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27/Aug/2020

When the eye isn’t getting enough oxygen in the face of common conditions like premature birth or diabetes, it sets in motion a state of frenzied energy production that can ultimately result in blindness, and now scientists have identified new points where they may be able to calm the frenzy and instead enable recovery.

In this high-energy environ, both the endothelial cells that will form new blood vessels in the retina — which could improve oxygen levels — and nearby microglia — a type of macrophage that typically keeps watch over the retina — prefer glycolysis as a means to turn glucose into their fuel.

Medical College of Georgia scientists have shown that in retinal disease, the excessive byproducts of this inefficient fuel production system initiate a crescendo of crosstalk between these two cell types. The talk promotes excessive inflammation and development of the classic mass of leaky, dysfunctional capillaries that can obstruct vision and lead to retinal detachment, says Dr. Yuqing Huo, director of the Vascular Inflammation Program at MCG’s Vascular Biology Center.

The major byproduct of glycolysis is lactate, which also can be used as a fuel, for example, by our muscles in a strenuous workout. Microglia also need some lactate from the endothelial cells. But in disease, the lactate is in definite oversupply, which instead supports this destructive conversation between cells, says Huo, corresponding author of the study in the journal Science Translational Medicine.

“This is a major problem in our country, loss of vision because of compromised oxygen for a variety of reasons,” says Dr. Zhiping Liu, postdoctoral fellow in Huo’s lab and the study’s first author. “We hope this additional insight into how that process destroys vision, will enable us to find better ways to intervene,” Liu says.

In a low-oxygen environ, endothelial cells produce not only a lot of lactate, but also factors that encourage nearby microglia to be more active, and to use glycolysis to get more active, Huo says.

In reality, microglia don’t need the encouragement because they already also seem to prefer this method of energy production. But the extra lactate sent their way does spur them to produce even more energy and consequently even more lactate, Huo says.

The normally supportive immune cells also start overproducing inflammation-promoting factors like cytokines and growth factors that promote blood vessel growth or angiogenesis, which, in a vicious loop, further turns up glycolysis by the endothelial cells, which are now inclined to proliferate excessively.

“The reciprocal interaction between macrophages and (endothelial cells) promotes a feed-forward relationship that strongly augments angiogenesis,” they write.

The destructive bottom line is termed pathological angiogenesis, a major cause of irreversible blindness in people of all ages, the scientists say, with problems like diabetic retinopathy, retinopathy of prematurity and age-related macular degeneration.

“Our eyes clearly do not have sufficient oxygen, and they end up trying to generate more blood vessels through this process called pathological angiogenesis, which is really hard to control,” Huo says.

The excessive sprouting and proliferation of endothelial cells is central to the destruction, and glycolysis is central to their sprouting and proliferation but the exact mechanisms that trigger all the glycolysis and crosstalk between endothelial cells and microglia have been unknown, they write.

“In all these conditions, there is something wrong with the tissue that causes the blood vessels to not behave properly,” says co-author Dr. Ruth B. Caldwell, cell biologist in the Vascular Biology Center. “It’s a bad state,” she says, which they want to help normalize.

As they are finding more about how the conversation goes bad between these two cells, they are seeing new logical points to do that. When they knock out the most potent activator of glycolysis, called Pfkfb3, from the microglia, lactate production clearly goes down and the cells no longer aid production of dysfunctional capillaries. Conversely, expression of both the messenger RNA that enables production of Pfkfb3 and lactate are significantly higher in the cells when oxygen levels are low.

Agents that stop these cells’ over-the-top use of glycolysis could be good therapeutic approaches, they say. Blocking excessive lactate production could be another. Stopping the microglia from lapping up too much lactate also significantly suppresses pathological angiogenesis in their lab studies. Agents that normalize endothelial cell growth might work as well.

While genetic manipulation was used for much of their lab work to date, the scientists are now looking at chemicals that might work at these various points. A problem is that many drugs that suppress glycolysis have numerous unwanted effects, so they are working to more selectively intervene. They note that since the use of glycolysis by macrophages is critical to support of a healthy immune response, localized inhibition should yield the desired response without affecting the immune response.

Current treatments for abnormal blood vessel development and related leaking and swelling include suppressing vascular endothelial growth factor, or anti-VEGF, which, as the name implies, is a key factor in endothelial cell growth, may require ongoing injections in the eye and gets decent results in conditions like diabetic retinopathy. But anti-VEGF therapy really does not facilitate repair, says Caldwell. The scientists have early evidence their intervention strategies may, because they intervene earlier and help normalize the “bad” environment. “We get repair and restoration,” Caldwell says.

Huo and his colleagues are among those who have shown that glycolysis is critical to the sprouting of endothelial cells and that mice lacking Pfkfb3 have impaired angiogenesis.

Endothelial cells, which line all our blood vessels, are one of the first things laid down when we make new blood vessels. In the retina, they start making tiny tunnels that ideally will become well-functioning capillaries, blood vessels so small that a single red blood cell may have to fold up just to get through. These thin-skinned blood vessels are the point where oxygen, fluid and nutrients are provided to body tissue, then blood gets routed back through the venous system to the heart where the process starts anew.

Endothelial cells grow accustomed to glycolysis when they are helping make our bodies in the early, no-oxygen days during development, Huo says.

The usual job of microglia includes keeping an eye out for invaders, like a virus, and keeping connections between nerves, called synapses, trimmed up.

Caldwell and Huo also are faculty members in the James and Jean Culver Vision Discovery Institute at Augusta University and the MCG Department of Cellular Biology and Anatomy.

The research was supported by the American Heart Association and the National Institutes of Health.


14/Aug/2017

Still a Glaring Problem: How a Solar Eclipse Can Fry Your Eyes

From chemical changes to thermal burns, a rundown on exactly what staring at the sun can do

During the Total Solar Eclipse on Aug. 21, millions of people will gaze at the sun to see the moon slowly pass in front of it, blocking out the light. But those who aren’t careful risk doing some nasty damage to their eyes.

You’ve probably been told that it isn’t safe to stare at the sun and that watching a solar eclipse without proper eye protection can make you go blind. That’s because the light from the sun is so intense that it can literally burn your eyeballs — even during a solar eclipse, when part of the sun’s disk is still visible.

Even the tiniest sliver of a crescent sun peeking out from behind the moon emits enough light to scorch your eyes, Ralph Chou, professor emeritus at the School of Optometry & Vision Science at the University of Waterloo in Canada, told Space.com. “I have seen instances where the patient has eventually shown up with crescents burned into the back of the eye, and you can almost tell exactly when they looked.”

HOW EYEBALLS GET “SUNBURNED”

Sunlight damages the eyes by triggering a series of chemical reactions in the retina, the light-sensitive part at the back of the eye. Retinas contain two types of photoreceptors: rods that help you see in the dark and cones that produce color vision.

When intense solar radiation hits the retinas, it can damage and even destroy those cells, in what doctors call a retinal photochemical injury, or solar retinopathy. Whether looking at the sun will cause this type of injury depends on both how long you look without protection and the sun’s position in the sky. Overhead, the sun is brighter and more dangerous to look at than when it is close to the horizon during sunrise or sunset.

“You can think of it in the same way as this: Let’s suppose you decide to really pig out for dinner, and afterwards you’re not feeling very well,” Chou said. “Well, [it’s the] same thing with all the light hitting the light-sensitive receptors at the back of the eye. They get so much of this light energy coming in that they really can’t handle [it].”

In severe cases, this type of photochemical damage may also come with thermal injuries, or literal burns, that destroy the rods and cones in the retina. This can happen to people who repeatedly look at the sun without any protection, those who stare at the sun for an extended time, or even those who glance through a telescope or binoculars without solar filters.

INSTINCT VS. WILLPOWER

Not many people look at the sun long enough to be blinded by the light, Chou said, but the risk is certainly exacerbated during a solar eclipse.

Under normal circumstances, it’s more difficult to look at the sun long enough to incur damage because of something called an aversion reflex. “We learn early on in life we just shouldn’t be looking at something that bright, because it is uncomfortable and we can’t see anything,” Chou said.

“The problem when it comes to looking at a partially eclipsed sun is that you are trying to see something that you know is going on that’s different, and willpower is an amazing thing to override an aversion reflex.”

To make matters worse, it’s possible to look directly at the sun “with a certain degree of comfort” when the sun is partially covered by the moon, Chou said. Even when the sun is almost completely covered, though, the tiny crescent that remains is still bright enough to burn your retinas.

SEEING WITH ECLIPSE BLINDNESS

One thing that makes eclipse blindness particularly dangerous is that a person who looks at the sun long enough to incur damage probably won’t notice any of the effects until the next morning, Chou said.

“Let’s say you take a look at the sun in the afternoon. The cells get overloaded, and they’re actually still able to function for a little while, but overnight while you’re asleep … the cells start to lose their function, and then they even start to die depending on exactly how badly they’ve been affected,” he explained.

People who wake up to discover their vision has become impaired may look in the mirror to find their face is a featureless blur, Chou said, or they may try to read the newspaper only to find that there are no words on the page. While peripheral vision is usually spared, the center of vision is affected the worst. That’s the part of the retina responsible for seeing in high resolution and in color.

“Most people, they don’t see a black spot,” Chou said. “For the most part they have damaged photoreceptors that just aren’t capable of doing more than just registering the presence of light but can’t really build up enough information for them to be able to see clearly.”

AN UNCLEAR PATH TO RECOVERY

Most patients with eclipse blindness are legally blind when they go to see an eye doctor, Chou said. Unfortunately, the prognosis for these patients is nearly impossible to determine.

“You just sort of end up having to wait it out, and that’s the really unfortunate part about it,” Chou said. “The typical person who’s been injured is going to wait six to 12 months before they know what their ultimate status is going to be.”

Statistically, about half of those who are diagnosed with eclipse blindness will recover full vision in six months, he said. The other half either partially recover or are stuck with the problem for the rest of their lives. And when it comes to treatment, there really aren’t any options. “Over the years, certainly ophthalmologists have tried various ways, pharmacological and otherwise, to try and reduce the amount of damage and swelling that is thought to be the main cause for the loss of vision,” Chou said. “For the most part, those types of treatments don’t seem to be effective.”

The only thing doctors can do to help these patients is to treat the case as any other case of visual impairment, Chou said, by teaching the individuals how to get around in the world and function without central vision.

WHEN IT’S SAFE TO LOOK

The only time it’s safe to look at the sun without eclipse glasses or other solar filters is during totality, when the moon is completely blocking out the sun’s rays and only the corona is visible. If you’re planning on watching any kind solar eclipse, whether it’s of the total, annular or partial variety, you absolutely must use proper eye protection if you want to spare your eyes. Otherwise, you’ll risk long-term or even permanent blindness.

But definitely don’t forget to take off your solar eclipse glasses during totality, when the sun is 100 percent covered by the moon. In fact, if you don’t remove your solar filters during totality, you won’t be able to see anything at all.

While official recommendations by NASA and the American Astronomical society say you shouldn’t look directly at the sun when any part of it is showing, experienced eclipse watchers like Chou say it’s safe to remove your eclipse glasses during the 2-3 seconds before and after totality to see the so-called diamond ring effect, or “Baily’s beads.” During this phase of the eclipse, the light of the crescent sun forms points of light on the edge of the disk for just a few seconds.

OTHER SAFETY TIPS

Anyone who plans to observe the eclipse with a telescope, binoculars or cameras should practice using the equipment before the eclipse, Chou said. Don’t wait until the eclipse starts to figure out how to insert and remove the filters from your lenses. For those using eclipse glasses or handheld viewers, make sure to put the filters in front of your eyes before looking up at the sun, not the other way around, Chou said. And children observing a solar eclipse should always be supervised to ensure they’re practicing proper eye safety.

By Hanneke Weitering, SPACE.com on June 21, 2017


11/Aug/2017

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Don’t Miss Eclipse 2017!

Date of  Eclipse: Monday, August 21, 2017

There hasn’t been an event like this in nearly 100 years! A total solar eclipse viewable coast to coast on August 21, 2017. It is NEVER safe to look directly at the sun, even when wearing protection, but check out these materials for safe ways to view the eclipse. While it’s only one day, you should protect your eyes year round from glare, UV rays and harmful blue light.

WHAT IS A TOTAL  SOLAR ECLIPSE?

A total solar eclipse occurs when the moon passes between the Earth and the sun, so it totally or partly obscures the image of the sun. Everyone in the U.S. will be able to see at least a partial eclipse on Monday, August 21, 2017. And those in the path of totality will see the moon completely cover the sun in this exciting celestial event!

 

FAST FACTS

  • The total solar eclipse will begin at 10:15 a.m.  PDT  near Lincoln City,  OR 7:15 a.m. locally.
  • Totality ends at 2:48 p.m. EDT near Charleston, SC Totality will last for about two minutes and 40 seconds.
  • The path of totality is about 70 miles wide and extends from Oregon to South Carolina.
  • A total solar eclipse can only be observed when the moon is approximately 400 times closer to the earth than the sun.
  • The last time the contiguous U.S. saw a total eclipse was in 1979, although there is only one other coast-to-coast eclipse to compare this upcoming eclipse to, and that happened nearly 100  years ago on June 8, 1918.
  • It is predicted that between 1 and 7.4  million people may commute into the path, causing heavy traffic delays that day.
  • The next total solar eclipse in North America (after August 21, 2017) will occur on April  8, 2024

ECLIPSE EYE SAFETY  

  • It is NEVER safe to look directly at the sun, even when wearing eyeglasses or sunglasses.
  • Don’t be fooled by the eclipse – it’s still not safe to look at the sun!  The ONLY exception is if you’re in the path of totality and the moon completely covers the sun and there is no longer any direct sunlight coming toward you. That will not be the case in Michigan.
  • If you’re in the path of totality, it is still very important to be vigilant to protect your eyes before and after totality. The total eclipse only lasts a minute or two in some locations.
  • It’s important to check local information on timing of when the total eclipse will begin and end in your area. Check out  NASA’s Website to get started

Solar Retinopathy

  • Solar retinopathy occurs when bright light from the sun floods the retina and is caused by staring at the sun for too long. Most people can’t stand to look at the sun long enough to cause damage, but the eclipse (partial or total) makes it more comfortable to stare at the sun.
  • The retina is home to the light-sensing cells that make vision possible. When they’re over-stimulated by sunlight, they release a flood of communication chemicals that can damage the retina. This damage is often painless, so people don’t realize they’re damaging their vision.
  • Sunglasses block the harmful UV rays, but not harmful infrared or intense visible light that can cause solar retinopathy from staring at direct sunlight. Sunglasses are never safe for looking directly at the sun.
  • Photokeratitis (Snow Blindness) is a painful eye condition that happens when your eyes are exposed to excessive UV rays. It is like having sunburned eyes. This condition can be prevented by wearing eye protection that block UV radiation.

HOW TO SAFELY VIEW THE ECLIPSE

The only safe way to look directly at the sun is through special glasses that have met the ISO 12312-2 international standard. Only four manufacturers have met this standard: Rainbow Symphony, American Paper Optics, Thousand Oaks Optical and TSE 17.

Solar eclipse glasses have met the following standards for becoming ISO certified:

  • 100% harmful UV
  • 100% harmful infrared
  • 99.99% of intense visible light

An alternative method for safe viewing of the partially eclipsed sun is pinhole projection. Visit  https://eclipse2017.nasa.gov/safety for directions on this indirect viewing method.

YEAR-ROUND EYE SAFETY

The eclipse is only one day, but eye safety should be practiced year-round!

Sunlight consists of two types of harmful rays: UVA rays and UVB rays. UVA rays penetrate deep into the skin  – leading to signs of premature aging such as wrinkling or age spots. UVB rays are the sun’s burning rays and are the primary cause of sunburn.

Excessive UV exposure is dangerous for eyes as well  as your skin.  It can lead to a number of serious, sight-stealing diseases such as cataracts and macular degeneration – making ongoing protection from UV rays a must.

You don’t have to avoid enjoying the sun – but you should wear lenses that help protect your eyes from glare, harmful UV rays, and harmful blue light.

Transitions lenses block 100 percent of UVA and UVB rays. Transitions lenses help protect against harmful blue light emitted by the sun and electronic devices and screens to reduce eye strain and fatigue.[/vc_column_text][/vc_column][/vc_row]


11/Feb/2017

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Mag-iskedyul ng appointment upang subukan Clariti lenses. 1-Day disposable lenses para sa mga tao na may astigmatism o na gusto ng isang multifocal disenyo sa isang pang araw-araw disposable lens. Ngayon ay maaari kang magkaroon ng sa kaginhawahan ng isang disposable lens kahit na wala kang astigmatism o kailangan ng isang multifocal. 517-393-2660

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24/Jun/2016

video-gamesWhether it’s on your phone, tablet, PC, or television, chances are you’ve played some kind of video game recently. From Candy Crush to Angry Birds to Minecraft, video gaming long ago entered – and conquered – the mainstream.

But what does that mean for your eye health? Are video games actually bad for your eyes, or is that just an old wives’ tale?

Computer Vision Syndrome

It’s true that prolonged video gaming sessions can have short term negative effects on your eye health. This is due to what the American Optometric Association calls computer vision syndrome, or digital eye strain. Excessive use of digital devices like tablets and computers can lead to eye strain, headaches, dry eye, and fatigue in your shoulders and neck.

This is caused by a number of factors, including glare and low screen contrast forcing your eyes to work harder than usual. Since video games require constant use of screens, and often by design encourage players to continue playing for extensive periods of time, you may experience computer vision syndrome more often when gaming than during normal use of your devices.

To help prevent eye strain, make sure you have proper lighting to reduce glare, take frequent breaks to rest your eyes and blink often. You might miss that power up, but your eyes will thank you for it.

What About 3D?

The rise of 3D gaming has brought with it a new set of concerns, which were exacerbated when Nintendo issued a warning that small children should not be allowed to use the 3D mode on Nintendo’s portable 3DS game system. However, while research is still ongoing, the AOA says it may be beneficial for children to play 3D games. That’s because playing 3D video games can actually help identify early warning signs of ocular disorders; difficulty perceiving 3D game images can be a sign of eye problems that might otherwise go unnoticed and undiagnosed.

How Gaming Helps Your Eyes

But that’s not the only way playing video games might actually help your eyesight. According to the National Institute of Health, studies prove that playing action video games enhances key aspects of visual processing, including spatial resolution – meaning gamers can actually see things easier and clearer. And some doctors have even successfully used video game therapy to treat and correct amblyopia, better known as lazy eye.

So go ahead and play video games. Just remember to do it in moderation. Because when it comes to your eyes, sometimes there really can be too much of a good thing.


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