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

20 Facts About Eye Color and Blinking

7/15/14

Eye color is one of the first things a person notices about another person, but blinking is so automatic we rarely think about it. Here are some intriguing facts about eye color and blinking:

1. The world’s most common eye color is brown.

2. Brown eyes are actually blue underneath.

3. Melanin affects the color of your eyes so brown eyes have more melanin than blue eyes.
Person with different colored eyes - eye color and blinking
4. Heterochromia is when you are born with two differently colored eyes.

5. Blue-eyed people share a common ancestor with every other blue-eyed person in the world.

6. We blink more when we talk.

7. It is impossible to sneeze with your eye open.

8. The average person blinks 12 times per minute or about 10,000 blinks per day.

9. The eye is the fastest muscle in the body – in the blink of an eye. They are also the most active muscles in the body.

10. A blink usually lasts 100 to 150 milliseconds making it possible to blink five times in a second.

11. You blink less when you’re reading.

12. Infants blink 10 times less than adults.

13. One blink isn’t always the same as the next.

14. Our eyes close automatically to protect us from perceived dangers.

15. The older we are the less tears we produce.

16. Tears are made of three main components – fat, mucous and water. This is so tears won’t evaporate.

17. Your nose gets runny when you cry as the tears drain into your nasal passages.

18. You blink on average 4,200,000 times a year.

19. Tears kill bacteria because they contain lysozyme, a fluid that can kill 90 to 95 percent of all bacteria.

20. A newborn baby will cry, but not produce any tears. Babies do not produce tears until they are around six weeks old.

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

End of the Day Syndrome

4/2/14

“Dr. S., my eyes are red and burning at the end of my work day.”

“Patient, what sort of work do you do?  Tell me something about your work conditions.”

“I am a computer graphics artist.  I sit and stare at my twenty-seven inch HD screen for hours on end gently adjusting the composition of each pixel.  My studio is air-conditioned but not humidified, so after some hours of work, I feel dry as a bone.”

“One more question…can you cry tears?  Say, when you peel and slice an onion?”

Rule of 20 - blinking

The need to blink

Blinking is a complex function of the eyelids that when completed results in a clean, refreshed, re-wetted corneal surface.  The tears that are washed across the outside of the eye with each blink bring oxygen and other nutrients to the outer cell layer aiding in the rebuilding and revitalizing of the surface tissue.

Blinking is characterized by a full sweep of the upper lid over the eye to meet the lower lid.  The completion of this motion is performed gently without squeezing.  And, to be effective full eye closure needs to be repeated fairly often.  Blink rates vary according to investigators but most sources report an average of between six and ten full blinks per minute under normal viewing circumstances.

The anti-blink problem of our generation

In olden times – say the years between 1750-1950 – the most aggravating problem to the ocular surface was a good book or intense study.  The reader would concern himself with the text at hand and slowly his eyes would dry until a “rest break” was necessary.

Environmental or vocational changes to our lifestyle over the generations have promoted reduced blink rates.  Most recently in this negatively developmental progression is the effect of the television screen, the CRT, the LED screen, the handheld and pocket computer on the blink rate.  It appears that as attention level increases, blinking suffers.  First the eyes close less, then incompletely, and finally rarely only when surface dryness drives the individual to desperate measures.  He must blink or (so he feels) his eyes will pop out of their sockets.

Adding insult to injury increasingly over the decades is air conditioning – both heating and cooling – when not humidified.  Staring at console screens in dry environs speeds the desiccation of the cornea and results in discomfort.

The surface of the eye is a biological system.  Living systems require some degree of moisture.  If the cells of the eye – or any biological surface — are permitted to dry out, they will die.  Dead corneal cells fall off the cornea and float in the tears on the surface of the eye until washed away with a blink.  Until the surface is cleaned the dead cells are considered by the eye to be foreign bodies with the consequent irritation and induced reflex to blink.

When cells die and fall off, the underlying nerve endings send pain signals to the nervous system.  The sensation can be felt as pain, burning, or mere irritation or itching depending upon the severity of cell loss.

How to handle environmentally induced dry eye

After the ocular surface is dry most treatments will seem to make matters worse:  to cause burning and stinging, perhaps, even more than the dry eye itself.  Any tear substitute, any amount of blinking will be irritating at first. But, that is really all that can be done at this stage:  wetting and blinking.

Prevention

As in many conditions, the best treatment, in fact a cure, for recurrent environmentally induced dry eye is prevention.  For the eye that has a naturally flowing tear supply, the act of blinking is the surest prevention to stinging and burning after a day’s work at the computer.  Additionally, many sources recommend using the ‘rule of 20’:  after each twenty minutes of work, look up from the text or away from the screen; blink and refocus on the page twenty times.  This repetitive exercise simultaneously re-wets the eye and relaxes the focusing mechanism of the eye.

The result is relaxed and comfortable eyes that can continue to provide important and high quality information for longer hours of work.

Bezalel-SchendowichBezalel Schendowich, OD
Chairperson and Education Coordinator, JOS
Fellow, IACLE
Member, Medical Advisory Board NKCF
Sha’are Zedek Medical Center, Jerusalem, ISRAEL

Help for Computer Users

Working long hours in front of the computer requires a fairly unchanging body, head and eye position which can cause discomfort.  Correct working position, periodic stretch breaks, frequent eye blinking, artificial tears for lubrication are all very important.  However, it’s not always easy to remember this when you are engrossed in work. Here are a few fun, free and easy-to-install “break reminders” to help:

WorkSafe Sam - break reminder
WorkSafe Sam

WorkSafe Sam is a desktop tool that provides stretching tips to help reduce eye and muscle strain for office workers (clicking on this link will open a file on your computer because this is a zip file).

Workrave is break reminder program that alerts you to take “micro-pauses” and stretch breaks.

Take Your Break is another break reminder designed to prevent or minimize repetitive strain injury, computer eye strain and other computer related health problems.  It has a friendly interface and a tray icon status indicator.  It runs quietly in the background, monitoring your activity and reminding you to take regular breaks.

And remember to blink.  Blinking cleans the ocular surface of debris and flushes fresh tears over the ocular surface. Each blink brings nutrients to the eye surface structures keeping them healthy. The flow of tears is responsible for wetting the lower third of the cornea. This is very important in KC, since this area is generally below the bulge of the cone and in many cases irritated by wobbly RGP lenses.  Maybe your job requires hours of work at a computer. Maybe you like to spend your free time surfing the internet. Whatever the reason, your body is probably feeling the effects of spending too much time staring at a computer monitor, which could result in Computer Vision Syndrome (CVS).  The most common symptoms are: eye strain, dry or irritated eyes,redness in eyes,difficulty in refocusing eye,neck pain,double vision,blurred vision, fatigue, and headaches.

Please join us on Thursday when Dr. Bezalel Schendowich will be providing a detailed insight into the importance of blinking, going beyond computer usage.

CathyW headshotCathy Warren, RN
Executive Director
National Keratoconus Foundation