Age-Related Eye Diseases (AREDs) Explained
Your eyes are one of the most important organs in your body, and perform what many believe to be the most important of the 5 senses. As people get older, their bodies become more susceptible to diseases and ailments, and their eyes are no exception. The National Eye Institute (NEI), as part of the National Institute of Health, has performed extensive studies on age-related eye diseases, now coined AREDs.
Age-related eye diseases, in many cases, are not sudden but tend to develop slowly as a person ages. This is the reason why many age-related eye diseases go unnoticed; people regularly comment that their "eyes are going in their old age" but do not realize that many age-related eye diseases can be prevented or treated if detected early enough. Of the many age-related eye diseases, there are four major ones that are recognized by the NEI and that can be detected and treated if a comprehensive eye examination is performed. These four age-related eye diseases are Macular Degeneration, Cataracts, Glaucoma, and Diabetic Retinopathy. These eye diseases are discussed more thoroughly below.
Macular Degeneration can be particularly difficult to live with because it affects the central vision. This means that the loss of vision takes place at the spot where your eyes are trying to focus, and not necessarily the peripheral vision. People who suffer from Macular Degeneration have difficulties recognizing faces, driving, reading, and taking part in any daily activities that require direct sight. Macular Degeneration is the leading cause of non-preventative blindness in the United States and affects over 2 million people over the age of 65.
- caused by deposits in the eye or abnormal blood vessel growth in the eye
- affects central vision
- can go unnoticed while it develops; can develop rapidly resulting in legal blindness
- no known cure
The macula is a small oval layer of ganglion cells at the center of the retina (the retina is located at the back of the eye where come cells absorb light and enable you to see). The macula is usually about 5mm in diameter and is yellowish in color (it is sometimes called the macula lutea, or "yellow spot"). Its position in the center of the retina is conducive to its job of providing central vision. Macular Degeneration is grouped into two types: dry and wet. 'Dry' Macular Degeneration affects about 90% of people with this age-related eye disease, and ‘wet’ Macular Degeneration affects about 10%.
Dry Macular Degeneration (Nonexudative Macular Degeneration):
Dry Macular Degeneration refers to a condition where the cells below the retina, on the retinal pigment epithelium, start to break down due to a build-up of drusen. Drusen is a common extra-cellular deposit in the eye that tends to become more frequent with age. When this deposit starts to interfere with the retinal pigment epithelium, rod and cone cells in the area start to degenerate or atrophy. Because rod and cone cells literally absorb and decipher light, thereby enabling us to see, the atrophy of rod and cone cells impairs our vision. Because of the area of atrophy (the macula, or the center of the retina), the result is central vision loss. About 90% of all people who suffer from Macular Degeneration are diagnosed with the dry or nonexudative type. Dry Macular Degeneration seems to have less of an effect on vision than does Wet Macular Degeneration because the atrophy of rod and cone cells tends to be much slower.
Wet Macular Degeneration (Exudative or Neovascular):
Wet Macular Degeneration is similar to Dry Macular Degeneration in the sense the macular degenerates, resulting in the loss of central vision. In this degeneration type, abnormal blood vessel growth is triggered in the choriocapillaries (the choroids is also located behind the retina), resulting in the leakage of blood and protein. The resulting fluid leakage and overgrowth of blood vessels can quickly damage the macula and its rod and cone cells, resulting in severe loss of central vision. The major symptomatic difference is that Wet Macular Degeneration progresses quickly and can cause legal blindness in a relatively short time. Although Wet Macular Degeneration only affects about 10% of people suffering from Macular Degeneration, the quickness of degeneration and the massive amount of vision loss can be devastating.
About 10% of people between the ages of 66 and 74 are detected to have Macular Degeneration. These statistics can increase fourfold if someone else in your family has suffered from Macular Degeneration. Although the disease is not curable, research studies by the National Eye Institute have found that certain vitamins and minerals can significantly reduce the risk of Macular Degeneration. Some of these include Beta-Carotene, Vitamin C, Vitamin E, zinc, bilberries, lutein, and certain fish oils, vitamins, and nutrients your body needs but are sometimes either neglected or not absorbed properly in elderly people.
Glaucoma is the second leading cause of blindness worldwide, affecting one person in every 200. The disease (or group of diseases) usually goes undetected until it is fairly advanced. Because of this ‘creeping’ effect, it has often been called the "thief of the night" or "sneak thief of sight" - indeed, its progression can be so slow that people with glaucoma don’t even realize that their vision has deteriorated by up to 50%.
- caused by increased intraocular pressure (IOP)
- starts by affecting peripheral vision
- usually goes unnoticed until relatively advanced
- no known cure
Glaucoma is the result of high intraocular pressure, resulting in optic nerve damage and damage to retinal ganglion cells. The eye itself is constantly being irrigated by a flow of clear liquid that both replenishes the cells of the eye, but also maintains a certain pressure on the eye, called intraocular pressure. This pressure varies from person to person; an intraocular pressure that causes optic nerve damage in one person may be a perfectly healthy intraocular pressure for another.
Glaucoma causes permanent damage to the optic nerve, which results in the gradual loss of the visual field. So, unlike Macular Degeneration, the peripheral vision is affected first, slowly 'tunneling' off to the central vision. The fact that Glaucoma affects peripheral vision explains why so many people do not even know they have Glaucoma until it has advanced significantly.
There is no cure for Glaucoma. Some surgeries can be performed for some types of Glaucoma, but their results are temporary. Prescription drugs are available to control intraocular pressure (IOP); some examples are Physostigmine, Litanoprost, Bimatoprost, Epinephrine and Dorzolamide.
With the resurgence of natural healing and remedies, recent studies have shown that many natural compounds and ingredients can not only help reduce IOP, but can actually nourish the optic nerve and help regulate eye irrigation. Some of these natural compounds include fish oil, bilberries, Vitamin A, C, and E, Beta-carotene, Selenium, and many more.
Cataracts are a clouding of the lens within the eye, which causes a lack of vision and can lead to blindness. The clouding affects the crystalline lens of the eye, and is particularly common in aged people (called senile cataracts) and is considered an age-related eye disease. If untreated, cataracts can cause a person to lose perception of certain colors (usually blue) and can lead to vision loss.
- Various causes including genetics, diabetes, radiation exposure, trauma, and denaturation of lens protein
- Affects central vision
- Can cause blindness if left untreated
- Can be cured with surgery and prevented with certain vitamins
Cataracts affect over 18 million people worldwide and are the leading cause of blindness in some underdeveloped countries. Predominant in elderly people, cataracts affect over 40% of people between 52 and 64 and more than 60% of people over the age 65. Some statistics show a 90% prevalence of cataracts in the elderly over the age of 90.
Cataracts are caused, as mentioned, by the denaturation of proteins in the crystalline lens of the eye. The crystalline lens is located behind the cornea (the bulge on the outer front of the eye) and the aqueous humor (the liquid pocket behind the cornea). The lens is made of various elements including water and proteins which are important for the lens’ structure and flexibility and are arranged in such a way to focus light onto the retina at the back of the eye. Certain triggers can cause the proteins to ‘cloud’ causing loss of vision and the onset of a cataract. A good analogy of this is the proteins in the ‘white’ of an egg. Initially clear, if you add heat to the egg white, it will start to cloud until, with enough heat, it becomes completely white (opaque).
Denaturation of the proteins in the crystalline lens works the exact same way. The triggers, however, are numerous and not completely understood by medical research. Heat and thermal trauma to the eye can cause a cataract in exactly the same way an egg white turns white. Other factors, particularly radiation, can cause the proteins to cloud over. Other causes have been related to allergies, ultraviolet light (or severe sun exposure), corticosteroid use, and vitamin deficiencies. Cataracts can appear and never get worse (stationary cataracts) or can progressively get worse even if the assumed cause has been isolated and eliminated (progressive cataracts).
Unlike many age-related eye diseases, cataracts can be treated and cured through surgery. In many cases, the lens of the eye is actually replaced by a plastic lens which is impervious to protein denaturation. When surgery is performed, lenses are created that will also cure certain sight issues, particularly short-sightedness, which can be a symptom of cataracts.
Like many eye diseases, research has shown that proper nutrition and the intake of daily recommended vitamins such as Vitamin A, C, and E may help to prevent cataracts. Studies are now being done on the efficacy of these antioxidants. It should be noted that the use of ultraviolet protecting sunglasses can help reduce the chance of getting a cataract or slow the progression of a cataract.
Retinopathy generally means damage to the retina. Diabetic retinopathy is damage to the retina caused by the effects of diabetes mellitus. Diabetic Retinopathy affects almost 80% of people who have had diabetes for more than 10 years. Although diabetic retinopathy may not always cause blindness, the symptoms of the eye disease can come and go very quickly, often overnight. Diabetic Retinopathy affects people with both Type I and Type II diabetes.
- blood vessels in the eye weakening and/or hemorrhaging due to diabetes mellitus
- can affect central or peripheral vision or both
- can cause blindness if left untreated
- can be treated with surgery or certain steroids
When a person has diabetes, their blood vessels (particularly the smaller vessels like those in the eye) can become weakened and prone to hemorrhaging due to over-accumulation of blood sugar (glucose/fructose). When the blood vessels at the back of the eye are weakened, they cannot provide proper nutrients to the retina. At this stage, called nonproliferative diabetic retinopathy (NPDR), the person may experience a blurring of the vision but in many cases will not notice any change in their vision. Once the blood vessels are weakened enough, they start to hemorrhage. The resulting fluids can then obstruct the macula, causing a condition called macular edema (swelling of the macula) and causing blurring vision.
Proliferative Diabetic Retinopathy (PDR) occurs when NPDR advances to the point where lack of oxygen to the retina (caused by weakened or hemorrhaging blood vessels) stimulates the growth of new blood vessels directly on the retina. The new blood vessels will cause blurred vision. If the blood vessels then start to bleed (as is common), the resulting fluid can block the retina (causing spotted vision or complete loss of sight), and can actually damage the retina or cause it to detach.
PDR can be treated in a variety of ways, but it cannot be cured and must be frequently monitored to make sure the retina is not being damaged. Some surgeries, such as laser surgery, can be used to eliminate new blood vessels growing on the retina.