What determines the eye’s ability to focus images?
The ability to focus images on the retina of the eye is determined by primarily by two components of the eye, the lens and the cornea. The cornea has a refractive power of approximately 45 diopters (ability to bend light rays). The lens has a variable refractive power (accommodation) of 1-18 diopters as a youth, but there is a progressive deterioration in accommodation so that the 50 year old pilot/controller may have less than 2 diopters of accommodation. The retina and macula may be affected by certain conditions that preclude good vision regardless of the status of the lens and cornea.