|
Digital Lens Explanation:
Digital prescription lenses are the most important improvement in prescription eyewear in the last 100 years. The benefits of a digital Rx lens are even more critical in sports sunglasses that wrap around your head. Putting a prescription in a curved frame has historically caused a visual distortion called the “Fishbowl Effect”. The digital lens design eliminates this problem.
A traditional prescription lens has the same curve all the way across the lens surface. For example, if your prescription is a -2.00 and you put this on an 8-base frame the curve all the way across the back of the lens will be -10.00. This will produce perfectly in-focus vision through the optical center of the lens, but as you look away from the center this amount of correction will deteriorate. When you look through the peripheral portions of the lens you are looking through a prism. This can create more distortion than correction.
In a Digital lens your prescription is recalculated at every point on the lens. This computer aided design produces sharp, clear vision throughout the entire lens, not just the optical center.
The Maui Jim Passport prescription lens is produced with digital technology. Maui Jim still gives you the option of purchasing prescription lenses made with the spherical technology, but we expect them to be all-digital fairly soon. All Kaenon Polarized prescription lenses are produced with digital lens technology, and all Switch Vision magnetic interchange lenses are digitally surfaced.
We have been selling prescription sports sunglasses for about 10 years. For most of this time we have been telling prescription patients to allow plenty of time to get acclimated to changes in base curve or lens material. Most people require 2 – 10 days before they feel comfortable wearing new prescription sports glasses on an 8-base frame. We have been selling the new digital lenses in our retail store for the past two years. Most patients are acclimated to these new lenses before they walk out of the store.
Digital lenses are available in single vision or progressive lenses. You cannot get a digital bifocal lens. Patients with stronger prescriptions or a narrow PD measurement may have digital lenses as their only option.
Other names for digital lenses include Freeform or Freestyle lenses.
Quick Digital Lens illustration:
The best illustration of how a digital lens is created came from a Maui Jim representative who compared a lens blank to a sand box. If we use the example above of a -2.00 lens on an 8-base frame you could imagine your shoulder as the pivot point as you just scoop out a 10 diopter divot of sand to make a traditional lens. Now to create a digital lens in this imaginary sandbox we would remove the sand one grain at a time to create a surface where every point in this sandbox (or lens) is directing light to the exact point on your retina where you need it to create perfect vision.
Everything to this point is important information to have before selecting an Rx lens.
=================================================================
Everything that follows is just good to know, but you could probably live without it.
Getting Acclimated to New Sports Glasses:
Most people require some time to get comfortable wearing new prescription lenses. Factors that make this process more difficult include changes in prescription; changes in base curve; and changes lens material. If we put your prescription in a frame that is curved enough to block UV rays from every angle, and you are accustomed to wearing a fairly flat frame with CR-39 plastic or high index lenses, you should allow some time for your brain to get dialed in to this new input before you do anything death defying. Do not put your new prescription glasses on and immediately jump on a motorcycle, ride a bicycle, drive a car, catch a baseball, etc. Just walk around for a while until everything feels normal.
When you change the curve of a lens or the type of lens material the biggest change in what you see is in the peripheral parts of your vision. Any prescription lens will provide the most perfect vision through the optical center. Your brain has the power to adjust the imperfections in the peripheral portions of the lens to make this input more useable. When you change the curve of a lens or the index of refraction your brain has to learn to reshape this new input to give you a clear picture. Naturally, the first time you do this will be the most difficult.
Most people who routinely wear glasses will have their prescription on a fairly flat frame. Most sports eyewear has a wrapped design to protect your eyes from UV light and give you better peripheral vision. As you might expect, it can be a bit disorienting to switch from one to the other if you do not have a digital prescription lens in the curved frame.
The most common illustration of how our brains adjust visual input can be seen when people get a new pair of glasses. Most people know someone who got a new prescription; bought new prescription glasses; and decided that they like their old glasses much better than the new ones. This is usually because their brain has been adjusting the input from their old prescription and tweaking everything into a more usable picture. If they would wear the new glasses, and discard all their old prescription glasses, eventually their brain will relax they will see much better with the new prescription. They may also have more energy and fewer headaches.
One Extreme Example
Our favorite example of people getting acclimated to new glasses is an experiment done by students at the University of Michigan*. This test group wore goggles that flipped everything up-side-down, and they wore these goggles 24-hours a day. This caused everybody to get a big headache, but after a few days the entire test group could see everything as if they were not wearing the goggles at all. Then they took off the goggles, and everything was upside down. They all got headaches for a few days as their brain flipped everything back to right side up.
This illustrates what your brain does with the input from an outdated prescription. It also provides some insight into why we can be sensitive to changes in the input that we send to the optic center of our brain.
* Footnote: This story has been told for decades; almost everyone in the eye care business has heard it; but I can’t find any documentation of this anywhere. This would have happened around the 1970’s or 80’s, so a digital record will be almost impossible to find. If you know where a record of this study exists please let me know. I’d love to give credit where it is due. I might be giving U of M more credit than they deserve.
|
