Eyes

1.    Eye Structure

The optical devices as a whole cannot be separated from the two parts of the organ and the organ part in the outer organs. The shape is round and slightly flattened inclined on the inside consists of:

Outside

a.      Eyelash

Eyelashes, eyes or hair rather, is part of the eyelid that form strands of hairs. These hairs that serve to protect the dust, sweat or water dripping from the forehead do not get into eyes. Eyelashes also serve to filter the light to be received. Eye hair is very soft hair. The lashes are very instrumental for eye protection from the outside.

b.      Eyebrow

Eyebrows serve as a sensitive eye protection from sweat droplets falling from the forehead, rain water, or excessive sunlight. Human shape eyebrows like the crescent moon usually with rather sharp bends in the temples. Not infrequently also found people with eyebrows the left and right parts are concatenated into one. Eyebrow shape and direction of the hair growth on eyebrows meant to sweat or water can flow to the forehead and fell to the cheek, or toward the cheek over the top of the nose. Bone shape on the forehead also eyebrows protect the eyes from sweat and water droplets.

c.      

Eyelid

Eyelid is the soft folds of skin on the outside of the eye and function serves to cover and protect the eyes. Some diseases are associated with, among others, eyelid ptosis or eyelid dependent, which in most cases occurs when the levator palpebrae muscle is not strong enough to hold the eyelids. Handling above pathological conditions this can be done using local anesthesia surgery, and eye conditions can be improved after surgery.

Inside

a.      Pupils

Pupil or child's eyes are opening in the center of the eye. A slit -shaped pupils are in the middle of the circle of iris. Pupil serves as a place to set up more or less light into the eye which entered. Light enters through the pupil and passed through the eye lens, which focuses the shadow onto the retina. Pupil lies behind the middle part of retina. The size of pupil is controlled by muscles. If you need more light, the pupil enlarges. When the light grew brighter, the pupils become smaller. These changes occur as a reflex. Pupils can be compared with the white balance on the camera. Pupils will be more clearly seen when viewed with a microscope.

b.     

Iris (Rainbow Membrane)

Iris or rainbow membrane is annular region of the eye bounded by the pupil and the sclera the white part of the eye). Iris regulates the amount of light that enters the eye by changing the size of the pupil. Iris is the annular region of the eye bounded by the pupil and the sclera the white part of the eye). Visual texture of the iris is formed during fetal development and stabilize itself during the first two years of the life of the fetus. Complex iris texture brings a very unique and useful information for personal recognition. Speed ​​and accuracy of the Iris -based recognition system is very promising and it is possible to use the large-scale identification systems. Each iris is unique and like fingerprints, iris texture is different from identical twins. The texture of the iris is very difficult to surgically destroyed. Weakness of the iris recognition is a tool for data acquisition is relatively expensive, because the acquisition of equipment should ensure user comfort in wear.

c.       Aqueous humor ( watery fluid ) function produces fluid in the eye

d.      Humor/entity nodes. Humor is located behind the lens. The shape of the transparent substance like jelly. Function humor (clear body) is to pass the light from the lens to the retina of the eye (retina).

e.       Tear glands

Lachrymal glands located inside the eyelid. Lachrymal glands function to produce a fluid called tears. Tears useful to keep eyeball to keep it moist. Additionally tears useful for cleaning the eyes of foreign substances that enter the eye so keep it clean.

f.       Lacrimal glands (Tear)

Lacrimal gland (lacrimal) function Generate tears to moisten the eyes useful maintain eye moisture, clean the eye from dust and kill germs that enter the eye.

g.      Conjunctiva is a thin protective membrane (network layer) of the eye. Conjunctiva serves as a protective membrane of the eye.

h.      Choroid Layer (middle layer)

Choroid layer or middle layer located between the sclera and retina, blackish brown to black. The middle layer (choroid layer) serves to give nutrition to the outer retina. Choroid are dark color serves to prevent light reflection. Very dark layer also prevents the reflected light beam around the eyes.

i.        Retina

Retinal function as a screen to capture the shadow object, in this place there are the vertices of the optic nerve. The retina is the innermost layer of the wall of the eyeball. Containing retinal receptor cells that are sensitive to light. The portions were very sensitive to light in the retina called the yellow spots (the fovea) . The part that is not sensitive to light and is the exit of the optic nerve to the brain is called the blind spot.

j.        Lens

The lens is the part that serves to focus the eye shadow on retina. Lens located in the middle of the eyeball, behind the child's eye (pupil) and the iris (iris). The main function of the lens is focused and forward light entering the eye to fall precisely on the retina (retina). Thus the eye can see clearly. Eyepiece has the ability to focus the light. Another function of the lens is also to cast a shadow on the retina that is real, inverted and scaled

k.      Ciliated  Muscles

Ciliated muscles function Set the lens shape. Ciliary muscle function is to regulate the eye accommodation.

l.        Optic Nerve (Eye nerve)

Eyes nerve serves to continue the light stimuli that have been received. Light stimuli are passed the set central nervous located in the brain. Thus we can see an object. Optic nerve or optic nerve function also send visual information to the brain or pass on information about the strong light and color to the brain.

m.   

Cornea

The cornea is the eye that protects the eye surface from contact with the outside water. Clear membrane (cornea) is very important for our visual acuity. The main function of cornea (cornea) is forwarding incoming light to the eye. Cornea is the eye that can be donated for the healing of blindness. Clear membrane (cornea) also serves as a protective inner eye.

n.      Sclera/white membrane

Sclera or white membrane layer located at outside. Sclera is the tough outer layer. This layer is white, except for the front which is not colored or clear. White sclera layer consists of collagen fibers are disorganized and not vascular blood, except the episclera. Sclera layers serve to protect the eyeball. Sclera of the eye looks bubbly and transparent front called the cornea. Iris is a thin membrane that serves to regulate the needs of light in the formation of shadows.

o.      Suspensor Ligamen

Suspensor ligament’s function is always keep the lens in place.

2.    Eyes work systems

The human eye has a way of working that perfect auto, eyes formed with 40 different main element to all of this section and has an important function in the process of looking at the damage or absence of a functioning part of it will make impossible the eye can see. Opaque layer at the front of the eye is the cornea, iris are right behind him, besides giving color to the eye, the iris can also resize automatically according to the strength of the incoming light, with the help of muscles attached to it. For example, when in the dark iris will grow to include as much light as possible. When the light power increases, the iris will shrink to reduce the light entering the eye. Automatic control system that works on the eye works as follows.

When light hits the eye is formed and nerve signals sent to the brain, to deliver a message about the presence of light, and the power of light. Then the brain sends signals back and ordered the extent to which the muscles around the iris must shrink. Other parts of the eye that work in conjunction with this structure is the lens. The lens focuses light duty that enters the eye on the retina at the back of the layers of the eye. Because the muscles around the lens the light coming into the eye from different angles and distances can always be focused onto the retina. All the systems we have mentioned earlier are smaller, but far superior to mechanical equipment designed to mimic the design of the eye by using the latest technology, even the most artificial image recording system in the modern world it is still too modest when compared to the eye . If we reflect on all the hard work and thought has gone into making this artificial image recording devices we will understand how much more eye creation of superior technology.

If we observe the parts of a cell smaller than the eye of creation is increasingly revealed. Suppose we are looking at a crystal bowl filled with fruit, light coming from the bowl into our eyes penetrate the cornea and iris then focused on the retina by the lens so what happens to the retina, so that retinal cells can sense the presence of light as particles light called photons of the retinal cells. When they produce effects like a row of dominoes chain arranged in neat rows. The first domino in retinal cells is a molecule called 11 - cis retinal. When a photon about it this molecule changes shape and then push changes to other proteins that bind strongly with the rhodopsin.

Rhodopsin has now turned into a form that enables it to bind to other proteins that transducin. Transducin is already present in the cell but cannot join because of mismatches form rhodopsin. This unification followed a combined one another molecule called GTP now the two proteins rhodopsin and transducin and 1 chemical molecule called GTP has fused but the actual process has just begun compound called GDP now has a form suitable for binding of another protein called phosphodiesterase that is always there in the cell . After the resulting shape of the molecule binds to move a mechanism that will initiate a series of chemical reactions in cells.

This mechanism produces ion reactions in cells and produces electrical energy, this energy stimulates the nerves that lie just behind the retina cells. Thus when the eye shadow intangibles such as photons of light to continue his journey in the form of electrical signals. This signal contains visual information object outside the eye. So that the eyes can see the electrical signals generated in the retina should be forwarded in the visual center in the brain. However, nerve cells do not relate directly to one another there is a small gap that separates their connection points and how the electrical signal is on his way here a series of complex mechanisms occur electrical energy is converted into chemical energy without losing the information that is being taken and in this way information passed from one nerve cell to the next nerve cell. The carrier of chemical molecules located at the connection point of the nerve cells managed to bring information coming from the eyes of one nerve to another nerve.

When moved to the next nerve, the signal is converted back into electrical signals and continue his journey to the other connection point. In this way the signal made ​​it to the visual center in the brain, the signal here compared the information in the center of the shadow memory and interpreted the end we can see a bowl full of fruits, as we saw earlier because of the perfect system consisting of hundreds of small parts this and all of this amazing series of events that occurred in less than 1 second .

Shadow Formed on Eye

 Simply as a tool optics of the eye forms a real image , inverted , and reduced in the retina . Focusing is done by changing the focal length of the lens . Objects will be apparent if the shadow to fall on the surface of the retina. The stages of the formation of the eye shadows are as follows :

Light entering the eye through the pupil hole, the first light penetrates the cornea, aqueous humor, lens, and viterus humor that shadow falls exactly on the retina . Then the retina form propogated into nerve impulses that the brain II, and then to the brain to be interpreted as vision .

 Light entering the eye is focused by the lens of the eye to the back of the eye called the retina . Falling objects form shadows on the retina as if recorded and transmitted to the brain via the optic nerve . The shadow is what up to the brain and gives the impression to the eye to see objects . Thus , the eye can see objects clearly when the shadow of the object ( real image ) is formed precisely on the retina .

Eye sight Range

The ability of human vision is limited to a certain range or the range of vision is called the area in front of the eye bounded by two points  Farthest point ( punctum remotum abbreviated PR ) and the closest point ( punctum proximum abbreviated PP ) . PR is the furthest point in front of the eye, where the object is still clearly visible. PP is the closest point in front of the eye, where the object is still clearly visible.

Would object if the object is clearly visible in the range of vision, and the object will not be visible clearly if the object is beyond the scope of vision ( the eyes are too close or too far away from the eye ).

Accommodation power of eye

Power of accommodation (the custom) is the ability of the ciliary muscle to thicken or flatten the curvature of the eye lens is adapted to close or distance of objects seen. Humans have two limits of accommodation (sight range) are:

1.      Point near the eye ( punctum proximum ) is the distance of objects in front of the nearest eye can still be seen clearly . To the normal eye ( emetropi ) nearby points within 10cm s / d 20cm ( for the kids ) and is 20cm s / d 30cm ( for adult ) . Also called a point near the normal reading distance.

2.      Eyes distant point ( punctum remotum ) is the farthest object distance in front of the eye which can still be seen clearly . For normal eyes away point is "infinity" .

When the eyes see close objects, the lens will become more convex accommodating that shadow that falls right in the retina form. Conversely, when viewing distant objects, the lens will be more compressed to focus precisely on the retina shadow.

3.    Eye Defect

Eye defects occur because of the eyesight changed. This is caused by the ability of eye accommodation changed. Power of accommodation is the ability to change the lens focus distance so that the shadow falls on the retina of the eye. Here are three different types of eye defects is based on the ability of the accommodation.

a.      Myopia

 Myopia eye defect occurs when the sight is berakomodasi shadows fall in front of the retina, this happens because the lens can not be very flat (too convex). To be able to see distant objects clearly it needs to be assisted by a diverging lens (concave lens). Diverging lens is a lens that can spread the light beam. Here is a chart of the formation of a shadow on the eye defect myopia before and after lens wear.

Point distant eye nearsighted people who are at a certain distance (normal eye has a far point of infinity). Nearsightedness can be corrected by using a diverging lens that is spread (diffuse) rays. Diverging lens or concave lens or a negative lens can help to be able to focus the lens of the eye shadow right on the retina. Myopia corrected using basic principle is negative lens negative lens is used to move (promote) the object at a distance so as not to be a shadow in the eyes of the far point so the eye can see objects clearly . Strength or power spectacle lenses required in accordance with the following formula:

With the PM is the lens for myopia in dioptric units and PR are remotum punctum (point distant eyes) in units of cm .

b.              Hipermetropi

People who suffer from nearsightedness or hipermetropi not able to see clearly objects that are located in the nearby point but still able to see distant objects clearly (not up) . Point close to the eyes of people who suffer from nearsightedness farther than normal reading distance (PP > 25 cm ) .

Hipermetropi corrected using a positive lens. The basic principle is a positive lens is used to move the (reverse) object at normal reading distance of a shadow at a point near the eye so that the eye can see objects clearly. Here is a chart of the formation of a shadow on hipermetropi before and after lens wear

Hipermetropi eye defect occurs when normal vision at reading distance of the lens of the eye resulting in a shadow falls behind the retina, it is because the lens can not be very convex (too flat). To be able to see objects clearly at a normal reading distance (Sn) then this eye defect needs to be assisted by using a converging lens (convex lens). Converging lens is a lens that can collect light beam. Lens strength required in accordance with the following formula .

Where PH is the power of spectacle lenses in dioptric units, s is the distance of objects in front of the glasses, and the PP is proximum punctum (point near the eye) in units of cm. If the object distance s is not mentioned in the question, the value of s taken from a point near the normal eye, which is 25 cm so that the power of the lens to hipermetropi equation becomes:

c.               Presbiopi 

Presbiopi eye defect (old eyes or nearsightedness and farsightedness caused by weakening of accommodation) occurs because the shadows fall behind the retina when viewing near and shadows fall in front of the retina when viewing far, this happens because of a weak eye lens accommodation. To be able to see objects clearly both near and far it needs to be assisted by using a combination of convex lens (converging) and concave (diverging) . This eye defect is often also known as the old eye defect. By using the means described on disability and disability hipermetropi myopia, lens size is known

d.             Astigmatism

Astigmatism is caused because the cornea is not spherical shape (iris of the ball), but is more curved in one area than in other areas. As a result in the form of objects as a focus point line. Astigmatism eye also focuses the rays in the vertical plane is shorter than the rays in the horizontal plane. Astigmatism helped/assisted with cylindrical glasses.

Astigmatism or cylindrical eye is a disorder of the eye that is caused by the curved cornea is uneven. Refractive disorders can be about anyone regardless of social status, age and gender.

Eyeball in the normal state is shaped like a ball so that the incoming light or shadows can be captured at a single point in the retina (the sensitive area of ​​the eye). At the astigmatism, eye -shaped oval like an egg so that the light or shadow into the eye a little spread alias does not focus on the retina. This causes a visible shadow will be blurred and only visible on one point only. In addition, a rather distant shadow will appear blurry and wavy.

What causes astigmatism?

Astigmatism is generally lowered and often appeared since a child. In addition, astigmatism can also be caused by excessive pressure on the cornea, poor reading habits and the habit of using the eye to see objects that are too close .

What are the complaints of patients astigmatism?

Untreated patients with astigmatism will often complain of headaches, eye fatigue and blurred when viewing objects near and far away. If you experience these symptoms in the long term, you should get to the eye doctor to see the possibility of the occurrence of astigmatism.

How to treat astigmatism?

Almost all degrees of astigmatism can be corrected with glasses or contact lenses. In patients with even mild degrees do not require correction for astigmatism at all it is not accompanied by nearsightedness or farsightedness. Glasses for astigmatism sufferers using cylindrical lenses. Another option for treating astigmatism is with surgery, but the action is very terggantung of the patient's condition. Performed using laser surgery to correct curved cornea.

e.               Color Blind

Color blindness is a condition where a person has no way to distinguish colors. Which can be seen only in black, gray, and white. Color blindness is usually a hereditary disease. It means that if a person is color blind, almost certainly the son also color blind. Color blindness is a disorder caused by the inability of the eye cone cells to capture a certain color spectrum due to genetic factors. Color blindness is a genetic disorder / congenital inherited from parents to their children, because the disorder is carried by the X chromosome It means that the Y chromosome does not carry the color blind factor. This is what distinguishes between people with color blindness in men and women. A woman found the term 'hereditary' it shows there is one X chromosome that carries the nature of color blindness. Woman with the nature, physically abnormal color blind as normal women in general. But women with hereditary factors potentially reduce color blind to his future. If on the second X chromosome containing the color blind factor TSB woman suffering from color blindness. Nerve cells in the retina consists of stem cells that are sensitive to black and white, and the cone cells that are sensitive to other colors. Color blindness occurs when light receptors in the retina nerve changes, especially cone cells. To know you have this or not can be determined by the color blind test.

Color blindness itself can be classified into 3 types: type trikomasi Color blindness is a change in the color sensitivity of one or more types of cone cells. There are three kinds trikomasi namely:

• Protanomali red color which is a weakness

• Deuteromali the green color weakness ,

• Tritanomali (low blue) the blue color weakness.

Type of color blindness is the most commonly experienced than other types of color blindness.

Dikromasi is not any one of the three types of cone cells, consisting of:

• protanopia the absence of red cone cells so that the brightness of the red color and the combination of them is reduced ,

• deuteranopia kerujut the absence of cells that are sensitive to green

• tritanopia to blue.

While monokromasi characterized by vision loss or reduction in all colors, so it looks just white and black on the kind of typical and atypical types little color  This type of color blindness prevalence is very rare.

f.                Cataract

Cataract is an eye disease characterized by the presence of fog on the lens of the eye. Cataract is an eye disease in which the lens of the eye becomes opaque due to thickening of the Eye Lens and occurs in the elderly (seniors). Interventions should be performed cataract surgery or surgery.

Normal eye lens is transparent and contains a lot of water, so that light can penetrate easily. Although the new cells in the lens will always be formed, many factors can cause the area in the lens becomes opaque, hard, and solid. Lenses that are not clear will not be able to continue the light onto the retina to be processed and sent through the optic nerve to brain. On many cases, the cause is unknown. Cataract occurs in many tropical countries like Indonesia. It is related to factors associated with cataracts, the ultraviolet rays coming from the sun. Other causes include nutritional deficiencies that can speed up the process of developing cataracts.