Higher-order aberrations or HOAs are the more complex vision errors which have more familiar names such as nearsightedness, farsightedness and astigmatism. Aberrations are the deviations from normal vision, such as blurring in an image.

Higher order aberrations are present in all human eyes, but in normal, un-operated eyes HOAs are so minor in such a way that they are not noticeable.

Basically, a higher-order aberration is a distortion acquired by a wave front of light when it passes through an eye with irregularities of its refractive components. Higher order aberrations are measured with wave front aberrometers and expressed in terms which describe the shape and severity of the deviated light rays when they pass through the eye's optical system and strike the retina.