YOUR EYE HEALTH
There are many conditions that can cause long-term vision loss if not detected and treated early. It is only through routine and thorough assessment and dilated examinations that many of these conditions can be found. Some of the most common eye diseases are shown below.
The human eye is approximately one inch in diameter. Sclera is dense white tissue that encloses delicate tissues of the eye. Conjunctiva is analogous to skin for the sclera. It is the tissue that gets red and inflammed in "pink eye".Cornea occupies an opening in the sclera in the front and provides two thirds of the refractive power of the eye. Iris and pupil can be seen behind the transparent cornea and control entry of light into the eye. Pupil dilates in dim light to allow more light to enter the eye, and constricts in bright light to prevent excessive light from entering the eye. Lens lies behind the pupil and accounts for about 20 diopters, or one third of refractive power of human eye. Cloudiness of lens that commonly occurs with age is called cataract. Cornea, iris, pupil and lens are collectively known as anterior segment of the eye.
The retina is transparent nerve tissue that lines the inside of most of the eye. It is only about one tenth of a millimeter in thickness, but has three layers of nerve cells. The outermost layer of nerve cells is called photoreceptors that consist of rods and cones. These cells act as sensors and send electric signal in response to light. Bipolar cells connect rods and cones to ganglion cells which exit the eye via optic nerve and transmit electrical signal to the brain. The optic nerve is about 1.5 mm in diameter and contains more than a million nerve fibers. The arteries and veins that nourish the retina also enter and leave the eye via the optic nerve.
The macula (fovea) provides central or reading vision. It is an area of slight depression in the contour of the retina that measures about the same size as the optic nerve and has more pigment than surrounding retina. The center of the macula is called foveola and measures only about 0.35 mm in diameter. Foveola is densely packed with cones and is responsible for fine vision, color vision and depth perception. Part of the retina within major blood vessels temporal to the nerve is called posterior pole. The rest of the retina is called peripheral retina, has more rods than cones and provides peripheral or side vision, or “seeing out of the corner of the eye.” Night vision also comes from rods which are primarily located in the peripheral retina.
There are many conditions that can cause long-term vision loss if not detected and treated early. It is only through routine and thorough assessment and dilated examinations that many of these conditions can be found. Some of the most common eye diseases include:
GLAUCOMA (optic nerve head cupped out)
Glaucoma is a group of eye disorders that leads to progressive damage to the optic nerve, and it is characterized by loss of nerve tissue resulting in loss of vision. The optic nerve is a bundle of over one million individual nerve fibers and it transmits the visual signals from the eye to the brain. The most common form of glaucoma, primary open-angle glaucoma, is associated with an increase in the fluid pressure inside the eye. This increase in pressure can cause progressive damage to the optic nerve and loss of nerve fibers. Vision loss may result. Advanced glaucoma may even cause blindness. Not everyone with high eye pressure will develop glaucoma, and many people with normal eye pressure will develop glaucoma. When the pressure inside an eye is too high for that particular optic nerve, whatever that pressure measurement may be, glaucoma will develop.
Glaucoma is the second leading cause of blindness in the U.S.
DIABETIC EYE DISEASE (bleeding in eye)
Diabetic retinopathy is a condition occurring in persons with diabetes, which causes progressive damage to the retina, the light sensitive lining at the back of the eye. It is a serious sight-threatening complication of diabetes.
Diabetes is a disease that interferes with the body's ability to use and store sugar, which can cause many health problems. Too much sugar in the blood can cause damage throughout the body, including the eyes. Over time, diabetes affects the circulatory system of the retina.
The longer a person has diabetes, the more likely they will develop diabetic retinopathy. If left untreated, diabetic retinopathy can cause blindness.
Symptoms of diabetic retinopathy may include:
• Seeing spots or floaters in your field of vision
• Blurred vision
• Having a dark or empty spot in the center of your vision
• Difficulty seeing well at night
Better control of blood sugar levels in patients with diabetes also slows the
onset and progression of diabetic retinopathy. Routine diabetic eye examinations
are recommended for all patients with diabetes.
Age-Related Macular Degeneration (AMD) is the leading cause of severe vision loss in adults over age 50. The CDC estimates that 1.8 million people have AMD and another 7.3 million are at substantial risk for vision loss from AMD. Caucasians are at higher risk for developing AMD than other races. Women also develop AMD at an earlier age than men. AMD occurs when there are changes to the area of the retina called the macula. The macula is the area of your vision that is responsible for detailed sight and color vision.
Some common symptoms are: a gradual loss of ability to see objects clearly, distorted vision, a gradual loss of color vision, and a dark or empty area appearing in the center of vision. Central vision that is lost to macular degeneration cannot be restored. However, low vision devices, such as telescopic and microscopic lenses, can be prescribed to maximize existing vision.
Researchers have linked eye-friendly nutrients such as lutein/zeaxanthin, vitamin
C, vitamin E, and zinc to reducing the risk of certain eye diseases, including
Dry eye is a condition in which there are insufficient tears to lubricate and nourish the eye. Tears are needed for maintaining the health of the surface of the eye and for maintaining clear vision. People with dry eyes usually do not produce enough tears or they may have poor quality of tears. Dry eye is a common and often chronic problem, particularly in older adults, but also may commonly occur in younger people as a result of heavy computer use or medications.
People with dry eyes may experience symptoms of irritated, gritty, scratchy, or burning eyes, a feeling of something in their eyes, excess watering, and blurred vision. Advanced dry eyes may damage the front surface of the eye and impair vision.
Treatments for dry eyes aim to restore or maintain the normal amount of tears in the eye to minimize dryness and related discomfort and to maintain eye health.
Conjunctivitis, often called “pink eye,” is a common eye disease, especially in children. It may affect one or both eyes. Some forms of conjunctivitis can be highly contagious and easily spread in schools and at home. While conjunctivitis is usually a minor eye infection, sometimes it can develop into a more serious problem. There are many different possible causes for “pink eye” and their treatments vary.
A cataract is a cloudy area in the normally clear lens of the eye. Depending upon its size and location, it can interfere with normal vision. Most normal cataracts develop in people over age 55. Some of the most frequent symptoms of an early cataract may be increased glare with night driving and increased sensitivity to bright lights during the daytime. Usually cataracts develop in both eyes, but one may be worse than the other. Reasearchers have linked eye-friendly nutrients such a lutein, vitamin C, vitamin E, and zinc to reducing the risk of certain eye diseases, including cataracts.
(for more information on these and other common eye conditions visit: aoa.org)