Q: Are you familiar with the high-index glass materials from Zeiss and Corning (up to 1.9)? I have a
prescription of approximately -8.5/-3 and 9.25/-3. The frames I'm looking into are size 38 to 40. Based on my research, the advantages of plastic (lighter, shatter-resistant) may not be an issue with the
high-index and lens size. I've been told that Corning lenses are tempered and ball dropped. — P.C., Delaware
A: I agree. Modern high-index glass lenses can be thin, light and safe. However, in my opinion, polycarbonate lenses are safer. — Dr. Dubow
Q: What is the best eyeglass tint? — B.H., Idaho
A: It depends on what "is" is! Really and truly, there is no best tint. Different tints help with different things. There are some tints that help shooters, some that help golfers, some that help tennis players, some that help computer users, etc. But each person is different. Go to a good optical shop and talk to a trained dispenser who can help you figure out what would be best for you. — Dr. Dubow
[Read more about tints and coatings.]
Q: I have recently purchased new glasses. My lenses are "mid" index, and for the first time I got the anti-reflective coating. This is my second week wearing them, and in bright light, if I'm not looking directly through the center, I see a thin halo-type effect of blue and yellow on either sides of objects — even on my computer screen. Is this normal, or are the lenses defective? — L.G., Canada
A: In my experience, anti-reflective (AR) coatings do not cause this to occur. You may see a shimmery colored coating when looking at the fronts of the lenses, but not usually while wearing them and looking from the back. The index may be causing this phenomenon — I'm not sure. It's possible it's just normal distortions caused by looking off-center. — Dr. Dubow
I recommend you go back to where you got your glasses and let them figure this one out! — Dr. Dubow
Q: Please explain all the numbers and terms on my eyeglass prescription. Thank you. — B.J., Texas
A: An eyeglass prescription is written in a standardized format with standardized notation so it can be interpreted worldwide. Let's look at one and break it down:
-2.00 -1.00 x 180. The first number (-2.00) tells us the spherical refractive error (farsightedness or nearsightedness). In this case, because there is a minus sign in front of the 2.00, this patient is nearsighted. A plus sign would indicate farsightedness.
The second number (-1.00) is the astigmatism.
If there is no astigmatism, we generally write the letters DS or SPH after the first number to let the optician know that we didn't just forget to write in the astigmatism.
The final number (180) is the direction of the astigmatism. Astigmatism, a football-shaped eye, can be measured in any direction around the clock. We use the numbers from 1 to 180 to indicate the orientation of the football shape.
There may be additional numbers in a glasses prescription. For instance, if the basic prescription is followed by a small number with a superscript (1^) it indicates prism correction.
There may be more than one set of prism numbers for each eye.
Lastly, there can also be numbers denoting the amount of near reading strength needed (bifocal or progressive). They usually go from +0.75 to +3.00, depending on age and visual need.
The letters OD and OS in front of a prescription let us know which eye each string of numbers is for. OD stands for right eye and OS for left eye, while OU means both eyes. — Dr. Dubow
[Read more about eyeglasses, nearsightedness, farsightedness, astigmatism and presbyopia.]
Q: What is the best possible type of eyewear to wear while driving at night to eliminate glare from other vehicles' headlights? — R.B., New Jersey
A: Easy! Get lenses with anti-reflective coating. This coating reduces glare by 90 percent or more and works great. I never get glasses without it! — Dr. Dubow
[Read more about anti-reflective lens coatings.]
Q: Is it true that the longer you wear glasses, the worse your sight will be? — Nicole, Canada
A: No. This is a myth. — Dr. Dubow
Q: Can you tell me what the difference is between anti-reflective lenses and polarized lenses? No one seems to want to, or perhaps they're just not able to answer this question for me. — D.L., New York
A: Anti-reflective lenses simply cut out most of the reflections caused by light bouncing between the two lens surfaces and interfering with good, comfortable vision.
Polarized lenses cut out light from one whole meridian, typically the horizontal one. This minimizes the glare from light that bounces off water, the hood of your car, or a shiny road surface. Polarization is useful for fishermen or people that do a lot of driving, though many outdoors people prefer polarized sun lenses.
Polarization is usually applied only to sun lenses, whereas anti-reflective coatings can be used on both indoor and outdoor glasses with success. — Dr. Dubow
[Read more about anti-reflective lens coatings or polarized lenses.]
Q: I recently went to my local optometrist for new frames and lenses. By the time I left his office I had "the best" progressive lenses, titanium frames, scratch coat, AR coating and a bill for over 420 bucks.
Three weeks later I brought the pair of glasses back to the OD due to scratches on the lenses and was told he would split the cost with me for replacement lenses.
Is this any way to treat a customer? I did not drop my glasses or take a sledgehammer to them. I thought I paid extra for the scratch coating so I wouldn't have this problem. Is this common practice for an OD today? — K.F., New Jersey
A: Good question! Although I hesitate to speak against a colleague, it is my view that new and exciting technology should not take the place of customer service.
A lot depends on how you define "recently." If you bought your glasses within the past 3-6 months, it is my opinion that your
doctor should have used the warranty given to him or her by the laboratory that supplied the lenses. If your problem happened a year ago, then the offer to split the cost is probably fair depending on what caused the scratches. Circular scratches usually indicate that the patient used the wrong cleaning cloth or forgot to rinse dirt particles off the lenses before rubbing.
Most importantly, if you are unhappy be sure to tell the doctor. Most private practitioners are very tuned in to their patients' complete satisfaction. And remember, it is best to use an appropriate cleaning solution and cleaning cloth on your high-tech lenses. You can also clean your lenses with warm water and a mild detergent and dry them with a clean cotton dish towel. — Dr. Dubow
Q: What is "prescribed prism?" Why is it necessary, and how does it help me see? — J.C., Colorado
A: Prism is usually prescribed in lenses to help you use your eyes together. Some people's eyes have a tendency to try and pull apart when they are in use — some go up and down, and some go in, and some go out. These are called muscle imbalances, or "fixation disparities," in our lingo.
Prism can help ease the symptoms of these imbalances by making the brain think the eyes are working together. I have worn prism in my glasses since about age 5, and I
prescribe prism for many of my patients, with very positive results. In my opinion, you have a great eyecare practitioner! — Dr. Dubow
Q: I have a "prism" in my glasses, which is to help with the fact that I don't do the "lining up the horizontal/vertical bars" portion of the eye exam correctly. I would like to have my eyes fixed, but my doctor says that LASIK can't fix this condition and I'd have to wear glasses when I do computer work anyway. Is this true? I am in computer sales, so I use one ALL day long. Any ideas? Thanks! — J.P., Kansas
A: Take a look at my explanation of prism above. I have found that some of my patients who require prism can get along just fine after refractive surgery, while others require glasses for some tasks. I can't agree or disagree with your doctor without having examined you myself.
But before you jump on a plane to Minnesota, remember that you will have to wear glasses again anyway as you age — unless you have a monovision correction.
I suggest you get a second opinion on your prism and have a frank discussion about the pros and cons of refractive surgery with a practitioner you trust. — Dr. Dubow
Q: I have double vision and would like to know how prism in glasses helps to cure this. Also, is there any way I can wear contacts to correct this? — Tina, Florida
A: A prism bends light. Prism in glasses can kind of fool your eyes into thinking they are working together without strain. Prism can also help with double vision by aligning the two images into one. I prescribe a lot of prism for my patients, with excellent results.
Some patients who require prism can wear contact lenses, and some can't. It depends on the kind and the amount of the prism.
In fact, some kinds of prism are corrected better by contact lenses than by glasses! See your eyecare practitioner for more details. — Dr. Dubow
Q: What are prisms? How do they work? — B.M., Arizona
A: Prisms bend light and separate white light into its component colors. In vision correction, we like the light bending and don't want the color separation aspects of prism.
How do prisms work? It's complicated, but if you think of a prism as being a triangle pointing upwards, light goes in one side, bends down toward the base, and comes out the other side going in a different direction. Of course, in glasses and contact lenses this is much more sophisticated and doesn't really look like a triangle... but the effect is the same.
Prisms are used in lenses to help keep the eyes working together and aligned. They can make the difference between glasses that are OK and glasses that are wonderful. — Dr. Dubow
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