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Glass & Plastic Photochromics:


What are photochromic lenses?
Photochromic lenses are optical lenses that darken when exposed to ultraviolet rays going from a lens that is virtually clear or has a light shade of color to a dark sunglass like color.


What makes photochromic lenses better than other lenses?
Photochromic lenses will block out 100% of UV light automatically when going from indoors to outdoors with out needing to change eyewear. They will adjust to the varying light conditions you encounter every day.


Who should be recommended to wear photochromic lenses?
Anyone who wears glasses with regular lenses because they are as clear as regular lenses indoors and adjusts to any light in any condition and automatically filtering UV when present.


Do Photochromic lenses protect against UV rays?
Yes. When photochromic lenses are clear or dark they provide 100% protection from both UVA and UVB rays.


Can Photochromic lenses be worn while playing sports?
Yes. These lenses can be worn any place for any activity, especially outdoor activities because they are 100% UV protected. They are also available in impact resistant Trivex and Polycarbonate lenses which are also very lightweight.


Can Photochromic lenses replace sunglass lenses?
Photochromic lenses get dark outside but are not meant to replace as a sunglass lens. Some studies show that photochromic lens wearers are more likely to own sunglasses as a second pair of glasses because when being worn behind a windshield, the level of activation is not as high because most windshields block UV rays. Sunglasses are a specialty product for specific need. Photochromic lenses are worn for patients to see comfortably in any light.


How long do photochromic lenses last?
Photochromic lenses last as long as your prescription. Plastic photochromic lenses usually out last the lifetime of a patient’s prescription, about 2.5 years. Glass photochromic lenses never stop working; in fact glass Photochromics get better with age and will not slow down or loose the darkening ability.


How does AR coating affect a Photochromic lens?
All photochromic lenses are compatible with Anti Reflective treatments. AR coating will improve light transmission, much like regular lenses. Photochromic lenses with AR coating also add additional comfort for night driving.


Why don't my new glass photochromic lenses work as well as my old pair?
Glass photochromic lenses unlike plastic need to be worn and broken in unlike plastic photochromic lenses which have a life span of about 2.5 to 3 years. To speed up the break in period the lenses can be placed in the sun for the first day or two allowing the sun and UV like activate the photochromic crystals and with use will get darker and change faster until they meet the manufacturers performance levels.


Why don't the bifocals on glass photocromic lenses get dark?

Glass photochromic lenses unlike plastic lenses have high index glass bifocals fused into the photochromic lens blank. They are not able to make these higher index bifocals parts with photochromic properties.





How dark can Transitions® lenses get?
Transition Brown lenses achieves a level of 15% transmission having that be a tint of 85% and a Transitions® Gray lens achieves a level of 12% transmission, having that be a tint of 88%. These are achieved at 72° Fahrenheit and will vary with recapture and air conditions; slightly darker in colder temps and lighter in warmer temps, also air quality can diminish the color by restricting the amount of UV just as snow can increase UV by reflection, thus making the lenses darker.


Can Transitions® lenses get as dark as sunglass lenses?
Transitions® lenses do become as dark as a sunglass lenses. Both the gray and brown colors reach to 92% of there full activation in only one minute; 80% is considered a sunglass.


Why do my Transitions® lenses not get dark in my vehicle?
In today’s vehicles, windshields block most of the UV rays that cause Transitions® lenses to activate, or darken. When worn inside a car where less UV light is present, the ability of the lenses to darken is reduced. You may want to wear a pair of polarized prescription sunglasses for driving.


Is Transitions® Gray better than Transitions® Brown?
The only difference between the two lenses is personal preference. Both lenses block 100% of both UVA & UVB lighting. Both lenses are as clear indoors as a clear lens and become darker outdoors than any previous technology of Transition. Brown lenses block more blue light thus reducing haze and glare and are more popular in Europe. Gray lenses tend to be more popular in the US and are a good choice for bright conditions.


Will Transitions® lenses change under florescent lighting?
Florescent lights do emit UV light and therefore will make all photochromic lenses darken slightly.


Thin & Dark™:


What is a Thin & Dark™ Lens?
These are the latest family of material by Corning which is 5% lighter in density, can be safely ground to 1.5mm center thickness and has improved photochromic gray properties.


Are Thin and Dark lenses thinner because of the index of the lens?
No, these lenses have a 1.523 index. The lenses are patented from Corning allowing them to be ground to a target 1.5 center thickness, giving you a lens that is up to 30% lighter and thinner than standard glass.


I thought the FDA requires 2.0 CT on glass lenses, how can these be ground thinner?
Neither FDA nor ANSI requires a minimum thickness. The requirement is that chemically tempered lenses must pass the FDA drop ball test for dress eyewear.


Can any prescription be made in Thin and Dark?
Thin and Dark lenses are available in a wide variety of lens designs and Rx’s, including single vision, bifocals, trifocals and progressives. They are also available in glass-polarized styles. They have an Rx range of -9.00 to +5.50 total Rx power.


Why can’t these lenses be made in an hour?
This special formula of glass should be chemically tempered in the 2 to 16 hour process. Air tempering is not recommended.


Why is Thin and Dark darker than PGX®?
These lenses have more photochromatic micro-crystals per cc. This increased crystal density makes Thin and Dark lenses turn darker.


Will Thin and Dark get dark even on hot days?
Yes. Some Photochromic don’t but this lens will achieve 21% transmittance at 90 degrees F, far exceeding the performance of most other photochromatic materials on the market.


Will Thin and Dark darken behind a car windshield?
Yes. Thin and Dark will darken to some degree, behind a car windshield because they are activated by UV radiation and visible light.


Do Thin and Dark lenses block UV light?
Yes. They block 100% of UVB and 97% of UVA per ANSI Z80.3 requirements for special purpose UV absorption.


How will AR coatings affect my Thin and Dark in the lightened and darkened state?
AR is an excellent add-on for glass lenses. It is the ultimate material for glass lenses as it adheres better to glass increasing coating life. A glass lens with AR is more scratch resistant than a plastic lens with AR coating. AR coated Thin and Dark will transmit more light indoors so they will be clearer in color, and outdoors will transmit slightly more light so lenses may be slightly lighter outdoors.


Will Thin and Dark tint under fluorescent lights?
Yes. They will have a slight tint under fluorescent lights. Many people find this helpful in an average office environment.


How would you handle replacement of a single Thin and Dark lens?
Replace the single lens and then chemically temper both lenses together.


Is Thin and Dark available in other colors?
No, brown was available but now is discontinued.


How much darker and lighter does Thin and Dark get compared to PGX® and Transitions®?
Thin and Dark transmits 88% light indoors and 15% outdoors. PGX® transmits 85% indoors and 22% outdoors. Transitions® transmit 89% indoors and 15% outdoors at 72 degrees F. The Transitions® lens will be considerably lighter outdoors at higher temperatures.


How much lighter in weight is Thin and Dark than PGX® and how much heavier than a standard plastic lens?
Thin and Dark lenses can be up to 30% lighter than PGX®; they are 5% liter in density than PGX® and can be 25% thinner (1.5mm CT vs. 2.0mm CT). The difference in weight between single Thin and Dark lens and standard plastic lens with a –2.00d Rx and a 50-eye size is equal to about the weight of a dime.


Does Thin and Dark have a green hue like PGX®?
No, Thin and Dark lenses are clear indoors. PGX® and PBX® have slight indoor colors, while 1.6 index photochromic glass has a noticeable indoor color.



Trivex Lenses:


Trivex® is a new plastic lens monomer developed by PPG® Industries. It is a strong, light and thin material with a very high impact resistance equivalent to polycarbonate.


  • High impact resistance. Trivex® has been formulated to meet or exceed applicable impact resistance requirements.
  • Extremely thin and light. With a density of 1.11, Trivex is lighter than most other plastics, and can be made to a minimum center thickness of 1.0mm.
  • 100% UV protection from both UVA and UVB.
  • Chemical Resistant. Trivex® is unaffected by most common chemicals and solvents.
  • Ideal for coatings. Trivex® can be hard coated and anti-reflective coated.


Is there a special way to drill Trivex lenses?
Click here to view the link on tips for processing Trivex lenses.


Can you tint your Trivex lenses?
Yes. You are able to tint our Aris™ Trivex lenses. All FSV and all styles in the semi-finished form are tint-able prior to applying a backside coating. This may not be true of all Trivex lenses from other manufacturers but those from X-Cel are.


Polarized Lenses:


Do only polarized lenses block UV light?
No. There are a number of lenses out there that block UV lighting. Please see the link below for the performance chart of lenses.


Are Polarized Gray lenses more gray or green in color? (Both glass & plastic)
In all polarized lens materials the Gray C color is a true “Smoke” or “True” gray color with no green. If listed as a “Polarized G-15” or “Gray 15” these are a Green/Gray color and are the same as a G-15 color by Ray Ban.


Polycarbonate Lenses:


Are your Polycarbonate lenses tint-able?
Our polycarbonate lenses are only tint-able to 10%. A tint-able backside coating is required on these lenses also to be able to tint them.


General Topic Questions:


What is your return policy?


Are Prism Segs still available?
No, the one manufacture that had been making these in glass only is no longer offering these.


Do Fixed Tint glass lenses block UV light?
Yes, fixed tints in glass block from 89% to 100% depending on the color.


If you put glass photochromic lenses in the freezer will it go back to its original color quicker?
No, putting lenses in the freezer has no effect on the lenses once they are removed and reach room temperature. The effect only lasts as long as the lenses remain cold.


Is there an edge on our Polarized lenses?
On most polarized plastic and poly lenses there is a small portion of the outer diameter that is not usable; this is from the manufacturing process. The diameter listed for X-Cel’s polarized lenses is the usable size of the lens. So the answer is yes, but the size listed is without that un-usable portion.


In a 1.70 flat top 28 lens what would cause the seg to be foggy or hazy?
All flat top segments in glass are made from a high index piece, which is higher in index than the major portion of the lens and is “Fused” into the blank. As glass becomes higher in index it becomes more sensitive to chemical attack. Liquids, vapors and liquids, which are high in PH including the salt baths used to chemically strengthen the lens can “Etch” the segment glass making it, appear hazy. These can be polished to remove the haze.


Are the multifocals in glass fixed tints clear segs?
Only the Gray 1, 2 & 3 D-25 and D-28 have colored segments. All other colors and styles have clear segments including all Photochromics, which have always been clear.


What is a Kalichrome lens?
Kalichrome is another name for a yellow lens. Other names that could be in reference to this lens is Haze aster, Canary Yellow, Helios, Striking Yellow or the popular shooting yellow by Ray Ban. This lens is an extreme blue blocker, blocking 100% of all light up to 450nm.


What type of lens filters blue light?
Many colors will filter blue light to some degree but the best type of lens for that is a lens that blocks most light under 450nm such as Canary Yellow, Autumn Gold™, Polarized Autumn Gold™, CPF lenses and others tinted using a filtering tint.


What is the Abbe value of a Clear 1.6 lens?
The Abbe value of a Corning Clear 16 lens is 42.0


What is a PGX® lens?
Made by Corning these are the 3rd generation of glass photochromic lenses in gray; Photochromic Gray Extra Dark


What is a Corning Clear 16 lens?
These also are the latest family of material by Corning, which is 5% lighter in density, can be safely ground to 1.5mm center thickness and has improved clarity.


What is an Executive Bifocal?
These have been around since the time of Ben Franklin who invented them. This is a lens with a line running across the full width of the lens, the top half with your distance prescription and the bottom half with your reading prescription. Persons who say play a piano and need a large/wide reading area would benefit from a wider reading zone.


What is an Executive Trifocal?
The same as an executive bifocal except it has a 3rd line that has 50% of the reading prescription power. These are for those with the wider reading areas that are more advanced in presbyopia, which is Greek for older person.


What is a DD bifocal?
A Double-D bifocal is a lens used by those in occupations like plumbers, who need a reading zone for working overhead. They have 2 bifocals separated in the middle with the distance prescription. Similar would be a Quadrifocal, which is the same but has a trifocal on the lower half. These are available in glass only.


Are plastic double segs hard coated? And what is the separation?
Yes, all plastic standard thickness occupational lenses from X-Cel are hard coated. For both the DD-28 and DD-35 the separation is 14mm, 7mm down and 7 mm up.


What is the difference between an aspheric & non-aspheric lens?
The front surface of an aspheric lens has curves that gradually flatten or steepen as they move away from the optical center of the lens. A non-aspheric or spherical lens has the same radius curve over the entire surface. Aspheric lenses will provide a better peripheral image and can reduce edge thickness on higher prescriptions.


Are the High-X 1.67 lenses aspheric or non-aspheric?
The Finished Single Vision are aspheric, the SFSV and D-28’s are not; they are spherical in design.


How do you know what the intermediate power is on a trifocal lens?
Typically the intermediate power would be 50% of the prescribed add power. Other add powers are available; 61% Acclaim plastic trifocals and also in glass 40% & 70% specials.


Are the High-X 1.55 lenses coated?
Yes. All styles of lenses that we have in the 1.55 material are coated. A backside coating is not required to tint these lenses but is recommended for scratch protection on the backside.


Does an A.R. coating make my lenses darker?
No, A.R. coatings make the lenses more clear and reduces the amount of glare that you see and that reflect off the lens. They typically will not affect the photochromic performance of Transitions® or Photochromic glass lenses.


What is the difference between light transmittance & luminous transmittance?
These two phrases mean the same thing; they refer to how much light is passed through a lens material.


What is the fitting height on your Progressive lenses?
The Freedom ID™ is designed for 17mm, the Fashion Fit also 17mm and the Freedom 5 is 22mm.


What is the difference between OLT & XLT?
XLT is standard CR-39 plastic lenses made by X-Cel. OLT are regular plastic lenses we out source from another lens caster.


Do we have finished glass and plastic lenses?
X-Cel does not stock any finished glass or plastic lenses. We do stock Trivex, 1.67 and Poly finished single vision lenses at competitive prices. The reason for this is glass and plastic FSV are available from most other suppliers at lower prices than X-Cel could provide. We also have not seen much interest from our customers for those two products.


What lenses do we have that can be used for welding?
In the past there was a Green Didymium #4 & 5 available, but it is no longer made. ANZI standards are very clear on what welding shades are required for all types of welding and no glass is available to meet these requirements unless custom made. For these occupations welding helmets and goggles should be worn over the patient’s safety eyewear.


Does X-Cel Optical have on-line ordering?
No, but we will be looking at this as more customers request it.






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