emmetropic. Your vision is normal and you can see clearly at all distances and do not require glasses.

In order to see things sharply both in the distance and close up, the lens of the eye – located behind the iris – can change its shape. The closer the object, the more your eye-lens needs to bulge to be able to focus. This focussing on objects more closely situated is called accommodation.

Normal eye of a 40-year-old.
View into the distance without accommodation

Normal eye of a 40-year-old.
View into the closer vicinity with accommodation

The closer the observed object, the further back the image appears in the back of the eye. In a normal-sighted eye, the image is “moved” by the curvature of the lens (accommodation) to the retina, in order to be seen clearly.