It Is A Sphericalorgan Known Equally The Nub Ball Located Inward The Bony Socket Of The Skull

             mammalian Eye

The oculus is the organ of sight. It is a spherical organ known every bit the oculus ball located inwards the bony socket of the skull. Because of its wall of bones, alone a small-scale percentage of the oculus tin live seen. The oculus is sensitive to a detail stimuli of low-cal of moving ridge length 400nm – 700nm. This stimulus is detected past times specialized photoreceptors inwards the eye. Influenza A virus subtype H5N1 forepart sentiment of the oculus shows its protective accessories viz (a) oculus lids  (2) oculus brows  (3) oculus lashes  (4) tear gland  (5) conjuctiva

 Functions:

Eyelids: protect the oculus from external dangers

Eyelashes: prevents together with traps dust particles against the eye. Spreads tears to the oculus surface

Tear gland: products tears rich inwards lysosomes for washing together with clearing the eye

Conjuctiva: protect the corneas from external damage. When inflamed, results inwards Apollo or conjuctivities

FRONT VIEW OF THE HUMAN EYE

Each eyeball is attached to the human oculus socket past times a ready of half dozen muscles which enable the eyeball to movement inwards many directions. These muscles are the half dozen rotator muscles composing

-         superior rectus

-         inferior rectus

-         medial rectus

-         lateral rectus

-         inferior oblique

-         superior oblique

the muscles surround a thick band nervus called the optic nervus which transmit to the grain

STRUCTURE

A vertical department through the oculus shows the within of the eyeball to live fluid filled hollowed construction its walls consists of three layers viz

1.     the outer sclera

2.     the heart choroid

3.     the inner retina

SCLERA:

The sclera is a white tough fibrous connector tissue layer which protects together with maintains the spherical shape of the eyeball. In forepart it bulges out at the exposed component subdivision to shape a cornea. The oculus lids are covered on the within past times a transparent membrane called the conjuctiva. It covers together with protects the cornea

Functions:   -        it protects the eyeball from injury

                             It helps to keep the shape of the oculus ball

Cornea:       -        allows rays of low-cal into the eye

                             It helps to refract rays of low-cal entering the eye

Conjunctiva: -      protects the cornea from external damage

CHOROID

          This is a thick vascularized layer made of pigmented cells of melanin. The melanin content of the choroid is responsible for the colours of the eye. It is modified inwards forepart of the eyeball to shape the Iris which regulates the amount of low-cal entering the eye. It also forms a ciliary trunk whose circular together with radial muscles contract together with relaxes to vary the shape of the lens.

A sparse bands of ligament called the Suspensory ligament also originates from the choroid belongings the lens inwards position.

Functions: - it nourishes the oculus together with its structures

            It gives colouring to the eye

Retina:       the retina is the low-cal sensitive layers which is restricted to the dorsum of the eyeball. It has numerous photoreceptor cells called RODS & Cones.

About 125 i one one thousand thousand Rods together with seven i one one thousand thousand cones are responsible for dark together with white vision together with coloured vision respectively. The Rods run across at Dim low-cal piece the cones are active at brilliant light. The retina is modified behind to shape a Zone of dense concentration of rods together with cones called xanthous topographic point (Fovea centralis). It lies on the principal axis of the lens hence it is the part of sharpest vision.

The blind topographic point is deficient of rods or cones then is insensitive to light. The retina has a lot of bipolar neurons which synapse amongst the rods together with cones. These bipolar neurons larn out the oculus via the bindle of nervus called the Optic nervus to the brain.

Function: it serves every bit a covert for formation of image.

The cornea, the lens together with retina shape the optical instruments of the eye.

The infinite behind of the lens if filled amongst the jelly similar fluid called the vitreous sense of humor together with inwards forepart is the aqueous humour-both assistance inwards maintaining the shape of the oculus balls.

Step 2: functions of the eye

The oculus has two major functions viz

-         image formation

-         accommodation

Image formation

Light travels inwards a withdraw line of piece of job when rays of low-cal from an object go into the eye, the rays decease through the cornea, aqueous humours, lens together with vitreous sense of humor to a greater extent than oft than non along the optical axis. The rays are refracted together with brought to a focus on the retina where an icon is formed. The icon is real, inverted together with diminished. The points of low-cal falling on the retina cause the photoreceptors (Rod & cones). This initiates an electrical impulse transmitted to the optic lobe of the forebrain though the optic nervus where the icon is interpreted as.

-         Upright       -        same size    -        same distance

as the object. The clearest icon is i formed at the xanthous spot.

Accommodation:

This is the mightiness of the oculus to run across both far together with close objects clearly. Accomodation is possible because the oculus tin alter the shape of the lens inwards reply to the motor impulses reaching the iris from the brain. As the oculus changes its shape its focal length also changes then every bit to ensure that the icon of the object comes to focus on the retina at all times.

How it happens:

When the oculus is focused on a far object, the band muscles of the ciliary trunk released together with moves away radically from the lens. This flattens together with larn thinner. Light rays falling on it are thus refracted slightly to converge on the retina.

          When the oculus focus on close objects, the band muscles of the ciliary muscles contracts then that it moves radically towards the lens. This reduces the tension inwards the suspensory ligament together with the lens bilges out past times virtue of its elasticity. This causes the low-cal rays to live converged at the retina.

Evaluation

a.     List the 5 feel inwards animals

b.     Using a good labelled diagram, exhibit the construction of the mammalian eye

c.      How does the oculus run across or shape image.

Summary: special cells together with tissue that collect or have stimulus from the environ together with transmit to the encephalon assistance us to connect to our surroundings. The oculus is the feel of sight together with thus perform the component subdivision of icon formation together with accommodation.

Homework:

Compare the mammalian oculus together with an analogue or digital camera.

Step 1: Eye defects

Our eyes sometimes turn down inwards component subdivision every bit a final result of surely defect. Most of the defects are congenital piece sometime historic menses together with strain / stress contribute to other.

MYOPIA (SHORT SIGHTEDNESS)

Shortsightedness every bit the cite implies is the mightiness of the oculus to run across close (short) objects clearly but unable to run across distant (long) objects clearly.

CAUSE: the eyeball is likewise longer than normal

Effect: then images shape inwards forepart of the retina (shorter than necessary) hence out of focus together with blurred.

Formations of icon inwards brusque sight

Correction: using glasses amongst suitable concave lenses. Concave or diverging lenses diverge the rays of low-cal from a distance object to the right extent earlier focussing the retina

      LONGSIGHTEDNESS

This is an oculus defect where an private cannot run across close object clearly but tin run across distant objects clearly.

Cause: this is because the oculus ball is likewise shorter than normal or losing elasticity.

Effect: he images are forced behind the retina

Correction: this is corrected past times the utilisation of converging or converse lens which converges the rays closer earlier reaching the cornea together with lens.

1.                 Astigmatism:

This oculus defect is due to uneven curved shape of the cornea surface. This causes low-cal rays to live refracted unevenly then that distorted images are formed on the retina. In around cases vertical parts of the figure tin live run across clearly piece the horizontal components seem blurred.

This may live corrected past times using lenses of uneven surfaces that compensate the cornea. This lenses are called contact cylindrical lenses.

2.                 Presbyopia: this oculus defects results from the weakness of the ciliary muscles. It thus weakens the elasticity of the lens together with cornea.

Eye Diseases:

Some oculus diseases include

-         Night blindness

Causes: deficiency of Vitamin A

-         Conjuctivities

Causes: bacteria or viral invasion of the conjunctiva.

Cataract: cloudness or opaqueness of the lens causing piteous penetration of low-cal rays. It needs surgical removal of the fibrous opaque material.

Evaluation:

1.     Using diagrams together with sketches only, exhibit the cause, consequence together with correction of whatever two oculus defects

2.     Suggest why vision loses amongst sometime age.

Summary: the oculus tin bring defects such every bit myopia hypermetropia, presbyobia together with Astigmatism.

Homework:

Suggest whatever 10 possible causes of oculus problems on your society.

What are the dangers of using sunsheds non recommended past times the optician