Your Eyes
Key Terms
Cornea: The cornea is a clear, dome shaped covering and it serves as the eye's main lens.
Fovea: The fovea is located in the center of the macula, it is where vision is the most acute.
Iris: The iris controls the amount of light entering the eye. The color of the eye depends on the color of the iris.
Lens: The lens is secondary to the cornea and is used for fine tuning the focus.
Macula: The macula is a small, sensitive area of the central retina used for fine visual skills such as reading.
Optic Nerve: The optic nerve carries the signals from the retina to your brain. The brain translates this visual information into images that you see.
Retina: The eye focuses light on the retina. The retina is where light receptor cells translate light into signals that go to the brain. Cones and rods are specialized light-sensitive cells (photoreceptors) in the retina. Cones provide sharp central vision and color vision. Rods handle side vision and vision in dim lighting conditions.
Sclera: The sclera is the thick, white outer layer of the eyeball and it serves as protection along with the cornea.
Cornea: The cornea is a clear, dome shaped covering and it serves as the eye's main lens.
Fovea: The fovea is located in the center of the macula, it is where vision is the most acute.
Iris: The iris controls the amount of light entering the eye. The color of the eye depends on the color of the iris.
Lens: The lens is secondary to the cornea and is used for fine tuning the focus.
Macula: The macula is a small, sensitive area of the central retina used for fine visual skills such as reading.
Optic Nerve: The optic nerve carries the signals from the retina to your brain. The brain translates this visual information into images that you see.
Retina: The eye focuses light on the retina. The retina is where light receptor cells translate light into signals that go to the brain. Cones and rods are specialized light-sensitive cells (photoreceptors) in the retina. Cones provide sharp central vision and color vision. Rods handle side vision and vision in dim lighting conditions.
Sclera: The sclera is the thick, white outer layer of the eyeball and it serves as protection along with the cornea.
Vision Conditions
Normal Vision: With normal vision everything you see is clear and in focus, as in this picture.
Normal Vision: With normal vision everything you see is clear and in focus, as in this picture.
You might hear this called 20/20 vision. That means that you can see clearly at 20 feet what most people with normal vision can see.
Nearsighted (Myopia): Nearsighted people's vision is blurry at a distance. They might see something like this picture when they look at things far away.
Nearsightedness occurs when the eye has too much "plus power" and the eye focuses the light in front of the retina.
Farsighted (Hyperopia): Farsighted people's vision is blurry close up. They might see something like this picture when they try to read or do close-up work.
Farsightedness occurs because the eye does not have enough power to focus light on the retina.
Astigmatism: People with an astigmatism don't see clearly at any distance.
Astigmatism occurs when the cornea is not spherical. This causes the light that enters the eye to be focused at two different focal points in the eye.
Information courtesy of the National Eye Institute, National Institutes of Health.
Information courtesy of the National Eye Institute, National Institutes of Health.
Common Eye Diseases
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Age-related Macular Degeneration Age-related macular degeneration is the leading cause of blindness in the US. It is caused by changes in the macula, the part of the retina responsible for clear vision. As this condition advances, a distorted, dark or empty space appears in the center of view, as in the image to the right.
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Contact your eye doctor immediately if you have any of these symptoms. After age 60 the American Optometric Association recommends an annual comprehensive eye examination.
Cataract: A cataract is the clouding of all or part of your eye's lens. Your lens is normally clear. See your eye doctor if you think you may have cataracts. This condition is most often found in people over 55 but can occur in younger individuals. The cause of cataracts is not known but the cloudy lens is a result of a chemical change in the eye. This may be due to age, heredity, injury or disease. If you have cataracts, your eye doctor will be able to discuss treatment options with you. Cataracts can be removed by an eye surgeon by replacing your eye's lens with an artificial lens.
Cataract: A cataract is the clouding of all or part of your eye's lens. Your lens is normally clear. See your eye doctor if you think you may have cataracts. This condition is most often found in people over 55 but can occur in younger individuals. The cause of cataracts is not known but the cloudy lens is a result of a chemical change in the eye. This may be due to age, heredity, injury or disease. If you have cataracts, your eye doctor will be able to discuss treatment options with you. Cataracts can be removed by an eye surgeon by replacing your eye's lens with an artificial lens.
Diabetic Retinopathy: Diabetic retinopathy is one of many health problems that can be caused by diabetes. This eye disease is caused by the leaking, swelling or branching of the small blood vessels in the retina. As diabetic retinopathy progresses, you may notice your vision is cloudy and you might develop blind spots or floaters. Left untreated, diabetic retinopathy can cause blindness. Have your eyes examined regularly, especially if you or a family member has diabetes. Laser and other eye surgery can slow the progress of the disease and decrease the risk of blindness. However, early treatment is important. If you have diabetes, follow your doctors advice and get regular eye examinations.
Glaucoma: Glaucoma is caused by an increase in the internal pressure of the eye. The increase in pressure can damage the fibers in your optic nerve. This pressure occurs when the passages in your eye that normally drain fluid become blocked or clogged. Glaucoma is one of the leading causes of blindness in the US. Glaucoma can not be prevented but it can be controlled through treatment if it is diagnosed early. The American Optometric Association recommends that you have yearly examinations if you are at risk of glaucoma.
Retinitis Pigmentosa: Retinitis pigmentosa is a condition of the retina where the cells called rods degenerate over time. This is a condition that is inherited from your parents. As the disease progresses, individuals lose their ability to see in low light conditions and over time they may lose their peripheral vision. See your eye doctor if you think you have retinitis pigmentosa or if you have a family history of this disease.
Types of Eye Care Professionals
Optometrist or Optometric Physician (Doctor of Optometry, O.D.): The optometrist is the primary eye care physician the family doctor for general vision care. Training includes four years of college, four years of optometry school, and an optional residency for specialties such as pediatrics, contact lenses, and ocular disease. All optometrists provide the following services:
- Comprehensive eye examinations.
- Prescription and fitting of glasses and contact lenses.
- Diagnosis and treatment of eye disease conditions.
- Screening for general health problems like high blood pressure and diabetes.
- Many optometrists provide specialized services in the following areas: pediatric eye care, developmental vision disorders and vision related learning disabilities vision therapy low vision care for the partially-sighted and specialty contact lens fitting.
Ophthalmologist (Medical Doctor, M.D.): An ophthalmologist is a medical eye doctor whose primary role is to provide diagnosis and treatment for eye health conditions. Training includes four years of college, four years of medical school, one year of internship, and three years of residency. All ophthalmologists provide the following services:
- Diagnosis and treatment of eye diseases and general health conditions that affect the eyes.
- Surgical correction of eye conditions when necessary.
- Prescription of glasses and contact lenses.
- Screening for general health problems like high blood pressure and diabetes.
- Many ophthalmologists provide specialty services in the following areas: pediatric eye care, refractive surgery, and specific eye disease treatment for retinal disease, glaucoma, and cataracts.
Optician (COT): An optician is a optical specialist who designs, grinds, and fits lenses. There are many skill levels within the profession from persons who can measure and dispense glasses to board certified opticians with three years of education and apprenticeship. Opticians perform the following services:
- Fitting and dispensing of optical devices prescribed by optometrists or ophthalmologists.
- Some opticians perform the following specialty services: contact lens design and fitting, low vision device design and fitting, and the design and manufacturing of specialty lenses.
Ophthalmic Technician: Ophthalmic technicians are specifically trained to provide technical assistance to the optometrist or ophthalmologist. Typically they perform visual acuity measurement, visual field testing, and eye pressure measurement as well as other tasks. Most ophthalmic technicians receive training through a certified program.
Vision Therapist or Orthoptist: These individuals are specifically trained to assist the optometrist or ophthalmologist in providing therapy for eye coordination disorders and developmental vision disorders. The therapist works one-on-one with patients to help them overcome functional vision problems that cannot be corrected with glasses or surgery.
