EYE its structure ,parts ,functions pdf.

this pdf includes brief information about the human eye its structure parts, functions of each eye part and their clinical physiology

1. Cornea and functions
• outermost layer of the eye that covers the iris, Pupil and
anterior chamber.
PROTECTION: The cornea acts as a protective barrier
against dust , The cornea is the transparent, Dome-shaped
germs and other harmful particles. It also shields the eye
from ultraviolet [UV] light.
REFRACTION OF LIGHT : The cornea plays a crucial role in
focusing light into retina by refracting incoming light . It
provides about 65-75% of eye total focusing power.
TRANSPARENCY : Its transparent structure allows Light to
pass through unobstructed.
IRIS
The iris is the colored part of the eye that surrounds the
pupil. It is thin circular structure responsible for
controlling the size of the pupil and consequently , the
amount of light that enters the eye.
FUNCTIONS OF IRIS

REGULATION OF LIGHT:

▪ The iris controls the amount of light entering the eye by
adjusting the size of the pupil .

2. ▪ In bright light , the muscles of the iris contract to make the
smaller [miosis] , reducing light entry.
▪ In dim light ,the muscles relax , allowing the pupil to widen
[mydriasis] to let in more light . Focusing vision ; By controlling
the amount of light that reaches the retina , the iris helps
maintain clear and focused vision .

▪ Aesthetic Role ; The iris gives the eye its color [e.g., blue ,
brown , green ]due to pigmentation present , which can also
offer some protection against CV light

▪ The iris plays a critical role in adapting vision to different light
condition and protecting the eye from excessive light
exposure.


PUPIL

• The pupil is black circular opening in the centre of the iris of
the eye that allows light to enter the retina . Its size adjusts
automatically to control the amount of light entering the eye.
•
1. Regulating Light Entry : . In bright light, the pupil constricts
[gets smaller] to reduce the amount of light entering the eye ,
protecting the retina from excessive light..

• In dim light, the pupil dilates [gets larger] to allow more light
to enter, enhancing visibility.

2. Focusing Vision: By controlling the amount of light
entering the eye, the pupil helps maintain optimal focus and
clarity under varying lighting condition.

3. 3.Protective role ; By constricting in response in sudden
right light , the pupil helps to prevent light –induced damage to
the sensitive retinal cells .
• The size of the pupil is regulated by muscles in the Iris : the
Spherical pupillae (constricts the pupil ) and the Dilator
pupillae (dilates the pupil) .This process is called the pupillary
light reflex and is controlled by the autonomic nervous system.


AQUEOUS HUMOUR
• It is a thin fluid that fills the anterior and posterior chambers of
the eye.
• Anterior chamber lies between the cornea and iris.
• Posterior chamber lies between the iris and lens.
• Both the chambers communicate with each other through
pupil. Properties of Aqueous Humour.
PROPERTIES
• Volume : 0.13 mL
• Reaction and pH : Alkaline with a pH of 7.5
FORMATION OF AH
• Aqueous humor is formed by ciliary processes. It is formed
from plasma within capillary network of ciliary process by
diffusion, ultrafiltration and active transport through the
epithelial cells lining the ciliary processes.
• After formation, aqueous humor reaches the posterior
chamber by passing through the suspensory ligaments.

4. • From here, it reaches the anterior chamber via pupil.
• Rate of formation is about 2 to 3 µL per minute.
• Amount of aqueous humor in anterior chamber is about 230
µL to 250 µL and in posterior chamber it is about 50 µL to 60
µL
•
FUNCTIONS
• Maintains the shape of eyeball
• Maintains the intraocular pressure
• Provides nutrients, oxygen and electrolytes to avascular
structures such as lens and cornea
• Removes the metabolic end product from lens and cornea.

APPLIED PHYSIOLOGY: GLAUCOMA
• Glaucoma is a group of diseases characterized by increased
intraocular pressure, which causes damage of optic nerve,
resulting in blindness.
• In glaucoma, the drainage of aqueous humor through
trabeculae is blocked, resulting in increased intraocular
pressure.
• When the intraocular pressure rises above 60 mm Hg, the
optic nerve fibers at the optic disk are compressed.

5. • Initially it decreases the visual field (loss of peripheral
vision), which eventually leads to total blindness.

Types of Glaucoma

❖ Primary open-angle glaucoma:
• is the most common type of glaucoma, a progressive eye
disease that damages the optic nerve often leading to vision
loss or blindness is left untreated.
• The drainage angle between the cornea and iris remains open,
but the trabecular meshwork is partially blocked.
• The pressure builds up gradually in the eye over a long period
of time
❖ Primary angle-closure glaucoma (PACG) :

• It is a type of glaucoma caused by the blockage of the drainage
angle in the eye, leading to a rapid or gradual increase
intraocular pressure.
The iris may bulge forward, blocking the drainage angle.

Causes of Glaucoma:-
▪Major cause of glaucoma is the blockage in drainage system
of aqueous humor in trabeculae, resulting in increased
intraocular pressure.

6. ▪Common causes of secondary glaucoma are diabetes,
inflammation or injury to eye and excess use of drugs such as
corticosteroid.

Symptoms of Glaucoma:-
▪Primary open-angle glaucoma is a silent chronicc disease
without any early symptoms.
▪ Symptoms that develop in later stages include heaviness
around eyeball, headache and rapid reduction in visual
acuity and visual field.
▪Early symptoms of angle-closure glaucoma are severe pain in
eye or eyebrow, headache, nausea, blurred vision and rainbow
halo (colored rings) around bulb light.
Immediate care should be taken if two or more of these
symptoms appear together.

Treatment for Glaucoma:-
Treatment does not cure the disease but can prevent further
damage of optic nerve.
▪ Treatment is aimed at lowering the intraocular pressure.
▪ It is achieved by using eye drops or medicines alone or in
combination with laser treatment. ▪ If intraocular pressure
cannot be controlled by these methods, surgery is required.

7. VITEROUS HUMOUR
▪ Also known as vitreous fluid, fluid is present behind the
lens in space between lens and retina.
▪ Is a transparent, colourless and gel-like substance that
fills the space between the lens and retina with the eye.
▪ Main role to maintain the round shape of the eye.
▪ Also known as vitreous body ,highly vitreous formed bya
fine fibrillar network of proteoglycan molecules
▪ Major components in VH is albulin and hyaluronic body
from blood by means of diffusion.