3. POSITION
• The eyeball is situated in the anterior part
of the orbital cavity, closer to the roof than
the floor, and nearer the lateral than the
medial wall.
• One third of the eyeball is exposed.
4. IMPORTANT FACTS & DIMENSIONS
Anterior & posterior pole:
• The center of curvature of the anterior surface
of the eyeball is called the anterior pole.
• while that of the posterior surface of the
eyeball is called the posterior pole.
5. Length of the eyeball:
• The anterioposterior diameter of the eyeball is
commonly referred to as the length of the
eyeball
• which is 22mm-26mm averaging at 24mm.
6. Equator of the eyeball
• Midway between the anterior & the
posterior pole of the eyeball is the
imaginary plane of the equator of the eyeball.
7. Refractive Media Of The Eyeball
• Cornea
• lens
• aqueous & the
• vitreous
• The total refractive power of the eye is 58 to
60 diopters.
8. Factors responsible for the stability of
the eyeball in the orbit
• Optic nerve
• Fascial covering & ligaments
• Attachment of the muscles
• Orbital fat
9. COVERINGS OF THE EYEBALL
• The eyeball is enveloped in two important
coverings:
Fascial covering
• which covers the entire eyeball & the
Conjunctiva
• which covers the exposed part of the anterior
surface of the sclera & the under surface of
the eyelids.
10. • FASCIAL SHEAT of the eyeballl.
• It is also referred to as the fascia bulbi or the
tenon’s capsule.
• The space underneath it, is called the
episcleral space
• It is filled with delicate bands of connective
tissue fibres & blood vessels
11. • Anterioraly ,It is firmly attached to the sclera
about 1.5mm posterior to the cornealsclearal
junction(limbus).
• posteriorly it fuses with the coverings of the
optic nerve.
12. CONJUNCTIVA
• It is the mucous membrane which lines outer
surface of the exposed anterior part of the
eyeball and is reflected onto the back of the
lids.
• It forms a potential space called the
conjunctival space or the conjunctival sac
which is open at the palpebral fissure.
13. For the purpose of description it is divided
into:
Palpebral conjunctiva
• covers the under surface of the eyelids.
• It is firmly adherent to the undersurface of
the tarsal plate
14. Bulbar conjunctiva
• part which covers the outer anterior surface of
the eyeball.
• It is loosely adherent to the underlying sclera
and the tenon’s capsule
15. Conjunctival fornices
( singular;fronix;-plural; fornices)
• this is the part at which the conjunctiva
is reflected from the surface of the eyeball
to the under surface of the eyelids.
The superior fornix is situated about 10mmfrom the
limbus.& The inferior fornix is situated about
5mmfrom the limbus.
The ducts of the lacrimal gland open in to lateral part of
the superior fornix.Medially the fornix are absent
and are replaced by the caruncle and plica
semilunaris.on the lateral side the fornices are
extensive and lie about 14mm from the limbus
16. Histologically
It consists of the following important structures:
Epithelium
Glands
• Accessory lacrimal glands & the mucin secreting
goblet cells. Additional cells present in the
conjunctival epithelium include melanocytes.
• Lymphoid tissue--- in case of some infections the
lymphoid tissue of the conjunctiva get enlarged and
are then referred to as follicles
• The epithelial layer contains blood vessels, fibrous
tissue.
17. Blood vessels
• there are a lot of blood vessels in the
conjunctiva.
• These vessels get dilated even on minor
irritation and are most commonly responsible
for the red appearance of the eyes
18. Nerve supply
• Sensory innervation of the conjunctiva is manily
of the ophthalmic nerve which is the branch of
trigiminal nerve ,
so furtherly conjuctival innervation is divided into
four parts:
• Supraorbital nerve Supratrochlear nerve
Infratrochlear nerve ,from superior area
• Infraorbital nerve from inferior area .
• Lacrimal nerve (with contribution from
zygomaticofacial nerve)from lateral area.
• Long ciliary nerves from limbal area .
19.
20. FUNCTIONS OF THE CONJUNCTIVA
• It is a very vascular tissue and provides some
nourishment to the cornea when the eyes are
closed.
• At the limbus it provides nourishment to the
peripheral part of the cornea.
21. • It provides immunity to the ocular surface by
means of it’s lymphoid tissue.
• It provides secretions which keep the ocular
surface smooth, lubricated & healthy.
