sense of sight (structure of the eye.pptx)

Prepared by :Mrs. Shirley P. Valera

Grade 3 St. Francis / St. AugustineSY 2014-2015

Structure of the

protect our eyeball

Eyelid

Eyebrows, Eyelashes• Protect the

eyes from sweat, dust and other foreign materials

How do you see?

Looking to an object, the light rays reflected from the object enter the eye. The light reflected to cornea and passes through the aqueous humor, and the pupil to the lens.

How do you see?

As the light travels to our eyes, the lens focuses the image of the object on the retina. The object in the retina is inverted. As the image is formed the optic nerves send the message to the brain.

It is the brain that interprets and corrects the inverted image into an upright position.

Common Eye Ailments1. Conjuctivities- (sore eyes)

commonly caused by viral infection, but bacterial infections, allergies, other irritants and dryness are also common etiologies for its occurrence. Both bacterial and viral infections are contagious. Commonly, conjunctival infections are passed from person to person, but can also spread through contaminated objects or water

Common eye ailments2. Sty - results from an

infection of the oil glands of the eyelid (meibomian glands) that help to lubricate the eyeball. The infection occurs after these glands have become clogged. A sty also may arise from an infected hair follicle at the base of an eyelash.

Common Eye Defects

• Cataracts- do not have to change your life! They are a normal part of aging and can be treated. People regain most or all vision, and continue to do things they love to do. A cataract is a gradual clouding of the clear lens in the eye which results in a blurry or hazy image, and a sensitivity to light.

• To correct it, an ophthalmic surgeon removes the damaged lens and replaces it with a clear, artificial one. Surgery is short, and you can go home the same day and resume normal activities shortly after.

• A cataract is a progressive, painless clouding of the natural, internal lens of the eye. Cataracts block light, making it difficult to see clearly. Over an extended period of time, cataracts can cause blindness. They're often related to growing older, but sometimes they can develop in younger people

How Cataracts Affect Your Vision

• In a normal eye, light enters and passes through the lens. The lens focuses that light into a sharp image on the retina, which relays messages through the optic nerve to the brain. If the lens is cloudy from a cataract, the image you see will be blurry. Other eye conditions, such as myopia, cause blurry vision, too, but cataracts produce some distinctive signs and symptoms.

Cataract Symptom: Blurry Vision

• Blurry vision at any distance is the most common symptom of cataracts. Your view may look foggy, filmy, or cloudy. Over time, as the cataracts get worse, less light reaches the retina. People with cataracts may have an especially hard time seeing and driving at night.

Cataract Symptom: Double Vision

• Sometimes, cataracts can cause double vision (also known as diplopia) when you look with one eye. This is different from the double vision that comes from the eyes not lining up properly. With cataracts, images appear double even with one eye open.

Cataract Symptom: Color Changes

• Cataracts can affect your color vision, making some hues look faded. Your vision may gradually take on a brownish or yellowish tinge. At first, you may not notice this discoloration. But over time, it may make it harder to distinguish blues and purples.

What Causes Cataracts?

• The exact cause of cataracts is unknown. While the risk grows as you get older, these factors may also contribute:

• Diabetes• Smoking• Excess alcohol use• Eye Injury• Prolonged use of corticosteroids

Common Eye Defects

•Glaucoma- is a leading cause of blindness. Anyone can develop glaucoma, with most people not knowing they have it. You are at greater risk when:

Common Eye Defects• Graves Disease

- is typified by an apical enlargement of the eye muscles which stimulates other fibroblasts. Fluid is drawn into the muscle and stored, eventually leading to the development of scar tissue. In addition, the swelling of the muscles pushes the eye forward causing it to protrude.

Common Eye Defects• Graves Disease

-As a result patients may

have trouble closing their eyes, which causes drying, irritation and increased inflammation. Increased effort to bring the eyelids together may result in a frown, or swollen muscles may compress the optic nerve leading to loss of vision if treatment is not sought early on.

Common Eye Defects• Low Vision

• There are a variety of disorders that can affect the eye and the visual system causing low vision. These are: birth defects, injuries, certain diseases of the body and aging. The most common cause of low vision is macular degeneration. Macular degeneration is a disease of the retina or the inner layer of the eye that senses light and allows you to see.

• Reduced central or reading vision is the most common type of low vision. Other types of low vision are reduced side vision (peripheral), and loss of color vision. Your eyes also might lose the ability to adjust to light, contrast or glare. Different types of low vision may require different types of aids.

Common Eye Defects• Astigmatism

This defect is when the light rays do not all come to a single focal point on the retina, instead some focus on the retina and some focus in front of or behind it. This is usually caused by a non-uniform curvature of the cornea. A typical symptom of astigmatism is if you are looking at a pattern of lines placed at various angles and the lines running in one direction appear sharp whilst those in other directions appear blurred. Astigmatism can usually be corrected by using a special spherical cylindrical lens; this is placed in the out-of-focus axis.

Common Eye Defects

• Hyperopia (farsightedness) This is a defect of vision in which there is difficulty with near vision but far objects can be seen easily. The image is focused behind the retina rather than upon it. This occurs when the eyeball is too short or the refractive power of the lens is too weak.

• Hyperopia can be corrected by

wearing glasses/contacts that contain convex lenses.

Common Eye Defects• Myopia

(nearsightedness) This is a defect of vision in which far objects appear blurred but near objects are seen clearly. The image is focused in front of the retina rather than on it usually because the eyeball is too long or the refractive power of the eye’s lens too strong. Myopia can be corrected by wearing glasses/contacts with concave lenses these help to focus the image on the retina.

Common Eye Defects• Strabismus (/strəˈbɪzməs/,

from Greek strabismós[1]), also known as squint andheterotropia (and including the two variants cross-eye and walleye),[

- a condition in which the eyes are not properly aligned with each other. Strabismus can present as manifest (heterotropia) or latent (heterophoria) varieties, and can be either a disorder of the brain in coordinating the eyes, or of the power or direction of motion of one or more of the relevant muscles moving the eye

Common Eye Defects

• A squint is a condition where the eyes do not look together in the same direction. While one eye looks straight ahead, the other eye turns to point inwards, outwards, upwards or downwards. Squints are common and affect about 1 in 20 children. You might even spot that your baby has a squint. Most squints develop before preschool age, usually by the time a child is three years old. Sometimes squints develop in older children, or in adults.

How to take care of our eyes• Eat lots of fruits and

veggies! Carrots, loaded with beta carotene are especially helpful in maintaining healthy eyes. That's because beta carotene is an antioxidant that reduces the risk of macular degeneration.[1]

How to take care of our eyes• Avoid wearing contact

lenses for more than 19 hours. This can cause permanent sight damage as well as extreme discomfort to your eyes. Don't wear glasses too long either. Especially 3-D glasses!

How to take care of our eyes

• Never sleep with your contact lenses in unless specifically instructed to do so.

• Your eyes need regular supplies of oxygen, and lenses block the flow of oxygen to the eyes, especially during sleep. So doctors recommend a normal period of break for your eyes during the night.

How to take care of our eyes

• Avoid wearing your contact lenses when swimming. Your lenses could easily slip off your ideas when they come in contact with the surface area of the water. If you are wearing goggles, your contact lenses may be used while swimming.

How to take care of our eyes• Use allergen-reducing eye

drops sparingly. Using an allergen-reducing eye drop during allergy season to 'get the red out' and sooth itchiness may help on a limited basis, but chronic daily use can actually make the problem worse.

• Allergen-reducing eye drops work by constricting the blood flow to the cornea, thereby depriving it of oxygen. So while your eyes don't feel inflamed and itchy anymore, they're actually not getting any oxygen from blood. That's not ideal.

• Using redness-relieving eye drops chronically will cause more redness in your eyes. Your body gets so accustomed to the chemicals in the eye drops that they no longer work effectively.

• Read the labels of eye drops carefully; many drops cannot be used while wearing contacts.

How to take care of our eyes• Wear UV protective

sunglasses. Get polarized lenses, NOT just darker lenses. The lenses that only make the world darker will just make your pupils dilate and don't do a thing to stop the UV rays.

• Prolonged exposure to UV rays can harm your eyesight, protection in youth can help prevent loss of eyesight in later years. Exposure to UV rays has been linked to cataracts, macular degeneration, pingueculae and pterygia, harmful conditions for the eyes.

• Since the damage to eyes from UV rays builds up over a lifetime, it's important to shield children from harmful rays. Make sure your children wear hats and protective glasses when they are out in the sunlight for prolonged periods.

• Be sure to wear sunglasses even if you're in the shade. Even though shade lessens UV and HEV exposure significantly, you're still exposing your eyes to UV rays reflected off of buildings and other structures.

How to take care of our eyes• Try not to spend so

much time looking at your computer screen.It is a good time to give your eyes a break, since you're not doing anything too important.)

• it may cause eye strain and dry eyes.The glare from computer screens causes muscle fatigue in the eyes, either from being too bright or too dark.

• People blink less when they're looking at a screen, causing drier eyes. Make a conscious effort to blink every 30 seconds when you're sitting down and looking at your computer screen to combat dry eyes.

How to take care of our eyes• Wear goggles when

appropriate. Be sure to wear goggles or other eye protective wear when working with chemicals or any place with harmful airborne particulates.

• Minimize the transmission of harmful particulate matter into eye region.

How to take care of our eyes

• Exercise your eyes, and also be sure to relax them.

• Try focusing your eyes on objects that are near to you, then objects that are far away. Repeat this process multiple times.

• Sit down, place your elbows on your hips, close your eyes and bring your closed eyes down, resting them on your palms. Keep your palms covering your eyes for 10 seconds. Open your eyes and repeat as necessary.

• Stretch your arm out and place your thumb in the hitchhiker position. Focus your vision on your thumb while you slowly bring your outstretched arm closer to your body, until your thumb is about five inches from your face. Slowly zoom the thumb back to its original position, focusing on it with your eyes all the while.

How to take care of our eyes• Do not read in dim light.

Reading in dim light can cause eye strain but will not damage your eyes. If your eyes feel tired, stop for a while and take a break.

How to take care of our eyes• Do not look at a

bright light directly. Never focus your eyes on the sun directly, as it can damage your eyes.

First Aid for Eye Injuries• If you wear contact lenses, remove them immediately if you get

chemicals in your eyes. Keeping them in your eyes may hold the chemical against the cornea, causing unnecessary damage and pain.

• If you suspect chemicals have entered your eye, begin flushing it immediately with cool water and continue to do so for approximately

15 minutes.• Seek immediate medical attention by dialing 911 or going to the

nearest emergency room. If possible, take the container of the offending substance with you so that you can tell your doctor what you have been exposed to.

First Aid for Eye Injuries• First Aid When You Have Something in Your Eye• If you have an object in your eye, do not irritate your eye by rubbing it. You may try to remove the particle if it is not embedded in the

eye. But, follow these first aid tips first:

• First wash your hands thoroughly with soap and water. This will prevent further contamination or infection.

• Try flushing the eye with water. Using your finger and thumb, gently pull the upper eyelid down over the top of the lower eyelid. This should cause tearing and flush the object out. You may need to repeat this several times.

• If you can see the object, you may try to remove it from your eye with a washcloth. Gently lift the upper or lower eyelid, and use a clean, wet washcloth to wipe the object away. If this does not work, seek immediate medical attention.

Identify the parts of the eye