The eye lids are two movable folds
situated above and below the
front of the eye .
• Skin-The thinnest part of human
• Muscle-Open & close the eyelid
• Connective tissue-Give rigidity &
• Conjunctiva-the mucous
membrane acting as a lubricating
film between the eyelid & sclera
The Blinking of the eyelids helps to spread the tears
evenly over the eye and by renewing the tear film as
it evaporates, prevents the eye drying out.
Normal blinking occurs about 12 times per
During each blink, Our eyes are shut for around
The eye is spherical hollow, the periphery of which
composed of the three major layer or
Outer Fibrous Layer (Cornea-Sclera)
Middle Vascularized Layer (Uvea:
Inner Neural layer(Retina)
Thin, transparent mucous membrane lining posterior
surfaces of eyelids and covering anterior surface of
the eyeball, excluding cornea
What are the parts of the conjunctiva?
Clinically, the conjunctiva divided into three parts:
•The Palpebral (Latin word “palpebrae” means “an eyelid) -- which
lines the under-surface of the eyelids,
•The Bulbar -- which coats the anterior portion of the sclera
•The Fornix – Conjunctival junction between the The Palpebral
and The Bulbar conjuntiva
Function of Conjunctiva
Contains goblet cells which secrete lubricating
mucus and helps keep they eyeballs moist
It also helps the sclera protect the eye.
Protects the inside of eye from infection and
damage from foreign bodies
Cornea – "window of the
Transparent structure forming the front portion of eye.
The average adult cornea is 1.0 mm thick and 11.5 mm in
The cornea is avascular (contains no blood vessels). Its
nutritional and metabolic needs are met by:
blood vessels supplying the (the junction of the sclera
fluids that make up the precorneal tear film components
of the tear film aqueous oxygen from the external
Layers of cornea
The cornea has five main layers of cells:
1. Epithelium: The outer layer of the cells that
acts as a barrier against damage and infection
2. Bowman's membrane:
A thin, tough
3. Stroma: Consist of collagen fibers and account
for 90% of the cornea's thickness
4. Descemet's membrane: A thin membrane of
collagen and elastic fiber
5. Endothelium: A layer very delicate cells that
cannot regenerate and are Responsible for
maintaining partial corneal dehydration and
Function: Provide the principal refracting medium for the eye
Sclera – "white of the
Sclera:The tough white outer coat of the eyeball, continuous with
cornea. The sclera is completely opaque, preventing light from entering
the eye .
•Function: Forms the shape & maintain the shape of the eyeball
(Middle Vascular Layer)
The iris, ciliary body, and the choroid are all continuous
with each other and are collectively called the uvea.
•The iris, which is the colored part of the eye, contracts and dilates
to control how much light enters the eye.
•It is made up of smooth muscle fibers that adjust pupil size .
•By adjusting, it allows us to see under a variety of lighting
The pupil is a black hole in the centre of the iris . The size of the
pupil determines the amount of light that enters the eye. The pupil size
is controlled by the dilator and sphincter muscles of the iris.
•Pupil diameter :In healthy eye, ranges from 2 to 8
If you are in a very bright room , or in bright sunlight , our pupils
will be very small. This is because not much light needs to be let in
to the eye for it to be able to see well. In a dimly-lit room your
pupils will be bigger, to let as much light into the eye as possible.
Function of iris and pupil
• Regulate the amount of light entering the eye
The choroid is a layer of connective tissue and blood vessels,
located between the sclera (white of the eye) and the retina.
Function: Provides nourishment to surrounding eye structure
The ciliary body (Middle
The ciliary body releases aqueous humor , which
nourishes the front part of the eye. It also contains the
ciliary muscle, which changes the shape of the lens to help you
The ciliary body is made up of:
• Aqueous humor is the fluid
contained in the eye between the
lens and cornea.
•This fluid is produced by the
ciliary body and drains through the
•nourishes & baths cornea, iris and
lens and maintain intraocular
•It carries the nutritional elements
needed for the avascular cornea
filling the posterior chamber (space
between the iris and the lens.)
flows through the pupil into
the anterior chamber
(between the cornea and the iris.)
outwards into the angle
(formed by the iris and cornea. )
Filtering through the trabecular
Pass through Canal of Schlemm
returns back into the blood circulation.
Ciliary body Drainage system
CANAL OF SCHLEMM
The canal of schlemm provides a route for excess aqueous humor
to drain out of the eye. Canal transfers approximately 2-3
micro liters of aqueous humor/minute
Function : It lies near the junction of cornea and sclera, this
canal passes circularly around the cornea, and drains the
The crystalline lens is a biconvex,
transparent & avascular
structure. It is located
immediately behind the iris.
Suspended by fine ligament
(Zonules), attached between
completely transparent structure
about 4 mm thick and 9 mm in
Function: Focuses image on the
Lens can be divided into three regions
2. The anterior epithelium/lens
3. The lens fibre / lens nucleus.
CHAMBER OF THE
There are actually three
chambers in the eye.
The anterior chamber
The posterior chamber
The vitreous chamber
The cavity in the front part of the eye between the iris
and cornea is called the Anterior Chamber.
It is filled with Aqueous, a water-like fluid. This fluid is
produced by the ciliary process.
The posterior chamber is the fluid-filled space immediately
behind the iris but in front of the lens.
VITREOUS CAVIT Y /VITREOUS
The vitreous cavity fills the space from the lens to
the retina and contains vitreous humor, a jelly-like
material that maintains internal pressure to support
the eyeball and transports nutrients to the cornea.
The vitreous humor is a clear, transparent gel of semisolid
consistency which fills the chamber between the posterior
surface of the lens and the inner surface of the retina. It is
99% water, with the remainder being mostly a viscous
substance called hyaluronic acid. It occupies two-thirds of
the volume of the globe (eyeball)
Function: 1. Provide physical support
2. Transmit light to retina
Retina(Innermost Neural Layer)
The retina is a very thin layer of tissue
that lines the inner part of the eye. It is
connected to the brain.
Function: Received and transmit
The retina contains photoreceptor cells (rods
Rod cell functions in less intense light
Cone cell functions in bright light.
The optic nerve transmits electrical impulses from the
retina to the brain. It connects to the back of the eye
near the macula.
The optic nerve is a bundle of more than 1 million nerve
endings. It connects the retina to the brain
Tears are secretions of various
gland that clean and lubricate
Types of Tear
Some of the different types of tears
the brain tells the eyes to produce
1.Basal tears that coat your eyes
on a day-to-day basis to keep them
2.Irritant/reflex tears that form
in response to pain or to flush foreign
objects out of the eye. Their
composition is similar to basal tears,
but they contain more healing
3.Emotional tears that appear in
response to feelings of sadness,
stress, joy and extreme emotion.
Layers of tear film
Composed of three layers
1.Outermost lipid layer: secreted by meibomian glands.
2.Middle aqueous layer:
Secreted by lacrimal gland
3.Innermost mucin layer: Produced by the conjunctival goblet cel ls
Canal of Schlemm