{"id":3318,"date":"2026-04-13T19:08:40","date_gmt":"2026-04-13T17:08:40","guid":{"rendered":"https:\/\/www.first-sight.ch\/?post_type=glossary&#038;p=3318"},"modified":"2026-04-13T19:10:45","modified_gmt":"2026-04-13T17:10:45","slug":"anatomy-of-the-eye","status":"publish","type":"glossary","link":"https:\/\/www.first-sight.ch\/en\/glossar\/anatomy-of-the-eye\/","title":{"rendered":"Anatomy of the Eye"},"content":{"rendered":"<p>The human eye is a complex sensory organ that receives light stimuli and converts them into electrical signals that the brain processes into images. For patients who wish to better understand an eye disease or operation, it is helpful to know the main structures of the eye. The following provides a clear overview of the external and internal components of the eye.<\/p>\n<h2>External structures of the eye<\/h2>\n<h3>Eye muscles (extraocular muscles)<\/h3>\n<p>Each eye is moved by six muscles that can rotate it in all directions:<\/p>\n<ul>\n<li><strong>Superior rectus muscle:<\/strong> Moves the eye upward<\/li>\n<li><strong>Inferior rectus muscle:<\/strong> Moves the eye downward<\/li>\n<li><strong>Medial rectus muscle:<\/strong> Moves the eye toward the nose (inward)<\/li>\n<li><strong>Lateral rectus muscle:<\/strong> Moves the eye toward the temple (outward)<\/li>\n<li><strong>Superior oblique muscle:<\/strong> Passes through a pulley (trochlea) and rotates the eye inward, moves it downward and outward<\/li>\n<li><strong>Inferior oblique muscle:<\/strong> Rotates the eye outward, moves it upward and outward<\/li>\n<\/ul>\n<p>These six muscles work together like the strings of a puppet and ensure that both eyes gaze synchronously in the same direction. In strabismus disorders, the coordination of these muscles is disrupted.<\/p>\n<h3>Conjunctiva (Conjunctivitis membrane)<\/h3>\n<p>The conjunctiva is a thin, transparent mucous membrane that covers the inside of the eyelids and the visible white part of the eye. When irritated or infected, it becomes red \u2013 this is called conjunctivitis.<\/p>\n<h3>Lacrimal gland<\/h3>\n<p>The lacrimal gland is located beneath the outer edge of the eyebrow and produces tear fluid that keeps the eye moist, protects it from infection, and enables clear vision.<\/p>\n<h3>Sclera (white of the eye)<\/h3>\n<p>The sclera is the firm, white outer wall of the eye. It consists of collagen fibers, gives the eye its shape, and serves as the attachment point for the eye muscles.<\/p>\n<h3>Cornea<\/h3>\n<p>The cornea is the clear, curved \"window\" at the front of the eye. It lets light in and refracts it so that it focuses on the retina. Contact lenses rest directly on the cornea.<\/p>\n<h2>Internal structures of the eye<\/h2>\n<h3>Anterior chamber<\/h3>\n<p>The space filled with aqueous humor between the cornea and iris. The aqueous humor nourishes the cornea and lens and maintains intraocular pressure.<\/p>\n<h3>Iris and pupil<\/h3>\n<p>The iris is the colored part of the eye. In its center lies the pupil \u2013 the opening through which light enters the eye. Muscles in the iris regulate pupil width: in bright light the pupil becomes narrow, in darkness it becomes wide.<\/p>\n<h3>Lens<\/h3>\n<p>The lens sits behind the iris and focuses incoming light on the retina. Fine fibers (zonular fibers) hold it in position and allow it to change shape to sharply focus on both near and distant objects. This process is called accommodation. When the lens becomes cloudy, it is called a cataract.<\/p>\n<h3>Ciliary body<\/h3>\n<p>The ciliary body lies beside the iris. It produces the aqueous humor and contains the ciliary muscle, which changes the lens shape for near and distance focusing.<\/p>\n<h3>Vitreous humor<\/h3>\n<p>The vitreous humor fills most of the eye\u2019s interior behind the lens. It consists of a gel-like, transparent substance that gives the eye its shape and keeps the light path to the retina clear.<\/p>\n<h3>Retina<\/h3>\n<p>The retina lines the inner wall of the eye and functions like the image sensor of a camera. It receives light and converts it into electrical signals that are transmitted to the brain via the optic nerve. The retina contains two types of light-sensitive cells:<\/p>\n<ul>\n<li><strong>Rods:<\/strong> Responsible for vision in dim light, peripheral vision, and perception of movement<\/li>\n<li><strong>Cones:<\/strong> Responsible for color vision and sharp vision in the center<\/li>\n<\/ul>\n<h3>Macula and fovea<\/h3>\n<p>The macula is a small area in the center of the retina responsible for the highest visual acuity \u2013 for example, when reading or recognizing faces. At its center lies the fovea, the point of sharpest vision.<\/p>\n<h3>Choroid<\/h3>\n<p>The choroid lies between the retina and sclera and is rich in blood vessels. It supplies the outer layers of the retina with oxygen and nutrients.<\/p>\n<h3>Optic nerve<\/h3>\n<p>The optic nerve bundles over one million nerve fibers and transmits visual information from the retina to the brain. At the optic chiasm, parts of the optic nerves from both eyes cross over, so each brain hemisphere receives image information from both eyes.<\/p>\n<h3>Visual cortex<\/h3>\n<p>The visual cortex is located in the occipital lobe of the brain. Here the signals received by the eye are processed into a conscious image: with all information about color, shape, depth, and movement.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>The human eye is a complex sensory organ that receives light stimuli and converts them into electrical signals that the brain processes into images. For patients who wish to better understand an eye disease or operation, it is helpful to know the main structures of the eye. The following provides a clear overview of the [&hellip;]<\/p>\n","protected":false},"featured_media":0,"template":"","meta":{"_acf_changed":false,"_wpce_doc":"eyJndWlkIjoiNzVjMzQzMjMtODUwMC00N2RhLTk4YTEtZGNkMjhiNjI4Yzc0IiwiaWQiOiJyb290IiwiY2hpbGRyZW4iOlt7InZpc2libGUiOnRydWUsInByb3BlcnRpZXMiOnsiY29udGVudCI6IjxwPlRoZSBodW1hbiBleWUgaXMgYSBjb21wbGV4IHNlbnNvcnkgb3JnYW4gdGhhdCByZWNlaXZlcyBsaWdodCBzdGltdWxpIGFuZCBjb252ZXJ0cyB0aGVtIGludG8gZWxlY3RyaWNhbCBzaWduYWxzIHRoYXQgdGhlIGJyYWluIHByb2Nlc3NlcyBpbnRvIGltYWdlcy4gRm9yIHBhdGllbnRzIHdobyB3aXNoIHRvIGJldHRlciB1bmRlcnN0YW5kIGFuIGV5ZSBkaXNlYXNlIG9yIG9wZXJhdGlvbiwgaXQgaXMgaGVscGZ1bCB0byBrbm93IHRoZSBtYWluIHN0cnVjdHVyZXMgb2YgdGhlIGV5ZS4gVGhlIGZvbGxvd2luZyBwcm92aWRlcyBhIGNsZWFyIG92ZXJ2aWV3IG9mIHRoZSBleHRlcm5hbCBhbmQgaW50ZXJuYWwgY29tcG9uZW50cyBvZiB0aGUgZXllLjxcL3A+XG48aDI+RXh0ZXJuYWwgc3RydWN0dXJlcyBvZiB0aGUgZXllPFwvaDI+XG48aDM+RXllIG11c2NsZXMgKGV4dHJhb2N1bGFyIG11c2NsZXMpPFwvaDM+XG48cD5FYWNoIGV5ZSBpcyBtb3ZlZCBieSBzaXggbXVzY2xlcyB0aGF0IGNhbiByb3RhdGUgaXQgaW4gYWxsIGRpcmVjdGlvbnM6PFwvcD5cbjx1bD5cbjxsaT48c3Ryb25nPlN1cGVyaW9yIHJlY3R1cyBtdXNjbGU6PFwvc3Ryb25nPiBNb3ZlcyB0aGUgZXllIHVwd2FyZDxcL2xpPlxuPGxpPjxzdHJvbmc+SW5mZXJpb3IgcmVjdHVzIG11c2NsZTo8XC9zdHJvbmc+IE1vdmVzIHRoZSBleWUgZG93bndhcmQ8XC9saT5cbjxsaT48c3Ryb25nPk1lZGlhbCByZWN0dXMgbXVzY2xlOjxcL3N0cm9uZz4gTW92ZXMgdGhlIGV5ZSB0b3dhcmQgdGhlIG5vc2UgKGlud2FyZCk8XC9saT5cbjxsaT48c3Ryb25nPkxhdGVyYWwgcmVjdHVzIG11c2NsZTo8XC9zdHJvbmc+IE1vdmVzIHRoZSBleWUgdG93YXJkIHRoZSB0ZW1wbGUgKG91dHdhcmQpPFwvbGk+XG48bGk+PHN0cm9uZz5TdXBlcmlvciBvYmxpcXVlIG11c2NsZTo8XC9zdHJvbmc+IFBhc3NlcyB0aHJvdWdoIGEgcHVsbGV5ICh0cm9jaGxlYSkgYW5kIHJvdGF0ZXMgdGhlIGV5ZSBpbndhcmQsIG1vdmVzIGl0IGRvd253YXJkIGFuZCBvdXR3YXJkPFwvbGk+XG48bGk+PHN0cm9uZz5JbmZlcmlvciBvYmxpcXVlIG11c2NsZTo8XC9zdHJvbmc+IFJvdGF0ZXMgdGhlIGV5ZSBvdXR3YXJkLCBtb3ZlcyBpdCB1cHdhcmQgYW5kIG91dHdhcmQ8XC9saT5cbjxcL3VsPlxuPHA+VGhlc2Ugc2l4IG11c2NsZXMgd29yayB0b2dldGhlciBsaWtlIHRoZSBzdHJpbmdzIG9mIGEgcHVwcGV0IGFuZCBlbnN1cmUgdGhhdCBib3RoIGV5ZXMgZ2F6ZSBzeW5jaHJvbm91c2x5IGluIHRoZSBzYW1lIGRpcmVjdGlvbi4gSW4gc3RyYWJpc211cyBkaXNvcmRlcnMsIHRoZSBjb29yZGluYXRpb24gb2YgdGhlc2UgbXVzY2xlcyBpcyBkaXNydXB0ZWQuPFwvcD5cbjxoMz5Db25qdW5jdGl2YSAoQ29uanVuY3Rpdml0aXMgbWVtYnJhbmUpPFwvaDM+XG48cD5UaGUgY29uanVuY3RpdmEgaXMgYSB0aGluLCB0cmFuc3BhcmVudCBtdWNvdXMgbWVtYnJhbmUgdGhhdCBjb3ZlcnMgdGhlIGluc2lkZSBvZiB0aGUgZXllbGlkcyBhbmQgdGhlIHZpc2libGUgd2hpdGUgcGFydCBvZiB0aGUgZXllLiBXaGVuIGlycml0YXRlZCBvciBpbmZlY3RlZCwgaXQgYmVjb21lcyByZWQgXHUyMDEzIHRoaXMgaXMgY2FsbGVkIGNvbmp1bmN0aXZpdGlzLjxcL3A+XG48aDM+TGFjcmltYWwgZ2xhbmQ8XC9oMz5cbjxwPlRoZSBsYWNyaW1hbCBnbGFuZCBpcyBsb2NhdGVkIGJlbmVhdGggdGhlIG91dGVyIGVkZ2Ugb2YgdGhlIGV5ZWJyb3cgYW5kIHByb2R1Y2VzIHRlYXIgZmx1aWQgdGhhdCBrZWVwcyB0aGUgZXllIG1vaXN0LCBwcm90ZWN0cyBpdCBmcm9tIGluZmVjdGlvbiwgYW5kIGVuYWJsZXMgY2xlYXIgdmlzaW9uLjxcL3A+XG48aDM+U2NsZXJhICh3aGl0ZSBvZiB0aGUgZXllKTxcL2gzPlxuPHA+VGhlIHNjbGVyYSBpcyB0aGUgZmlybSwgd2hpdGUgb3V0ZXIgd2FsbCBvZiB0aGUgZXllLiBJdCBjb25zaXN0cyBvZiBjb2xsYWdlbiBmaWJlcnMsIGdpdmVzIHRoZSBleWUgaXRzIHNoYXBlLCBhbmQgc2VydmVzIGFzIHRoZSBhdHRhY2htZW50IHBvaW50IGZvciB0aGUgZXllIG11c2NsZXMuPFwvcD5cbjxoMz5Db3JuZWE8XC9oMz5cbjxwPlRoZSBjb3JuZWEgaXMgdGhlIGNsZWFyLCBjdXJ2ZWQgXCJ3aW5kb3dcIiBhdCB0aGUgZnJvbnQgb2YgdGhlIGV5ZS4gSXQgbGV0cyBsaWdodCBpbiBhbmQgcmVmcmFjdHMgaXQgc28gdGhhdCBpdCBmb2N1c2VzIG9uIHRoZSByZXRpbmEuIENvbnRhY3QgbGVuc2VzIHJlc3QgZGlyZWN0bHkgb24gdGhlIGNvcm5lYS48XC9wPlxuPGgyPkludGVybmFsIHN0cnVjdHVyZXMgb2YgdGhlIGV5ZTxcL2gyPlxuPGgzPkFudGVyaW9yIGNoYW1iZXI8XC9oMz5cbjxwPlRoZSBzcGFjZSBmaWxsZWQgd2l0aCBhcXVlb3VzIGh1bW9yIGJldHdlZW4gdGhlIGNvcm5lYSBhbmQgaXJpcy4gVGhlIGFxdWVvdXMgaHVtb3Igbm91cmlzaGVzIHRoZSBjb3JuZWEgYW5kIGxlbnMgYW5kIG1haW50YWlucyBpbnRyYW9jdWxhciBwcmVzc3VyZS48XC9wPlxuPGgzPklyaXMgYW5kIHB1cGlsPFwvaDM+XG48cD5UaGUgaXJpcyBpcyB0aGUgY29sb3JlZCBwYXJ0IG9mIHRoZSBleWUuIEluIGl0cyBjZW50ZXIgbGllcyB0aGUgcHVwaWwgXHUyMDEzIHRoZSBvcGVuaW5nIHRocm91Z2ggd2hpY2ggbGlnaHQgZW50ZXJzIHRoZSBleWUuIE11c2NsZXMgaW4gdGhlIGlyaXMgcmVndWxhdGUgcHVwaWwgd2lkdGg6IGluIGJyaWdodCBsaWdodCB0aGUgcHVwaWwgYmVjb21lcyBuYXJyb3csIGluIGRhcmtuZXNzIGl0IGJlY29tZXMgd2lkZS48XC9wPlxuPGgzPkxlbnM8XC9oMz5cbjxwPlRoZSBsZW5zIHNpdHMgYmVoaW5kIHRoZSBpcmlzIGFuZCBmb2N1c2VzIGluY29taW5nIGxpZ2h0IG9uIHRoZSByZXRpbmEuIEZpbmUgZmliZXJzICh6b251bGFyIGZpYmVycykgaG9sZCBpdCBpbiBwb3NpdGlvbiBhbmQgYWxsb3cgaXQgdG8gY2hhbmdlIHNoYXBlIHRvIHNoYXJwbHkgZm9jdXMgb24gYm90aCBuZWFyIGFuZCBkaXN0YW50IG9iamVjdHMuIFRoaXMgcHJvY2VzcyBpcyBjYWxsZWQgYWNjb21tb2RhdGlvbi4gV2hlbiB0aGUgbGVucyBiZWNvbWVzIGNsb3VkeSwgaXQgaXMgY2FsbGVkIGEgY2F0YXJhY3QuPFwvcD5cbjxoMz5DaWxpYXJ5IGJvZHk8XC9oMz5cbjxwPlRoZSBjaWxpYXJ5IGJvZHkgbGllcyBiZXNpZGUgdGhlIGlyaXMuIEl0IHByb2R1Y2VzIHRoZSBhcXVlb3VzIGh1bW9yIGFuZCBjb250YWlucyB0aGUgY2lsaWFyeSBtdXNjbGUsIHdoaWNoIGNoYW5nZXMgdGhlIGxlbnMgc2hhcGUgZm9yIG5lYXIgYW5kIGRpc3RhbmNlIGZvY3VzaW5nLjxcL3A+XG48aDM+Vml0cmVvdXMgaHVtb3I8XC9oMz5cbjxwPlRoZSB2aXRyZW91cyBodW1vciBmaWxscyBtb3N0IG9mIHRoZSBleWVcdTIwMTlzIGludGVyaW9yIGJlaGluZCB0aGUgbGVucy4gSXQgY29uc2lzdHMgb2YgYSBnZWwtbGlrZSwgdHJhbnNwYXJlbnQgc3Vic3RhbmNlIHRoYXQgZ2l2ZXMgdGhlIGV5ZSBpdHMgc2hhcGUgYW5kIGtlZXBzIHRoZSBsaWdodCBwYXRoIHRvIHRoZSByZXRpbmEgY2xlYXIuPFwvcD5cbjxoMz5SZXRpbmE8XC9oMz5cbjxwPlRoZSByZXRpbmEgbGluZXMgdGhlIGlubmVyIHdhbGw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