Emmetropia

Emmetropia refers to the condition of a normal, healthy eye where no refractive error is present. In an emmetropic eye:

• Light rays entering the eye are perfectly focused on the retina.
• The person can see clearly at both distance and near without the need for glasses or contact lenses (assuming proper accommodation at near).
• The shape of the eye is ideally proportioned—the cornea and lens focus light directly on the retina.

It's the opposite of refractive errors like:

• Myopia (nearsightedness)
• Hyperopia (farsightedness)
• Astigmatism (irregular curvature of the cornea or lens)

In short, emmetropia is what we aim for in vision correction—it means "perfect vision" without correction.