eyes
Each eye forms it own image, and it is the brain's job to fuse the two images into one. For the brain to do its work, the eyes must be aligned, move together and produce images of similar size and shape. When the eyes are not coordinated, they have to work hard to see clearly, often causing eyestrain or headaches.
Good vision is all about curves. A correctly shaped cornea and lens direct the light to the right spot on the retina to produce a clear, sharp image. When the curvature is too flat, too steep or inconsistent, the image does not fall precisely on the retina, and curved lens (or possibly LASIK surgery) are used to correct myopia (nearsightedness), hyperopia (farsightedness), astigmatism (distorted vision) and/or presbyopia (difficulty adjusting to close distances when one becomes 40 or older).
Good vision is all about curves. A correctly shaped cornea and lens direct the light to the right spot on the retina to produce a clear, sharp image. When the curvature is too flat, too steep or inconsistent, the image does not fall precisely on the retina, and curved lens (or possibly LASIK surgery) are used to correct myopia (nearsightedness), hyperopia (farsightedness), astigmatism (distorted vision) and/or presbyopia (difficulty adjusting to close distances when one becomes 40 or older).
To your eye doctor, your eyes are window to your overall health. Many illnesses show their earliest signs in the eyes, and many diseases can affect your vision. During your eye examination, your Today's Vision doctor will look for signs of:
- Hypertension: The appearance of irregular blood vessels on the retina can indicate high blood pressure.
- Diabetes: Small, circular areas of bleeding on the retina may be an early sign of diabetes. Increases and decreases in blood sugar level can cause blurred vision and retinal changes.
- Headaches: These may be caused by or worsened by vision problems such as eye strain.
- Stroke: The vessels in the eye may point to a risk of stroke.
- High Cholesterol: Hypertension and high cholesterol levels are often linked. The condition of the veins and arteries in the eyes can be a warning.
About the Eyes
The most common vision disorders are astigmatism, hyperopia (farsightedness), myopia (nearsightedness) and presbyopia. Astigmatism, hyperopia and nearsightedness are also known as refractive errors. All are correctable with lens (contacts or eyeglasses) or LASIK surgery.
The most common vision disorders are astigmatism, hyperopia (farsightedness), myopia (nearsightedness) and presbyopia. Astigmatism, hyperopia and nearsightedness are also known as refractive errors. All are correctable with lens (contacts or eyeglasses) or LASIK surgery.
Astigmatism: Astigmatism comes from the root words "A" meaning without and STIMGA meaning point. In the astigmatic eye, a point of light is unable to focus sharply due to the oval "football" shape of the cornea (the front surface of the eye). Light rays entering the vertical (north-south) curve of the cornea may focus on the back of the eye, but ray entering the horizontal axis (east-west) may not. This causes a blur at both distance and near.
Hyperopia: In the farsighted eye, light that should focus on the retina (the back of the eye) instead focus behind the retina. People with hyperopia compensate by using muscles in the eye which can lead to eyestrain, fatigue and even headaches. Close-up work such as reading or computer use may be especially uncomfortable. Children with hyperopia often pass school vision screenings by unnaturally focusing their eyes. This may lead to poor reading abilities and can only be detected by a complete vision exam.
Myopia: In the nearsighted eye, light that should focus on the retina instead focuses before it gets to the back of the eye. Either the cornea or the lens of the eye is too curved or long. Either way, distance vision is blurred, but close-up vision is generally good. Again, early and regular eye exams are important for children to detect this problem.
Presbyopia: At about age 40, the lens of the eye loses some of its ability to focus "near objects" due to less flexibility of the lens fibers and the muscles that control the lens. This condition is known as presbyopia. Because presbyopia involves the lens, it is different from refractive errors which involve the shape of the cornea.
Hyperopia: In the farsighted eye, light that should focus on the retina (the back of the eye) instead focus behind the retina. People with hyperopia compensate by using muscles in the eye which can lead to eyestrain, fatigue and even headaches. Close-up work such as reading or computer use may be especially uncomfortable. Children with hyperopia often pass school vision screenings by unnaturally focusing their eyes. This may lead to poor reading abilities and can only be detected by a complete vision exam.
Myopia: In the nearsighted eye, light that should focus on the retina instead focuses before it gets to the back of the eye. Either the cornea or the lens of the eye is too curved or long. Either way, distance vision is blurred, but close-up vision is generally good. Again, early and regular eye exams are important for children to detect this problem.
Presbyopia: At about age 40, the lens of the eye loses some of its ability to focus "near objects" due to less flexibility of the lens fibers and the muscles that control the lens. This condition is known as presbyopia. Because presbyopia involves the lens, it is different from refractive errors which involve the shape of the cornea.
In the beginning only the fine print becomes blurred. But over time, even larger print and objects at increasingly farther distances become difficult to see. Your Today's Vision doctor may recommend bifocal eyeglasses, progressive (invisible line) eyeglasses, rigid gas permeable contact lenses or soft contact lenses. With contacts, your doctor may advise using the "monovision" technique in which one eye is corrected for near, the other to see far - or bifocal or progressive contacts in either the rigid or soft lens design.
If the patient can tolerate monovision contacts, this can sometimes be simulated in LASIK surgery, also.
Multiple Sclerosis: Double vision, visual field loss and uncoordinated or involuntary eye movements may be an early sign of MS.
Take a few minutes to learn more About the Eye, Eye Exams, Disorders and Treatments. You only have one set of eyes - and your good health.
The eye is susceptible to its own diseases, many of which have minimal symptoms associated with them. Your Today's Vision doctor routinely tests and looks for signs and symptoms of many eye diseases, including:
Glaucoma: High levels of pressure inside the eye due to failure of the eye to regulate its own internal pressure. Early detection is crucial to prevent loss of sight.
Glaucoma: High levels of pressure inside the eye due to failure of the eye to regulate its own internal pressure. Early detection is crucial to prevent loss of sight.
Cataracts: The internal lens of the eye becomes cloudy and must be removed and replaced with a synthetic lens implant.
Anatomy
CORNEA: The cornea is the clear front surface of the eye that covers the colored part of your eye (iris). It is similar to the front window of your camera. The cornea is comprised of five layers: Corneal epithelia, Bowman's membrane, Stroma, Decemet's membrane, and the endothelium. The stroma is the tissue which is ablated during laser surgery.
IRIS: The iris is the colored portion of the eye. It is similar to the aperature of a camera. The iris regulates the amout of light entering the eye. During dilation, drops increase the size of the pupil so that your Today's Vision doctor can evaluate the health of the eye internally.
LENS: The lens is similar to the lens in a camera. It provides the focusing ability of the eye. At the age of 40-45, presbyopia presents this is when the lens begins to lose its focusing ability and a bifocal may be required. When the lens becomes opacified or cloudy, it is termed a cataract. The vision with a cataract can be simulated by trying to view through a stained glass window. A cataract can be removed and replaced with an artificial lens implant.
MACULA: The macula is a small area located at the back portion of the retina. It is comprised of cones and functions in crisp 20/20 central vision. Diseases that affect this area can cause a decrease in vision. Disease processes such as macular degeneration, retinal detachments, diabetes, and hypertension can potentially cause blindness. Dilation allows your Today's Vision doctor the ability to inspect the macula more fully.
MUSCLES: Ocular muscle alignment is critical in developing sharp three- dimensional vision. During a routine eye exam, an eye care professional evaluates the integrity of the muscles and the nerves which supply them. Eye turns and double vision should be evaluated by your Today's Vision doctor.
NERVES: The visual pathways of the eyes are equivalent to the co-axial cable that connects your video camera to the VCR. These nerves transmit visual information from the retina to the occipital lobe of the brain where the information is processed. During a routine eye exam an eye care professional evaluates the integrity of these nerves. Through examination brain lesions such as tumors and aneurysms can be detected in many cases.
OPTIC NERVE: The optic nerve is similar to the cable that connects your video camera to the VCR. The images seen in the eye is transported to the occipital lobe of the brain where the image is processed. The optic nerve head can be seen by an eyecare practitioner when the eyes are dilated. Your doctor evaluates the nerve for such disease processes as glaucoma, papilledema (increased pressure in the brain), multiple sclerosis or brain tumors.
RETINA: The retina is similar to the film in a camera. This is where the picture seen by the eye is converted to electrical signals and then transported to the occipital lobe via the optic nerve. The retina is made of cells called rods and cones. Rods are primarily used to aid with night and peripheral vision, while cones are designed to aid with color vision and crisp 20/20 vision.
SCLERA: The sclera is the white portion of the eye. It is comprised of tough connective tissue that gives the eye its shape.
CORNEA: The cornea is the clear front surface of the eye that covers the colored part of your eye (iris). It is similar to the front window of your camera. The cornea is comprised of five layers: Corneal epithelia, Bowman's membrane, Stroma, Decemet's membrane, and the endothelium. The stroma is the tissue which is ablated during laser surgery.
IRIS: The iris is the colored portion of the eye. It is similar to the aperature of a camera. The iris regulates the amout of light entering the eye. During dilation, drops increase the size of the pupil so that your Today's Vision doctor can evaluate the health of the eye internally.
LENS: The lens is similar to the lens in a camera. It provides the focusing ability of the eye. At the age of 40-45, presbyopia presents this is when the lens begins to lose its focusing ability and a bifocal may be required. When the lens becomes opacified or cloudy, it is termed a cataract. The vision with a cataract can be simulated by trying to view through a stained glass window. A cataract can be removed and replaced with an artificial lens implant.
MACULA: The macula is a small area located at the back portion of the retina. It is comprised of cones and functions in crisp 20/20 central vision. Diseases that affect this area can cause a decrease in vision. Disease processes such as macular degeneration, retinal detachments, diabetes, and hypertension can potentially cause blindness. Dilation allows your Today's Vision doctor the ability to inspect the macula more fully.
MUSCLES: Ocular muscle alignment is critical in developing sharp three- dimensional vision. During a routine eye exam, an eye care professional evaluates the integrity of the muscles and the nerves which supply them. Eye turns and double vision should be evaluated by your Today's Vision doctor.
NERVES: The visual pathways of the eyes are equivalent to the co-axial cable that connects your video camera to the VCR. These nerves transmit visual information from the retina to the occipital lobe of the brain where the information is processed. During a routine eye exam an eye care professional evaluates the integrity of these nerves. Through examination brain lesions such as tumors and aneurysms can be detected in many cases.
OPTIC NERVE: The optic nerve is similar to the cable that connects your video camera to the VCR. The images seen in the eye is transported to the occipital lobe of the brain where the image is processed. The optic nerve head can be seen by an eyecare practitioner when the eyes are dilated. Your doctor evaluates the nerve for such disease processes as glaucoma, papilledema (increased pressure in the brain), multiple sclerosis or brain tumors.
RETINA: The retina is similar to the film in a camera. This is where the picture seen by the eye is converted to electrical signals and then transported to the occipital lobe via the optic nerve. The retina is made of cells called rods and cones. Rods are primarily used to aid with night and peripheral vision, while cones are designed to aid with color vision and crisp 20/20 vision.
SCLERA: The sclera is the white portion of the eye. It is comprised of tough connective tissue that gives the eye its shape.
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