Tag Archives: glasses

How do 3D Movies Work

3D Glasses, image courtesy of Flicker user Phillip CasablancaThis weekend Taylor and I went with a group of dads and daughters to see A Christmas Carol in 3D.  A popular question was, “so how do they do the 3D effect?”

We can judge depth because our eyes are about 2 1/2 inches apart, allowing each eye to have a slightly different view of an object.  The brain interprets these differing views, allowing us to note that the objects are at varying distances.

In a movie theater, the image is projected onto a flat screen, therefore we must show each eye a slightly different image, this is accomplished by using either polarized lenses (the better method) or red and green lenses (think headache).  Polarized lenses are, by far, the preferred method.  Typically, light radiates in all directions, polarized lenses filter the light so that it radiates in only one direction, with all of the light waves parallel to each other.

The 3D movie glasses use polarized lenses that filter the light 90 degrees apart for each eye, thus allowing each eye to see a different image.  Two movie projectors are then used to show the movie.   Each projector’s image is slightly offset on the screen simulating the distance between our eyes.  While wearing your polarized 3D glasses the movie looks clear and sharp.  If you take your glasses off the movie looks fuzzy with a shadow off to the left.  Your brain will fuse these views giving depth to the image.

An Interesting Experiment

If you take a friend’s 3D movie glasses and hold their left lens in front of your right lens you will see that no light gets through, turn the lenses perpendicular to each other and once again you can see through both lenses.

So How Was The Movie

A Christmas Carol 3D 2009 The last 3D movie I saw used red and green glasses so it was great seeing a 3D movie that did not give me a headache.  The picture looked great and the 3D effects were well done, however that’s about it.  The chase scenes were way to long and really done mostly to show off the movie’s 3d effects.  Jim Carrey was good in his role as Ebenezer Scrooge and the movie stuck to the original book.  So the bottom line, it’s not a bad movie as a matter of fact they did a good job, however the only reason to see this movie, is to see the 3D effects.

What Kind of Eyeglass Lenses are Recommended for Children?

Assessing the visual needs of your child with an eye exam is the first step in protecting your child’s vision.  It is equally important to select lenses that will not only make them see well but also protect their eyes.

Polycarbonate or Trivex lenses are the only lens types that have the potential to reduce—not increase—the risk of serious eye injury.   Polycarbonate and Lexan are used in bullet-proof windshields, safety glasses, helicopter canopies and many other hi performance applications.   Other lens types, including glass and regular plastic (CR-39)  will break into pieces upon impact.  Often the impact from an object does less damage to the victim than the broken eyeglass lenses.

Both polycarbonate and Trivex are thin, lightweight and highly impact resistant.   Kids can do crazy things and accidents can happen, therefore polycarbonate and Trivex are not just recommended for sports but should be used to protect their eyes everyday.

Trivex is highly scratch resistant making it the best option for children.  Polycarbonate is much softer and therefore less scratch resistant, however it is slightly less expensive.  Both lens materials naturally block 100% of UV light without any additional coatings.  The optical qualities of Trivex are much better than those of polycarbonate, therefore there is less distortion and reflection from an ophthalmic lens made of Trivex.  Both lens materials are available in Transitions (get darker outside, lighter inside) and accept an antireflective coating, which prevents reflections, making the lenses look transparent.

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Why Should Contact Lens Wearers Have Backup Glasses?

Almost all contact lens wearers feel like “I wear contacts because I don’t like glasses”. That begs the question why is it important for everyone to have backup glasses? The simple answer is that your eyes need a break. The incidence of eye infections in contact lens wearers is much lower for patients that have an adequate backup pair of glasses.

A contact lens wearer that lacks a pair of backup glasses will have to wear their contacts when their eyes are irritated. By continuing to wear the contacts the eyes never have a chance to recover. Most contact lens related eye irritations will resolve in less than a day if the contacts are not worn. If your eye is not back to 100% within one day you should be seen by our office.

So what criterion qualifies for making an adequate pair of backup glasses? Here is what I think is important.

  • The frame and lens styles are not so out of date that you don’t mind being
    seen in public wearing them
  • You can see well enough to pass your driver’s test (20/30 or better), and last but
    not least, the most important one……….
  • You can find them

At Total Eye Care we feel it is important to have a backup pair of glasses, therefore, when purchased at time of a contact lens evaluation, a complete pair of glasses starts at $99.

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Visual Ergonomics – Setting Up Your Computer Workstation For Maximum Visual Comfort

The older we get and/or the more time we spend at the computer the more important it is to set up your work environment for the maximum visual comfort. Generally, from a visual standpoint, laptops, placed on a desk, are set up rather well for the maximum visual comfort. They have us looking down allowing a user that wears bifocals to see the screen through their bifocal and because the screen is directly in front of the keyboard it is close
enough the bifocal, whether it is a progressive lens or a flat top lens, the distance is correct.

A desktop is another matter. Placement of the monitor is very important. The new LCD monitors make it much easier to place them in a positions allowing for easy, comfortable viewing. The monitor should be placed in a position that is typically 20 inches or more away and positioned low enough that when you are looking straight ahead you are looking over the top of the monitor. This last point is especially important for bifocal wearers, especially those 50 or older that rely on the intermediate portion of their progressive or trifocal lenses.

Why is monitor height important? If the monitor is too high you have to tilt your chin up to focus with the intermediate portion of your progressive lens. If you are only at the computer for a few minutes this may be tolerable, however if you sit at the computer for an extended period moving your chin up like this spells a neck ache. If you don’t tilt your chin up to use your bifocal to focus the monitor you are looking though the top part of your glasses instead of the intermediate zone and thus straining your eyes. Neither option is acceptable for any reasonable length of time.

So how should we set up our workstation? First, if your monitor is sitting on top of the CPU, place the CPU under the desk and the monitor directly on the desk. Having a chair with an adjustable seat will allow you to raise your seat thus further improving your position.

Second, never place your monitor where there is a bright light behind it such as in front of a window. Also having a window directly behind you may cause bothersome reflections unless you have an antireflective screen on your monitor.

Third, place the monitor 20 to 30 inches from you. If neither of these options is sufficient or simply not possible computer glasses are an option. Progressive or bifocal computer glasses are generally not necessary for those under 50, however anyone over 50 that spends more than a couple hours a day at the computer will benefit from computer glasses. Most patients simply leave their glasses at the computer. Computer glasses are progressive lenses prescribed so that the top part is set to focus at computer distance, roughly arms length, and the bottom will focus at near, usually 16-18 inches. An antireflective coating will eliminate reflections and also make for better visual comfort.

Lastly, a good, adjustable chair with a foot stool is a great idea.


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