What you’ll pay: Tints cost an average of $74.67, according to the Vision Council’s VisionWatch market research for December 2019. Blue blocking costs $50 at Warby Parker and starts at $19 at EyeBuyDirect.

What you’ll pay: It’s usually included, especially with sunglasses. Otherwise, an upgrade to 100 percent UV protection may be available. At EyeBuyDirect, for instance, it’s included with an upgrade to thinner lenses. And note that polycarbonate lenses, which are natural UV blockers, offer 100 percent protection, as do many high-index lenses, Vitale says.

Chromatic aberration occurs because the lens refracts the various colors present in white light at different angles according to their wavelengths.  Red light, for example, is not refracted at the same angle as green or blue light so the focal point on the optical axis of the lens is farther away from the lens for red light.  Likewise, green light is focused closer to the lens than red light and blue light is focused in a plane that is closest to the lens.  This phenomenon is commonly referred to as dispersion and occurs to a certain degree in all spherically shaped lens elements.  The inability of the lens to bring all of the colors into a common focal plane results in a slightly different image size and focal point for each of the three predominant wavelength groups.  The result is a colored fringe or halo surrounding the image, with the halo color changing as the focal point of the objective is varied.

Scan the warranty. Many glasses will be backed up by some kind of warranty, but it might not cover coatings. Or warranties may vary in terms of which ones are covered and for how long. What can you expect? “Virtually all coatings today are designed to last the life of the prescription,” says Vitale, which, on average, is about 28 to 30 months.

But once you’ve picked frames and lenses, there’s a wide variety of lens coatings to consider, each with its own properties—from light reduction to scratch resistance.

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What to know: Tinted lenses are often touted as “curing” color blindness, Brodie says. The truth: A tint may make some color contrasts more visible to people with partial color impairment but may make other contrasts harder to see, so it’s a trade-off.

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This coating will make your glasses less vulnerable to scratching if you happen to drop them or clean them with an abrasive cloth. “Many glasses wouldn’t last a day without this,” Vitale says. “Polycarbonate and high-index lenses are very soft.”

Spherical aberration and chromatic aberrationdifference

Think about how you use eyeglasses. Indoors and outdoors? For sports or only for reading or desk work? Driving day and night? Your lifestyle and habits should inform your coating decisions.

The experienced lens professionals at Esco Optics can work with lens designers to eliminate chromatic aberration in spherical lenses by recommending the best combination of specialized materials and manufacturing techniques for the designer’s specific application.

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What to know: The AAO recommends getting 100 percent protection from UVA and UVB rays. Lenses that offer this should be labeled 100 percent UV protection or UV400.

Some of these are strictly cosmetic, but depending on your vision needs, others may “potentially improve your comfort and safety,” says Andrew Iwach, MD, clinical spokesperson for the American Academy of Ophthalmology (AAO).

Distinguish betweenspherical aberration and chromatic aberration andcite a remedy for each

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Ask for an itemized description. In many cases, eyeglass lenses come bundled with certain coatings, commonly those that reduce reflections or bolster scratch resistance. Be sure you don’t pay extra for a coating that’s already supposed to be part of your package.

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No matter what your warranty says, if a coating starts to degrade within a year, Vitale recommends taking the glasses back to see whether you can get the problem fixed or the glasses replaced.

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Put price in perspective. Some types of coating, like those that are anti-reflective (sometimes called glare-reducing), come in a range of prices. But experts say the most expensive option offered isn’t necessarily of significantly higher quality. “I know some ‘house brands’ out there that are pretty similar to the premium versions,” says master optician Michael Vitale, vice president of membership and technical affairs at The Vision Council.

What isaberration

The types of lenses you choose can make a big difference in the quality of your eyeglasses. Depending on what your eye doctor advises, some people can get along just fine with basic plastic CR-39 lenses, while some may want to consider thinner and pricier polycarbonate or high-index types, which may be more appropriate for stronger prescriptions.

Typically applied on both sides of an eyeglass lens, this coating, also known as AR or anti-glare, “reduces the amount of light reflected off the surfaces of spectacle lenses, and may enhance the contrast of certain scenes,” says Scott E. Brodie, MD, PhD, professor of ophthalmology at NYU Langone Health in New York City. This means you’re getting the maximum light from the environment you’re in, but without any visual interference that can occur from that light bouncing off your lenses. (The term “anti-glare” is a misnomer, however, says Brodie, and glare—think oncoming headlights—is better addressed with polarized lenses than with AR.)

Who might consider: People who just like the look, of course. But tints may also help improve contrast for those with degenerative retinal disorders or light sensitivity. “Tinted lenses may reduce discomfort in bright light,” Brodie says. In some cases, even light tints may increase contrast, which can be helpful to pilots and marksmen working in outside light, he says.

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Here, dyes are applied to lenses to cut down on the visible light (but not necessarily UV rays) entering the eye. Hues range from light tints like a pastel blue or pink to deeper shades used for sunglasses.

Spherical lenses, those whose radius of curvature remain constant from edge to edge, are subject to various types of optical aberrations.  These aberrations are not caused by defects in materials or manufacturing techniques, but rather by the laws of optics themselves.  One common type of aberration associated with light rays passing through the optical axis of the spherical lens is known as chromatic aberration.

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Chromatic aberrationin lenses

What to know: AR may get a bad rap from consumers who remember it being prone to degrading and developing cracks called “crazing” or “spiderwebbing” in its earlier days. But, according to Vitale, such problems were mostly resolved at the beginning of the 2000s. In the past, AR coatings also tended to attract dust and grime, but they now generally include an anti-static treatment that helps repel water and oil and keeps the coating cleaner. “Most of the AR coatings on the market today perform extremely well,” Vitale says.

And while some coatings may be included in your eyeglass package price, others may add as much as $100-plus to your bill.

Chromatic aberration in spherical lenses is compounded by the difference in image magnification that occurs as a result of the varying focal planes for each color group, an effect termed chromatic difference of magnification.  Aberrations of this type can be significantly reduced or eliminated, by making compound lenses that are composed of individual elements having different color-dispersing properties.  Esco Optics provides a wide variety of optical glasses that are now available to lens designers.  For example, crown glass has dispersive properties that enable it to be paired in a lens doublet with a flint glass element to produce an achromatic doublet lens system that focuses blue and red wavelengths in the same image plane.  Additional refinement of an optical system with even more sophisticated glass formulas and shapes can reduce chromatic aberration even further.

To eliminate virtually all glare on your eyeglass lenses, ask for Neverglare Advantage, an anti-reflective coating for your lenses.

Spherical and chromatic aberrationpdf

How do you know what’s right for you? Your eye doctor may have some suggestions. “These are, by and large, personal decisions,” Iwach says. “One size doesn’t fit all.”

Over time, exposure to the sun’s ultraviolet rays can lead to vision problems such as cataracts and retinal damage. But many eyeglass lenses have a substantial amount of UV protection built in. You can also sometimes buy an additional treatment to safeguard your eyes fully or opt for lenses with 100 percent protection.

To help you sort through the common choices, we’ve gathered advice and cost information from vision experts and major eyeglass retailers, and December 2019 VisionWatch market research from the Vision Council, a nonprofit trade association for the optical industry.

Spherical aberration

Who might consider: Most people, but AR coating may be especially useful for those who often drive at night (it can reduce reflections from headlights at night) and read on computers. It’s strongly recommended with polycarbonate or high-index lenses, which reflect more light than basic plastic CR-39 or glass lenses.

Be even more cautious about anything that feels high-pressure if you’re in an eyeglass store, he says. If you feel pressured, Vitale says, “you may want to look elsewhere.”

Difference betweenchromatic andmonochromaticaberration

As for blue blockers, “there’s probably no harm, though anything that limits the light reaching you can lessen your vision,” Iwach says. “But the benefits have not been proven.” He has also recently seen an increase in interest in yellow-tinted lenses for night driving but cautions that these “can actually complicate things, since in low-light conditions, you want to get the most light in that you can.”

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What you’ll pay: Usually included in the price of glasses, but more robust scratch resistance may be built in to some upgraded lens packages.

What isspherical aberrationin Physics

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What to know: “Everything on the market now except your most basic standard plastic CR-39 lens [which still made up about 36 percent of the prescription lenses sold in the U.S. in 2019, according to the Vision Council] is probably going to come with scratch-resistant coating already on it,” Vitale says. “And that’s because CR-39 is already pretty scratch-resistant.” To further help keep lenses scratch-free, store your glasses in a case when you’re not wearing them and use a microfiber nonscratch cloth to clean them.

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Lenses tinted yellow are sometimes marketed as “blue blockers” for their supposed ability to reduce exposure to the light emitted by electronics such as smartphones. The theory is that this may ease both eyestrain and any sleep problems associated with using the devices too close to bedtime.

Avoid the hard sell. Even if you’re buying the glasses from your ophthalmologist, “by the time you get to the eyeglass purchase point in the eye exam cycle, you’re in a retail environment and may be working with the staff, rather than the doctor,” Vitale says.