Columbia Eye Clinic

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Why Do Humans Have Eyebrows and Eyelashes?

Is there a biological or functional reason we have hair above and around our eyes?

Eyebrows Move Moisture Away from Eyes and Help Us Communicate Non-Verbally
Our eyebrows channel unwanted moisture—sweat and rain in particular—away from the eye to help keep vision clear. The shape and direction of eyebrow hairs make it easier for moisture to flow sideways around the eyes, along the side of the head. They also help to block out light and filter dust and dirt that may fall into the eyes.

Experts also believe that eyebrows play an important role in human communication and facial expression. Eyebrows can exaggerate expressions such as happiness, surprise and anger. A study found that eyebrows may be a more recognizable indicator of identity than even the eyes themselves.

Hair loss in the eyebrows can be indicators of certain autoimmune diseases and hormonal imbalances, such as alopecia, hypothyroidism and lupus.

Eyelashesclose up of blue eye with eyelashes Prevent Irritation and Act as Human Whiskers
Eyelashes are unique among body hair. They are among the shortest hairs on the body with the longest lifespan and healthy lashes are believed to never go gray.

Eyelashes operate as air filters for the eye, catching dust, protecting the eye from debris that can obstruct vision or cause infection or injury. They are like human whiskers. Lashes act as sensors for objects coming close to the eye—like insects—and trigger a reflexive and protective blink. A study conducted using man-made eye and eyelash mockups, showed that lashes also reduce tear evaporation up to 50 percent, helping to keep eyes sufficiently lubricated.

 

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New Contact Lenses May Offer Remedy for Digital Eye Strain

The hottest product debuted at the International Consumer Electronics Show, CES 2017, is not the latest new gadget. A new contact lens, designed for digital device users, can help relieve eye tiredness, dryness and redness associated with prolonged time in front of a digital screen.

Digital eye strain or fatigue, most commonly felt after two or more hours in front of a digital screen, has become a reality as we increase our dependence on technology in our work and personal lives. Biofinity diagram illustrating the moisture retention properties of the Biofinity Energys lens.Energys™ contact lenses employ breakthrough technology in the construction of the lens to minimize strain on the eye muscles as the wearer moves their eye from on-screen to off-screen and back. We have a tendency to blink less when we use digital devices, disrupting our body’s natural way of keeping our eyes moist. Biofinity Energys™ lenses also retain moisture better than standard contact lenses, increasing hydration, breathability, and lens softness. The lenses also have a special rounded edge, increasing the length of comfortable wear time by reducing resistance
between the lens and the inside of the eyelids.

Biofinity Energys™ contact lenses are designed for all-day wear, helping people’s eyes better adapt so they can seamlessly and continuously shift focus between digital devices and offline activities. The lenses are designed to be replaced monthly and require similar care and handling as other soft contact lenses.

Ask your doctor if Biofinity Energys™ contact lenses can be a sight for sore eyes for your digital lifestyle.

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Facts About Eye Color

facts about eye color: hazel and blue eye image up closeAbout 10,000 years ago, every human on Earth had brown eyes. Now, half of all people in the U.S. have brown eyes. Worldwide, that number could be even greater.

Brown eyes get their color from melanin, the same pigment that colors your hair, skin and other cells. But blue eyes don’t have any blue pigment in them. Blue eyes get their color the same way water and the sky get their blue color. They scatter light so that more blue light reflects back out.

The colored part of the eye is called the iris. It’s a structure that contains muscle and other kinds of cells. You can see the iris in action when it squeezes or relaxes to let in more, or less light through the pupil. The iris is made up of two layers. For almost everyone — even people with blue eyes — the back layer (called the pigment epithelium) has brown pigment in it. The more melanin there is in the iris, the darker brown it will be.

The front layer of the iris (called the stroma) is made up of overlapping fibers and cells. For people with brown eyes, some of the cells also have brown pigment in them. If there is no pigment at all in this front layer, the fibers scatter and absorb some of the longer wavelengths of light that come in. More blue light gets back out and the eyes appear to be blue. For people with green or hazel eyes, one, or both, of the layers of the iris also has some light brown pigment in it. The light brown pigment interacts with the blue light and the eye can look green or speckled. Many people have variations in the color of their irides, often with one color near the pupil and another at the edge. This variation happens when different parts of the iris have different amounts of pigment in them.

Since blue eyes get their color from the light that’s coming in and is then reflected back out, they can appear as different colors depending on the lighting conditions. Green and hazel eyes are a mixture of pigment color and color from scattered light, so they can also look different in different lighting conditions.

Eye Color Is Not Inherited from A Single Gene
Scientists used to think that a single gene determined your eye color. More current research suggests that as many as 16 different genes could be responsible for eye color. This helps explain why two parents with the same eye color can have children with an entirely different eye color.

When babies are born, their eyes may sometimes appear blue while their melanin is still developing. Within about 12 months, cells will begin to produce melanin, and as more melanin builds up in the iris, eye color may darken.

 All Blue-Eyed People May Have a Common Ancestor
Scientists trace the historic change back to a single common ancestor in Europe about 6,000-10,000 years ago. That person had a change in a gene that controls melanin production. This change, or mutation, is believed to have reduced the production of melanin in the iris.

Brown Eyes Are More Common in Hotter Climates
High levels of melanin in the eyes, hair and skin help protect people from the sun’s damaging rays. That explains why brown eyes occur more frequently in the hotter climates of Africa and Asia than in Europe. In Iceland, brown eyes are in the minority. As people move to less sunny locations, their need for protective pigment decreases. Eye color may have evolved as our early ancestors moved toward cooler parts of the world.

 

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Facts About Tears

Tears

A happy ending to a story, a sad break-up, an onion chopped into pieces—they all can trigger your tears. Tears serve many purposes, and your eyes produce them all the time. In fact, you make 15 to 30 gallons of tears each year. Tears are essential to help you see clearly and maintain the health of your eyes. They can also help communicate your emotions.

Your body makes three types of tears:
Basal tears are in your eyes all the time to lubricate, nourish and protect your cornea. Basal tears act as a constant shield between the eye and the rest of the world, keeping dirt and debris away.

Reflex tears are formed when your eyes need to wash away harmful irritants, such as smoke, foreign bodies or onion fumes. Your eyes release them in larger amounts than basal tears, and they may contain more antibodies to help fight bacteria.

Emotional tears are produced in response to joy, sadness, fear and other emotional states. Some scientists have proposed that emotional tears contain additional hormones and proteins not present in basal or reflex tears.

Tears are not just saline. They have a similar structure to saliva and contain enzymes, lipids, metabolites and electrolytes. Each tear has three layers:

  1. An inner mucus layer that keeps the whole tear fastened to the eye.
  2. A watery middle layer (the thickest layer) to keep the eye hydrated, repel bacteria and protect the cornea.
  3. An outer oily layer to keep the surface of the tear smooth for the eye to see through, and to prevent the other layers from evaporating.

Lacrimal gland and accessory glands produce your tears. As you blink, tears spread across the surface of the eye. Then the tears drain into puncta, tiny holes in the corners of your upper and lower eyelids. Your tears then travel through small canals in the lids and down a duct before emptying into your nose. There, tears will either evaporate or be reabsorbed.

Sometimes babies are born with a blocked tear duct, a condition that usually resolves on its own. Adults can also develop a blocked tear duct. This can be a cause of tearing and rarely an infection.

When a lot of emotional or reflex tears are made, they overwhelm the lacrimal drainage system. That’s why these tears can spill out of your eyes, run down your cheeks and sometimes dribble out of your nose. 

Basal tear production slows with age, and this can lead to the development of dry eye. Dry eye is a common problem for people undergoing hormonal changes, especially women during pregnancy and menopause. Contact lenses and certain medications can also cause dry eye. If you have dry eye, you may also be prone to blepharitis, a common cause of irritation or swelling of the eyelids. In addition to seeing an ophthalmologist, the American Academy of Ophthalmology has tips for some simple things you can do at home to keep your eyes moist.

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What Does 20/20 Vision Mean?

Generally, the goal of correcting vision with glasses or contacts is to bring a person’s vision to 20/20, but what does that really mean?

eye chart measures how your vision Compares with normal 20/20 vision
A standard Snellen vision testing chart.

An eye chart measures the clarity or sharpness of vision. The top number refers to your distance in feet from the chart. The bottom number indicates the distance at which a person with normal eyesight can read the same line.

20/20 vision is considered to be “normal” vision. A person with 20/20 vision sees the same line of letters on an eye chart from 20 feet away that a person with normal vision sees at 20 feet.

If you have 20/30 vision, it means your vision is below 20/20. When you are standing 20 feet from the chart, you can read letters that most people see when they are 30 feet away.

A person can have 20/15 vision, which is sharper than 20/20. If you have 20/15 vision, you can see a line in the eye chart at 20 feet that the average person can only see when they are 15 feet away.

Only about 35% of all adults have 20/20 vision without glasses, contact lenses or corrective surgery. With corrective measures, approximately 75 percent of adults have 20/20 vision. In almost every state, visual acuity of 20/40 or better is required for an unrestricted driver’s license. People are considered “legally blind” if their corrected vision (with eyeglasses or contacts) is 20/200 or worse.

Visual acuity as measured by an eye chart is only one part of an eye exam. Other tests performed during an exam by an Ophthalmologist can detect early signs of eye diseases that can result in vision loss if untreated.

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