The eye develops around day 22 of embryo development from several primordia, including the optic vesicle, lens placode, surrounding ectoderm, and mesenchyme surrounding the optic vesicle. The eyeball is a cystic structure kept distended by internal pressure, with dimensions of about 24mm anteroposteriorly and 23mm horizontally in adults. It has three coats - the fibrous outer coat including the sclera and cornea, the vascular middle uveal coat including the iris, ciliary body and choroid, and the inner nervous coat of the retina.

2. Embryology of the Eye

3. • Development of the eyes commence around day 22 when the embryo
has eight pairs of somites and is around 2 mm in length.

4. • The eyeball and its related structures are derived from the
following primordia:
• Optic vesicle,an outgrowth from prosencephalon(a neuroectodermal
structure),
• Lens placode, a specialised area of surface ectoderm, and the surrounding
surface ectoderm.
• Mesenchyme surrounding the optic vesicle, and
• Visceral mesoderm of maxillary process.

10. Anatomy of the Eye

11. Eyeball
• Each eyeball is a cystic structure kept distended by the pressure inside
it.
• The central point on the maximal convexities of the anterior and
posterior curvatures of the eyeball is called the anterior and
posterior pole, respectively.
• The equator of the eyeball lies at the mid plane between the two
poles

12. Dimensions of an adult eyeball

15. EXTRAOCULAR MUSCLES

18. A series of small veins which drain blood from the iris,
ciliary body and choroid join to form the vortex veins.
The vortex veins are four in number–
superior temporal, inferior temporal, superior
nasal and inferior nasal.
They pierce the sclera behind the equator and drain into
superior and inferior ophthalmic veins which in turn drain
into the cavernous sinus.

19. A thin fascial membrane, the vagina bulbi (fascia bulbi or Tenon's capsule), envelops the eyeball from the optic
nerve to the corneoscleral junction, separates it from the orbital fat, and forms a socket. Its ocular aspect is
loosely attached to the sclera by delicate bands of episcleral connective tissue.

20. The spaces between the main structures of the orbit are occupied by orbital fat.

21. Parts of conjunctiva

23. Coats of the eyeball
1. Fibrous coatAnterior 1/6th cornea.Posterior 5/6th sclera.
2. Vascular coat (uveal tissue). iris,ciliary body and choroid.
3. Nervous coat (retina).

24. Segments and chambers of the eyeball
• 1. Anterior segment. crystalline lens, iris, cornea and two aqueous
• Posterior chamber.
• 2.5 mm deep in the centre in normal adults.
• 0.25 ml of the aqueous humour.
• Posterior chamber.
• 0.06 ml of aqueous humour.

25. • 2. Posterior segment. vitreous humour, retina, choroid and optic disc.

27. Uveal tissue
• middle vascular coat of the
eyeball.

29. Lamina cribrosa is a sieve-like sclera from which
fibres of optic nerve pass.