The Way Eyes Work

9/16/14

Eyes are an amazing part of your body and not just because of what they do helping you see. The are also fascinating be because of the way eyes work. Here are 20 facts about how your eyes function.
Colorful eye - the way eyes work

      1. The pupil dilates 45% when looking at something pleasant.

2. An eye’s lens is quicker than a camera’s.

3. Each eye contains 107 million cells that are light sensitive.

4. The light sensitivity of rod cells is about 1,000 times that of cone cells.

5. While it takes some time for most parts of your body to warm up their full potential, your eyes are always active.

6. Each of your eyes has a small blind spot in the back of the retina where the optic nerve attaches. You don’t notice the hole in your vision because your eyes work together to fill in each other’s blind spot.

7. The human eye can only make smooth motions if it’s actually tracking a moving object.

8. People generally read 25% slower from a computer screen compared to paper.

9. The eyes can process about 36,000 bits of information each hour.

10. Your eye will focus on about 50 things per second.

11. Eyes use about 65% or your brainpower – more than any other part of your body.

12. Images that are sent to your brain are actually backwards and upside down.

13. Your brain has to interpret the signals your eyes send in order for you to see. Optical illusions occur when your eyes and brain can’t agree.optical illusion - the way eyes work

14. Your pupils can change in diameter from 1 to 8 millimeters, about the size of a chickpea.

15. You see with your brain, not your eyes. Our eyes function like a camera, capturing light and sending data back to the brain.

16. We have two eyeballs in order to give us depth perception – comparing two images allows us to determine how far away an object is from us.

17. It is reported that men can read fine print better than women can.

18. The muscles in the eye are 100 times stronger than they need to be to perform their function.

19. Everyone has one eye that is slightly stronger than the other.

20. In the right conditions and lighting, humans can see the light of a candle from 14 miles away.

Susan DeRemerSusan DeRemer. CFRE
Vice President of Development
Discovery Eye Foundation

Ways to Reduce the Harmful Effects of Sun Glare

During the height of summer sunshine (and heat!), it’s helpful to discuss the importance of eye protection, including ways to reduce the harmful effects of sun glare.

Fundamentally, we need light to see. Approximately 80% of all information we take in is received through the sense of sight. However, too much light – and the wrong kind of light – can create glare, which can affect our ability to take in information, analyze it, and make sense of our surroundings.

Facts about Sunlight

Every type of light has advantages and disadvantages, and sunlight is no exception:

Advantages:

• Sunlight is the best, most natural light for most daily living needs.
• Sunlight is continuous and full-spectrum: the sun’s energy at all wavelengths is equal and it contains all wavelengths of light (explained below).

Disadvantages:

• It is difficult to control the brightness and intensity of sunlight.
• Sunlight can create glare, which can be problematic for many people who have low vision.
• Sunlight is not always consistent or reliable, such as on cloudy or overcast days.

Visible Light and Light Rays

An important factor to consider is the measurement of visible light and light rays, beginning with the definition of a nanometer:

• A nanometer (nm) is the measurement of a wavelength of light.
• A wavelength is the distance between two successive wave crests or troughs:

Wavelength - glare

• A nanometer = 1/1,000,000,000 of a meter, or one-billionth of a meter. It’s very small!

The human visual system is not uniformly sensitive to all light rays. Visible light rays range from 400 nm (shorter, higher-energy wavelengths) ? 700 nm (longer, lower-energy wavelengths).
Visible Light Spectrum - glare
The visible light spectrum occupies just one portion of the electromagnetic spectrum, however:

• Below blue-violet (400 nm and below), is ultraviolet (UV) light.
• Above red (700 nm and above), is infrared (IR) light.
• Neither UV nor IR light is visible to the human eye.

Ultraviolet Light and Blue Light

Ultraviolet (UV) light has several components:

• Ultraviolet A, or UVA (320 nm to 400 nm): UVA rays age us.
• Ultraviolet B, or UVB (290 nm to 320 nm): UVB rays burn us.
• Ultraviolet C, or UVC (100 nm to 290 nm): UVC rays are filtered by the atmosphere before they reach us.

Blue light rays (400 nm to 470 nm) are adjacent to the invisible band of UV light rays:

• There is increasing evidence that blue light is harmful to the eye and can amplify damage to retinal cells.
• You can read more about the effects of blue light at Artificial Lighting and the Blue Light Hazard at Prevent Blindness.

A new study from the National Eye Institute confirms that sunlight can increase the risk of cataracts and establishes a link between ultraviolet (UV) rays and oxidative stress, the harmful chemical reactions that occur when cells consume oxygen and other fuels to produce energy.

Sunlight and Glare

Glare is light that does not help to create a clear image on the retina; instead, it has an adverse effect on visual comfort and clarity. Glare is sunlight that hinders instead of helps. There are two primary types of glare.

Disability glare

• Disability (or veiling) glare is sunlight that interferes with the clarity of a visual image and reduces contrast.
• Sources of disability glare include reflective surfaces (chrome fixtures, computer monitors, highly polished floors) and windows that are not covered with curtains or shades.

Discomfort glare

• Discomfort glare is sunlight that causes headaches and eye pain. It does not interfere with the clarity of a visual image.
• Sources of disability glare include the morning and evening positions of the sun; snow and ice; and large bodies of water, (including swimming pools).

Controlling Glare

You can protect your eyes from harmful sunlight and minimize the effects of glare by using a brimmed hat or visor in combination with absorptive lenses.

• Absorptive lenses are sunglasses that filter out ultraviolet and infrared light, reduce glare, and increase contrast. They are recommended for people who have low vision and are also helpful for people with regular vision.
• Lens colors include yellow, pink, plum, amber, green, gray, and brown. Ultra-dark lenses are not the only choice for sun protection.
• Lens tints in yellow or amber are recommended for controlling blue light.
NoIR Medical Technologies: NoIR (No Infra-Red) filters absorb UVA/UVB radiation and also offer IR light protection.
Solar Shields: Solar Shields absorb UVA/UVB radiation and are available in prescription lenses.
• You can find absorptive lenses at a specialty products store, an “aids and appliances store” at an agency for the visually impaired, or a low vision practice in your area. Before you purchase, it’s always best to try on several different tints and styles to determine what works best for you.

More Recommendations

• Always wear sunglasses outside, and make sure they conform to current UVA/UVB standards.
• Be aware that UV and blue light are still present even when it is cloudy or overcast.
• Make sure that children and older family members are always protected with UVA/UVB-blocking sunglasses and brimmed hats or visors.

Maureen Duffy-editedMaureen A. Duffy, CVRT
Social Media Specialist, visionaware.org
Associate Editor, Journal of Visual Impairment & Blindness
Adjunct Faculty, Salus University/College of Education and Rehabilitation

My New Vision With A Telescope Implant

6/19/14

What it’s like to see with the CentraSight telescope implant

Like many people, I’ve set goals in my life, both professionally and personally and like being an active and engaged member of my community and my country. I love to teach: I taught history, geography and special education for years in Banning, California and now live in Moreno Valley, California, with my wife of 32 years, Kay. I love my country: I’m a proud veteran of both the Army Reserve and the Navy. And I love an open road. My wife and I traveled the country visiting historical monuments in our 32-foot RV. I guess I’ve got what you’d call a real zest for life. But, over the past twenty years, all the things I enjoyed doing in my life, even the simple day-to-day activities, started to decline because I was slowly losing my vision due to age-related macular degeneration. For example, six years ago, my wife took over all the driving because I couldn’t see well enough to drive safely.

Roy Kennedy - telescope implant
Roy Kennedy

That was a real turning point for me. My wife had to help me so much because I just couldn’t see. I needed help shopping because I couldn’t read labels. I started to avoid social situations, like visiting with friends because I was embarrassed that I couldn’t recognize faces any longer. As you can imagine it was heartbreaking for both me and my wife.

But then my doctor told me about a treatment I wasn’t yet aware of called the telescope implant. The device is very small (smaller than a pea!), and it is implanted in one eye to restore vision. My doctor explained that it works like a real telescope in that it magnifies images, which reduces the effect of the blind spot on my straight-ahead vision. The other eye does not get an implant because you need to keep some peripheral vision to help with orientation and balance. This sounded like science fiction! But I wanted to see if it could help me and I decided to give it a try.

I worked with a great team of specialists, who were part of a treatment program called CentraSight. My retina doctor, cornea surgeon, low vision optometrist and a low vision occupational therapist all counseled me about what to expect from the outpatient procedure, particularly afterwards. For example, I learned there was a significant amount of occupational therapy required to adjust and become proficient at using my new vision. I also was warned that my sight would not be like it was in my youth. I wouldn’t be able to do everything I used to nor would I be able to see, differently, the minute I opened my eyes.

I had my surgery in early 2013. The cost for the telescope implant and visits associated with the treatment program were covered by Medicare, which was very helpful. Thinking back, I was nervous on surgery day, but afterwards, I was told by my occupational therapist that I was one of the quickest to recover from surgery. I give lots of credit to my OT folks as well as my wife who helped me with the exercises at home. The most amazing part is being able to see my wife’s face again for the first time in six years! I’ve regained the ability to do many everyday tasks, like reading, working on my computer and watching old Westerns on TV. My wife and I are even back to traveling the open road in our RV (which she drives)!

I would recommend people learn more about the telescope implant to see if it might help them, the way it helped me. There are CentraSight teams across the country. When you call 1-877-99-SIGHT or visit www.CentraSight.com a trained CentraSight information Specialist will point you to the team closest to your home and can even help schedule the appointments for you. The telescope isn’t for anyone, but it can make such a difference in your life. It certainly did in mine.

Roy Kennedy - telescope implantRoy Kennedy

What Are Floaters? | Causes and Treatment

6/12/14

Floaters can be anything seen in your vision that moves “to and fro” with your eye movement. The movement is not stationary compared to a blind spot which is fixed or stationary in your field of vision.

Example of floaters
Example of floaters
The key is that the position changes with eye movement. Size, shape, color, etc. don’t matter. Anything that moves in your vision is called a floater.

Remember, if you experience new floaters; please see an eye doctor for an examination.

Here are some common causes of floaters:

  • Posterior Vitreous Detachment (PVD)
  • Retinal Tears
  • Blood (Vitreous Hemorrhage) can be caused by;
  • Advanced Diabetic Retinopathy
  • Retinal Tears
  • Retinal Vascular Occlusions
  • Inflammation or Infection
  • Asteroid Hyalosis

Posterior Vitreous Detachment
A posterior vitreous detachment (PVD) is a common cause of floaters. A PVD occurs when the vitreous separates from the retinal surface. This is a normal event and will eventually occur in everyone. Retinal tears are more likely to occur right after a PVD has started.

The vitreous is usually a clear watery gel. As we age, enough of the proteins in the vitreous liquefy and degenerate. Eventually, there is a physical separation of the vitreous from the retina due to this liquefaction.

“Floaters” can develop due to opacities/haziness due to the aging gel which is no longer absolutely clear due to changes in the optical properties of the gel or the interface between the vitreous and water inside the eye.

Tears in the Retina
Retinal tears can cause floaters by either causing a small vitreous hemorrhage, or by dislodging cells into the vitreous which are normally located underneath the retina.

Vitreous Hemorrhage
Blood in the vitreous can also cause floaters. A so-called vitreous hemorrhage may result from either a retinal tear or advanced diabetic retinopathy. Occasionally, retinal vascular occlusions can also lead to bleeding in the vitreous.

Blood in the eye often absorbs, but only your doctor can determine the exact nature of the floaters and if they are associated with a retinal tear. It’s impossible for you to tell the cause of floaters without a proper dilated eye exam.

Inflammation
Certain types of inflammation or infection can cause significant floaters. Actually, these are white cells which migrate to the retina and vitreous and can be seen a floaters.

Asteroid Hyalosis
This is a common entity where lots of fine white opacities are suspended in the vitreous. In most cases, these are not noticed by the patient. Sometimes, however, the so-called asteroid bodies are so dense they prevent good examination of the retina. Other times, especially after a PVD, the asteroid bodies are noticed and patients may complain of floaters.

New Floaters: Evaluation
All new floaters must be examined by your eye doctor within 24-72 hours after occurring. Even if the floaters disappear in that time frame, you should be examined to look for a possible tear in the retina.

Again, you, the patient, can NOT tell the cause of the floaters or if you’ve sustained a retinal tears. Retinal tears can cause a retinal detachment – a potentially blinding problem.

Treatment of Floaters
There are no medicines or eye drops to treat floaters. Most doctors advise simply putting up with the floaters.

For patients who have chronic problems with floaters, I recommend a vitrectomy. A vitrectomy is an eye operation, performed by a retinal specialist. The operation is comparable to a cataract operation in terms of safety and possible complications.

There are a handful of doctors who perform Yag laser to break up floaters.

Randall E. Wong MDRandall V. Wong, MD
Retina Specialist
Fairfax, Virginia

Living With the Argus II

5/27/14

Last year Discovery Eye Foundation spoke to Dean Lloyd, who lost his sight to retinitis pigmentosa (RP), about his experiences with the Argus II “bionic eye.”  After FDA approval, when the article came out, more people across the country have been fitted with the Argus II, using its 60-electrode system to help them regain some part of their vision.  Researchers continue to try and improve upon the “bionic eye” such as this research for a 24-electrode version from Australia.  Here is that article:

Dean Lloyd wearing the ArRgus II
Dean Lloyd wearing the Argus II

As one of only 30 people in the world with a “bionic retina,” Dean Lloyd has gained a bit of notoriety of late. The Argus II Retinal Prosthesis System received US market approval from the FDA on Feb. 14, and Lloyd has been part of the clinical trial since he was implanted with the device in 2007.

 

Lloyd’s vision difficulties began in the early 1960s, while he was in medical school at the University of South Dakota. He realized he wasn’t seeing the same thing as his classmates when looking through a high-powered microscope. He was misdiagnosed with Usher Syndrome, a rare genetic disorder that can result in deafness, blindness and dementia. While he was later correctly diagnosed with the less-dire x-linked retinitis pigmentosa (RP), he was asked to leave medical school due to his vision impairment.

“I had a moment of self-pity, then I needed to do some introspection to figure out how to find my future,” he says. “I decided I can’t give up on life. My brain works well … If your brain works, it can solve a lot of difficult problems. I realized I would survive.”

Seeing Stars

Armed with a BS in chemistry and an MS in bio-chemistry, Lloyd became a research chemist, then a software engineer. At the time, RP was having only one real effect on his life: reduced night vision. “I always thought people were seeing more stars than I saw. They’d see the big dipper and little dipper, and I didn’t see any dippers,” he recalls. Other than being extra-careful when driving at night, Lloyd’s daily life remained relatively unaffected until 1974, when he developed cataracts at age 34.

Lloyd’s wife decided she did not want to deal with any impact the disability would have on his ability to support their family. “She left and got the best divorce lawyers,” he says. “The court thought, because I was visually impaired, I wouldn’t be able to take care of my children. There were a lot of issues around disability and parent-ability in the mid- to late 70s.” Because of his vision loss, Lloyd lost custody of his two children. Believing disabled people were not treated fairly and seeing “the power of the court over people in their everyday lives,” Lloyd decided to go to law school. He passed the bar in 1982, “as a disabled person in a closed room,” and has been practicing law for more than 30 years.

He underwent two cataract surgeries, and a pair of convex lenses he wore on his nose was used in place of the actual lenses that had been removed from his eye. He had no difficulty with daytime mobility for nearly 14 years. But in 1989, he lost image formation. “I got an edema within the macula area, which didn’t go away,” he says. “I lost the ability to form images — that’s the point when you lose the opportunity for safe mobility.”

Lloyd had already been practicing law for seven years, and RP didn’t stop him. “I had quite a bit of experience in the courtroom,” he says. “I am fortunate to have a good memory, and I memorized everything I used there. I usually work with a junior or associate attorney; I do all the talking, and they handle all the documents and things. It didn’t change my career.”

A cane helped with his mobility, and for a few years, he says, “A doctor at Stanford pulled me in for some non-FDA experiments, because he knew I was a four-eyed guinea pig and was willing to try anything that might help RP.” None worked.

Lloyd was involved with several vision-related organizations and followed the progression of research and experiments to see if any might benefit him. In early 2007, he attended a Foundation Fighting Blindness meeting run by his daughter, who has “the recessive expression for RP.” The speaker that day was Dr. Jacque Duncan of UCSF, who interviewed all the attendees. Soon after, she contacted Lloyd to ask him to participate in the Argus II clinical trial.

He agreed immediately: “I figured if I lost the eye, I wouldn’t lose much, because it didn’t work anyway.”

The Bionic Retina

The Argus II Retinal Prosthesis System consists of three parts: an implant, glasses and a belt-worn video-processing unit (VPU).

The implant is surgically implanted in and on the eye. It includes an antenna, an electronics case and an electrode array. The glasses contain a tiny video camera that captures a scene. The video is sent to the VPU, where it is processed and turned into electrical stimulations — instructions — that are sent back to the glasses through a cable. The glasses then transmit the instructions wirelessly to the implant antenna, which sends signals to the electrode array, which emits electric pulses. These pulses bypass damaged photoreceptors (RP damages photoreceptors and impedes image formation) and stimulate the retina’s remaining healthy cells, which transmit the information along the optic nerve to the brain. If all goes well, it creates the perception of patterns of light, which wearers can learn to interpret as visual patterns.

Chicken Dance

Duncan, working with another UCSF doctor, had Dr. Eugene de Juan put the Argus II implant in Lloyd’s right eye on July 17, 2007. A few weeks after an initial infection subsided, he did his first test walk with the device outside, looking for boundaries and points of light.

“Human eyes naturally move around, using a rapid ‘saccade’ movement,” Lloyd explains. “With the device, you have to physically move your head back and forth to find boundaries — like a chicken, which does not have moving eyes. They move their heads back and forth to see things. During my walk, the field-service worker would say, ‘Dean, Dean, more chicken movement.’”

After about a year and a half spending a half-day a week at UCSF for the trial, he had a second operation. “The device didn’t satisfy me,” he says. “I went through all that, and all I could see was a little point of light. Only nine of 60 electrodes were working. I said, ‘This isn’t going to cut it for me, because I want to see images.’ They reset the implant closer to the retinal tissue, and that dramatically improved the device.”

Lloyd conducted his own tests of the device at home. “I was one of first to use it to sort socks. I wear black socks to court and white socks to the gym. I went home after the implant and wanted to see how I could make it practically useful. So I went to my socks and found the device worked. I always got the white ones right!”

While he is generally pleased with the Argus II, the most he will say is, “It shows potential.”

“The improvement was not very good at first. I wasn’t very impressed. There was a rumor going around that the implant restored vision. My vision wasn’t restored at all; I was not ascertaining images,” he says. “I do see boundaries. I can create an image. I know what a car should look like. I know what a tree should look like. I know what houses should look like. I know what objects should look like, and I have those images as memories in my brain. With this device, you can start to create an image by going back and forth, checking the boundaries and borders. We don’t have natural saccade movement helping us. The camera is right above my nose in a fixed position. It doesn’t move. You can create an image, but it takes a lot of time and a lot of work. It’s a labor-intensive task, and you have to have a good memory.”

The Argus II was approved by the FDA in February, and Lloyd is actively involved with Second Sight, the company that makes the device: “I am helping with new improvements,” he says. “I want this device to work. I didn’t go through all this for nothing.” He hopes an improved version will be approved this coming September, and he doesn’t rule out getting a new implant in the future if the improvements are worth it. To be honest, he says, “I find it annoying to move like a chicken.”

Susan DeRemerSusan DeRemer, CFRE
Vice President of Development
Discovery Eye Foundation