emmetropia

Emmetropia refers to normal vision, where the eye's optical system precisely focuses images of distant objects directly onto the retina. This perfect alignment of the eye's focal power and its axial length is remarkable, as even a millimeter's deviation can necessitate corrective lenses.1

In contrast, myopia (nearsightedness) occurs when light focuses in front of the retina, blurring distant objects. This happens when the eye's refractive power is too strong for its length. Conversely, hyperopia (farsightedness) occurs when light focuses behind the retina, indicating insufficient refractive power for the eye's length. Astigmatism is another refractive error where uneven corneal curvature causes distorted vision at all distances. These common refractive errors are typically correctable with glasses or contact lenses.12