How Glasses Change Your Look

February 11, 2008

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Cell Phones and Driving

February 4, 2008

cell-phone-driving_small.jpgOver 55% of the U.S. own cell phones. Given our love of convenience, we love our cell phones. Add that to our attraction to large shiny metal objects, we love our cars. It’s only logical that the average person drives and talks on their cell phone at the same time.

Ever pull up beside someone who’s using their cell phone in the next lane and wonder if you’re in danger? Apparently, some optometrists felt that way and did some research. In a recent article in Optometry: Journal of the American Optometric Association the question was asked, “Does cell phone conversation significantly affect the user’s peripheral vision?” I’ll save you from the long, boring story of how they setup the research and just give you the result. The article reports,

“Our research showed that the cognitive task involved in processing a conversation on a cell phone is reflected in a significantly reduced visual field area.”

Translation? Cell phone conversation detracts attention from the visual system. This means objects in a person’s peripheral vision are not noticed as readily. As you can imagine this is a major concern. The researchers even minimized the effects of dialing and holding the phone. So conversation in and of itself is the culprit. That means even hands-free devices won’t likely improve the peripheral vision issue.

In defense of those of us who do drive and talk at the same time, the researchers said, “More experienced drivers have an advantage, because driving becomes more of a subconscious task with increased driving experience.” For those of you who may be wondering, they also reported no significant difference between male and female peripheral vision decrease.


Ordering Cheap Contact Lenses; Hazardous To Health

January 31, 2008

contacts.jpgMore than 30 million people wear contact lenses. Many of those wearers purchase their lenses through low-cost outlets, like online retailers (i.e. 1-800 Contacts) or discount brick and mortar clubs (i.e. Costco). However, a recent study indicates that bargain shopping may effect your eye health.

The medical journal Optometry: Journal of the American Optometric Association (JAOA) reports “The findings indicated that online and store purchasers . . . are less likely to adhere to healthy eye care practices, as recommended by their eye doctors.” “Those who bought contact lenses at their doctor’s office followed a number of FDA recommendations more so than those who bought contact lenses elsewhere.”

Other interesting findings were:

  • 86 percent of individuals who purchased their lenses from an eye doctor received a yearly comprehensive eye exam. But, only 76.5 percent of those individuals who purchased their lenses via the Internet saw an eye doctor on a routine basis.
  • 35 percent of online purchasers did not check that the prescription was correct.
  • Fifty-seven percent of individuals who purchased their lenses from an eye doctor went in for a follow-up appointment; as compared to only 29 percent of online purchasers.
  • The majority of consumers feel more confident purchasing their contact lenses from a familiar and reliable place such as their eye doctor or store rather than through the Internet.
  • 89 percent and 91 percent of respondents respectively said they felt confident purchasing contact lenses from their familiar, reliable eye doctor or store. That number decreased to 77 percent when surveying individuals who made a purchase via the Internet.

“Although buying contacts online can be more cost-effective and convenient, we strongly urge patients to understand that there are risks involved to wearing contact lenses,” said Dr. Sclafani, one of the researchers. “Because of this, it’s necessary that patients visit their eye doctor on a regular basis and communicate any recent visual changes and discomfort experienced as a result of contact lens wear.”


Why Do Women Have More Eye Diseases?

January 10, 2008

Within the past 20 years there has been a surge of research into women’s health issues. This movement was spurred by studies showing that women suffer from significantly more illnesses than men. Relating to the eye, women comprise more than two-thirds of the nation’s cases of blindness or visual impairment! Why does sickness favor women? Many doctors and researchers blame it on hormones. This is especially suspected with eye diseases. However, science still is uncertain how or why hormones influence women’s health.

woman-with-flower_small.jpgIt is well known that women suffer from dry eye problems much more than men. A very common cause of dry eye is inflammation in the eye tissues, and who do you think suffer more with inflammatory diseases? You guessed it, women. Lupus, rheumatoid arthritis, fibromyalgia, polymyalgia, and thyroid dysfunction are just a few diseases that cause inflammation in the body and result in eye dryness. Are hormones and inflammatory diseases related? The fact that the risk of dry eye (an inflammatory disease) skyrockets at post-menopausal age (marked by extreme hormone level changes in the body) makes me wonder.

Determining for sure if women have more eye illnesses is a difficult task for one main reason, women are more likely to seek medical attention. So do more women get cataract surgery because they are more prone to cataract formation or just because they go to the doctor more often? In my experience, men hold off as long as possible to seek professional help. Similar to not asking for directions until they are lovingly (or not) encouraged by their female counterpart.

Visit a wonderful website created by the Women’s Eye Health Task Force for more information.

EDIT (added March 26, 2008): Health News Digest has a very good article with statistics.


What’s Up With My Eyebrows?

December 28, 2007

The other day my four-year-old asked me out of the blue, “Dad, why do we have eyebrows?” I was baffled for two reasons: 1) that my son was so pensive and 2) that despite being an eye doctor, I didn’t have an immediate, scientific response. I replied how any baffled parent would and shot the ball to his court, “Why do you think we have eyebrows?” He replied after a brief pause, “So we don’t look funny.”

Reason #1

Eyebrows are one of those things that we take for granted until we have to do without them for a while. After doing some searching, I found many stories from individuals who, for one reason or another, had their eyebrows removed. Many said that liquids like sweat or rain would run right into their eyes. So that’s reason #1 for the existence of those furry things on our face. The arching shape and sideways hair growth direct liquids and debris away from the eyes.
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Reason #2

A less critical, but important social function is to aid in facial expression. Communication of emotions such as surprise, fear, and displeasure is executed with the eyebrows. If you’re interested in facial muscle anatomy and the expressions of each muscle, visit artnatomia.com to play with a simulator. The picture shows all superficial muscles that control facial and scalp movement. (Courtesy: http://www.medicalook.com)

EDIT (June 2, 2008): A recent U.S. study from the journal Plastic and Reconstructive Surgery indicates that eyebrow shape was deemed to be the greatest indicator of mood, drooping of the eyelids was considered the biggest indicator of tiredness, and raising the lower eyelid and the presence of crow’s feet were associated with happiness.

Unibrows

Those individuals with the fortune (or misfortune, depending on your perspective) of having one long, continuous eyebrow perhaps have the best eye protection. So think twice before you wax that unibrow into two brows. By the way, the fancy-schmancy scientific term for unibrow is synophrys.


Why Don’t We Get Dizzy When Moving Our Eyes?

December 19, 2007

Have you ever heard that the eye is like a camera? Generally that’s true. But look through a camera and move it from side to side. Notice the churning sensation in your gut and how it feels like you’re watching the car chase scene from The Bourne Supremacy all over again. Now move your eyes from side to side. Immediately you’ll notice a significant difference. We normally don’t loose our last meal every time we look around with our eyes.

suppression.pngThe brain is very good at minimizing sensory input so we don’t get over stimulated. (Autism is where the brain doesn’t do it’s job and allows too much stimulation, making it extremely difficult to pay attention to anything.) A camera, on the other hand, can’t filter out motion.

Experiment #1

Ok, ok, enough suspense. Let’s find out how the brain filters motion. To demonstrate this phenomenon, let’s set up an experiment, which I actually did in optometry school. An observer is seated in front of a large section of construction paper at eye level bend into a semicircle. Points A and B are just marks on the paper. Directly in front of the observer is a narrow cut-out section through which a light is seen. (Here’s the impressive part.) If the observer looks at point A then quickly looks at point B (or vice versa) the light is not seen. During this quick movement, we know at one point the eyes were briefly pointed directly at the light. Why didn’t we see the light? The phenomenon here is that actually the eye DID see the light, but the brain didn’t.

Experiment #2

Just about everyone has already done this experiment. Simply sit in a rotating chair and spin yourself really fast. Did you get dizzy? Ready for a second chance to taste that spinach salad with walnuts you had for lunch? The spinning simulated quick eye movements just like shifting our eyes from points A to B, but why did we get dizzy this time?

The Brain Categorizes the Type of Motion

To filter the visual sensation of motion, the brain considers not only the motion the retina sees but also if the eye is in motion at the time and if the motion was initiated by choice (voluntary) or forced (involuntary). Imagine (don’t try this yourself) numbing up the eye, then someone gently grabbing the white part of your eye with tweezers and having that person moving your eye side to side for you. (We actually do this in the exam room on certain patients to determine neurological dysfunctions.) You would get dizzy because your brain isn’t filtering out the motion.

Wow! That’s Cool!

Let’s put this all together now. Here’s a play-by-play of what happened in our experiment #1 that caused the brain to filter.

  1. The observer looks at point A.
  2. The observer starts to move their eye away from point A.
  3. The retina, sensing an image moving across it, sends impulses to the brain. (But, as we saw from experiment #2 and the tweezer test, this isn’t enough for the brain to filter.)
  4. Nerve impulses are sent to the brain from the eye muscles that initiated the movement. This combination of retina and muscle input tells the brain that the observer made a voluntary eye movement.
  5. The brain shuts down the visual system for a split second during the eye movement. This is called visual suppression. We’ve been using the layperson term “filtering” in this post.
  6. Once the eye reaches point B, the retina and muscles send impulses again to the brain telling it the eye movement has stopped.
  7. The brain turns the visual system on again. That explains why we don’t see the light in experiment #1.

You, being the bright person that you are, would now ask, “Why don’t we see black when the brain turns the visual system off?” This is quite a complex process, but suffice it to say, the brain has the amazing ability to cover up visual interruptions. Our world doesn’t go black each time we blink either. I may go into more detail on this in a future post.


The Amazing Moon Illusion

November 21, 2007

One of my favorite illusions involves the moon. It’s common knowledge that the moon looks huge when close to the horizon, but appears smaller when higher in the sky. Many theories have attempted to explain this phenomenon. (Feel free to read about them on Wikipedia. However, the article wasn’t written in layman’s terms and can be confusing.)

a-blue-moon_small.jpgThe moon is actually the same size regardless of where it is in the sky. To prove this just take a picture of it at the horizon and at other positions and compare the size in the pictures. It is not an illusion caused by the atmosphere, as commonly believed. The illusion occurs at the brain level and deals with the brain’s inability to judge large distance differences.

To understand this you have to realize that the brain manipulates image sizes in an attempt to match up the image with the relative distance from the viewer. Here’s an example. Have someone lay down on their back on the floor. Take a picture of them by aiming the camera so that their feet are in the foreground and their head is in the background. Notice how small the person’s head is in the picture. Now assume the same position you were in to take the picture, but this time without the camera. Notice that the person’s head doesn’t look as small.

Your brain realizes that their head isn’t that far away from their feet, so it “enlarges” the head to match the perceived distance. The camera, on the other hand, doesn’t realize the head is only about 5 feet away from their feet and fails to match up the head size with the short distance. Now imagine the horizon is the “feet” and the moon is the “head”. Your brain doesn’t realize that the moon is actually 200,000 miles away. It sees it as being just beyond the horizon. Therefore, it “enlarges” the image of the moon just like it did with the person’s head.

Truly amazing!


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