Human Anatomy
Eyeball
Eyeball anatomy for MBBS: three coats, cornea, uvea and retina, refractive media, aqueous humour flow, cataract and glaucoma, mapped to NMC codes AN41.1 to AN41.3.
MedNext Academy | 3 min read
Eyeball
Eyeball anatomy for MBBS: three coats, cornea, uvea and retina, refractive media, aqueous humour flow, cataract and glaucoma, mapped to NMC codes AN41.1 to AN41.3.
The eyeball chapter covers the three coats of the eye, the refractive media and the flow of aqueous humour. It is the anatomical basis for cataract, glaucoma and the vascular emergencies of the retina.
High-yield: Eyeball
- The eyeball has three coats: the outer fibrous, the middle vascular and the inner nervous layer.
- The fibrous coat is the transparent cornea in front and the opaque sclera behind.
- The vascular coat, or uvea, is made up of the choroid, ciliary body and iris.
- The ciliary body contains the ciliary muscle, which changes the shape of the lens for accommodation.
- The iris controls the size of the pupil through the sphincter and dilator pupillae muscles.
- The sphincter pupillae is supplied by parasympathetic fibres and constricts the pupil, while the dilator is supplied by sympathetic fibres.
- The retina is the inner nervous coat and contains the rods and cones that respond to light.
- The macula lutea has the fovea centralis at its centre, the point of sharpest vision, rich in cones.
- The optic disc is where the optic nerve leaves and has no photoreceptors, forming the blind spot.
- The central artery of the retina is an end artery, so its occlusion causes sudden painless blindness.
- The lens is avascular and transparent, and its clouding produces a cataract.
- Aqueous humour is produced by the ciliary body and drained through the canal of Schlemm at the iridocorneal angle.
- Blockage of aqueous drainage raises intraocular pressure and causes glaucoma.
- The vitreous body is a clear gel that fills the space behind the lens and supports the retina.
The three coats of the eyeball
- **Fibrous coat:** Cornea in front for refraction, sclera behind for protection.
- **Vascular coat (uvea):** Choroid, ciliary body and iris. Controls the lens and the pupil.
- **Nervous coat:** Retina with rods and cones, the macula for sharp vision, the optic disc as the blind spot.
- **Aqueous flow:** Made by the ciliary body, drained via the canal of Schlemm. Blockage causes glaucoma.
NMC competencies in this chapter
- **AN41.1:** Coats of the eyeball and their features
- **AN41.2:** Refractive media and the production and drainage of aqueous humour
- **AN41.3:** Applied anatomy of the eyeball including cataract and glaucoma
Frequently Asked Questions
What causes a cataract?
A cataract is a clouding of the normally transparent lens, which scatters light and blurs vision. The lens has no blood supply and depends on the surrounding fluids for nutrition.
How does glaucoma develop anatomically?
Aqueous humour made by the ciliary body normally drains through the canal of Schlemm at the iridocorneal angle. If this drainage is blocked, pressure rises and damages the optic nerve.
Why is the optic disc a blind spot?
It is where the optic nerve fibres leave the eye, so it has no rods or cones and cannot respond to light, creating a natural blind spot in the visual field.
How does this chapter help in NEET-PG?
The coats of the eye, aqueous dynamics and retinal blood supply are central to ophthalmology, so the eyeball is directly high-yield for PG preparation.
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