Pupils Respond To More Than Light

Everyone knows that your pupils will change size according to the amount of light you are experiencing. With more light, the pupil constricts and becomes smaller. Less light and your pupil dilates, letting more light into the back of the eye. It is the muscles of the iris working with your autonomic nervous system (ANS) to adjust the iris so the right amount of light enters the eye – like the aperture of a camera.

The iris is made up of two types of muscle:

Sphincter muscles that are like concentric rings that constrict the pupil to as small as two millimeters across
Dilator muscles that are laid out like the spokes of a bicycle wheel and can expand the pupil up to eight millimeters across

But the ANS is not only concerned with light reflex, it also reveals emotional and mental responses. The sympathetic branch of the ANS responds to a person being under stress, triggering the “fight or flight” response, which will cause the pupil to dilate. On the other hand, the parasympathetic branch known for “rest and digest” will cause pupil constriction. At any given time, your pupil is balancing between both the light and emotional reactions.

Here are some of examples of mental responses:

Princeton University psychologist Daniel Kahneman demonstrated that pupil size increases in proportion to the difficulty of the task being performed. Calculating 8 x 21 will cause your pupil to dilate slightly, however calculating 8 x 47 will cause them to dilate even more. Whatever the problem, they will remain dilated until you come up with the answer or give up.

Even memory recall creates a pupil response. When subjects were instructed to remember and recite a series of seven digits, their pupils would grow steadily as they learned each number, but reduce as steadily when they recited back each of the numbers.

Wolfgang Einhauser-Treyer, a neurophysicist at Philipps University Marburg in Germany, found that “pupil dilation can betray an individual’s decision before it is openly revealed.” He asked people to push a button at any point during a span of 10 seconds. Dilation began about one second before they pressed the button and continued to peak one to two seconds after the push.

This study of pupil size is known as pupillometry and is used to investigate a wide range of psychological phenomena including sleepiness, introversion, sexual interest, racial bias, schizophrenia, moral judgment, autism and depression. Kahneman said he has “never done any work in which the measurement is so precise.” And while “nobody really knows for sure what these changes do,” according Stuart Steinhauer, director of Biometric Research Lab at the University of Pittsburgh, pupillometry is a valuable tool for psychological research.

So the next time you look into someone’s eyes, know that you have the potential to see more than just their eye color. You might have a clue as to what is going on in their mind.

2/3/15

Susan DeRemer, CFRE
Vice President of Development
Discovery Eye Foundation

Uveitis Explained

12/18/14

Uveitis is defined as inflammation of the uveal tissue. The uvea includes the iris, ciliary body, and the choroid of the eye. The iris is located in the anterior compartment of the eye and acts like the aperture of the camera, precisely filtering the amount of light entering the eye. The ciliary body, which is attached posteriorly to the iris, is involved in both the production of the aqueous fluid in the eye as well as the accommodation of the lens apparatus. The choroid is a dense layer of blood vessels that sits underneath the retina on the back wall of the eye, helping to nourish and remove metabolic waste products from the retina. Inflammation of any of these structures will consequently cause disruption of the visual pathway and over the long term can cause permanent visual loss. In fact, uveitis is the third most common cause of preventable blindness in the developed world.

Symptoms of uveitis include blurry vision, ocular pain, photophobia, redness, and floaters. These can be acute in nature, lasting a few days to weeks, and in some cases can be chronic, lasting weeks or months. Anyone with any of these symptoms should see their eye care provider as soon as possible, as faster treatment of uveitis has shown to result in better long term visual outcomes.

Uveitis can affect virtually any part of the eye, from front to back. Anterior uveitis or iridocyclitis is confined to the iris, ciliary body, anterior chamber, and cornea. Inflammation affecting the vitreous is termed intermediate uveitis, or pars planitis, and any inflammation affecting only the retina or choroid is termed posterior uveitis. The term panuveitis may be used when multiple layers of the eye are affected.

There are many possible causes of uveitis, including infection, inflammatory diseases, autoimmune diseases, and trauma. However, the majority of cases of uveitis, approximately half, are considered idiopathic, where no etiology is ever found. Trauma is the next most common cause of intraocular inflammation, accounting for approximately 20% of all cases. The remaining cases are secondary to a systemic disorder or localized ocular condition. Systemic etiologies can include inflammatory disorders such as sarcoidosis, infections such as tuberculosis and syphilis, as well as autoimmune diseases such as rheumatoid arthritis and lupus.

Treatment of uveitis is aimed at both blunting the intraocular inflammation as well as addressing any underlying systemic etiology. The most common treatment is the use of corticosteroids. These can be taken orally, or used topically as eye drops. In some cases, corticosteroids can be injected in or near the eye as well. If the uveitis is caused by an infection, such as tuberculosis or syphilis, the patient is also given antibiotics. Systemic corticosteroids can have major side effects when taken chronically, such as weight gain, hair loss, osteoporosis, hypertension, secondary diabetes, psychosis, and reduced growth in children. Because of these potential problems, the chronic use of systemic corticosteroids is not recommended. In cases of chronic uveitis that require long term treatment, immunosuppressive agents with less known side effects such as methotrexate, cyclosporine, and mycophenolate mofetil (Cellcept) are more commonly used. However, these biologic agents have their own set of potential side effects and therefore, it is recommended that a rheumatologist should also be involved in the care of the patient when using these agents. Topical and intraocular steroids localized to the eye can cause elevated intraocular pressure as well as cataracts. In most cases, elevated intraocular pressure can be controlled with topical glaucoma drops, but in some cases surgical intervention is required to prevent severe glaucomatous damage.

The most common type of uveitis is acute anterior uveitis or iridocyclitis. Many cases of anterior uveitis are idiopathic though almost half of all cases are associated with the HLA- B27 haplotype. Systemic diseases associated with HLA-B27 include psoriatic arthritis, ankylosing spondylitis, reactive arthritis, and inflammatory bowel syndrome. Signs of anterior uveitis include redness of the eye, sometimes termed ciliary flush. The conjunctiva can become extremely red, and when associated with ocular pain and photophobia, is a strong indicator of anterior uveitis. Inflammatory cells found in the anterior chamber are the hallmark of anterior uveitis, sometimes deposited on the corneal endothelium (keratic precipitates) or iris (Bussaca nodules). Patients with anterior uveitis are typically treated with topical corticosteroid and cycloplegic eye drops. A laboratory workup for systemic etiologies is usually not necessary unless the patient experiences a recurrent episode.

Inflammation affecting primarily the vitreous cavity is known as intermediate uveitis or pars planitis. Inflammatory cells in the vitreous, known as vitritis, are typically bilateral, and when severe, can be found clumped in the vitreous cavity (snowballs) or deposited on the inferior pars plana (snowbanking). Intermediate uveitis is typically idiopathic though sarcoidosis, multiple sclerosis, and Lyme disease are also possible causes. Certain malignancies such as lymphoma can also ‘masquerade’ as intermediate uveitis, and when seen in older patients, should be suspected and ruled out.

Posterior uveitis involves the retina, choroid, and/or the retinal vasculature, and usually is more difficult to treat than anterior uveitis.

Uveitis Explained — This patient with Cat-scratch disease, caused by infection with Bartonella henselae, is an example of posterior uveitis. Note the characteristic star-like pattern of exudate in the macula along with optic nerve swelling.

In many cases, patients with posterior uveitis will exhibit characteristic exam findings that help narrow the differential diagnosis. For instance, an area of active retinitis next to an old pigmented chorioretinal scar is highly suggestive of toxoplasmosis. The most common symptom in patients with posterior uveitis is blurred vision. One of the more typical findings in posterior uveitis is macular edema, which is usually treated with periocular or intraocular corticosteroids.

In summary, uveitis is a visually threatening inflammatory condition that should be diagnosed and treated immediately. It is important to determine as best as possible the etiology of the uveitis and treat appropriately. In general, most patients with uveitis have good visual recovery with the proper management. However, in some cases, severe damage can occur, either due to the inflammation itself (usually chronic) or as a side effect of therapy (corticosteroids).

Richard H. Roe, MD, MHS
Retina-Vitreous Associates Medical Group

Posterior Vitreous Detachment

10/30/14

Have you ever noticed floaters in your vision? Perhaps they looked like a bunch of small dots or maybe a cobweb swaying back and forth in your visual field. Were the floaters associated with flashing lights that made you think there was a lightning storm coming your way? These are typical symptoms of a posterior vitreous detachment (PVD), and if you have had these symptoms you are far from alone.

PVD is a natural process that occurs in the majority of people usually over the age of 50. The vitreous is a jelly-like substance that occupies the back portion of the eye. The vitreous is comprised primarily of water, which accounts for 99% of its volume, and the remaining 1% includes proteinaceous substances such as collagen fibers as well as hyaluronic and ascorbic acids. The collagen fibers act as a scaffold to allow the vitreous to maintain a formed shape as well as provide a means for the vitreous to attach to the retina, which is the light-sensitive tissue that lines the inner back wall of the eye and is critical for vision. As we age, changes in these fibers cause the vitreous to lose its shape and eventually pull away from the retina. When the vitreous separates from the retina, this is called a PVD.

As we age, the collagen components of the vitreous can clump together and are free to float in the eye. When the vitreous separates from the retina during the development of a PVD, the floaters may become more noticeable or numerous. It is common for patients to describe floaters of different shapes and sizes, and patients may notice just one or in some cases many. In many people, a PVD develops slowly and there may be no symptoms or just a few annoying floaters. In others, a PVD may occur abruptly and cause more dramatic symptoms that can be very anxiety provoking.

Since the normal process of PVD development involves the vitreous tugging on the retina until it can fully separate, this tugging can result in flashing lights that can commonly appear in the peripheral, or side, vision. These flashing lights are sometimes described as lightning streaks, and patients may notice them more readily in settings with low ambient light. The flashes of light typically resolve once the vitreous has fully separated from the retina and the tugging has ceased.

The good news is that PVD is usually harmless in the vast majority of cases, and the annoying floaters will become less bothersome over time. In approximately 5-10% of cases, the vitreous can tug too hard on the retina as it tries to separate and it may pull a hole or tear in the retina. Tears in the retina can predispose to retinal detachment, which is a serious condition that can lead to permanent vision loss.
It is important to recognize that the typical symptoms of a regular PVD are often similar to a PVD with an associated tear. For this reason, it is recommended that all patients with the new onset of floaters or flashes have a dilated eye exam. If a retinal tear or detachment is discovered, early treatment can help prevent loss of vision.

Treatment for PVD usually involves simple observation. With time, the flashes will go away, and the floaters will become less noticeable. More recently, few providers have claimed that floaters can be treated with a laser in order to make them less noticeable. I would caution that this is not mainstream therapy at the current time, and I do not advise my patients to pursue this option. Another treatment possibility is vitrectomy surgery, where the vitreous gel is removed as part of a surgical procedure. Due to safety advances in vitrectomy surgery, this is now a potential option for the rare patient who has floaters that are so numerous and bothersome that they are negatively impacting their activities of daily living. For the vast majority of patients this is not necessary.

When I see a patient with a PVD, I often recommend one follow-up visit in 4-6 weeks to make sure there are no retinal holes or tears that have developed in the interim. If the other eye has not had a PVD yet, I will counsel them that a PVD will most likely develop in that eye within the next few years, and when it does they need to be examined. I will also discuss the retinal detachment warning signs. Patients with retinal detachment will not only have symptoms similar to PVD, including flashes and floaters, but in addition they may also notice what looks like a black shade or curtain that starts in the peripheral vision and extends towards the central vision. My patients are taught that this symptom requires an immediate examination.

In conclusion, PVD is a natural process that the majority of people will experience in their lives. The symptoms can range from having no symptoms at all to many floaters with associated lightning flashes. In the majority of patients, there is no damage to the eye or threat to the vision. A dilated exam is recommended to look for possible holes or tears in the retina, and if these are uncovered, prompt treatment can prevent vision loss.

Daniel D. Esmaili, MD
Retina Vitreous Associates Medical Group

What Are A Macular Pucker and Macular Hole?

10/9/14

What is the macula?
The eye is very much like a camera, taking light from the outside world and converting it into picture information that our brains perceive as vision. The retina is the light sensitive layer in the back of the eye that is very much like the film in that camera. The central retina, also known as the macula, is essential for crisp, high definition vision. Conditions that damage or distort the macula can therefore result in blurred or distorted vision. Two common conditions that affect the macula are macular puckers and macular holes.

What is a macular pucker or macular hole?
A macular pucker is a thin layer of scar tissue that forms on top of the retina. The amount of scar tissue can range from mild to severe. Mild macular puckers may be barely noticeable during an eye exam and resemble a fine layer of cellophane resting on the macula. More severe macular puckers can cause wrinkling or distortion of the macula. In contrast to a macular pucker, a macular hole is a small gap that extends through the entire thickness of the macula.

What are the symptoms of a macular pucker or a macular hole?
At first, a macular pucker may lead to mild blurring of the central vision. Because the problem involves the back of the eye, glasses will not completely restore vision. More severe macular puckers may result in wavy or distorted vision. For instance, objects that normally appear straight, such as venetian blinds or a printed line of text, might appear to have a dip or bend in the center. Small macular holes can cause similar symptoms of blurring or distortion. Larger macular holes often result in a central blind spot. This can also result in straight lines appearing broken or having a piece missing in the middle. Patients with a macular pucker or hole do not normally experience difficulty with peripheral vision.

What can cause a macular pucker or macular hole?
Recall that a macular pucker is a scar tissue. Anything that causes scar tissue, such as trauma or inflammation in the eye, can result in scar tissue and hence a macular pucker. Certain diseases that affect the retinal blood vessels such as diabetes can also cause a macular pucker to form. However, one of the most common causes of macular pucker is simple aging of structures within the eye. As the eye ages, the clear jelly that fills it, called the vitreous gel, shrinks. When enough shrinkage occurs, the vitreous gel detaches from its normal position adjacent to the retina. This process of vitreous detachment can cause microscopic damage or inflammation leading to macular pucker formation. In some cases, the vitreous gel does not detach cleanly from the retina. Instead it can put traction on the macula, pulling its delicate structures apart in the center, resulting in a macular hole.

How are macular puckers and macular holes diagnosed?
A simple examination from an ophthalmologist or retina specialist is often enough to diagnose a macular pucker or hole. However, additional testing is often useful in diagnosing subtle cases or monitoring eyes for changes. An optical coherence tomography (OCT) scan is a specialized photograph that allows your physician to look for microscopic changes in the contour of the macula. The following figures show an OCT of a normal macula, a macular hole, and a macular pucker. Note that the normal macula has a central dip known as the fovea, shown in Figure 1. In Figure 2, the dip is replaced by a gap which is a macular hole. Finally, Figure 3 shows a macular pucker where the dip is no longer visible. This is because the macular pucker, seen as a thin white line is distorting the normal shape of the macula.

Normal - Macular Pucker and Macular Hole — **Figure 1: Normal Macula**

Hole - Macular Pucker and Macular Hole — **Figure 2: Macular Hole**

Pucker - Macular Pucker and Macular Hole — **Figure 3: Macular Pucker**

What treatments are available for macular puckers and macular holes?
Macular puckers can be quite mild. For mild cases in patients with minimal symptoms, periodic monitoring may be all that is required. When blurred vision due to a macular pucker begins to affect activities such as driving or reading, treatment in the form of surgery can be considered. Surgery for a macular pucker is known as a vitrectomy. Vitrectomy surgery is usually done under local anesthesia and as an outpatient procedure. During the surgery, fine instruments are used to remove the scar tissue from the surface of the macula. After surgery, patients usually experience an improvement in the blurring and distortion as the eye recovers gradually over a period of months. Some residual waviness can be normal. Vitrectomy is generally very safe although there is a chance of increased cataract growth and a small risk of infection or retinal detachment.

For patients with small macular holes, close monitoring can also be an option since some macular holes can close on their own. For larger holes, there are two options. In select cases where the vitreous gel is actively pulling on the macula, an injection of medication into the eye may cause the gel to release cleanly, allowing the hole to close. In other cases, vitrectomy is recommended. During the surgery, any pulling on the macula is relieved and a gas bubble is placed in the eye to help the hole close. After surgery, patients are asked to look down for a several days to allow the bubble to float up against the hole. Once the body absorbs the bubble, vision is usually significantly improved.
In summary, both macular puckers and holes are common causes of blurry or distorted central vision. If treatment or surgery by a retina specialist is needed, the results are generally quite good and lead to significant restoration of vision.

David Liao, MD, PhD
Retina-Vitreous Medical Group

Our First Three Months Of Eye Care

9/30/14

Discovery Eye Foundation Blog’s First Three Months

It is hard to believe, but this blog has been providing information and insights into eye disease, treatment options, personal experiences of living with vision loss, and other eye-related information for seven months.

All of this would not have been possible without the expertise of remarkable eye care professionals who took time out of their busy schedules to share information to help you cope with vision loss through a better understanding of your eye condition and practical tips. Since so much information was shared in the seven months, here is a look at the first three months, with the additional four months to be reviewed next Tuesday.

I am very thankful to these caring eye professionals and those with vision loss who were willing to share their stories:

Marjan Farid, MD – corneal transplants and new hope for corneal scarring

Bill Takeshita, OD, FAAO, FCOVD – proper lighting to get the most out of your vision and reduce eyestrain

Maureen A. Duffy, CVRT – low vision resources

M. Cristina Kenney, MD, PhD – the differences in the immune system of a person with age-related macular degeneration

Bezalel Schendowich, OD – blinking and dealing with eyestrain

Jason Marsack, PhD – using wavefront technology with custom contact lenses

S. Barry Eiden, OD, FAAO – contact lens fitting for keratoconus

Arthur B. Epstein, OD, FAAO – dry eye and tear dysfunction

Jeffrey Sonsino, OD, FAAO – using OCT to evaluate contact lenses

Lylas G. Mogk, MD – Charles Bonnet Syndrome

Dean Lloyd, Esq – living with the Argus II

Gil Johnson – employment for seniors with aging eyes

We would like to extend our thanks to these eye care professionals, and to you, the reader, for helping to make this blog a success. Please subscribe to the blog and share it with your family, friends and doctors.

Susan DeRemer, CFRE
Vice President of Development
Discovery Eye Foundation

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.

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.

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 DeRemer. CFRE
Vice President of Development
Discovery Eye Foundation

Rods and Cones Give Us Color, Detail and Night Vision

9/9/14

Function of Rods and Cones

Rods and cones are a vital part of the eye, helping define what we see. Here’s what you should know.

1. There are three types of color-sensing cones, red, blue and green. If you are color blind one or more of these cells is missing or not working properly.

2. Men have a higher chance of being color blind than women. 1 out of 12 vs. 1 out of 255.

3. The most common type of color blindness is the disability to tell the difference between red and green.

4. The eye can distinguish between 500 shades of gray.

5. A healthy human eye can detect over 10 million different colors.

6. About 2% of women have a rare genetic mutation that gives them an extra retinal cone allowing them to see more than 100 million colors.

7. During a major depression people see less contrast, making colors appear duller.

8. All babies are color blind when they are born. Color vision begins to develop within a week after birth and by 6 months your baby can see every color you can.

9. Your eyes contain 7 million cones which help you see color and detail.

10. The stars and colors you see when you rub your eyes are call phosphenes.

11. There are 120 million light-sensing cells called rods which help you to see better in the dark.

12. Smoking reduces your night vision.

And these are just fun facts about eyes:

The Mayans believed that cross-eyes were attractive and would make efforts to ensure their children became cross-eyed.

Pirates used to wear a gold earring, believing it improved their sight. They also used eye patches to quickly adjust their eyes from above to below deck. When going below deck where it was dark, they flipped up the eye patch to see with the eye that had not be affected by light.

The phrase “it’s all fun and games until someone loses an eye” comes from Ancient Rome, as the only rule for their bloody wrestling matches was “no eye gouging.”

Susan DeRemer, CFRE
Vice President of Development
Discovery Eye Foundation

32 Facts About Animal Eyes

8/5/14

For something different, and a little fun, here some interesting facts about animal eyes that you may not have known.

Shark corneas are similar to human corneas, which is why they have been used in human transplants.
A worm has no eyes at all.
An owl can see a moving mouse more than 150 feet away.
Guinea pigs are born with their eyes open!
Scorpions can have as many as 12 eyes, but the box jellyfish has 24!
Camels have three eyelids! This is to protect their eyes from sand blowing in the desert.
Most hamsters only blink one eye at a time.
Owls are the only bird which can see the color blue.
Goats have rectangular pupils to give them a wide field of vision.
A scallop has around 100 eyes around the edge of its shell to detect predators.
Snakes have two sets of eyes – one set used to see, and the other to detect heat and movement. They also don’t have eyelids, just a thin membrane covering the eye.
The four-eyed fish can see both above and below water at the same time.
Owls cannot move their eyeballs – which has led to the distinctive way they turn their heads almost all the way around.
A dragonfly has 30,000 lenses in its eyes, assisting them with motion detection and making them very difficult for predators to kill.
Dolphins sleep with one eye open.
The largest eye on the planet belongs to the Colossal Squid, and measures around 27cm across.
Geckos can see colors around 350 times better than a human, even in dim lighting.
The eyes of a chameleon are independent from each other, allowing it to look in two different directions at once.
A camel’s eyelashes can measure up to 10cm long, to protect its eyelashes from blowing sand and debris in the desert.
An ostrich’s eye is bigger than its brain.
Dogs can’t distinguish between red and green.
Polar bears have a third eyelid that helps filter UV light.
Human eyes are not the most highly evolved. The mantis shrimp has four times as many color receptors as the human eye and some can see ultraviolet light.
Pigeons can see millions of different hues, and have better color vision than most animals on earth.
Cat’s eyes have almost 285 degrees of sight in three dimensions – ideal peripheral vision for hunting.
Although color blind, cuttlefish can perceive light polarization, which enhances their perception of contrast.
A moth’s eyes are covered with a water-repellant, anti-reflective coating.
An ant only has two eyes, but each eye contains lots of smaller eyes, giving it a “compound eye.”
Eagles have 1 million light-sensitive cells per square millimeter of the retina – humans only have 200,000.
A honeybee’s eye is made of thousands of small lenses. A drone may have up to 8,600 and the queen be can have 3,000-4,000 lenses.
The night vision of tigers is 6 times better than humans.
Eyes on horses and zebras point sideways, giving them tremendous peripheral vision, to the point of almost being able to see behind them, but it also means they have a blind spot right in front of their noses.

Susan 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.

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 DeRemer, CFRE
Vice President of Development
Discovery Eye Foundation

20 Facts About the Amazing Eye

6/10/14

We don’t often give our eyes as much thought as we should, that is until something goes wrong and our vision is affected. But when you learn more about eyes, you realize just how amazing they are. Here are a few facts you may enjoy:

1. Eyes began to develop 550 million years ago. The simplest eyes were patches of photoreceptor protein in single-celled animals.

2. Your eyes start to develop two weeks after you are conceived.

3. The entire length of all the eyelashes shed by a human in their life is over 98 feet with each eye lash having a life span of about 5 months.

4. To protect our eyes they are positioned in a hollowed eye socket, while eyebrows prevent sweat dripping into your eyes and eyelashes keep dirt out of your eyes.

5. Your eyeballs stay the same size from birth to death, while your nose and ears continue to grow.

6. An eye is composed of more than 2 million working parts.

7. Only 1/6 of the human eyeball is exposed.

8. Corneas are the only tissues that don’t have blood.

9. The human eye weights approximately just under an ounce and is about an inch across.

10. An eye cannot be transplanted. More than 1 million nerve fibers connect each eye to the brain and currently we’re not able to reconstruct those connections.

11. 80% of our memories are determined by what we see.

12. Eyes heal quickly. With proper care, it takes only about 48 hours to repair a minor corneal scratch.

13. There are about 39 million people that are blind around the world.

14. 80% of vision problems worldwide are avoidable or even curable.

15. Humans and dogs are the only species known to seek visual cues from another individual’s eyes, and dogs only do this when interacting with humans.

16. A fingerprint has 40 unique characteristics, but an iris has 256, a reason retina scans are increasingly being used for security purposes.

17. People who are blind can see their dreams if they weren’t born blind.

18. “Red eye” occurs in photos because light from the flash bounces off the back of the eye. The choroid is located behind the retina and is rich in blood vessels, which make it appear red on film.

19. 80% of what we learn is through our eyes.

20. Eyes are the second most complex organ after the brain.

Susan DeRemer, CFRE
Vice President of Development
Discovery Eye Foundation

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