Human eye

The human eye is a sensory organ that detects light and converts it into neural signals. Its optics focus light on the retina, where photoreceptors begin visual processing.

Cornea: The transparent front surface of the eye that refracts most incoming light. Its curvature supplies most of the eye’s focusing power.
Iris: The colored muscular tissue surrounding the pupil that controls its diameter. Its muscles adjust the opening through which light enters.
Refraction (optics): The change in direction of light as it passes between materials with different refractive indices. Refraction by the cornea and lens determines where an image is focused.
Compound eye: An eye made of many optical units, each sampling part of the visual field. Its many facets form images differently from the human eye’s single-lens optics.
Retinal prosthesis: An implanted electronic device that stimulates surviving retinal or visual pathway neurons to produce visual sensations. It tests how much useful vision can be restored by replacing photoreceptor input.
Crystalline lens: A transparent, flexible structure that changes shape to focus images on the retina. Its changing curvature enables accommodation across viewing distances.
Sclera: The tough, opaque outer coat that forms most of the eye’s exterior. It protects the globe and provides attachment for eye muscles.
Accommodation (eye): The change in crystalline-lens shape that focuses the eye on objects at different distances. It describes the eye’s near-focus adjustment and its age-related decline.
Camera obscura: An optical device that projects an image through a small aperture onto an interior surface. It illustrates image formation without the eye’s neural sensing and processing.
Retinal regeneration: The replacement or repair of damaged retinal cells through biological or engineered processes. Limited natural repair makes restoration of retinal function a continuing challenge.

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OptometryNarrower topic: Knowledge of its structures underpins eye examinations and interpretation of clinical findings.