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Anatomy of the Eye

anatomyCornea – The clear outer part of the eye’s focusing system; located at the front of the eye.

Fovea – The center of the macula; provides the sharpest vision.

Iris – The colored part of the eye; regulates the amount of light entering the eye.

Lens – The clear part of the eye behind the iris that helps to focus light, or an image, on the retina.

Macula – The small sensitive area of the retina that provides central vision. It is located in the center of the retina and contains the fovea.

Optic Nerve – A bundle of more than one million nerve fibers that carries visual images from the retina to the brain.

Pupil – The opening at the center of the iris. The iris adjusts the size of the pupil and controls the amount of light that can enter the eye.

Retina – The light-sensitive tissue lining at the back of the eye. The retina converts light into electrical impulses that are sent to the brain through the optic nerve.

Vitreous Gel – A clear gel that fills the inside of the eye.

Eye Care Terms

Age-related macular degeneration (ARMD) – ARMD is a disease that blurs the sharp, central vision needed for “straight-ahead” activities such as reading, sewing, and driving. ARMD affects the macula, the part of the eye that allows you to see fine detail. ARMD causes no pain.

Amblyopia (Lazy Eye) – 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.

Anophthalmia – Anophthalmia is the absence of one or both eyes. These rare disorders develop during pregnancy and can be associated with other birth defects.

atigmatismAstigmatism – 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. An eye with astigmatism has a cornea that is curved more like a football, with some areas that are steeper or more rounded than others. This can cause images to appear blurry and stretched out.

Behçet’s disease – Behçet’s disease is an autoimmune disease that causes inflammation in blood vessels. It causes swelling in some parts of the eye.

Bietti’s Crystalling Dystrophy – Bietti’s Crystalling Dystrophy (BCD) is an inherited eye disease. The symptoms of BCD include: crystals in the cornea; yellow, shiny deposits on the retina; and progressive atrophy of the retina, choriocapillaries and choroid. This tends to lead to progressive night blindness and visual field constriction. BCD is a rare disease and appears to be more common in people with Asian ancestry.

Blepharitis – 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 – 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.

cataractCataract – A cataract is a clouding of the lens in the eye that affects vision. Most cataracts are related to aging. Cataracts are very common in older people. By age 80, more than half of all Americans either have a cataract or have had cataract surgery. A cataract can occur in either or both eyes. It cannot spread from one eye to the other.

Coloboma – Coloboma describes conditions where normal tissue in or around the eye is missing from birth.

Diabetic Eye Disease (Diabetic Retinopathy) – Diabetic retinopathy, which causes changes to the blood vessels of the retina, is the most common diabetic eye disease and a leading cause of blindness in American adults.

Dry Eye – Dry eye occurs when the eye does not produce tears properly, or when the tears are not of the correct consistency and evaporate too quickly.

Floaters – 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.

Glaucoma – Glaucoma is a group of diseases that damage the eye’s optic nerve and can result in vision loss and blindness. With early detection and treatment, you can often protect your eyes against serious vision loss due to glaucoma. Since there is no prevention for glaucoma, yearly examination, particularly in those over the age of 35, is highly recommended.

Histoplasmosis – Histoplasmosis is a disease caused when airborne spores of the fungus Histoplasma capsulatum are inhaled in the lungs. Histoplasmosis is sometimes so mild that it produces no apparent symptoms. However, later it can lead to a serious eye disease called ocular histoplasmosis syndrome (OHS), a leading cause of vision loss in Americans ages 20 to 40.

hyperopiaHyperopia – 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.

Low vision – Low vision means that even with regular glasses, contact lenses, medicine, or surgery, people find everyday tasks difficult to do. Reading the mail, shopping, cooking, seeing the TV, and writing can seem challenging.

Macular hole – 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.

Macular pucker – 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.

Microphthalmia – Microphthalmia is a disorder in which one or both eyes are abnormally small.

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

Presbyopia – 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.

Refractive errors – Refractive errors, which include nearsightedness and farsightedness, are very common eye conditions. Refractive errors can usually be corrected with eyeglasses or contact lenses.

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

Retinoblastoma – Retinoblastoma is a type of cancer that forms in the retina (the light-sensitive tissue at the back of the eye).

Retinopathy of prematurity – Retinopathy of prematurity (ROP) is a potentially blinding eye disorder that primarily affects premature infants weighing about 2¾ pounds (1250 grams) or less, born before 31 weeks of gestation.

Usher syndrome – Usher syndrome is an inherited autosomal recessive trait that affects both hearing and vision. The major symptoms of Usher syndrome are hearing loss and an eye disorder called retinitis pigmentosa, or RP.

Uveitis – Uveitis is a general term describing a group of inflammatory diseases that produce swelling and destroy eye tissue. These diseases can slightly reduce vision or lead to severe vision loss.

Vitreous detachment – Most of the eye’s interior is filled with vitreous. Millions of fine fibers, intertwined within the vitreous, are attached to the surface of the retina. As we age the vitreous slowly shrinks, causing these fibers to pull on the retina. Usually the fibers break, allowing the vitreous to separate from the retina. This is a vitreous detachment.

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