# What is the Eye and What is Its Anatomy?

Source page: https://www.kudretgozistanbul.com/en/blog/eye-diseases/the-eye-and-its-anatomy

**Author:** Kudret Eye İstanbul | **Medical Approval:** Op. Dr. Mehmet Ali Özdil | **Date:** 2026-09-12

> **Summary:** The eye is a complex organ that refracts light and sends images to the brain through the optic nerve. Knowing its anatomy helps explain and treat problems such as myopia, hyperopia, astigmatism, cataract and glaucoma.

## Quick Facts
- **Three layers:** Outer (cornea, sclera), middle or uveal (iris, ciliary body, choroid), inner (retina)
- **First structure light reaches:** The cornea
- **Optic nerves:** A single optic nerve leaves each eye

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## Why Eye Anatomy Matters
Myopia, hyperopia and astigmatism usually come from the length of the eyeball or the curvature of the cornea. Understanding the anatomy made intraocular lenses, cataract treatment and laser surgery possible, and helps locate where a problem arises. Regular check-ups help identify problems early.

## Parts of the Eye
- **Cornea:** The transparent, curved, multi-layered front layer over the iris and lens. It has no blood vessels, which keeps it transparent, refracts light for sharp vision and has nerves that trigger the blink reflex.
- **Aqueous humour:** Clear fluid in the anterior chamber (between cornea and iris) and posterior chamber (between iris and lens), produced by the ciliary body and drained through the canal of Schlemm to balance eye pressure; disturbed flow can cause glaucoma.
- **Iris and pupil:** The iris is the coloured part around the pupil and controls its size: the pupil narrows in bright light and widens in dim light.
- **Ciliary muscle:** Changes lens curvature through the zonular fibres, allowing focus at near and distance (accommodation).
- **Lens:** Transparent structure behind the iris and in front of the vitreous, forming a sharp image.
- **Vitreous humour:** Gel between lens and retina that keeps the eyeball's shape and supports the retina; it liquefies with age and can cause floaters.
- **Retina:** Multi-layered tissue at the back with photoreceptors (rods and cones), interneurons and ganglion cells.
- **Macula and fovea:** Centre of the retina, rich in cones, providing colour vision and high resolution.
- **Optic disc:** Area without photoreceptors where nerve fibres leave; the brain does not perceive it as a blind spot.
- **Optic nerve:** Carries retinal signals as electrical impulses from the posterior pole to the brain's visual centre.
- **Sclera:** The firm, durable white of the eye that protects it.
- **Eye muscles:** Move the eyes.
- **Tear glands and tear film:** Keep the eye moist and help remove foreign bodies. The tear film has an oil layer (meibomian glands, limits evaporation), a watery layer (cleans the cornea) and a mucin layer (spreads tears evenly).
- **Conjunctiva:** Thin mucous membrane lining the inner eyelids and front of the sclera, not covering the cornea; keeps the eye moist and protected.
- **Eyelids:** Protect the eye with the lashes and skin.

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## References
- Eye Anatomy: Parts of the Eye and How We See, AAO
- How the Eyes Work, NEI
- What Is Dry Eye?, AAO