Macular degeneration, often called age-related macular degeneration (AMD), is an eye disorder associated with aging and results in damaging sharp and central vision. Central vision is needed for seeing objects clearly and for common daily tasks such as reading and driving. AMD affects the macula, the central part the retina that allows the eye to see fine details. There are two forms of AMD, wet and dry.

Wet AMD: when abnormal blood vessel behind the retina start to grow under the macula, ultimately leading to blood and fluid leakage. Bleeding, leaking, and scarring from these blood vessels cause damage and lead to rapid central vision loss. An early symptom of wet AMD is that straight lines appear wavy.

Dry AMD: When the macula thins overtime as part of aging process, gradually blurring central vision. The dry form is more common and accounts for 70-90% of cases of AMD and it progresses more slowly than the wet form. Over time, as less of the macula functions, central vision is gradually lost in the affected eye. Dry AMD generally affects both eyes. One of the most common early signs of dry AMD is drusen.

Drusen: Drusen are tiny yellow or white deposits under the retina. They often are found in people over age 60. The presence of small drusen is normal and does not cause vision loss. However, the presence of large and more numerous drusen raises the risk of developing advanced dry AMD or wet AMD.

It is estimated that 1.8 million Americans 40 years and older are affected by AMD and an additional 7.3 million with large drusen are at substantial risk of developing AMD. The number of people with AMD is estimated to reach 2.95 million in 2020. AMD is the leading cause of permanent impairment of reading and fine or close-up vision among people aged 65 years and older.

Amblyopia, also referred to as “lazy eye,” is the most common cause of vision impairment in children. Amblyopia is the medical term used when the vision in one of the eyes is reduced because the eye and the brain are not working together properly. The eye itself looks normal, but it is not being used normally because the brain is favoring the other eye. Conditions leading to amblyopia include; strabismus, an imbalance in the positioning of the two eyes; more nearsighted, farsighted, or astigmatic in one eye than the other eye, and rarely other eye conditions such as cataract. Unless it is successfully treated in early childhood, amblyopia usually persists into adulthood, and is the most common cause of permanent one-eye vision impairment among children and young and middle-aged adults. An estimated 2%–3% of the population suffers from amblyopia.

Astigmatism is a common type of refractive error. It is a condition in which the eye does not focus light evenly onto the retina, the light-sensitive tissue at the back of the eye.

Bell's palsy causes the muscles in your face to become temporarily paralyzed. It usually affects just one side of the face. Symptoms appear suddenly - you can't shut your eye and your mouth droops. Symptoms are usually worst about 48 hours after they start.
Scientists think that a viral infection makes the facial nerve swell or become inflamed. You are most likely to get Bell's palsy if you are pregnant, diabetic or sick with a cold or flu.
Three in four patients improve without treatment. With or without treatment, most people begin to get better within 2 weeks and most recover completely within 3 to 6 months.
NIH: National Institute of Neurological Disorders and Stroke

Blepharitis is a common condition that causes inflammation of the eyelids. It can affect the inside or outside of the eyelids. The condition can be difficult to manage because it tends to recur.

Blepharospasm is an abnormal, involuntary blinking or spasm of the eyelids. Blepharospasm is associated with an abnormal function of the basal ganglion from an unknown cause. The basal ganglion is the part of the brain responsible for controlling the muscles.

Blindness is a lack of vision. It may also refer to a loss of vision that cannot be corrected with glasses or contact lenses.

• Partial blindness means you have very limited vision.
• Complete blindness means you cannot see anything and do not see light. (Most people who use the term "blindness" mean complete blindness.)

People with vision worse than 20/200 are considered legally blind in most states in the United States.
Vision loss refers to the partial or complete loss of vision. This vision loss may happen suddenly or over a period of time.
Some types of vision loss never lead to complete blindness.

A blocked tear duct is a partial or complete blockage in the pathway that carries tears away from the surface of the eye into the nose.

Cataract is a clouding of the eye’s lens and is the leading cause of blindness worldwide, and the leading cause of vision loss in the United States. Cataracts can occur at any age due to a variety of causes, and can be present at birth. Although treatment for the removal of cataract is widely available, access barriers such as insurance coverage, treatment costs, patient choice, or lack of awareness prevent many people from receiving the proper treatment.
An estimated 20.5 million (17.2%) Americans 40 years and older have cataract in one or both eyes, and 6.1 million (5.1%) have had their lens removed operatively. The total number of people who have cataracts is estimated to increase to 30.1 million by 2020.

A chalazion is a small bump in the eyelid caused by a blockage of a tiny oil gland.

Most of people see the world in color. People who have a color vision defect may see these colors differently than most people.
There are three main kinds of color vision defects. Red-green color vision defects are the most common. This type occurs in men more than in women. The other major types are blue-yellow color vision defects and a complete absence of color vision.
Most of the time, color blindness is genetic. There is no treatment, but most people adjust and the condition doesn't limit their activities.

This term describes a group of diseases that cause swelling, itching, burning, and redness of the conjunctiva, the protective membrane that lines the eyelids and covers exposed areas of the sclera, or white of the eye. Conjunctivitis can spread from one person to another and affects millions of Americans at any given time. Conjunctivitis can be caused by a bacterial or viral infection, allergy, environmental irritants, a contact lens product, eyedrops, or eye ointments.
At its onset, conjunctivitis is usually painless and does not adversely affect vision. The infection will clear in most cases without requiring medical care. But for some forms of conjunctivitis, treatment will be needed. If treatment is delayed, the infection may worsen and cause corneal inflammation and a loss of vision.

Some diseases and disorders of the cornea are:
Allergies, Pink Eye (Conjunctivitis), Corneal Infections, Dry Eye, Fuchs' Dystrophy, Corneal Dystrophies, Herpes Zoster (Shingles), iridocorneal endothelial (ICE) syndrome, Keratoconus, Lattice dystrophy, Map-Dot-Fingerprint Dystrophy, Herpes of the eye (ocular herpes), pterygium, and Stevens-Johnson Syndrome (SJS)

Corneal edema is loss of transparency of the cornea. Also called corneal opacification or a cloudy cornea.

Ulcers that appear on the outer covering of the eye, usually because of a bacterial or viral infection.

Diabetic retinopathy (DR) is a common complication of diabetes. It is the leading cause of blindness in American adults. It is characterized by progressive damage to the blood vessels of the retina, the light-sensitive tissue at the back of the eye that is necessary for good vision. DR progresses through 4 stages, mild nonproliferative retinopathy (microaneurysms), moderate nonproliferative retinopathy (blockage in some retinal vessels), severe nonproliferative retinopathy (more vessels are blocked leading to deprived retina from blood supply leading to growing new blood vessels), and proliferative retinopathy (most advanced stage). Diabetic retinopathy usually affects both eyes.
The risks of DR are reduced through disease management that includes good control of blood sugar, blood pressure, and lipid abnormalities. Early diagnosis of DR and timely treatment reduce the risk of vision loss; however, as many as 50% of patients are not getting their eyes examined or are diagnosed too late for treatment to be effective.
It is the leading cause of blindness among working-aged adults in the Uni ted States ages 20–74. An estimated 4.1 million and 899,000 Americans are affected by retinopathy and vision-threatening retinopathy, respectively.

The condition in which a single object appears as two objects.

Dry eye occurs when the eye does not produce tears properly, or when they evaporate too quickly. Dry eye can make it difficult to do some activities, such as using a computer or reading for an extended period of time, and it can decrease tolerance for dry environments, such as the air inside an airplane.

A form of strabismus which causes the eyes cross in. Strabismus involves an imbalance in the positioning of the two eyes. The condition is more commonly known as "crossed eyes."

Exophthalmos also known as bulging eyes is the abnormal protrusion (bulging out) of one or both eyeballs.

A form of strabismus which causes the eyes to turn out. Strabismus involves an imbalance in the positioning of the two eyes.

Cancer of the eye is uncommon. It can affect the outer parts of the eye, such as the eyelid, which are made up of muscles, skin and nerves. If the cancer starts inside the eyeball it’s called intraocular cancer. The most common intraocular cancers in adults are melanoma and lymphoma. The most common eye cancer in children is retinoblastoma, which starts in the cells of the retina. Cancer can also spread to the eye from other parts of the body.
Treatment for eye cancer varies by the type and by how advanced it is. It may include surgery, radiation therapy, freezing or heat therapy, or laser therapy.

Ocassionally flashes of light, or flashes, are experienced with floaters.
Floaters and flashes are very common and are usually not a sign of a dangerous medical condition. However, if both floaters and flashes begin suddenly, it may indicate a more serious eye problem, such as a retinal tear or retinal detachment.

Floaters are little "cobwebs" or specks that float about in your field of vision. They are small, dark, shadowy shapes that can look like spots, thread-like strands, or squiggly lines. They move as your eyes move and seem to dart away when you try to look at them directly. They do not follow your eye movements precisely, and usually drift when your eyes stop moving.
Most people have floaters and learn to ignore them; they are usually not noticed until they become numerous or more prominent. Floaters can become apparent when looking at something bright, such as white paper or a blue sky.
Those who experience a sudden increase in floaters, flashes of light in peripheral vision, or a loss of peripheral vision should have an eye care professional examine their eyes as soon as possible.

Fuchs' dystrophy is a slowly progressing disease that usually affects both eyes and is slightly more common in women than in men. Although doctors can often see early signs of Fuchs' dystrophy in people in their 30s and 40s, the disease rarely affects vision until people reach their 50s and 60s.
Fuchs' dystrophy occurs when endothelial cells gradually deteriorate without any apparent reason. As more endothelial cells are lost over the years, the endothelium becomes less efficient at pumping water out of the stroma. This causes the cornea to swell and distort vision. Eventually, the epithelium also takes on water, resulting in pain and severe visual impairment.

Graves’ eye disease or Graves’ ophthalmopathy (GO) occurs in patients with Graves’ disease (the most common form of hyperthyroidism in the US) when cells from the immune system attack the muscles and other tissues around the eyes. The result is inflammation and a buildup in tissue and fat behind the eye socket, causing the eyeballs to bulge. In rare cases, inflammation is severe enough to compress the optic nerve that leads to the eye, causing vision loss.
NIH: National Endocrine and Metabolic Diseases Information Service

Herpes of the eye, or ocular herpes, is a recurrent viral infection that is caused by the herpes simplex virus and is the most common infectious cause of corneal blindness in the U.S. Previous studies show that once people develop ocular herpes, they have up to a 50 percent chance of having a recurrence. This second flare-up could come weeks or even years after the initial occurrence.
Ocular herpes can produce a painful sore on the eyelid or surface of the eye and cause inflammation of the cornea. Prompt treatment with anti-viral drugs helps to stop the herpes virus from multiplying and destroying epithelial cells. However, the infection may spread deeper into the cornea and develop into a more severe infection called stromal keratitis, which causes the body's immune system to attack and destroy stromal cells. Stromal keratitis is more difficult to treat than less severe ocular herpes infections. Recurrent episodes of stromal keratitis can cause scarring of the cornea, which can lead to loss of vision and possibly blindness.
Like other herpetic infections, herpes of the eye can be controlled. An estimated 400,000 Americans have had some form of ocular herpes. Each year, nearly 50,000 new and recurring cases are diagnosed in the United States, with the more serious stromal keratitis accounting for about 25 percent. In one large study, researchers found that recurrence rate of ocular herpes was 10 percent within one year, 23 percent within two years, and 63 percent within 20 years. Some factors believed to be associated with recurrence include fever, stress, sunlight, and eye injury.

This infection is produced by the varicella-zoster virus, the same virus that causes chickenpox. After an initial outbreak of chickenpox (often during childhood), the virus remains inactive within the nerve cells of the central nervous system. But in some people, the varicella-zoster virus will reactivate at another time in their lives. When this occurs, the virus travels down long nerve fibers and infects some part of the body, producing a blistering rash (shingles), fever, painful inflammations of the affected nerve fibers, and a general feeling of sluggishness.
Varicella-zoster virus may travel to the head and neck, perhaps involving an eye, part of the nose, cheek, and forehead. In about 40 percent of those with shingles in these areas, the virus infects the cornea. Doctors will often prescribe oral anti-viral treatment to reduce the risk of the virus infecting cells deep within the tissue, which could inflame and scar the cornea. The disease may also cause decreased corneal sensitivity, meaning that foreign matter, such as eyelashes, in the eye are not felt as keenly. For many, this decreased sensitivity will be permanent.
Although shingles can occur in anyone exposed to the varicella-zoster virus, research has established two general risk factors for the disease: (1) Advanced age; and (2) A weakened immune system. Studies show that people over age 80 have a five times greater chance of having shingles than adults between the ages of 20 and 40. Unlike herpes simplex I, the varicella-zoster virus does not usually flare up more than once in adults with normally functioning immune systems.
Be aware that corneal problems may arise months after the shingles are gone. For this reason, it is important that people who have had facial shingles schedule follow-up eye examinations.

Hyperopia, also known as farsightedness, is a common type of refractive error where distant objects may be seen more clearly than objects that are near. However, people experience hyperopia differently. Some people may not notice any problems with their vision, especially when they are young. For people with significant hyperopia, vision can be blurry for objects at any distance, near or far.

Hyphema is blood in the front area of the eye.

The most common form of uveitis (swelling and irritation of the uvea, the middle layer of the eye) is anterior uveitis, which involves inflammation in the front part of the eye. It is often called iritis because it usually only affects the iris, the colored part of the eye.

This disorder--a progressive thinning of the cornea--is the most common corneal dystrophy in the U.S., affecting one in every 2000 Americans. It is more prevalent in teenagers and adults in their 20s. Keratoconus arises when the middle of the cornea thins and gradually bulges outward, forming a rounded cone shape. This abnormal curvature changes the cornea's refractive power, producing moderate to severe distortion (astigmatism) and blurriness (nearsightedness) of vision. Keratoconus may also cause swelling and a sight-impairing scarring of the tissue. It usually affects both eyes.
In most cases, the cornea will stabilize after a few years without ever causing severe vision problems.

People with vision worse than 20/200 are considered legally blind in most states in the United States.

Vision impairment, or low vision, means that even with eyeglasses, contact lenses, medicine or surgery, you don't see well. Vision impairment can range from mild to severe.

Macular degeneration, or age-related macular degeneration (AMD) is a leading cause of vision loss in Americans 60 and older. It is a disease that destroys your sharp, central vision. You need central vision to see objects clearly and to do tasks such as reading and driving.
AMD affects the macula, the part of the eye that allows you to see fine detail. It does not hurt, but it causes cells in the macula to die. In some cases, AMD advances so slowly that people notice little change in their vision. In others, the disease progresses faster and may lead to a loss of vision in both eyes. Regular comprehensive eye exams can detect macular degeneration before the disease causes vision loss. Treatment can slow vision loss. It does not restore vision.

Fluid can leak into the center of the macula, the part of the eye where sharp, straight-ahead vision occurs. The fluid makes the macula swell, blurring vision. This condition is called macular edema. It can occur at any stage of diabetic retinopathy, although it is more likely to occur as the disease progresses. About half of the people with proliferative retinopathy also have macular edema.

A macular hole is a small break in the macula, located in the center of the eye's light-sensitive tissue called the retina. The macular provides the sharp, central vision we need for reading, driving, and seeing fine detail.

A macular pucker is scar tissue that forms on the eye’s macula, located in the center of the eye’s light-sensitive tissue called the retina. The macula provides sharp, central vision. A macular pucker can cause blurred and distorted central vision.

Ocular melanoma is a malignant tumor deriving from the pigmented cells within or surrounding the eye. On the eyelids or the surface of the eye, called the conjunctiva, it can appear as an enlarging dark spot. However, not all melanomas are darkly colored. Within the eye, melanoma can arise from various tissues such as the retina or the iris. It is the most common form of cancer arising inside the eye, and it is capable of spreading to other parts of the body. Ocular melanoma is a very serious disease and should be treated by specialists familiar with cancers of the eye.

Myopia, also known as nearsightedness, is a common type of refractive error where close objects appear clearly, but distant objects appear blurry.

Nasolacrimal duct obstruction (NLDO) (a blocked tear duct) is a partial or complete blockage in the pathway that carries tears away from the surface of the eye into the nose.

Nystagmus refers to rapid involuntary movements of the eyes that may be:

• Side to side (horizontal nystagmus)
• Up and down (vertical nystagmus)
• Rotary

Depending on the cause, these movements may be in both eyes or in just one eye. The term "dancing eyes" has been used in regional dialect to describe nystagmus.

Orbital cellulitis is an acute infection of the tissues immediately surrounding the eye, including the eyelids, eyebrow, and cheek.

A cataract is any cloudiness or opacity of the lens of the eye. Cataracts can be very small, and may not interfere with vision, or they can affect the entire lens, resulting in severe loss of vision. A cataract causes decreased vision by interfering with the light ray path to the retina (back part of the eye). Abnormal vision development resulting in permanent loss of vision (amblyopia) occurs when a child has a cataract. Prompt and sometimes immediate treatment is necessary to prevent permanent vision loss.
About 3 children per 10,000 children have a cataract. Most pediatric cataracts are not associated with other abnormalities. However pediatric cataracts that occur in conjunction with other findings are often the result of a genetic or metabolic problem. Cataracts may be present at birth or develop during childhood.

Presbyopia is a common type of vision disorder that occurs as you age. It is often referred to as the aging eye condition. Presbyopia results in the inability to focus up close, a problem associated with refraction in the eye.

Presbyopia is a common type of vision disorder that occurs as you age. It is often referred to as the aging eye condition. Presbyopia results in the inability to focus up close, a problem associated with refraction in the eye.

Pseudotumor cerebri literally means “false brain tumor.” It is likely due to high pressure within the skull caused by the buildup or poor absorption of cerebrospinal fluid (CSF). The disorder is most common in women between the ages of 20 and 50. Symptoms of pseudotumor cerebri, which include headache, nausea, vomiting, and pulsating sounds within the head, closely mimic symptoms of large brain tumors.

Ptosis is also called "drooping eyelid." It is caused by weakness of the muscle responsible for raising the eyelid, damage to the nerves that control those muscles, or looseness of the skin of the upper eyelids.

Eye redness is due to swollen or dilated blood vessels, which cause the surface of the eye to look red, or bloodshot.
There are many possible causes of a red eye or eyes. Some are cause for concern; some are medical emergencies. Others are of no consequence or concern at all. The degree of redness or appearance of blood usually does not correlate to how serious the situation is. It is generally more important whether you also have eye pain or impaired vision.

Retinal artery occlusion is a blockage in one of the small arteries that carry blood to the retina. The retina is a layer of tissue in the back of the eye that is able to sense light.

The retina is the light-sensitive layer of tissue that lines the inside of the eye and sends visual messages through the optic nerve to the brain. When the retina detaches, it is lifted or pulled from its normal position. If not promptly treated, retinal detachment can cause permanent vision loss.

Retinal vein occlusion is a blockage of the small veins that carry blood away from the retina. The retina is the layer of tissue at the back of the inner eye that converts light images to nerve signals and sends them to the brain.

Retinitis pigmentosa is an eye disease in which there is damage to the retina. The retina is the layer of tissue at the back of the inner eye that converts light images to nerve signals and sends them to the brain.
Retinitis pigmentosa can run in families. The disorder can be caused by a number of genetic defects.
The cells controlling night vision (rods) are most likely to be affected. However, in some cases, retinal cone cells are damaged the most. The main sign of the disease is the presence of dark deposits in the retina.
The main risk factor is a family history of retinitis pigmentosa. It is an uncommon condition affecting about 1 in 4,000 people in the United States.

Retinopathy of prematurity (ROP) is a potentially blinding eye disorder that primarily affects premature infants weighing about 2 3/4 pounds (1250 grams) or less that are born before 31 weeks of gestation.

Strabismus involves an imbalance in the positioning of the two eyes. Strabismus can cause the eyes to cross in (esotropia) or turn out (exotropia). Strabismus is caused by a lack of coordination between the eyes. As a result, the eyes look in different directions and do not focus simultaneously on a single point. In most cases of strabismus in children, the cause is unknown. In more than half of these cases, the problem is present at or shortly after birth (congenital strabismus). When the two eyes fail to focus on the same image, there is reduced or absent depth perception and the brain may learn to ignore the input from one eye, causing permanent vision loss in that eye (one type of amblyopia).

Uveitis is swelling and irritation of the uvea, the middle layer of the eye. The uvea provides most of the blood supply to the retina.

Vitreous hemorrhage is bleeding into the clear gel that fills the eyeball between the retina and the lens.

Watery eyes occur when there is too much tear production or poor drainage of the tear duct.

Zoster (herpes), shingles: Extremely painful, blister-like skin lesions on the face, sometimes with inflammation of the cornea, sclera, ciliary body and optic nerve. Affects the 1st division (ophthalmic nerve) of the 5th (trigeminal) cranial nerve. Caused by the chickenpox virus.