Structure of the Human Eye

Flashcards defining key anatomical components and terminology related to the human eye from Class 10 Physics.

Eye-ball

A hollow and spherical ball-like structure with a diameter of about $2.3\,cm$.

Cornea

A transparent, slightly bulged out thin membranous structure, convex in shape, through which light enters the eyeball and where most of the refraction occurs at its outer surface.

Iris

A dark muscular diaphragm made of a contractile muscle girdle, situated between the cornea and lens, which controls the size of the pupil.

Pupil

A small aperture in the middle of the iris whose size is controlled by iris muscles to determine the amount of light entering the eye.

Eye-lens

A transparent biconvex lens of very short focal length made of flexible jelly-like protein, which provides finer adjustment of focal length to focus light on the retina.

Ciliary Muscles

Muscles that hold the eye-lens in proper position and can change its convexity (focal length) for the purpose of accommodation.

Presbyopia

A condition of poor accommodation caused by the weakening of the ciliary muscles.

Retina

A light-sensitive layer serving as the screen of the eye, consisting of sensory cells known as rods and cones.

Rods

Sensory cells in the retina that help see objects in dim and diffused light.

Cones

Sensory cells in the retina that are helpful in coloured and contrast vision.

Fovea (Yellow spot)

The point on the retina that is in line with the optical axis of the lens, serving as the point of best vision.

Blind spot

The point located at the junction of the optic nerve and retina where no light-sensitive cells (rods or cones) exist.

Optic Nerve

A thick sensory nerve arising from the retina that conveys electrical signals (impulses) to the brain.

Aqueous humour

The liquid that fills the space between the cornea and the eye-lens.