Archive for the ‘Eye Care’ Category
But if you have a strong prescription and you’re ordering your glasses online, figuring out how to get the thinnest lenses possible can be perplexing.
Not to worry!
We’re going to make it easy for you.
All you’ll need is your prescription and a handy online tool that will estimate how thin your lenses will be.
This handy online tool is the Lens Thickness Calculator. It can be found here, at the OptiCampus website.
Before we talk about how to use the Lens Thickness Calculator, let’s look at the factors that can thin your lenses:
1) Your prescription. This you cannot change to get a thinner lens. Doing so would be counterproductive, in that you would not be able to see well if you take it upon yourself to lower your prescription below what your eye doctor has prescribed.
As a general rule, single vision prescriptions result in thinner lenses than multifocal prescriptions, all things being roughly equal. Multifocal prescriptions are those with an NV-ADD (Near Vision reading ADDition). Having an NV-ADD, or just an ADD, as it’s usually written, enables you to get bifocals and progressive glasses.
In addition, prescriptions with astigmatism corrections – if you have this, there will be numbers in the Cylinder (CYL) and Axis (sometimes abbreviated X) fields – generally result in thicker lenses than those without astigmatism corrections.
2) Your lens index. The lens “index” is short for the lens’s “index of refraction.” That means how much the lens bends the light that enters it. That’s what refraction is. Bending the light focuses it right into the middle of your visual sweet spot, the retina, so you can see well.
You can change the index to thin the lens, up to a point. After that point, the law of diminishing returns kicks in. The lens that is recommended for your prescription will be the thinnest lens. Choosing a lens index that’s higher than the recommended lens index won’t make the lens thinner, and you’ll end up paying more for no improved result.
If this is confusing, don’t worry. We’ll clearly explain where the point of diminishing returns shows up when we look at the various lens indexes. In addition, you’ll be able to see it too, when you start playing with the Lens Index Calculator.
3) Your lens width. This can have a considerable effect on your lens thinness. Once you have settled on the correct lens index, having determined that going to a higher lens index number won’t result in a thinner lens, the lens width – also known, weirdly, as the “eye size” – will be the last, and in some situations, the most important – factor in thinning your lens.
OK, are you confused enough yet?
Yes? Let’s fix that right now.
We’re going to look at a prescription to see how different index numbers can make the lenses thinner. We’ll change the lens width – remember, that’s also known as the “eye size” (even though it doesn’t refer to the size of your eye) – to see how this affects the thinness of the lens.
To do this, we’re going to use a fairly common prescription. Most eyeglasses wearers are nearsighted, which means that the number in the Sphere (SPH) section on the prescription will be minus.
Most people who have an SPH correction also have an astigmatism correction. So we’re going to create a common prescription, with an average Pupillary Distance (meaning the distance between your pupils measured in millimeters, PD for short), 63; an average lens width (all together now: also known as “eye size”), 50 mm; and an average bridge (that’s the part of the frame that goes over your nose), 18 mm.
Here it is:
SPH -2.00, CYL -1.00, AXIS 90, PD 63, Lens Width 50, Bridge 18.
(For the sake of simplicity, we’ll assume that the prescription is the same for both eyes.)
Let’s put these numbers into the Lens Thickness Calculator and see what we come up with when we use different lens indexes.
With nearsighted prescriptions, the lens is concave. With farsighted prescriptions, the lens is convex. A concave lens is thinner at the center, thicker at the outer edge. A convex lens is the opposite.
You will see then, that with nearsighted prescriptions, the Center Thickness of the lens will be a lower number than the Edge Thickness.
Here’s what our formula yields with the 1.50 standard-index lens, which comes free on an order of single-vision glasses:
Center Thickness (CT): 2.0 mm / Edge Thickness (ET): 4.4 mm
Nice and thin at the center, but maybe not as thin as it could be at the outer edge. Let’s try it with the 1.57 mid-index lens and see what we get:
CT: 1.5 mm / ET: 3.6 mm
That makes the lens thinner at both the center and edge, and the lens is still free. Now let’s try it with the 1.59 pure polycarbonate single-vision lens, which costs $9.00, and see what happens:
CT: 1.5 mm / ET: 3.5 mm
You’re spending $9.00 for this lens, which is not a huge amount, but this slightly higher index doesn’t make the eyeglasses lens perceptibly thinner than the free 1.57 lens does. Now we’re starting to see the law of diminishing returns come into play.
However, even if the lens would be just as thin with the 1.57 lens, it would be worth it to spend the $9.00 on the 1.59 pure polycarbonate lens if you’re getting rimless glasses or if you’re buying glasses for kids who can be expected to treat the glasses roughly.
That’s because the 1.59 lens is a more impact-resistant lens than the 1.57, which is still a fine lens for people who treat their glasses with care.
Now we’re really going to see the law of diminishing returns at work when we go up a notch, to the 1.61 high-index single-vision lens. Here are the results of this lens:
CT: 1.5 mm / ET: 3.5 mm
No change, and you’re now (theoretically) spending $19.95 on a lens that isn’t any thinner than the 1.59 pure polycarbonate lens that’s $9.00, and is only a tiny bit thinner than the 1.57 mid-index lens that’s free.
But even after you’ve selected the lens index that will give you the thinnest lens, you can still thin the lens further, if you narrow its width.
Let’s lower the lens width to 48 mm and see what happens with each lens. First, the 1.50 lens:
CT: 2.0 mm / ET: 4.1 mm
The Edge Thickness is a tiny bit better, 4.1 mm as opposed to 4.4 mm on the 50 mm-wide lens. How about the 1.57 lens?
CT: 1.5 mm / ET: 3.3 mm
Now we’re talking! We’ve shaved half a millimeter from the center and almost a whole millimeter on the edge, just by lowering the lens width.
How about with the 1.59 lens?
CT: 1.5 mm / ET: 3.2 mm
No change on the center, only one tenth of a millimeter on the edge. Stand and salute the diminishing returns on parade!
Let’s take a quick look at the 1.61 lens, just to make sure it doesn’t make the theoretical eyeglass lenses any thinner:
CT: 1.5 mm / ET: 3.2 mm
That would cost $10.95 more for no improved result.
So unless you want a pure polycarbonate lens for its impact-resistance feature, you’re wasting your money by spending $9.00 to get a higher-index 1.59 lens that won’t be any thinner than the free, 1.57 mid-index lens.
But once you’ve confirmed which lens index that will result in the thinnest lens for your prescription, and you want to thin the lens even further, play around with the lens width on the Lens Thickness Calculator. Go as low as you can and still keep the lenses wide enough for a comfortable field of vision and attractive look.
For example, the 48 mm wide lens may be just as narrow as you can go without making the glasses look too small. But if you can narrow the lens even more, you will see that the lens will continue to become thinner.
If you do check out the Lens Thickness Calculator to see the estimates of different thicknesses that different lens indexes and lens widths yield, keep a few things in mind: When you are selecting the Lens Material Type, the categories listed on the Lens Thickness Calculator don’t exactly correspond to the lens index categories on our website, although they are basically the same.
For example, the Hard Resin lens is the 1.50 lens. The 1.56 mid-index is essentially the same as the 1.57 mid-index. The polycarbonate lens is the 1.59 mid-index lens. All of the 1.60 lenses on the Lens Material Type list are the equivalent of the 1.61 high-index lens.
So to recap, stick with the lens that our website recommends when you enter your prescription. That will get you the thinnest lens for your prescription, if you also select the lowest lens width that will also work well for your face size and shape.
Thursday, February, 13 2014 by Matthew Surrence
If you’re a Star Wars fan and lucky enough to to have received a handheld blue laser for Christmas, beware. While you may be geeking out with your new, light saber-like toy, keep in mind that your laser can turn into a weapon if you aren’t careful.
Johns Hopkins recently sent out a press release reminding consumers that lasers aren’t child’s play and laser exposure can permanently damage a person’s eyesight. In addition, laser manufacturers themselves note that a poorly handled laser can start fires or burn a person’s skin. The press release was triggered by a the publication of Saudi Arabian study documenting numerous instances of eye injury caused by blue lasers. In most of the cases, individuals with eye injuries sought medical treatment right away and were able to regain lost eyesight, though some suffered permanent damage to the retina, resulting in partial blindness.
Individuals have also been harmed while handling a laser in a room with a mirror: The reflected light was so powerful that it caused vision damage.
If you are a gamer or serious sci-fi fan, keep in mind that while these lasers look really cool, they can also cause serious damage. Some laser companies have even developed lasers with locks that prevent children or teens from using your laser inappropriately. It is also important to wear eye protection that has been approved for use with your laser.
Wednesday, January, 8 2014 by Lainie Petersen
The loss of the ability to read, or to read easily and comfortably, can have an enormous impact on the lives of people with low vision. While alternatives to printed text exist, such as audiobooks, many people prefer reading to listening. Vision aids, such as illuminated magnifiers, can assist with reading, but are often large, making them inconvenient to store, travel with, and use.
Fortunately for low-vision readers, a recent study shows that tablet computers now offer a realistic alternative to audiobooks and magnifiers.
A recent article on EyeSmart, an online publication by the American Academy of Ophthalmology, reported on a study at the Robert Wood Johnson School of Medicine showing that tablet computers can help people with low vision increase their reading speed. The study tested the difference in reading speed in low vision subjects who read text in print and on a tablet. All study participants increased their reading speed by at least 42 words per minute when reading a tablet set with 18 point text.
What You Can Do
If someone you care about suffers from low vision and would like to be able to read again, consider buying that person a tablet computer or helping them to buy one for themselves. Study subject with the “poorest eyesight” had the most success with iPad or Kindle, so you could begin your search for a tablet by researching both these products. Your best strategy may be to bring your friend or relative to a store that sells these tablets so he or she can try them out.
In situations where affordability is a problem, buying a used device is a good strategy. Many people also sell or give away their tablets when they upgrade to a next generation device, providing an opportunity to buy a used device at a lower cost than brand new items. Just be sure to thoroughly test used devices before making an in-store or in-person purchase. If you buy a used device online, check whether the retailer offers a warranty or guarantee and check the device as soon as you receive it so that you can get your money back if it doesn’t work as advertised.
Vision Screening Apps
The EyeSmart article also points out that various eye health apps are now available for tablet and smartphone users, so those who invest in a tablet might want to purchase one or more of these programs. Eye health apps range from medication trackers to vision tests that can help physicians and patients identify changes in eyesight. These apps are low cost and can make a great adjunct to a program of regular eye exams, medication and other vision treatments.
Monday, January, 6 2014 by Lainie Petersen
- Many eye diseases can be cured, or at least slowed, with early detection.
- Headaches, neck and shoulder pain can sometimes be a sign that you need eyeglasses.
- Some eye symptoms can be connected to more serious medical conditions.
By resolving to take care of your eyesight, you’re resolving to care of your whole body. Here are some resolutions to think about:
1. Get Your Eyes Checked
Regular eye exams help detect eye diseases and let you know if you need glasses or to change your prescription. Talk to your eye doctor about how often you should get your eyes checked: The recommended frequency of exams varies according to your age and whether you have a history of eye problems.
2. Develop an Eye Rest Routine
Constant exposure to computer, smartphone and tablet screens causes eye strain. Be sure to regularly move away from the screen and look off into the distance for 30 seconds or so. If you need to, set a timer to remind you to do this throughout the day.
3. Wear Activity-Appropriate Eye Protection
Many activities present dangers to our eyes, including sports, construction work and even some crafts. If you are in a situation where your eyes are exposed to chemicals, flying/swinging objects (such as balls, bats, tennis rackets or bits of wire during jewelry making) or you are at risk of crashing into a floor (such as on the basketball court), make sure you are wearing protective eyewear. If you aren’t sure what kind of eyewear is right for you, talk to your doctor.
4. Protect Your Eyes Against UV Exposure
Sun exposure can cause eye strain, ocular melanoma, and eye damage. At minimum, wear glasses with a anti-UV coating and strongly consider wearing sunglasses whenever you are out in the sun. For extra protection, use facial moisturizers, concealers and foundations that contain sunscreen.
5. Practice Good Eye Hygiene
Poor eye hygiene can lead to inflammation of the eyelid, a condition known as blepharitis. If you wear eye makeup, use eye makeup remover at the end of the day. If you don’t use eye makeup, you should still keep the eye area clean by using a gentle cleanser around the eyes.
6. Throw Out Old Eye Makeup
Old and contaminated eye makeup can cause eye irritation and infections. Toss mascara after it’s been open for three months. Dump eyeshadows, eye creams and eyeliners after 6 months. If a product’s container has been damaged, toss the product to avoid applying a contaminated product to your eye area.
Have a happy, safe and healthy 2014!
Friday, December, 27 2013 by Lainie Petersen
As the packages pile up under the tree, it’s important to keep in mind that while toys are fun, they can also be dangerous. In fact, emergency rooms in the United States treated over 265,000 toy-related injuries last year. This makes safety a significant factor when selecting toys for children.
Recently, The American Academy of Ophthalmology (AAO) recently issued a warning to parents about the risks that some toys present to children’s vision (almost half of toy-related injuries that result in an ER visit involve the face or head). If you plan to give gifts to children this year, you should keep eye safety in mind before making a purchase.
Based on the AAO’s recommendations, here are some tips for keeping your kids safe while they enjoy their holiday presents:
Risky Toys and Prevention
According to the AAO statement, toys that can contribute to eye injuries include:
- BB, airsoft and paintball guns
- Laser toys
- Sports equipment
- Toys with sharp or protruding parts
Accidents involving toys can cause serious eye injuries, some of which could permanently damage a child’s eyesight.
In addition to being aware of the types of toys that can result in eye injury, it’s also important for gift givers and parents to:
- Read toy labels for age group recommendations. What may be safe for a 10 year old may not be a good choice for a child of seven.
- Provide adequate supervision while playing with toys.
- Seek medical attention if a child receives an eye injury, even if it doesn’t initially appear to be serious.
The AAO recommends that parents purchase adequate eye protection for their children in the form of glasses or goggles with polycarbonate lenses. Zenni provides a full range of affordable children’s glasses and sports goggles that may be appropriate for your children. You should, of course, always talk to your eye doctor about the type of eye protection that is best for your child’s needs.
Tuesday, December, 24 2013 by Lainie Petersen