2. AN ASSINGMENT ON
UNDER THE DEPARTMENT OF
PHARMACOLOGY, BIOCHEMISTRY & PHYSIOLOGY
SUBMITTED BY:
Sudipta Nag Himel(11/26)
An undergraduate student of
Chittagong Veterinary and Animal Sciences University
Khulshi, Chittagong-4225.

3. EYE :
The organ of VISION
Eyes are the paired organs
that detect light and convert it
into electro-chemical impulses
in neurons.

4. Types of eye:
Simple eye
is presence in
all chordates
Compound eye
is presence in
case of arthopods

6. Parts of EYE
EYE
component mainly
divided into
parts

7. Parts of EYE
1.Eyeball
• Three layers:
– Fibrous outer layer
• Sclera
• Cornea
– Vascular middle layer
• Choroid,
• Ciliary body and
• Iris
– The inner nervous layer
• Retina
• Pupil
• Structures inside the eyeball are the
lens, aqueous fluid and vitreous body.

8. Parts of EYE
2.Accessory structures
•Conjunctiva
•Eyelid
•Eyelashes
•Lacrimal gland
•Extraocular muscles

9. Fibrous outer layer
Cornea
Thin, transparent epithelium
 Allow the free entry of light.
 Act as refractive media.
Sclera
“White part of the eye”
 Maintaining the shape and
form of the eye ball.
 Contains BVs and insertion
site for extrinsic eye muscles.

10. Vascular middle layer
Choroid
– Pigmented to absorb excess
light
– Supplies the retina with
nutrients and oxygen via
blood supply
Iris
“Colored part” of the eye
which contains BVs, pigment
cells, loose connective tissue and
pupillary muscle.
Adjusts the pupil
Regulates amount of light

11. Vascular middle layer
Ciliary Body
Ring of smooth muscle around lens
Regulates the shape of the
lens for accommodation
Suspensatory Ligaments
– Attach the ciliary body to the lens

12. The inner nervous layer
Retina
is a light-sensitive layer of
tissue, lining the inner surface
of the eye.
Functions
It helps in
Photopic vision
Scoptic vision
Mesopic vision
Steroscopic vision
Acuity of vision
Color vision
Perception of movement

13. The inner nervous layer
Cells of retina-
I. Photoreceptor cells
II. Bipolar cells
III.Horizental cells
IV.Amacrine cells
V. Ganglion cells
• The photo receptor cells
are 2 types -
(1)The cone cells
(2)The rod cells

14. Difference betweem CONE cell and ROD cell
Property Cones Rods
Location In the fovea Outside the fovea
Resolution and visual Large Small
acuity
Total number of 5 million 120 million
elements
Color sensitivity Yes No
Brightness sensitivity Small, for daylight Large, for night vision
vision
Figure

15. The inner nervous layer
Special Areas of the Retina
 The macula lutea and fovea
Optic disc
Macula lutea centralis
 The blind spot
Artery Vein  Retinal blood vessels.
The macula or macula lutea
is an oval-shaped highly
pigmented yellow spot near the
center of the retina
Fovea centralis (fovea)
is a depresion, located in the
center of the macula region of
the retina.

16. The inner nervous layer
Pupil
Is a hole located in
the center of the iris.
It helps to pass
the light into the
eye.

17. Structures inside the eyeball
 Closely-packed concentric
columnar cells
Focuses image on the retina.
 The lens and ciliary body
divide the eye into two
cavities.
The anterior cavity
The posterior cavity

18. Anterior Chamber of Eye
Contains aqueous
humor which is
secreted by ciliary
body
 Maintains shape
of anterior eye. Anterior
Chamber
Constantly
produced - leaves
eye thru canal
that carries it to
bloodstream.

19. Posterior Chamber of Eye
Contains vitreous
humor
 Maintains shape of
posterior eye.
 Refracts light rays.
Is not constantly
being produced.
Loss of vitreous Vitreous Chamber
humor may mean
loss of eye.

20. Accessory structures
Lacrimal gland
The lacrimal glands are the sites of tear
production.
Tears function to keep the
conjunctiva and corneal epithelium
moist and wash away foreign material
from the eye.
Lacrimal apparatus
Secretes and drains tears from
the eye

21. Accessory structures
Eyelashes
Eyelashes are short hairs of eye that
may occur in double or triple rows.
They function to protect the eye
from debris.
Lashes may also have different
lengths and diameters to one
another.

22. Accessory structures
Conjunctiva
The conjunctiva refers to the lining of the
eye.
It has 2 parts
Palpebral conjunctiva
Bulbar conjunctiva
It helps lubricate the eye by secreting
mucous, and serves as a protective
barrier again microbes.
It contains many goblet cells which
secrete a component of the tears that
bath the eye.

23. Accessory structures
Eyelid
The main function of the eyelid
is to provide the eye with
protection. There are several
types of glands in the
eyelids, including tarsal glands
that produce a sebaceous
secretion that results in an oily
surface of the tear film to
prevent the evaporation of the
normal tear layer.

24. Accessory structures
Extraocular Muscles
i. Rectus dorsalis
ii. Rectus ventralis
iii. Rectus medialis
iv.Rectus lateralis
v. Obliqus dorsalis
vi.Obliqus ventralis

25. Functions of Extraocular Muscles
IO SR IO/SR SR/IO SR IO
These six muscles responsible for eye movement.
 Four rectus muscles control the movement of the eye
in the four cardinal directions:
LR MR MR LR
Up,
Down,
SO IR Left and
SO/IR IR/SO IR SO
Right.
 The remaining two muscles control the adjustments
MR MR
involved in counter acting head movement.
CONVERGENCE

26. Vision
Steps of vision
Light
Refraction
•Cornea and lens
Accommodation
Photo-pigments
Photo-transduction
Photoreceptor activity
•In the dark
•When exposed to light

27. Visual Pathway
Pathway
of
LIGHT

28. Refraction
 Refraction is the phenomenon which makes image formation
possible by the eye as well as by cameras and other systems of
lenses.
 The eye, is optically equivalent to the usual photographic
camera.
 The lens system of the eye is composed of four refractive
interfaces.
 Formation of an Image on the Retina.
The lens system of the eye can focus an image on the retina.
The image is inverted and reversed with respect to the object.
However, the mind perceives objects in the upright position
because the brain is trained to consider an inverted image as the
normal.

29. Accommodation
 The process of changing the
shape of the lens while
focusing on an object is
termed as accommodation.
 At rest focused on distant
objects, needs to increase
focal power than focus on
close objects.
 The ciliary muscles contract
and release tension in the
ligaments and the lens
becomes rounder in case of
close objects.

30. Photopigments
 There are four types of photopigments, one in the rods and one in
each of three types of cones.
The pigment in the rods is called rhodopsin.
Rhodopsin absorbs all visible wavelengths, so that rods
provide vision only in shades of grey by detecting different
intensities rather than colours.
The three types of cones - red, green and blue
photopsin, can respond selectively to various
wavelengths of light, giving rise to colour vision.

31. Rhodopsin
 The photon is absorbed by rhodopsin.
 The light receptor molecule tightly-packed in the
disk membranes
 One rod contains 10 billion rhodopsin molecules,
which ensures an optimum photon capture rate
Rhodopsin has 2
components
Retinal- Vitamin A aldehyde
Opsin- single polypeptide
containing 7
transmembrane domains

33.  Vitamin A is present both in
the cytoplasm of the rods
and in the pigment layer of
the retina.
Therefore, vitamin A is
normally always available to
form new retinal when
needed.
 Conversely, when there is
excess retinal in the
retina, it is converted back
into vitamin A, thus reducing
the amount of light-sensitive
pigment in the retina.
 Night blindness.

34. Phototransduction
The retina therefore signals the brain
Light stimulation through an inhibitory
response involving a series of
physiological reactions
Action potentials,
Only originate in the ganglion cells,
The first neurons in the chain that carry
the visual stimuli to the brain.
Vision occurs
This process is called
phototransduction.

37. ERRORS OF REFRACTION
• Astigmatism– defective
curvature of the cornea
or lens of the eye.
• Presbyopia– impaired
vision of the cornea or
lens of the
eye, associated with
aging.
• Hyperopia– can’t see
close objects, rays of
light focus behind retina
• Myopia- can’t see far
away objects, rays of
light focus in front of the

38. COMMON DISORDERS OF THE
EYE
(A) Acute bacterial conjunctivitis.
(B) Anisocoria.
(C) Color Blindness
 Monochromacy
lack of 2 of the 3
types of cones
 Dichromacy:
lack of 1 type of
normally-function
cones
 Anomalous trichromacy
shift in the normal
spectrum

39. Some other Symptoms found
in a serious
Ocular condition
Visual loss
Double vision
Severe eye pain
Foreign body sensation

40. Books
Textbook of medical physiology /
C. Guyton, John E. Hall.—11th ed
Review of Medical Physiology /
William F . Ganong .—22nd ed
Animal Physiology /
Eckert & Randall -2nd ed
Internet

42. QUESTIONS