Accommodation of the Eye
The automatic adjustment process by which ciliary muscles alter crystalline lens focal length to focus objects at varying distances onto the retina.
Governing formula
Power range ΔP = P_near - P_far
SI unit
Diopters (D)
In depth
To view close objects, ciliary muscles contract, relaxing lens tension and making it more spherical (higher power). To view distant objects, ciliary muscles relax, flattening the lens.
Examples in the real world
The human eye shifting focus instantly from a mobile phone screen at 30 cm to a distant mountain.