Human eye

eyeeyeseyeballocularophthalmiceyeballseyes of humanshuman eyesDimensions vary only 1–2 mm among humansene
The human eye is an organ which reacts to light and pressure.wikipedia
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Light

visible lightvisiblelight source
The human eye is an organ which reacts to light and pressure.
The word usually refers to visible light, which is the visible spectrum that is visible to the human eye and is responsible for the sense of sight.

Mammalian eye

external eyeeye in mammalseyes of most mammals
As a sense organ, the mammalian eye allows vision. Similar to the eyes of other mammals, the human eye's non-image-forming photosensitive ganglion cells in the retina receive light signals which affect adjustment of the size of the pupil, regulation and suppression of the hormone melatonin and entrainment of the body clock.
Dimensions vary only 1–2 mm among humans.

Rod cell

rodsrodrod cells
Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth.
Rod cells are photoreceptor cells in the retina of the eye that can function in less intense light than the other type of visual photoreceptor, cone cells.

Cone cell

conesconecone cells
Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth.
Cone cells, or cones, are one of 3 types of photoreceptor cells in the retina of mammalian eyes (e.g. the human eye).

Cornea

cornealcorneal diseasecorneal diseases
The outermost layer, known as the fibrous tunic, is composed of the cornea and sclera.
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber.

Iris dilator muscle

dilator muscledilator pupillaeradial muscle
The size of the pupil, which controls the amount of light entering the eye, is adjusted by the iris' dilator and sphincter muscles.
The iris dilator muscle (pupil dilator muscle, pupillary dilator, radial muscle of iris, radiating fibers), is a smooth muscle of the eye, running radially in the iris and therefore fit as a dilator.

Sclera

sclerotizedsclerotisedwhites of the eyes
The outermost layer, known as the fibrous tunic, is composed of the cornea and sclera.
The sclera, also known as the white of the eye, is the opaque, fibrous, protective, outer layer of the human eye containing mainly collagen and some elastic fiber.

Iris sphincter muscle

sphincter pupillaepupillary sphincteriris constrictor muscle
The size of the pupil, which controls the amount of light entering the eye, is adjusted by the iris' dilator and sphincter muscles.
The iris sphincter muscle (pupillary sphincter, pupillary constrictor, circular muscle of iris, circular fibers) is a muscle in the part of the eye called the iris.

Ciliary body

ciliaryciliary epitheliumannular
The middle layer, known as the vascular tunic or uvea, consists of the choroid, ciliary body, pigmented epithelium and iris.
The ciliary body is a part of the eye that includes the ciliary muscle, which controls the shape of the lens, and the ciliary epithelium, which produces the aqueous humor.

Iris (anatomy)

irisirisesirides
The middle layer, known as the vascular tunic or uvea, consists of the choroid, ciliary body, pigmented epithelium and iris.
In humans and most mammals and birds, the iris (plural: irides or irises) is a thin, circular structure in the eye, responsible for controlling the diameter and size of the pupil and thus the amount of light reaching the retina.

Vitreous body

vitreousvitreous humorvitreous humour
The spaces of the eye are filled with the aqueous humour anteriorly, between the cornea and lens, and the vitreous body, a jelly-like substance, behind the lens, filling the entire posterior cavity.
The vitreous body is the clear gel that fills the space between the lens and the retina of the eyeball of humans and other vertebrates.

Anterior chamber of eyeball

anterior chamberanterior chamber of the eyeanterior
The aqueous humour is a clear watery fluid that is contained in two areas: the anterior chamber between the cornea and the iris, and the posterior chamber between the iris and the lens.
The anterior chamber (AC) is the aqueous humor-filled space inside the eye between the iris and the cornea's innermost surface, the endothelium.

Pupil

pupilspupillaryanatomical pupil
The pupil of the human eye is its aperture; the iris is the diaphragm that serves as the aperture stop.
The pupil is a hole located in the center of the iris of the eye that allows light to strike the retina.

Field of view

FOVfields of viewwide-field
The approximate field of view of an individual human eye (measured from the fixation point, i.e., the point at which one's gaze is directed) varies by facial anatomy, but is typically 30° superior (up, limited by the brow), 45° nasal (limited by the nose), 70° inferior (down), and 100° temporal (towards the temple).
Humans have a slightly over 210-degree forward-facing horizontal arc of their visual field, while some birds have a complete or nearly complete 360-degree visual field.

Circadian rhythm

circadian rhythmscircadiansleep-wake cycle
Similar to the eyes of other mammals, the human eye's non-image-forming photosensitive ganglion cells in the retina receive light signals which affect adjustment of the size of the pupil, regulation and suppression of the hormone melatonin and entrainment of the body clock.
Thus, the information of the time of the day as relayed by the eyes travels to the clock in the brain, and, through that, clocks in the rest of the body may be synchronised.

Fovea centralis

foveaarea centraliscentral
Frontal-eyed animals have a small area of the retina with very high visual acuity, the fovea centralis.
The fovea centralis is a small, central pit composed of closely packed cones in the eye.

Absolute threshold

thresholddetection thresholddetection thresholds
At the low end of the range is the absolute threshold of vision for a steady light across a wide field of view, about 10 −6 cd/m2 (0.000001 candela per square meter).
They tried to measure the minimum number of photons the human eye can detect 60% of the time, using the following controls:

Ocular tremor

Fixational eye movements include drift, ocular tremor, and microsaccades.
Ocular microtremor (OMT) is a constant, physiological, high frequency (peak 80Hz), low amplitude (estimated circa 150-2500nm (1)) eye tremor.

Inferior oblique muscle

inferior obliqueinferioroblique
Each eye has six muscles that control its movements: the lateral rectus, the medial rectus, the inferior rectus, the superior rectus, the inferior oblique, and the superior oblique.
The inferior oblique is an extraocular muscle, and is attached to the maxillary bone (origin) and the posterior, inferior, lateral surface of the eye (insertion).

Ciliary muscle

ciliary musclesciliaryciliaris
Changing the curvature of the lens is carried out by the ciliary muscles surrounding the lens; this process is called "accommodation".
The ciliary muscle is a ring of smooth muscle in the eye's middle layer (vascular layer) that controls accommodation for viewing objects at varying distances and regulates the flow of aqueous humor into Schlemm's canal.

Eye care professional

ophthalmologistECPeye care hospitals
These specialists, or eye care professionals, serve different functions in different countries.
An eye care professional (ECP) is an individual who provides a service related to the eyes or vision.

Zonule of Zinn

zonular fibersciliary zonuleciliary zonules
The lens is suspended to the ciliary body by the suspensory ligament (Zonule of Zinn), made up of hundreds of fine transparent fibers which transmit muscular forces to change the shape of the lens for accommodation (focusing).
The zonule of Zinn (Zinn's membrane, ciliary zonule) (after Johann Gottfried Zinn) is a ring of fibrous strands forming a zonule (little band) that connects the ciliary body with the crystalline lens of the eye.

Vergence

convergenceconvergedivergence
To look at a nearby object, the eyes rotate 'towards each other' (convergence), while for an object farther away they rotate 'away from each other' (divergence).
A vergence is the simultaneous movement of both eyes in opposite directions to obtain or maintain single binocular vision.

Cataract surgery

cataract extractionintracapsular cataract extractioncataract
Ophthalmologists may also specialize within a surgical area, such as cornea, cataracts, laser, retina, or oculoplastics.
Cataract surgery also called lens replacement surgery, is the removal of the natural lens of the eye (also called "crystalline lens") that has developed an opacification, which is referred to as a cataract, and its replacement with an intraocular lens.

Aperture

aperturesaperture stoplens aperture
The pupil of the human eye is its aperture; the iris is the diaphragm that serves as the aperture stop.
The biological pupil of the eye is its aperture in optics nomenclature; the iris is the diaphragm that serves as the aperture stop.