ABOUT HUMAN EYE & THEIR DEFECTS

ANIMAL, BIRDS AND INSECTS EYE

BY

MOHAMED BASITH A

B.E (ELECTRICAL ELECTRONICS

ENGINEERING)

ABOUT EYE

• Eye is one of the important organ in

human body as compared with other

organs

• We can clearly understand many things

by the use of eye alone

• Without eye nothing can come visually

• So eye is one of the precious organ to

every living beings

Mechanism of vision

• Whenever we saw any objects it will

reach the brain then only we sense it is an

object

• These mechanism can done with a small

amount of time to reach the brain

• A healthy eye has a size of 22mm

• The intresting thing is all have two eyes

and each eye can see the object by the

way we get two different visuals at the

same time but it does not happen why?

,

• Each eye can see the objects but the

final output is single vision

• These works were done by the

muscles and the nerves that found

inside the eyes

• Finally these images send through

optic nerves to brain and transformed

to brain’s synapses

• We all know our brain is divided into

two hemispheres

Eye fact

• The another fact is , our left eye is

connected to the right side of our brain

similarly our right eye is connected to

the left side of our brain

• But both eyes can merge the images

and then send to the brain by using the

OPTIC CHIASMA

• This membrane merges two eye

information into single information and

then it sends to brain

Vision mechanism

Vision fact

• When we see any object it actually

falls in the retina like inverted form and

it can be corrected by our brain

Parts of human eye

Major parts in eye;

1) Cornea

2) Lens

3) Retina

Functions

1) Cornea;

• cornea is a protective covering of the

lens and all the visual rays initially

meets these cornea and then it allows

to meet the lens

• Between the cornea and the lens a

fluid called AQUOUS HUMOR and the

fluid between the lens and the retina

called VITREOUS HUMOR

,

2) Lens;

• lens is the important thing in the eye it

makes exact action of camera

• The lens can changes the path of the

object rays and meet to the retina

• If the lens is not working properly the

object cannot be identified by the

retina

,

3) Retina;

• Retina is the sensing area inside our

eyes

• It sense the entire objet and their

shape and color also

• Retina contains lot of sensory nerves

connected together to make a

combined network to sense the objects

Types of sensory organs

• Retina contains two sensory organs

namely

1) RODS

2) CONES

• All the living organism have these

sensing organs to sense

Rods & cones

Functions of rods & cones

• Both of these sensory organs can do

various jobs

RODS;

It detects only the colors of BLACK

& WHITE

CONES;

It detects All the colors including

black and white

Vision mechanism

Defects in human eye

• According to the eye ball structure changing

the defects can be classified as

1) Myopia (short sightness)

2) Hyperopia ( long sightness)

3) Nyctalopia ( night blindness )

4) Presbiopia

5) Cataract

6) Glaucoma

Myopia (short-sightness)• Inability to see long objects clearly due

to some enlargement in the eye ball

• So the objects cannot able to fall the

retina it converges infront of the retina

• It can be corrected by CONCAVE LENS

negative meniscus (-):

a diverging lens

Myopia corrective method

Image focuses BEFORE

reaching the retina

Hyperopia

(long sightness)

• Inablity to see the near objects clearly

due to the shortening of the eye ballSo

the objects fall beyond the retina

• So the retina cannot able to analyse the

near objects clearly

• It can be corrected by using CONVEX

LENS

Hyperopia corrective method

positive meniscus (+):

converging lens

Images focused

BEHIND the retina.

Nyctalopia

• Nyctalopia is not a serious eye problem

it come due to the deficiency of

VITAMIN A

• The sensory organs like RODS &

CONES need vitamin A to degenerate

its work continously

• If a deficiency in VITAMIN A occurs

these organs cannot able to

degenerate itself so the patient cannot

able to see at night timings

Presbiopia

• Presbiopia syndrome occurs due

ageing of human lens

• After attainig a age of 50 the elasticity

of the lens is reduced so the lens

unable to make correct vision to retina

• This phenomenon leads to blurry vision

Presbiopia effect

Cataract

• Cataract is a special type of problem

that came rarely but, it comes it may

lead to blind

• These disease has a appearance of a

cloud formation inside the eye lens

leads to reduce in vision

• Thus the formation of cloud pigments

can interrupt with the light rays so it

cannot clearly strikes the retina

Causes of cataract

• Our eye lens is made up of mostly

WATER & PROTEINS

• After we attain some age these

proteins may clump together with each

other to form a new shape like a cloud

that stagnate inside the lens

• So such proteins cannot help during

vision when a person is affected by

cataract

Cataract treatment

• Now a days cataract surgery is widely

implanted in many places and

successfully done by many specalist

• These surgery can done by removing

the damaged lens and the cloudy

substances and then place a artificial

lens

• If these surgery cannot done the

patient may lead to meet complete

blindness

Cataract

Glaucoma

• Glaucoma is one of the major eye

problem that spread widely in

developed countries

• Glaucoma came due to the liquid

pressure variations inside our eyeball

• Our eye contains a special liquid but,

sometimes these liquid can

pressurized and it interupt with the

optic nerve and damage it

Causes of glaucoma

• Glaucoma can come of due to anger and

blood pressure

• When a person is under such conditions

the pressure inside the eyeball also

changes that pressure can push the optic

nerve and slowly damages it

• These pressure is indicated by the name

of INTRA OCCULAR PRESSURE (IOP)

• Normally the IOP range of a normal

human is “12-22 mm Hg”

IOP calculations

• The IOP of an eye is determined by the

balance of the liquid in the eyeball that

is calculated by the formula

Po = (F/C) + Pv

Where,

Po – IOP

F – Aqueous flow rate

C – outflow of fluid

Pv – episcleral venous pressure

Glaucoma

Eye of an animals

• Animals also have a similar

arrangement of human eye but they

have different features compared to

human eyes

• Most of you note that during night all

the animal eyes have light glowing

appearance

• These is the fact that animals contain

a fluid name as TYNAPTUM

• This liquid membrane can glow like a

light during night

Eye of birds

• Birds have different arrangement of

eyes compared to humans

• They can see their prey during it fly in

the sky so birds eye have more

sensitive arrangement

• The fact is a HAWK can able to see the

movement of an ant when it fly at the

height of 100 metres and above

• Birds have side arrangement of eyes to

capture 270*

Eye of insects

• Insects eye arrangement is completely

different from all the above

arrangements

• All insects have a eye name as

COMPOUND EYE

• Compound eye means connection of

many eyes in the form of network

combined together to gather

information and sends to their sensory

networks

Other eye facts

• A CHEETAH has a clear eye sight , it

can able to see a movement of

anything when it see from a distance

of 100 yards

• CHAMELEON has special eye among all

insects it can capture 360*

• All we know that SNAKE does not

have a ear so it’s eye use as a ear

The OWL

• Owl’s have clear night vision than day

vision why?

• They have a similar arrangement like

human eye but some modifications

make it see clearly in night

• During day times it can see but cannot

able to capture many things

How it make this possible

• Owl’s have the same sensing organs

like human ( RODS & CONES )

• But, the arrangement is not like a

humans

• In humans cones are found 70% and

the rods are found 30%

• But in owls rods are found about a

huge amount of 95% and the cones are

about a small range of just 5%

,• We already know that rods have

support BLACK & WHITE colors only

• During night we only see the colors of

black and white so it is the advantage

of owl to see clearly during night

• All owls have white colored eye that

also gives the presence of more rods in

owls eye arrangement