Packed into a relatively small space is a myriad of complex and coordinated muscles, tendons, ligaments, tissue, fluids, blood vessels, nerve fibers, and glands that bring us immediate information about the world around us; our eyes. How our eyes work and what allows us to see has fascinated scientists for decades. Of all the sensory receptors in your body, 70% are in your eyes. Most people would say that sight is the sense they value the most.
Your eyes are at work from the moment you wake up in the morning until you close your eyes at night. All-seeing, they are constantly taking in any and all information about the world around us and sending this information, via the optic nerve, to our brains to be deciphered and processed, all within a matter of nano-seconds. This information is what lets us make crucial decisions about our immediate environment and how our body might be affected by it.
In this month’s article, we’ll discuss how your eye works, some typical eye conditions, take a fun little “eye-Q” test, talk about how often you should have an eye exam, and offer some links to, and suggestions about, supplements that have been identified, through extensive research studies, as beneficial for your eyes. So read on as we’ve prepared some very interesting factoids, F.Y. – Eye!
How does your eye work? – A little anatomy F.Y.- Eye
Light entering the eye is first bent, or refracted, by the cornea — the clear window on the outer front surface of the eyeball. The cornea provides most of the eye’s optical power or light-bending ability.
After the light passes through the cornea, it is bent again — to a more finely adjusted focus — by the crystalline lens inside the eye. The lens focuses the light on the retina. This is achieved by the ciliary muscles in the eye changing the shape of the lens, bending or flattening it to focus the light rays on the retina.
This adjustment in the lens, known as accommodation, is necessary for bringing near and far objects into focus. The process of bending light to produce a focused image on the retina is called “refraction”. Ideally, the light is “refracted,” or redirected, in such a manner that the rays are focused into a precise image on the retina.
Even with the light focused on the retina, the process of seeing is not complete. For one thing, the image is inverted, or upside down. Light from the various “pieces” of the object being observed stimulate nerve endings — photoreceptors or cells sensitive to light — in the retina.
We make sense of light through two types of receptors – rods and cones. Rods are mainly found in the peripheral retina and enable us to see in dim light and to detect peripheral motion. They are primarily responsible for night vision and visual orientation. Cones are principally found in the central retina and provide detailed vision for such tasks as reading or distinguishing distant objects. They also are necessary for color detection. These photoreceptors convert light to electrochemical impulses that are transmitted via the nerves to the brain.
Millions of impulses travel along the nerve fibers of the optic nerve at the back of the eye, eventually arriving at the visual cortex of the brain, located at the back of the head. Here, the electrochemical impulses are unscrambled and interpreted. The image is re-inverted so that we see the object the right way up.
Typical Eye Problems – Nearsightedness, Farsightedness, Astigmatism
Most vision problems occur because of an error in how our eyes refract light. In nearsightedness (myopia), the light rays form an image in front of the retina. In farsightedness (hypermetropia), the rays focus behind the retina. In astigmatism, the curvature of the cornea is irregular, causing light rays to focus to more than one place so that a single clear image cannot be formed on the retina, resulting in blurred vision. As we age, we find reading or performing close-up activities more difficult. This condition is called presbyopia, and results from the crystalline lens being less flexible, and therefore less able to bend light.
What’s Your Eye-Q?
Here’s a fun little quiz to see how much you know about common eye health concerns. TIP: Some questions have more than one right answer.
1. True or False, the following things can cause damage to your eyes:
a) household chemicals and hair products
b) bacterial infections and viruses
c) exposure to the sun’s UV rays
d) the wrong shade of eye shadow
2. True or False: Your eyes can get sunburned.
3. Which of the following things can help protect your eyes:
a) sunglasses
b) proper reading and task lighting
c) regular eye exams
d) avoiding bad movies
4. What is color blindness?
a) trouble seeing the difference between certain colors
b) not being able to see colors at all, or
c) having bad taste in colors
5. A cataract is:
a) clouding of the eye
b) a condition that causes blurring or dimming of vision
c) an expensive automobile
6. The most common cause of cataracts is:
a) UV rays from the sun
b) genetic predisposition
c) overuse of TV’s and computers
d) not hiring an interior decorator
7. Why do your eyes water?
a) As a sort of eye wash that protects your eyes
b) Tears contain enzymes that destroy bacteria
c) Because you’re hungry and that chocolate cake looks too good
Answers:
1. a, b, & c – True
2. True
3. a, b, & c
4. a & b
5. a & b
6. a
7. a & b
Explanations To Question Answers
QUESTION #1a
Perming lotion is a product used to create permanent hair curls. It contains chemicals that can cause poisoning symptoms if exposure occurs. The type and severity of damage variesy depending on the amount of chemical involved and the nature of the exposure. 1
Household chemicals like bleach, ammonia, cleaning agents, pesticides and others can burn your eyes’ delicate tissues. When using any chemicals in your home, wear goggles, make sure the area is well-ventilated and be sure the nozzle is pointed away from your face before you spray. 2
QUESTION #1b
Conjunctivitis is an inflammation of the conjunctiva, a thin, transparent layer covering the surface of the inner eyelid and a portion of the front of the eye and is caused by a contagious virus or bacteria. Commonly known as “pink eye”, this condition can be recognized by the appearance of red eyes, inflamed inner lids, watery eyes, blurred vision and sandy or scratchy feeling in the eyes. With the infectious form, there may be a discharge around the eyelids.
To avoid giving infectious conjunctivitis to others, keep your hands away from your eyes; thoroughly wash your hands before and after applying eye medication; do not share towels, washcloths, cosmetics or eye drops with others and seek treatment promptly. Certain forms of conjunctivitis can develop into a serious condition that may harm your vision. Therefore, it’s important to have your condition diagnosed and properly treated quickly.
QUESTION #2
Preventing sunburn and taking care of your eyes should be a top concern for all no matter the time of the year, but especially during the hot summer months of June, July and August. Sunglasses provide one of the best sources of UV protection. In order to properly protect your eyes, choose sunglasses that over at least 95 percent UV protection. Also, choose a lens tint that blocks 80 percent of transmissible light, but no more than 90-92 percent of light because lens tint does not protect you from UV rays, and can affect your ability to see correctly. Large lenses that fit close to the eyes are best. Those that block visible blue light are even safer.
QUESTION #3
Through much recent study, researchers have found that there is no conclusive evidence suggesting that reading in dim light will increase your chances of becoming nearsighted or farsighted, but why take the chance. Some adverse effects of reading in dim light include headache, dizziness, and temporary blurred vision.The proper lighting level for comfortable reading is approximately 600 lux, or about the typical lighting level of a bright office. This can also be attained with a normal reading lamp or table lamp, placed about 2-3 feet away from the reader.
QUESTION #4
The correct name for color blindness is color vision deficiency. Color vision deficiency is a term used to describe a number of different problems people have with color vision. These problems may range from a slight difficulty in telling different shades of a color apart to not being able to identify any color. It is estimated that 8% of males and less than 1% of females have color vision problems. Most color vision problems are hereditary and already present at birth. Another cause for color vision deficiency is aging. The eye’s clear lens can darken and yellow over time, which can cause older adults to have problems seeing dark colors. Certain medications or eye diseases can affect color vision. 3
QUESTION #5 & #6
A cataract is a cloudy area in the lens of the eye. A normal lens is clear and focuses light into the back of the eye (see right photo). When a cataract develops some of this light is blocked out and or scattered. As this cataract develops, it becomes harder for a person to see. Cataracts are a normal part of aging. About half of Americans ages 65 to 74 have cataracts. Over 90 percent of those age 75 and over have this condition. Most people with cataracts have a cataract in both eyes. However, one eye may be worse than the other because each cataract develops at a different rate.
QUESTION #7
When your eyes water, they’re making tears. The tears from watering eyes help protect your eyes by keeping them moist and washing out dust and other foreign matter that can get into your eyes. The tears from watering eyes might only fill your eyes or they might trickle down your face. Whether you’re crying or your eyes are just tearing, the liquid in your eyes is created the same way. All tears come out of tear glands, or lacrimal (lah-krum-ul) glands, found under your upper eyelids. Tears wash down from the glands and over your eyes.
Some of the tears drain out of your eyes through tear ducts, or lacrimal ducts. These ducts are tiny tubes that run between your eyes and your nose. Each tear duct is like a tiny bathtub drain. When the tears fill up your eyes, they drain out through the tear ducts. You have two tear ducts – one near the inside corner of each eye. You can see these holes if you gently pull down your lower eyelid a bit.If tears are flowing quickly, the ducts can’t drain them all, so tears run down your face. And have you ever noticed that your nose sometimes runs when you cry? That’s because some of the tears making their exit through the ducts end up coming out of your nose.
How often should I get my eyes checked?
The Canadian Association of Optometrists’ guidelines for preventive eye health suggest that everyone should have their eyes examined at least every year or two regardless of vision correction problems. More frequent visits are recommended for those at high risk, with medical conditions, as well as the elderly and young children.
Vitamins, Nutrition and Your Eyes
Research has shown that nutrition can impact the development of cataracts and age-related macular degeneration (AMD), which are the two leading causes of blindness and visual impairment among millions of aging Americans. Nutrition may be particularly important given that currently, treatment options after diagnosis for these eye diseases are limited.
Antioxidants and Age-Related Eye Disease
The Age-Related Eye Disease Study from the National Eye Institute (NEI) is the first large clinical trial to test the effect of a high dose antioxidant vitamin combination plus zinc on preventing or delaying the progression of AMD and its associated vision loss. The antioxidant vitamins and zinc supplement reduced the risk of developing advanced AMD by about 25 percent in the study subjects who were at high risk for developing the advanced stage of this disease.
To read more about this topic, or to print out this information, CLICK HERE for the full article by The Canadian Association of Optometrists.
Lutein and Zeaxanthin Eye-Friendly Nutrients
The carotenoids lutein (pronounced loo-teen) and zeaxanthin (pronounced zee-uhzan-thin), which are antioxidants and the only carotenoids located in the eye, may protect against cataracts and AMD. One of the first large studies on carotenoids is the Eye Disease Case Control Study, in which diet was compared to the risk for developing AMD. Results found a significantly lower risk for developing the eye disease in people with high amounts of lutein+zeaxanthin in their blood.
To read more about this topic, or to print out this information, CLICK HERE for the full article by The Canadian Association of Optometrists.
Nutrition and Age-Related Macular Degeneration
The macula is the part of the eye responsible for turning light into fine color images in the brain, which allows people to read, drive and perform other daily activities. Though the exact cause of damage to the macula is unknown, a breakdown in the macular area can lead to a loss in people’s central vision.
Approximately ten million Americans show early signs of AMD and a half million people or more may have significant vision loss from late-stage AMD.
Certain nutrients, such as vitamins C and E, beta-carotene and the mineral zinc, have been found to protect our eyes against AMD and the loss of vision that may result from it. In addition, the carotenoids lutein (pronounced loo-teen) and zeaxanthin (pronounced zee-uh-zan-thin), which are antioxidants and the only carotenoids located in the eye, may also protect our eyes from this disease.
To read more about this topic, or to print out this information, CLICK HERE for the full article by The Canadian Association of Optometrists.
Nutrition and Cataracts
Cataracts develop when the proteins in the lens of the eye are damaged, causing them to become translucent or opaque. There are three types of major cataracts, depending on the location in the lens: nuclear, cortical and posterior subcapsular.
Several research studies show that the antioxidant properties of vitamins C and E may protect against the development and progression of cataracts. Early evidence also suggests that the carotenoids lutein (pronounced loo-teen) and zeaxanthin (pronounced zee-uh-zan-thin), which are also antioxidants, may also be protective against cataracts.
To read more about this topic, or to print out this information, CLICK HERE for the full article by The Canadian Association of Optometrists.