The Eye is like a camera because of its structures that function similar to those of a camera. The Cornea acts as the camera lens, the Iris acts like the diaphragm of a camera, the Crystalline lens functions like an auto focus camera lens, and the Retina is like the electronic image sensor or the film of a camera.
ANATOMY OF THE EYE:
- Cornea – is a transparent protective covering of the eye. It is where the focusing of light primarily occurs. Cornea allows you to see around you just like the camera lens.
- Iris – is the thin, circular colored structure, and the most visible part of the eye. It functions like the diaphragm of a camera. The iris controls the amount of light reaching the back of the eye, the retina, by adjusting the size of the pupil (aperture). The color of the iris is what is referred to as the eye color.
- Crystalline Lens – The lens is a transparent layer located at the back of the pupil that helps to focus light along with the retina. It changes its shape to adjust the focusing distance of the eye in order to get a good image of an object. This adjustment of the lens is called accommodation, which is similar to the auto focus of a camera lens.
- Retina – The retina is the innermost, light-sensitive layer of the eye. It functions like the film in a camera. It is consists of nerve tissues which sense the light that enters the eye. The Retina converts the light rays it receives from the lens into signals, and sends these signals to the brain via the optic nerves, which are then converted into visual images
Retina has 2 photoreceptors cells, named rods and cones. The rods are used in peripheral vision and are more sensitive than cone cells. The rods are responsible for our dark and night vision. The cones, on the other hand, provide the eye’s color sensitivity. They are less sensitive to light than the rods. They are used for daytime vision. - Macula – is a small, yellowish, and highly sensitive section of the retina. It is found in the center of the retina. It provides us the clearest and most detailed vision. The center of the macula is called the fovea , this tiny area is responsible for our sharpest vision.
- Optic Nerve or the cranial nerve II – like a wire that connects the eye to the brain. It transmits the impulses from the retina to the brain, which interprets them as visual images.
- Pupil – is the round, black circle in the center of the iris of the eye. It allows in and regulates the amount of light that enters the retina by adjusting its size (which is controlled by iris).
- Conjunctiva – The conjunctiva is a mucus layer that helps lubricate the eye. It also produces tears, (smaller amount of tears than that of lacrimal sacs) to help moisten the eye. It lines the inside of the eyelids. Infections to this area are known as “Pink Eye.”
- Sclera – The Sclera is the outer white part of the eye. It provides protection and structure for the inner sensitive parts of the eye.
- Lacrimal Sac – which drain tears from the eye’s surface.
- Lacrimal Glands – is a gland that produces the majority of the tears. Tears are produced to protect and lubricate the eye.
- Choroid – vascular and thickest layer of the eye. It is located between the retina and the sclera. The function of the Choroid is to nourish the retina with oxygen and nutrients.
CONDITIONS OF THE EYE:
1). Amblyopia (lazy eye):
Amblyopia is an eye disorder when one eye sees better than the other. One eye loses its ability to see details. This happens because the weaker eye (lazy eye) sends a blurred image to the brain, thus the brain ignores the image for interpretation. Amblyopia begins during infancy and early childhood.
Symptoms:
- Eyes that turn in or out
- Eyes that do not appear to work together
- Inability to judge depth correctly
- Poor vision in one eye
Treatment:
Patching the good eye – a patch is placed on the normal eye. This will force the brain to recognize the image sent from the weak eye. This treatment is more effective in childhood.
2). Astigmatism:
Astigmatism is caused by an eye that has an oval shape like that of a football. Our eye is normally shaped like a sphere, round like a Ping-Pong ball.. This abnormal curvature of the eye causes the light rays that enters the eye to not focus correctly on the retina, resulting in a blurry and wavy image. Astigmatism can be corrected with glasses, contact lenses, and some cases requires surgery.
Symptoms:
- Blurred vision
- Photophobia – sensitivity to light.
- Headaches
- Squinting.
3). Blepharitis:
Blepharitis is the inflammation of the eyelids, causing them to become reddened, itchy, and swollen accompanied by crusting or flaking on the eyelids. It can be treated and controlled through proper eyelid hygiene. Although the severity of the blepharitis and related symptoms may require supplemental medical treatment that includes topical or oral medications.
Lid hygiene:
- Soak a clean washcloth with warm water, squeeze to remove excess water and place on top of the affected eye. This will soothe the eye and also will soften the flakes. You can repeat this several times a day
- You can also use a small quantity of mild soap or shampoo to clean the eyelids, using the warm washcloth.
- Rinse well then pat dry.
- Supplemental treatment that includes a topical or oral antibiotic medication on doctor’s prescription may help reduce bacteria. Clean the eyelid first before applying the prescribed ophthalmic ointment.
- Avoid wearing eye make up till the symptoms have cleared up.
4). Cataracts:
Cataracts is a clouding of the lens inside the eye, causing blurred vision, thus a decrease in vision. It is the most common cause of blindness, although vision can be restored in most people with cataracts through surgery.
Symptoms of Cataracts:
- Cloudy and blurred vision
- Glare from lamps or sun
- Vision changes -Frequent changes in eyeglass prescription
- Poor night vision – Difficulty driving at night due to glare from headlights
Several studies suggest, that the risk of cataracts can be reduced with several factors that include:
- Adequate intakes of Vitamin A- Sources include sweet potatoes, carrots, dark leafy greens, squash and sweet red peppers.
- Higher dietary intakes of vitamin E – Good food sources of vitamin E include sunflower seeds, almonds, spinach, kale and other green, leafy vegetables
- Antioxidant vitamins such as vitamin C – Broccoli, Cauliflower, Brussels Sprouts, kale and other dark leafy greens. Strawberries, guavas, oranges, and clementine are also good food sources of vitamin C.
- Quit smoking
- Maintaining a healthy weight
- Wearing protective sunglasses against the sun’s UV rays when you are outdoors can reduce your risk of cataracts
Treatments:
- For mild cataracts a regular eye exam and updating eyeglasses or contact lenses prescription may be adequate to improve vision.
- For more advanced cataracts, surgery is the treatment to restore good vision.
5). Chalazion:
Chalazion is a bump or cyst that forms on the eyelid. This condition occurs when an oil gland in the eyelid becomes blocked and inflamed. An internal stye that doesn’t drain and heal can turn into a chalazion. Chalazion often clears up in a few months without treatment. A chalazion is not contagious and does not affect eyesight. A chalazion can sometimes be mistaken for a “stye“. Chalazion grows more slowly than a stye. Unlike stye, chalazia are usually painless.
Treatment:
- Apply warm compresses over the affected eyelid for 10-15 minutes, 4 times a day.
- Do not “pop” the chalazion.
- A prescribed antibiotic drops or anointment to be used immediately after the warm compresses.
- Surgery may be needed if the chalazion persist, is not healing, and are becoming bigger.
6). Conjunctivitis:
Conjunctivitis also called “pink eye” is an inflammation of the conjunctiva caused by a virus, bacteria, irritants, or by allergies. Infection caused by virus or bacteria can spread from person to person through direct or indirect contact hence practice and observe contact precautions.
Symptoms of Conjunctivitis:
- Redness in the white of the eye or inner eyelid
- Thick yellow discharge that builds up overnight to form a crusts over the eyelashes (Bacterial conjunctivitis)
- Clear and watery eye discharges (Viral Conjunctivitis)
- Itchy eyes
- Discomfort and pain in the affected eye
- Increased sensitivity to light
Neonatal Conjunctivitis – Is a type of conjunctivitis that occurs in newborn babies. The baby’s eyes are contaminated during delivery, from a mother infected with either Neisseria Gonorrhoeae or Chlamydia Trachomatis. Neonatal ophthalmia is a serious condition and can result in blindness in the infant if left untreated.
7). Corneal Abrasion:
Corneal abrasion is a scrape or scratch on the cornea that can lead to severe pain. It can be prevented by wearing protective eyewear when doing any activities that may cause an eye injury.
Symptoms of a Corneal Abrasion:
- Moderate to severe pain
- Watery eye
- Swollen eyelids
- Redness in sclera
- Photophobia or sensitivity to light
Typical Causes of Corneal Abrasions:
- Foreign bodies get into your eyes, such as small solid particles
- Rubbing your eyes too hard, can scratch your cornea
- Removing contact lenses incorrectly can scratch your cornea, especially when you have rough and sharp edged long nails
8). Diplopia (double vision):
Diplopia is a symptom that may require an immediate medical attention. Some causes of diplopia are relatively minor, but others may need urgent medical intervention such as brain problems and nerve problems. Impairment with any part of the eye can lead to double vision.
9).Dry Eyes:
Dry eyes are a common problem that occurs when tears are inadequate to moisten and lubricate your eyes, usually due to decreased secretion of tears from the lacrimal gland. Excessive tear evaporation can also cause dry eyes. If there is a decrease in blinking, like when reading, or working in front of the computer, dry eyes will result. Also if the eyelids cannot be closed, as in cases of people with Bell’s palsy, these will allow excessive tear evaporation that leads to dry eyes.
Symptoms of dry eyes:
- Burning
- Photophobia or Sensitivity to light
- A feeling of a foreign body
- Itching
- Redness of the eye
- Blurring of vision
Treatments for dry eyes:
- Use a humidifier to add moisture into the air, this can help alleviate symptoms of dry eyes
- Hot compresses to eyelids to promote oil secretions from the oil-producing glands in the eyelids thus preventing tears from evaporating too quickly
- Lubricating eye ointments to be used at night at bedtime
- Frequent use of artificial tears and lubricating eye drops during the day
- Increasing the intake of high quality sources of omega-3 fatty acids (or through a supplement) every day can be helpful in relieving the symptoms of dry eye
- Drinking more water can help, too
- Wear sunglasses when outdoors to reduce exposure to sun, wind and dust
- Certain nutrients such as vitamins A, C, D, and E may relieve dry eyes
10).Glaucoma :
Is a group of eye disorders combined that cause damage to the optic nerve. It can lead to irreversible loss of vision due to the increased fluid pressure in the eye (IOP). The increased IOP may be due to the over production of or decreased drainage of aqueous humour. Glaucoma is the second leading cause of blindness.
Symptoms:
Open – Angle Glaucoma: This type of glaucoma has no early symptoms It can go unnoticed for years because the initial vision loss is of side (peripheral vision). The central vision is usually retained and the sharpness of vision (visual acuity) remains intact until later stages. It is characterized by gradual vision loss and usually has no pain. It is recommended to see an eye doctor regularly to benefit from early detection.
Closed – Angle Glaucoma: this type of glaucoma develops quickly that requires urgent medical attention. Symptoms are very noticeable and include:
- Red eyes
- Seeing rainbow colored circles (halos) around bright lights
- Severe eye and head pain
- Nausea or vomiting
- Sudden severe ocular pain
- Sudden decrease in vision
- Sudden increased IOP
Treatments:
- Prescribed eye drops can lower IOP
- Surgery
11). Hyperopia (farsightedness):
Hyperopia is a condition where the eye can see distant objects clearly, and near objects appear blurry. This happens when your eyeball is too short or the cornea is not curved correctly which causes the light entering the eye to focus at the back of the retina. Sometimes eye muscles that have weakened with age can also cause hyperopia. Prescription eyeglasses or contact lenses can correct farsightedness.
Know your prescription:
- For Hyperopia or farsightedness – on your eyeglasses prescription or contact lens prescription, the first number under the heading “sphere” has a plus sign (+) or is not preceded by either a (+) or (-) sign.
- Sphere (SPH). This indicates the amount of lens power,
- OD means right eye (RE)
- OS means left eye (LE)
12). Macular Degeneration:
Macular Degeneration – is also called age-related macular degeneration (AMD or ARMD) because the disease develops as a person ages (over 60 years). This eye condition refers to the deterioration of the macula which is found in the center of the retina responsible for the sharpest, clearest, and most distinct vision. When the macula is affected, you may lose your central vision, which would make it difficult for you to read or recognize faces. AMD is the major cause of blindness in older adults.
Two types of age-related macular degeneration:
- Dry (atrophic) form: .Most people with age-related macular degeneration begin with the dry form, which is more common than the wet form. Single or multiple, small, round, yellow-white spots called drusen are present in the macula. As these spots increase in size and numbers, they may cause dimming of the vision that can be noticeable when reading. In advanced stages of dry AMD, atrophy develops due to the thinning of the cells in the macula. In the atrophic form the person may have blind spots in the center of their vision and may lead to lose of central vision.
- Wet (exudative or neovascular) form: in the wet form of AMD, abnormal blood vessels grow from the choroid under the macula. This is referred as choroidal neovascularization. The blood vessels leak blood and fluid into and scar the retina, leading to permanent loss of vision. Vision loss may be faster in wet type of AMD compared to the dry type.
Causes of Macular Degeneration include:
- Genetic – having a family history of AMD
- Smoking
- High blood pressure
- Obesity
Treatment / Prevention:
- Quit smoking
- Controlling blood pressure
- Weight loss and maintaining a healthy diet
- Increasing intake of brightly colored fruits and vegetables; oranges, strawberries, sweet peppers, spinach, carrots and others.
13). Myopia(nearsightedness or shortsighted):
Myopia is the opposite of hyperopia. This condition is the inability of the eye to see clearly at a distance. The eyeball is too long or the cornea has too much curvature causing the light rays entering the eye to bend too much, so they can’t focus directly on the retina but at a point in front of the retina.
Treatment includes:
- Prescribed eyeglasses
- Contact lenses prescription
- Refractive surgery such as Lasik and PRK (photorefractive keratectomy)
Know your eyeglasses prescription:
- For Hyperopia or farsightedness – on your eyeglasses prescription or contact lens prescription, the first number under the heading “sphere” has a plus sign (+) or is not preceded by either a (+) or (-) sign.
- For Myopia or nearsightness – on your eyeglasses prescription or contact lens prescription, the first number under the heading “sphere” will be preceded by a minus sign (–).
- Sphere (SPH). This indicates the amount of lens power,
- OD means right eye (RE)
- OS means left eye (LE)
14). Retinal Detachment:
Retinal detachment is a serious disorder of the eye in which the retina separates from its layer of supporting tissue. A detached retina doesn’t hurt, but it can lead to vision loss and blindness if not given immediate medical treatment.
Causes or Risk Factors:
- Trauma
- Cataract Injury
- Malignant Hypertension
- Diabetes
- Severe Myopia
- Smoking and Passive smoking
Symptoms:
- Flashes of light
- Seeing more “floaters” (small flecks or threads)
- Darkening of your peripheral (side) vision
- Feeling of heaviness in the eye
**Floaters:
are small moving floating spots that appear in your field of vision. They are more noticeable when you look at white sheet of paper or at the bright sky.
If you notice any of the above mentioned symptoms, contact your eye doctor immediately.
15). Scotoma:
a blind spot or dark spot in the visual field that is usually surrounded by an area of normal vision.
Symptoms:
- A need for additional light
- Difficulty in identifying some colors
16). Strabismus: Other names for strabismus: Cross-eye, Walleye, Squint, Heterotropia.
Strabismus is a condition in which the eyes do not look in the same direction at the same time. The other eye points in, out, up or down while the first eye is focused. There is lack of coordination between the eyes. Someone with strabismus may also have: Poor depth perception and Vision loss.
Treatment:
- Eyeglasses or contact lenses are used to help correct the alignment of the eye, hence straightens the eye.
- Eye patch – covering the stronger eye and correcting the focusing problem of the abnormal eye.
- Prism lenses – are not corrective lenses to improve bad vision. They are triangle in shape, which are then mounted in glasses. They are designed to modify the focus of the eyes that points in different directions instead of the same point at the same time. It lets the eyes focus towards a middle point, directing the middle point between the two eyes, thus allowing the eyes to see the same object and a clearer image. They help prevent double vision. Prisms are also used before eye surgery to determine the degree of the misalignment thus knowing how much adjustment is needed on the eye muscles.
- Vision therapy is a non-surgical form of treatment used to improve eye movement and eye coordination. It includes several procedures that can be done at home and in the office, under the supervision of a professional orthoptist or optometrist. Vision therapy also involves some eye muscle exercises.
- Eye surgery – is a surgical procedure to correct the misalignment of the eyes by adjusting the extraocular muscles.
17). Stye (hordeolum):
Stye or hordeolum are bacterial infection at the base of the hair follicle of an eyelash causing a painful and tender red lump. The entire eyelid may become edematous. The main cause of stye is the staphylococcal organisms. Normally styes swell for about 3 days,” but never squeeze a stye”, because they rupture and drain on its own. It is usually harmless.
Common Causes of Stye:
- Stress
- Hormonal changes
- Eye mascara, eyeliner or other eye products
- Poor eye hygiene
Treatment:
- Apply a very warm, wet, clean wash cloth to the tender and painful area 8-10 minutes 3-4 times a day.
- Add small amount of mild soap or shampoo to warm, wet and clean wash cloth to clean the affected eye or you can use a cotton swab instead of wash cloth.
- Prescribed Ointment or Oral Antibiotic may help with recurrent or persistent styes
- Surgical drainage may be necessary if the treatments are not working on the stye.
18). Uveitis
Uveitis is an inflammation and swelling of the eye that can damage the eye tissues leading to poor vision or permanent blindness.
The uvea is the pigmanted middle layer of the eye. It’s between the outer layer (sclera -white part of the eye) and the inner layer of your eye (retina).
Different types of uveitis:
- Anterior uveitis is the most common. Affects the front of the eye
- Intermediate uveitis . Swelling of the uvea in the middle of the eye
- Posterior uveitis affects the back layer of your eye.
- In severe cases wherein the entire uvea is inflamed, you have panuveitis.
