Aberration

In an optical context, aberration is any perceived or real imperfection in the formation of a visual image. Aberrations can be regular and measurable, such as spherical aberration, chromatic aberration, and coma; or can be irregular, as might be noticed when looking through a pane of hand-blown glass. Instruments that measure aberrations of the visual system are called ‘wavefront analyzers’ or aberrometers. See also Higher-Order Aberrations, below.