Archive for the ‘Eye Facts’ Category
Forget that tired old question about who’s hotter, Ginger or Mary Ann.
In this corner, weighing 150 pounds (and that’s just his forearms), is everybody’s favorite sailorman. Look at him nuzzle his anorexic extra-virgin girlfriend and inhale his spinach right from the can.
In that corner, weighing oh, probably 20 pounds (and that’s just his ears), is Elmer Fudd’s favorite nemesis. Look at him nonchalantly lean on the ropes while he chomps on a fresh carrot.
So who’s it going to be? The perpetually squinting Bluto-battler or the Cwazy Wabbit? Amazingly, the winner by a knockout is Popeye!
Spinach before carrots? How can that be? Didn’t our moms tell us to eat our carrots because they’re good for our eyes?
Yes they did. But they also told us that if we keep crossing our eyes, one day they’re going to get stuck that way. We love our moms, but maybe they’re not the most reliable source of information when it comes to eyes.
Nope, the consensus is in from nutrition and vision experts: the nutrients in spinach are actually better for the health of your eyes than the ones in carrots.
Let’s look, with both eyes open, at some facts surrounding nutrition and vision.
These facts come courtesy of the Age-Related Eye Disease Study (AREDS) and its follow-up, AREDS-2, both conducted by the National Eye Institute (NEI), which is part of the United States’ National Institutes of Health (NIH).
Keep track of those acronyms. There will be a test later. Not.
Results from AREDS, begun in 1992, were published in 2001. Results from AREDS2, begun in 2006, were published this year. Each study examined the two most common forms of eye disease, age-related macular degeneration (AMD) and cataracts.
What are those, exactly? Let’s start with macular degeneration.
The macula is part of the eye’s retina, which serves a similar function to the film in a camera. We should probably explain that before there were digital cameras there was this thing called film. Google it.
Just like a camera lens, the eye’s lens receives an image. The image is transmitted to the retina, like the way an image taken by a camera lens used to be transmitted to the film in the camera.
The macula is in the center of the retina. When light comes to a point of focus on the center of the macula, you can see objects and colors sharply.
The macula is yellow, which enables it to absorb harmful blue and ultraviolet light that enters the eye, blocking this harmful light like a pair of sunglasses.
AMD comes two ways: dry and wet. Dry is when the tissue of the macula deteriorates. Wet is worse – that’s when the blood vessels behind the retina leak blood and other fluid into the macula.
AMD is the leading cause of blindness in the U.S. of people over 60, according to research conducted under the auspices of Johns Hopkins Medicine. Some estimates put the number of affected people as high as 15 million. However, many of those people are only mildly affected or won’t experience a decline in vision at all. But about 2 million Americans with AMD are severely affected, to the point of acute vision loss.
Check out this picture, which you can look at to test to see if you have any form of macular degeneration:
Click here for the full grid and explanation
Now let’s examine cataracts.
Cataracts form when the eye’s lens becomes cloudy, leading to blurred vision and vision loss. Cataracts happen because the lens of the eye is made up mostly of water and protein. As we age, the protein begins to clump together, creating the cloudy effect on the lens.
Most cataracts are related to aging and are very common in older people. By age 80, more than half of all Americans either have a cataract or have had cataract-removal surgery, according to statistics compiled by the American Academy of Ophthalmology (AAO). In addition, almost 22 million Americans have cataracts in at least one eye, and the number is expected to increase to 30 million by 2020.
OK, so now that we know what AMD and cataracts are, let’s look at which nutrients AREDS and AREDS2 found helpful in addressing these eye diseases.
The first study, AREDS, examined whether taking vitamins E and C, zinc, and beta-carotene – which makes carrots orange – reduced the onset of these diseases.
For AREDS2, the NEI scientists added omega-3 fatty acids and the antioxidants lutein (pronounced LOO-teen) and zeaxanthin (zee-ah-ZAN-thin) – both of which are abundant in spinach, kale, and other leafy green vegetables. Both of these antioxidants are also present in the macula.
In addition to being antioxidants – which are molecules that help maintain the health of cells – lutein and zeaxanthin are carotenoids. Carotenoids are what give plant foods their colors.
Lutein is especially important because it gives the macula its yellow pigment. When this pigment degenerates – causes of this degeneration include aging, a poor diet, smoking, being a female, and having blue eyes – the macula degenerates, too, because the protection the pigment supplies gets lost. It’s like a dark, polarized sunglass lens getting replaced by a clear lens on a bright, sunny day.
Now let’s go back to the studies and their findings.
Contrary to the preliminary results of AREDS, the AREDS2 results show that taking vitamins E and C, beta-carotene, zinc, and the omega-3s had no effect on decreasing the onset or reducing the effects of either disease.
However, there were significant reductions in AMD from lutein and zeaxanthin.
Moreover, when beta-carotene was removed from the study, the scientists found that the AMD-reducing effects provided by lutein and zeaxanthin doubled.
Sorry, Mom. Sorry, Bugs.
AREDS2 also found that neither lutein nor zeaxanthin prevented cataracts from forming. But that’s not to say that there are not foods that help prevent cataracts. A 1993-2009 study conducted by researchers at the University of Oxford in England found that vegetarians and vegans were less likely than meat eaters to develop cataracts – vegetarians 30 percent less likely, vegans 40 percent– and that the more meat people ate, the greater the likelihood they would develop cataracts.
But let’s say you’re a young whippersnapper who hates carrots and spinach. You are years away from getting cataracts, and you spend more time thinking about getting MDMA than AMD.
We can hear you now:
“Dude. Why should I care about this? My vision’s 20/20. I’m sticking with the four major non-food groups – doughnuts, candy bars, 64-ounce sodas, and cigarettes!”
Go ahead, knock yourself out. But remember Dud, uh, Dude, what you eat now affects your eyes today and in the future.
Keep eating junk food and smoking cigarettes, and you could be setting yourself up for type 2 diabetes. Almost 400 million people around the world have diabetes, and 25 million of them are Americans, according to the American Diabetes Association (ADA). Close to half of all American diabetics have some form of diabetic retinopathy, which, after macular degeneration, is the second leading cause of blindness of people in the U.S. Also, people with diabetes get cataracts earlier, and diabetics are 60 percent likelier to get cataracts than non-diabetics, the ADA states.
Type 2 diabetes used to be known as adult-onset diabetes, but the number of children and adolescents who have this type of diabetes has greatly increased during the past 20 years. Consequently, the name of the disease has changed to reflect this appalling reality.
But if you eat a diet rich in – you know what’s coming – fruits and vegetables, that will not only improve your chances of maintaining good vision but improve your overall health, too.
And that’s what’s up, doc.
Eye Diagram Via: Wiki Media Commons
Monday, November, 25 2013 by Matthew Surrence
You’ve probably seen drugstore sunglasses labeled “polarized.” Maybe you looked at those next to sunglasses that weren’t polarized, and wondered what the difference was. Or maybe your eye dr. recommended getting polarized lenses, but you weren’t sure how they worked and what benefit they offered.
Well, we’re going to tell you! Very simply, here’s what polarized lenses do: they reduce glare by blocking horizontal light rays.
Why horizontal? Here’s a little background on how polarization works: light comes from the sun in all directions, and it is reflected in every direction, too. When it reflects from light-colored horizontal surfaces – such as a white sidewalk, a white-sand beach, snow, or sunlight reflecting on water – it is said to be polarized horizontally. Light that is polarized horizontally is responsible for most of the glare that interferes with our vision.
How do polarized lenses work? To understand this, it’s useful to think of window blinds. Let’s start with Venetian blinds, which are horizontal. When Venetian blinds are open, light comes into the room in horizontal stripes, depending on the angle of the sun and the angle the blinds are open.
Polarized lenses are more like vertical blinds. When vertical blinds are open at a certain angle, light comes into the room in vertical stripes. Since horizontally reflected light is responsible for most of the glare we see, the polarized tint is placed on the sunglass lens in vertically angled strips. These vertical strips of tint allow vertically reflected light into the eye but block horizontally reflected light – greatly reducing horizontally polarized glare.
Most polarized lenses are sunglasses. Polarized sunglasses are especially popular with boaters, since water is a very reflective surface on a sunny day. Polarized sunglasses are also great for other outdoor activities, such as golfing and tennis, since they can help to sharpen the focus on the ball. They can also be good for driving, since polarized lenses reduce the glare that reflects from the shiny hood of a car, or the glare from the surface of the road on a hot, sunny day.
However, in some situations there can be drawbacks to polarized lenses. They can be problematic for skiing, since blocking the reflected glare off an icy patch might prevent the skier from noticing and steering away from a potential hazard.
In addition, it can sometimes be difficult to read liquid crystal display (LCD) or light-emitting diode (LED) screens on a boat or plane’s instrument panel while wearing polarized sunglasses. This could interfere with the pilot’s ability to clearly read and quickly respond to the information on the instrument panel. This could also apply to the global positioning system (GPS) and other displays of a car’s dashboard, a smart-phone, an ATM, or a self-service gas pump.
An oddity you may notice while wearing polarized sunglasses is that when you look at your car’s rear or side window from the outside, or perhaps the windows on an office building, you may see splotchy, iridescent spots. When you remove your polarized sunglasses, these spots are invisible.
This effect is created because you are looking at heat-tempered glass. The heat-tempering creates several stress points on the glass, enabling the glass, when broken, to crumble into small, granular chunks, which are safer than splitting the glass into sharp, jagged shards. The stress points also reflect the light in different directions from the parts of the glass that don’t have these stress points. The stress points prevent the polarized lens from filtering out the light evenly across the surface of the glass, creating the splotchy, iridescent effect.
If you are unsure if your sunglasses are polarized, here’s a fun, simple test to see if they are. Hold your sunglasses up to a computer screen, which has an anti-glare coating similar to the anti-glare coating on a polarized lens. Angle your sunglasses about 60 degrees, with one side of the frame at 10 o’clock and the other at 4 o’clock. If the lenses are polarized, they will turn black.
You could also take the test with two pairs of polarized sunglasses – hold one pair at a horizontal (180-degree) angle. Now hold the other pair in front of the first pair, but rotate this second pair of sunglasses a half-turn, till it’s straight up and down, at a vertical (90-degree) angle. You will see that the lenses of both pairs of sunglasses turn considerably darker where the two lenses overlap when they are perpendicular. This is because when you angle one polarized lens to another perpendicularly, they block glare both horizontally (the horizontal pair) and vertically (the vertical pair).
At Zenni Optical, we offer polarized sunglasses in our 1.50 and 1.59 index single-vision and progressive (no-line bifocal) lenses, and in our 1.49 index bifocal lens. All of our detachable sun shades, whether magnetic or clip on, whether standard (the same tint color and shade all the way through) or gradient (the tint is darker at the top, getting progressively lighter toward the bottom) are polarized.
A note of caution regarding drugstore sunglasses that are not polarized. If the lens is a non-polarized, darkly tinted lens not treated to block UV rays, it could be more dangerous to the eye than wearing clear, un-tinted glasses that have 100-percent UV protection. This is because the dark tint could cause the pupil to dilate, allowing more harmful UV rays into the eye.
You can rest assured that on every pair of glasses Zenni Optical makes, tinted or clear, we include a 100-percent UV-protection coating – for free.
In addition to polarized sunglasses, Zenni Optical also offers a different kind of sunglass lens that sometimes people confuse with polarized: photochromic lenses, which turn dark in the bright sunlight and become clear again in the shade or indoors.
Although you may have heard about a new technology that adds polarization to photochromic lenses, Zenni Optical does not offer these lenses at this time. Our polarized lenses are permanently tinted sunglasses that greatly reduce glare.
Friday, November, 15 2013 by Matthew Surrence
If your prescription (Rx) has a correction in the Cylinder (CYL) and AXIS sections, this means you have an astigmatism.
If you have an astigmatism correction on your Rx – and the vast majority of eyeglasses wearers do – you may be experiencing one or more of these symptoms when you are not wearing corrective lenses:
- Blurry vision
- Double vision
- Having to squint to see near and far
- Difficulty focusing on printed words
- Eye strain
- Tired eyes
What causes an astigmatism? It’s predominantly genetic, and it’s usually present to some degree at birth. It may increase or decrease with age. Someone may also develop an astigmatism following an injury to the eye, eye disease, or eye surgery.
An astigmatism results when one or both of the two parts of the eye that bring images into focus – the cornea and the lens – are aspheric. This means that they are not perfectly round and smooth spheres, like a ping pong ball.
An aspheric cornea or lens is more like the oblong shape of a football.
When the cornea and lens are round and smooth, they focus light directly onto the middle of the retina, at the back of the eye, making what you see look crisp and clear. In this case, your cornea and lens are perfectly spherical.
You don’t have an astigmatism if it says “SPH,” meaning “spherical,” on your Rx in the CYL section. Writing “SPH” in the CYL section is one of the ways an eye dr. indicates that the cornea and lens are perfectly round – spherical – and that no astigmatism is present. It’s not uncommon to have an astigmatism in one eye but not in the other.
Another abbreviation for “no astigmatism present” is DS, short for the Latin phrase diopter simplex, which means “unaffected,” indicating that this eye is unaffected by an astigmatism.
But let’s say you have an astigmatism correction on your Rx. If so, you will see a minus or plus number in the CYL section of your Rx.
If the CYL number is preceded by a minus, this means that the aspheric cornea or lens causes light to come to a focus point in front of the retina. It stops at a place that’s too near – not far enough to reach the retina – for you to see well. If the CYL number is preceded by a plus, this means that the aspheric cornea or lens causes light to come to a focus point behind the retina. It stops at a place that’s too far – not near enough to reach the retina – for you to see well.
Each type of astigmatism is corrected by the number in the CYL, which is literally a cylinder placed on your lens, which would be a convex (curved outward) cylinder if the Rx calls for a plus CYL, or a concave (curved inward) cylinder if the Rx calls for a minus CYL.
You will also see a whole number, somewhere between 1 and 180, in the AXIS section. If you have a plus or minus number for the CYL but nothing written in the AXIS field, call your eye dr.’s office. There must be an AXIS if there is a CYL.
Here’s why: the AXIS is literally the degree of angle at which the cylinder is placed on the lens.
For example: if the AXIS number is 180, the astigmatism is corrected by placing the cylinder horizontally on the lens. If the AXIS number is 90, the astigmatism is corrected by placing the cylinder vertically on the lens.
Sometimes the eye dr. will write the AXIS number with one or more zeros before the actual AXIS number, such as 005 or 090. Those preceding zeros are just placeholder digits and the actual AXIS number is 5 or 90. The preceding zeros won’t show up on the AXIS drop-down window on the Your Prescription page where you enter your Rx numbers. You can ignore those zeros.
Every Rx lens Zenni Optical offers can accommodate an astigmatism correction. A strong astigmatism correction would be one that has a number in the CYL category between 2.50 and 6.00, plus or minus on the Rx. The highest CYL number we can correct is plus or minus 6.00, and most of the lenses we offer can accommodate this CYL correction.
Because correcting a strong astigmatism is more complicated than correcting a mild astigmatism, an extra-strength charge is assessed on orders of glasses with single-vision lenses when the Rx indicates a strong astigmatism. Bifocal or progressive lenses with high CYL numbers that call for strong astigmatism corrections come with no extra-strength charge.
Tuesday, November, 5 2013 by Ryan
I recently read a column by journalist Nicholas Kristof about efforts to treat and eliminate several devastating and deadly diseases within the developing world. While I was familiar with some of these diseases, such as polio and leprosy, he also mentioned trachoma, a devastating eye disease of which I had never heard. When I read the article, I was not only shocked to learn of the disease’s existence, but also the importance of helping developing nations prevent and treat the disease before it claims its victim’s eyesight.
Trachoma: A Leading Preventable Cause of Blindness
As the World Health Organization explains, Trachoma is an eye disease caused by a bacteria called chlamydia trachomatis, which is spread through contact with contaminated water and infected flies, as well as person-to-person contact. If left untreated, the condition can eventually cause a malformation of the eyelid, which leads to cornea damage as a sufferer’s eyelashes repeatedly scratch the eye. The condition is not only painful, but can cause permanent blindness. Losing one’s eyesight is bad no matter where it happens, but for those living in the developing world, vision loss is particularly devastating, as there are often few social, educational or medical resources for the blind.
Tragically, the suffering caused by trachoma is preventable, but prevention depends on a number of factors, including access to education, clean water, and medical care. Programs in the developing world concentrate on improving hygiene standards and access to clean water while also providing proper diagnosis of the condition while it can still be treated with antibiotic medication. Once the disease has progressed to the point that the eyelid is deformed, surgery (with an 80%) can be performed by trained nurses. According to Helen Keller International, this cost of this surgery starts at only $40.
How You Can Help
If you are interested in helping to fight trachoma, consider making a donation to or volunteering for an organization that provides eye health care and education services in the developing world. Another option is to work with a charity that helps the developing world gain access to clean water supplies. Whichever option you choose, your help can help save people from horrific and completely unnecessary suffering
Monday, October, 7 2013 by Lainie Petersen
Good News For Visual Dyslexics!
While tinted lenses have been used with some success in helping people with the reading disability, dyslexia, a new study has resulted in US Food and Drug Administration (FDA) approval of a technique in which visual dyslexics read with two different colored lenses. Visual dyslexics have difficulty making sense of letters and words that often appear scrambled, reversed or like they’re moving or even missing from the page, but don’t have problems processing word meanings that also may be a part of dyslexia. The two tint breakthrough in visual dyslexic reading issues is credited to British optician, David Harris.
After successfully treating many of his color blind patients using two different colored lenses, Harris wondered if a similar technique could be used to lessen the frustration many of his visually dyslexic patients experience when reading. Along with Dr. Chaahan Zeidan, Harris developed an in-office study of his dyslexic patients in which each patient wore two different colored lenses.
Of the 434 visually dyslexic patients involved in the trial, over 91% showed an improvement in reading over a six month period. The patients tried out different lens color combinations to find the ones that worked best for them. Harris’ system is patented as “ChromaGen” and eye care professionals must be trained and certified to practice the new technique. The science of why using the two colored lenses seems to help slow the movement of the letters and words for many visually dyslexic children and adults is explained by Harris as a matter of speeding up the timing between the eyes and the brain in what is called the magnocellular system.
Magnocells are exactly what they sound like — super-large cells. They carry information from they eyes to the brain and work in synch with the central nervous system (CNS). As Harris notes, in many dyslexics, there is a deficiency in magnocells. Therefore, Harris’ Chromagen technique strives to speed up the interaction of information between the eyes and the brain by not relying on magnocells in dyslexics.
The American Optometric Association (AOA) supports Harris’ approach of treating visual dyslexics with glasses containing a different colored lens for each eye. It has concluded so far that using two different colored lenses, rather than both the same color, may allow a larger number of visual dyslexics to read longer with less frustration and eye strain symptoms such as headaches and watery or sore eyes.
As the situation stands now, it can be estimated — albeit optimistically so — that one in three visual dyslexia sufferers could experience faster, more efficient reading as a result of Harris’ technique. It should be noted too that “Reading” also refers to visually being able to accurately look at a map, or correctly see the numbers on a clock or in a math book, which is why dyslexia can really affect the daily lives of its sufferers.
Symptoms of Visual Dyslexia When Reading:
- Seeing motion — letters or words may seem to jump or float
- Seeing turned around letters — letters may appear backward or upside-down
- Not seeing all the letters or words on a page — some words may appear as having missing letters
- Seeing overlapping letters — text that looks overlapped or squished may make reading impossible for dyslexics
- Restarting sentences often rather than just occasionally — visual dyslexics may lose their place within a block of text several times or more and end up rereading sentences quite often
If you think you or your child may be dyslexic, speak to your eye doctor or family doctor about getting tested for the reading disorder.
Wednesday, September, 25 2013 by Ryan