The human eye has three layers: an outer fibrous layer, middle vascular layer, and inner nervous tissue layer. It contains several parts that work together to allow vision, including the iris, pupil, cornea, retina, and optic nerve. The cornea and pupil allow light to enter while the retina converts light to electrical signals transmitted by the optic nerve to the brain. Contraction and relaxation of the iris and ciliary muscles control the amount of light entering through the pupil and focus of the lens.

1. STRUCTURE
&
FUNCTION OF THE EYE
Prepared by
Mr. Vinayak Raju Bodhankar
M. Pharm. (QA)

2. Human Eye
► The human eye is an organ for sight.
► Situated in the orbital cavity supplied by the optic nerve.
► Spherical in shape & 2.5 cm in diameter.
► Structurally 2 eyes are separate but, some of their activities
are coordinated, so they function as pair
 THE HUMAN EYE

3.  STRUCTURE
There are 3 layers of tissue in the wall of eye
1. Outer fibrous layer: Sclera & cornea
2. Middle vascular layer: Choroid, ciliary body & iris
3. Inner nervous tissue layer: Retina

4.  PARTS OF HUMAN EYE
► The front part of the Eye includes:
► Iris: the colored part.
► Cornea: a clear dome over the iris.
► Pupil: the black circular opening in the iris that
lets light in.
► Sclera: the white of your eye.

5.  SCLERA & CORNEA
CORNEA
 Transparent covering of the front of the eye.
 Allows for the passage of light into the eye and functions as a fixed lens.
Function:
Allows for the passage of light into the eye and it also focuses the light on retina.
SCLERA
 A tough white skin (made of tissue) that covers all of the eyeball except the cornea.
Function: Supports eyeball and provides attachment for muscles.

6.  Iris, Choroid & Ciliary body
IRIS
 Colored part of eye.
 Lying behind the cornea in front of lens.
 It is a circular body composed of pigment cells & two layers of smooth muscle fibres.
 Controls the amount of light entering the eye.
CHOROID
 Lines the inner surface of sclera.
 Rich in blood vessel & is deep chocolate brown in colour.
 Light enters the eye through pupil, stimulate the nerve endings in retina & then absorbed by choroid.
CILIARY BODY
 It is the anterior continuation of the choroid.
 Consist of ciliary muscle & secretory epithelial cells.
 Contraction & relaxation of ciliary muscle changes the thickness of the lens.

7.  Retina
 Innermost layer of the wall of the eye.
 Layer is highly sensitive to the light.
 Contains light-receptive cells (rods and cones)
 Converts light to electrical signals

8.  Pupil (black hole)
 Black hole in iris where light enters.
 Function: Pupil size is controlled by iris muscles.
Pupil Expansion
 When the eye needs more light to enter (when it is dark), the pupils get
larger; allowing more light to enter the eye.
Pupil Contraction
 When the eye needs less light to enter (when it is very bright), the
pupils get smaller; allowing less light to enter the eye.

9.  Optic Nerve
 Transmits electrical impulses from retina to the brain.
 Creates blind spot.
 Brain takes inverted image and flips it so we can see.
Function:
Transmits electrical signals from retina to the brain.

10.  Functions
► The eye has many parts that must work together to produce clear vision:
► The sclera, or white part of the eye, protects the eyeball.
► The pupil, or black dot at the center of the eye, is a hole through which light can
enter the eye.
► The iris, or colored part of the eye, surrounds the pupil.