THE HUMAN EYE
The human eye receptors that detect light stimuli are known as photoreceptors and the
eye is responsible for sight in humans. The two eyes are positioned in bony eye sockets
(at the front of the skull). The shape of the eye is more or less spherical. Ciliary body
The structure of the eye (consists of three layers) Suspensory ligament Sclera
Choroid
• Outer fibrous layer Aqueous humour
cornea Retina
• Middle vascular layer Aqueous humour
• Inner light-sensitive retina Lens
Yellow spot
Blind spot
Iris
Upper eyelid
.
Eyelashes Conjunctiva Optic nerve
Vitreous humour
The internal structure of the eye
Sclera Outer fibrous layer
Lower eyelid
a Sclera
The sclera, also known as the white of the eye, is a tough, fibrous layer that makes up the
The external structure of the eye outermost layer of the eye.
Functions:
• The shape of the eyeball is more or less spherical. • Protects the internal parts of the eye.
• The eyelids protect the eye from injury, dust, and other foreign objects. The eyelid b Cornea
can quickly close to protect the eye and keep it moist by distributing tears over the The cornea is a clear, dome-shaped layer that forms the outermost layer of the eye’s front
surface of the eye. The eyelid also helps to regulate the amount of light that enters surface. It covers the iris, pupil, and anterior chamber, and acts as the primary refractive
the eye by opening and closing the pupil. element of the eye.
• The eyelashes serve as a physical barrier, which protect the eyes from dust, dirt, and Functions:
other foreign objects. They also help to filter out excess light, preventing it from • Allows light rays through to the inner layers of the eye.
entering the eye and causing discomfort or damage.
• The tear glands secrete tears that protects the eye from dehydration and bacteria. Middle vascular layer
a Choroid
Choroid is a thin, vascular layer of tissue located between the sclera (the white, outer
layer of the eye) and the retina (the inner layer of the eye that detects light)
functions:
• Supply oxygen and nutrients to the eye cells through blood vessels.
, b Ciliary body
The ciliary body is a ring-shaped structure located in the eye between the iris and the
choroid. Inter light-sensitive retina
Functions: a Yellow spot
• Contract and relax to change the shape of the lens during accommodation. (Allowing The yellow spot, also known as the macula lutea, is a small area located near the centre of
it to focus on object at different distance) the retina in the posterior chamber of the eye. It is approximately 5 mm in diameter and
is responsible for central vision, which is the ability to see fine details and colours in the
b Iris centre of the visual field.
The iris is a thin, circular, pigmented structure located in the front of the eye, behind the
cornea and in front of the lens. Functions:
• Forms clearest image.
Functions:
B Blind spot
• Controls the amount of light that enters the eye.
The blind spot, also known as the optic disc, is a small area located in the posterior
chamber of the eye where the optic nerve exits the eye and sends visual signals to the
d Suspensory ligaments
brain. It is approximately 1.5 mm in diameter and is located slightly to the side of the
The suspensory ligament are rope like which helps to adjust the lens shape.
centre of the visual field in each eye.
functions: Functions:
• Holds the lens in position. • no vision
• Connects the lens to the ciliary body.
E Lens c Optic nerve
The lens is a clear, flexible, and biconvex structure located behind the iris in the eye. It The optic nerve exits the back of the eye at the optic disc, also known as the blind spot,
plays a crucial role in focusing light onto the retina, which allows us to see objects clearly. where there are no photoreceptor cells. The optic nerve then travels through the orbit
(the bony socket that holds the eye) and enters the brain through a small hole in the skull
Functions:
called the optic canal.
• Change shape for near and far vision.
Functions:
F Retina
• Conduct nerve impulse from the retina to the brain (it’s a sensory neuron).
The retina is a thin layer of neural tissue that lines the back of the eye, opposite the lens.
D Vitreous humour
Functions:
The vitreous humour is a transparent, gel-like substance that fills the space between the
• capture light and convert it into electrical signals that can be interpreted by the brain
lens and the retina in the posterior chamber of the eye. It is composed mainly of water
to create visual images. and a network of collagen fibres that give it its structure and consistency.
G Aqueous humour Functions:
The aqueous humour is a clear, water fluid that fills the space between the cornea and
• Maintain the shape of the eyeball.
the lens in the anterior chamber of the eye. It is produced by the ciliary body, a structure
• Holds the retina in position.
located behind the iris.
Functions:
• maintain the shape of the eyeball.
• provide nutrients to the cornea and lens.
• regulate pressure inside the eye.
The human eye receptors that detect light stimuli are known as photoreceptors and the
eye is responsible for sight in humans. The two eyes are positioned in bony eye sockets
(at the front of the skull). The shape of the eye is more or less spherical. Ciliary body
The structure of the eye (consists of three layers) Suspensory ligament Sclera
Choroid
• Outer fibrous layer Aqueous humour
cornea Retina
• Middle vascular layer Aqueous humour
• Inner light-sensitive retina Lens
Yellow spot
Blind spot
Iris
Upper eyelid
.
Eyelashes Conjunctiva Optic nerve
Vitreous humour
The internal structure of the eye
Sclera Outer fibrous layer
Lower eyelid
a Sclera
The sclera, also known as the white of the eye, is a tough, fibrous layer that makes up the
The external structure of the eye outermost layer of the eye.
Functions:
• The shape of the eyeball is more or less spherical. • Protects the internal parts of the eye.
• The eyelids protect the eye from injury, dust, and other foreign objects. The eyelid b Cornea
can quickly close to protect the eye and keep it moist by distributing tears over the The cornea is a clear, dome-shaped layer that forms the outermost layer of the eye’s front
surface of the eye. The eyelid also helps to regulate the amount of light that enters surface. It covers the iris, pupil, and anterior chamber, and acts as the primary refractive
the eye by opening and closing the pupil. element of the eye.
• The eyelashes serve as a physical barrier, which protect the eyes from dust, dirt, and Functions:
other foreign objects. They also help to filter out excess light, preventing it from • Allows light rays through to the inner layers of the eye.
entering the eye and causing discomfort or damage.
• The tear glands secrete tears that protects the eye from dehydration and bacteria. Middle vascular layer
a Choroid
Choroid is a thin, vascular layer of tissue located between the sclera (the white, outer
layer of the eye) and the retina (the inner layer of the eye that detects light)
functions:
• Supply oxygen and nutrients to the eye cells through blood vessels.
, b Ciliary body
The ciliary body is a ring-shaped structure located in the eye between the iris and the
choroid. Inter light-sensitive retina
Functions: a Yellow spot
• Contract and relax to change the shape of the lens during accommodation. (Allowing The yellow spot, also known as the macula lutea, is a small area located near the centre of
it to focus on object at different distance) the retina in the posterior chamber of the eye. It is approximately 5 mm in diameter and
is responsible for central vision, which is the ability to see fine details and colours in the
b Iris centre of the visual field.
The iris is a thin, circular, pigmented structure located in the front of the eye, behind the
cornea and in front of the lens. Functions:
• Forms clearest image.
Functions:
B Blind spot
• Controls the amount of light that enters the eye.
The blind spot, also known as the optic disc, is a small area located in the posterior
chamber of the eye where the optic nerve exits the eye and sends visual signals to the
d Suspensory ligaments
brain. It is approximately 1.5 mm in diameter and is located slightly to the side of the
The suspensory ligament are rope like which helps to adjust the lens shape.
centre of the visual field in each eye.
functions: Functions:
• Holds the lens in position. • no vision
• Connects the lens to the ciliary body.
E Lens c Optic nerve
The lens is a clear, flexible, and biconvex structure located behind the iris in the eye. It The optic nerve exits the back of the eye at the optic disc, also known as the blind spot,
plays a crucial role in focusing light onto the retina, which allows us to see objects clearly. where there are no photoreceptor cells. The optic nerve then travels through the orbit
(the bony socket that holds the eye) and enters the brain through a small hole in the skull
Functions:
called the optic canal.
• Change shape for near and far vision.
Functions:
F Retina
• Conduct nerve impulse from the retina to the brain (it’s a sensory neuron).
The retina is a thin layer of neural tissue that lines the back of the eye, opposite the lens.
D Vitreous humour
Functions:
The vitreous humour is a transparent, gel-like substance that fills the space between the
• capture light and convert it into electrical signals that can be interpreted by the brain
lens and the retina in the posterior chamber of the eye. It is composed mainly of water
to create visual images. and a network of collagen fibres that give it its structure and consistency.
G Aqueous humour Functions:
The aqueous humour is a clear, water fluid that fills the space between the cornea and
• Maintain the shape of the eyeball.
the lens in the anterior chamber of the eye. It is produced by the ciliary body, a structure
• Holds the retina in position.
located behind the iris.
Functions:
• maintain the shape of the eyeball.
• provide nutrients to the cornea and lens.
• regulate pressure inside the eye.
