Optical Glossary

Glossary of Optical Terms

Authored by: Grant Lambert ABOC, Sunray Optical, Inc.

A.

Abbe Value:
Is a measurement to the degree of which light is dispersed with an existing lens. The average range of an ophthalmic lens is between 30 to 60. The higher the abbe value the less chromatic aberration will be found in the lens, adversely the lower the abbe value there is a greater dispersion of light causing more chromatic aberration when viewing through the periphery of the lens.
 

ABOC Certification:

— official and public recognition of your achievement that you have met a national set of standards as a qualified and competent optician or NCLE contact lens technician. Certification is official assurance to the public that you will handle their eye wear needs competently and carefully; certification is recognized by employers as a standard of competence.

Add (or add power):
If there is a value under the 'add' heading, then you have a bifocal (or Progressive) prescription.
 

Anti-Reflective Coating:

This coating can be applied to the outside or inside surface of any lens (clear or sun lens) to minimizing the amount of light reflected by your lenses thus reducing annoying reflections and distracting glare which may cause headaches or interfere with vision clarity. Regular lenses reflect a very small amount of light back into your eye, possibly skewing vision; anti-reflective coating helps to prevent this anomaly. It is best used on the back surface of a sun lens to minimize back glare.
 

Anti-Reflective Coating (Super):
The Super Anti Reflective coating comes with an extra-tough scratch resistant base coat, and has a hydrophobic/oleophobic topcoat. This topcoat repels oil and water, and makes the lens easier to clean.
 

Anti-Scratch Coating:
This is applied to the outside of the lens to minimize the likelihood of accidental scratching. This does not make the lens scratch proof, but helps tremendously in reducing fine hair line scratches. All polycarbonate lenses come with an anti-scratch coating.
 

ANSI Standard Z87+:
The new standard is now called the ANSI Z87+.there were previous standards in 2010 and 2003 , and is performance driven with two levels of performance for non-plano (prescription) lenses.
- Basic Impact
- High Impact

• The new standard requires that prescription safety frames must meet the lens retention (High Velocity and High Mass) test requirement with 2.0mm lenses.

Please be aware that an employee subjected to High Impact may not be adequately protected if wearing lenses tested only for Basic Impact. Description of the new ANSI testing requirements:
High Impact Level Prescription Lenses

• Must not be less than 2.0mm thick.
• The lenses shall be capable of resisting impact from a 6.35mm (1/4 in.) steel ball traveling at 45.7 m/s (150 ft/s).
• Marking by manufacturer with "W" as a trademark would look
  like this: W+ Basic Impact Level Prescription Lenses.
• Basic Impact lenses shall be a minimum 3.0mm thick except those lenses having a plus power of 3.00D or greater shall have a minimum thickness of 2.5mm (no change from the 1989 standard).
• Basic Impact lenses are not tested to stringent High Impact requirements.
• They will NOT be marked with a "+"
• Protectors with Basic Impact lenses will be delivered to the wearer bearing a Warning Label indicating that the protector only meets the Basic Impact Standard.

ANZI Prescription Frames:

• All prescription safety frames must meet High Velocity and High Mass impact resistance tests while retaining the lenses.
• The frame will be marked with Z87+
• All frames marked with Z87+ can be used for Basic Impact and High Impact protection.

ANZI Side shields:

• Lateral protection shall be assessed using a rotation point 10mm behind the corneal vertex, which means that shields must now provide more coverage.

Astigmatism:
Astigmatism is one of a group of eye conditions known as refractive errors. Refractive errors cause a disturbance in the way that light rays are focused within the eye. Astigmatism often occurs with nearsightedness and farsightedness, conditions also resulting from refractive errors. Astigmatism is not a disease nor does it mean that you have "bad eyes." It simply means that you have a variation or disturbance in the shape of your cornea.

What causes astigmatism?
Astigmatism usually occurs when the front surface of the eye, the cornea, has an irregular curvature. Normally the cornea is smooth and equally curved in all directions and light entering the cornea is focused equally on all planes, or in all directions. In astigmatism, the front surface of the cornea is curved more in one direction than in the other. This abnormality may result in vision that is much like looking into a distorted, wavy mirror. The distortion results because of an inability of the eye to focus light rays to a point.

If the corneal surface has a high degree of variation in its curvature, light refraction may be impaired to the degree that corrective lenses are needed to help focus light rays better. At any time, only a small proportion of the rays are focused and the remainder are not, so that the image formed is always blurred. Usually, astigmatism causes blurred vision at all distances. Some people with very high degrees of astigmatism may have cornea problems such as keratoconus.

Astigmatism is very common. Some experts believe that almost everyone has a degree of astigmatism, often from birth, which may remain the same throughout life. The exact reason for differences in corneal shape remains unknown, but the tendency to develop astigmatism is inherited. For that reason, some people are more prone to develop astigmatism than others.
 

Axis:
As mentioned above, a special cylindrical lens is needed in order to correct astigmatism. Not only does the strength of the cylindrical lens need to be specified, but the lens itself must be rotated into a specific position in order to provide the proper vision correction. The axis represents the amount of rotation of the cylindrical lens in degrees ranging from 1 to 180.

B.

Backside anti-reflective (AR) coating:
light that comes from behind you can cause you additional glare. Sunlight will hit the back of the lenses and bounces into the eyes. The purpose of a backside (AR) coating is to reduce the reflection off the lenses. Sometimes, you can actually see the reflection of your eye in the lens. If you are on the water or if you sunglasses do not fit snugly against your face the light will reflect off your lenses and back into your eye. We highly recommend backside AR in these circumstances.
 

Ballistic:
Ballistic is any projectile in a high velocity. Our ballistic series far exceed ANSI Z87+ safety standards as well military fragmentation standard MIL-STD-662.
 

Base:
The base is to the prism what the axis is to the cylinder. As you know, a prism is shaped like a triangle. The thicker the triangle at its base, the stronger the power. Much like the axis specifies the direction of rotation of the cylindrical lens for astigmatism, the prism must also be rotated into a specific position. But the rotation of the prism is simply specified as 'base in' or 'base out' (where 'in' means towards the nose) or 'base up' or 'base down'. Only these four positions exist as opposed to the 180 positions that can be specified for a cylindrical lens. However, orientations between these four positions can be specified by using combinations of horizontal and vertical prisms in the same lens.
 

Base Curve:
The base curve is the front curve of any sunglass lens. Sunglasses typically feature base curves between 6 and 9 measured curvatures. Sunglass models that feature a 6 base tend to be more flat relative to the front of the frame. While 9 base styles provide the maximum amount of wrap around your face. Base curves above 8 are not recommended for prescription lenses and the higher the Rx; the flatter the frame is advised. Many sunglasses replicate the look of an 8 base curve with larger temples to help block light coming in from the sides.
 

Bridge Size:
Is the distance between the lenses on any frame. Smaller bridge fits smaller noses.
 

Blue Blocker:
Is a type of lens that will block the visible blue light without darkening the overall light. These lenses are usually brown, orange or red.
 

Blue Blur:
Is the condition of unclear vision due to the blue light waves being short and scattering easily in the visible light spectrum. A blue blocker lens is recommended to remedy this aversion in visual acuity.
 

C.

Cataracts:
are the leading cause of blindness worldwide

Approximately 20.5 million Americans age 40 and older have cataracts. Cataracts are the clouding of the eye's clear lens-similar to a window that is "fogged" with steam. When the lens becomes cloudy, light rays cannot pass through it easily and vision becomes blurry. Cataracts are not a growth or a film over the eye.

Cataracts start out small (mild) and have little effect on vision at first. But as the cataract grows (becomes denser), so does the impact on vision.

How quickly the cataract develops varies among individuals, and may even be different between the two eyes. Most age-related cataracts progress gradually over a period of years.

Other cataracts, especially in younger people and people with diabetes, may progress rapidly over a short time. It is not possible to predict exactly how fast cataracts will develop in any given person.



CNC Edging:
This lens milling technology with 5 axes allows any kind of shape in any angle on a prescription lens. With the ability to bevel, to polish, to groove and to cut wrap sport lenses with steps, combined with the capacity to adapt the tool cutting angle to the lens curvature, makes complicated ophthalmic lenses to keep up with fashions latest trends.
 

Color-Coated Lenses:
When you look at a pair of sunglasses and you see a color on the outside of the lens, it has been coated. Lens mirror coating is an expensive process that usually involves a metallic oxide coating being applied to a lens in a vacuum deposition to get the coatings evenly deposited across the surface. There is only a hand full of these machines in the United Stated that are used in these processes because of their expense. Every time a color is applied to a batch of lenses, the vacuum chamber must be meticulously cleaned to keep the next batch of a different color from being affected by the previous operation. Most coating labs run certain colors just once a week to keep the labor and materials expense down. Adversely mass produced lenses that you would get in a stock pair of sunglasses is done in a assembly line fashion, running a huge batch of lens all the same color until the run is complete. Custom prescription lenses are not cycled this quickly and usually takes a week for the turnaround time.
 

Clip-On: 
Is a small device that holds colored lenses in front our your regular prescription eyewear. The normally come in grey amber and copper.
 

Contrast:
Contrast is the difference in brightness between the light and dark areas of a picture, such as a photograph or video image. A high contrast lens gives you great visual acuity between light and dark areas in your view.
 

CR-39 (plastic):
The advantages of plastic is that it is lightweight and easily tinted to just about any color. One of the disadvantages is that those lenses scratch easily. But the biggest danger is that they are not impact resistant. If an object strikes the lens it will break into shards that could permanently damage your eyesight. For this reason we only use shatter resistant lenses in any of our sports frames.
 

Chromatic Aberration:
is caused by a lens having a different refractive index for different wavelengths of light (the dispersion of the lens). Longitudinal and lateral chromatic aberration of a lens is seen as "fringes" of color around the image, because each color in the optical spectrum cannot be focused at a single common point on the optical axis.

Since the focal length f of a lens is dependent on the refractive index n, different wavelengths of light will be focused on different positions. Chromatic aberration can be both longitudinal, in that different wavelengths are focused at a different distance from the lens; and transverse or lateral, in that different wavelengths are focused at different positions in the focal plane (because the magnification of the lens also varies with wavelength).
 

Cylinder:
If there is no value under the cylinder heading, then you have a very simple prescription. If there is a value under this heading, then you have astigmatism. The majority of optometrists write the cylinder value with a minus sign in front while the majority of ophthalmologists (physicians who specialize in the eye) write the cylinder value with a plus sign in front. Regardless of which way this is written, your glasses will be made the exact same way -- these are just two different ways to write the same spectacle prescription. Like sphere power, the cylinder power is also measured in diopters.
 

D.

Day and Night (Photochromic Lenses):
New Photochromic lenses are so smart they go from clear indoors to as dark as sunglasses outdoors. Their advanced technology adjusts to changing light, so you see clearly and more comfortably in virtually any light condition.

Indoors, Photochromic lenses are as clear as your regular eyeglasses. Outdoors, they quickly darken, getting as dark as sunglasses if necessary. They work so well, in a recent clinical study, four out of five eyeglass wearers preferred Photochromic to their regular lenses, and photochromic provide 100% UV protection.

Ask your eye care professional about making photochromic lenses your every day lenses. And find out just how smart a lens can be.
 

Digital Surfacing:
means that the rate of curve changes from the center of the lens outward to accommodate the change in distance and angle of your eye to various points of the lens, optimizing the prescription throughout the entire lens. We have an entire page describing this technology with some of the different lens manufacturers information. Click Here
 

Diopter:
A unit of measurement of the optical power of lenses. For example; if a person has a prescription of -4.00, that person has 4 diopters of power in their lens. Diopters generally are measured in quarter steps like -4.00, -4.25, -4.50. Some doctors refine their measurements down to twelfth steps like -4.00, -4.12, -4.62. Diopters are also used to measure prism.
 

DriveWear transitional lenses:
are the first and only photochromic lenses to darken behind the windshield of a vehicle, with the ability to react to visible light as well as UV light.

By combining polarization with new photochromic technology, DriveWear lenses are capable of sensing and reacting to varying light conditions both outside and behind the windshield of the car. From bright sunlight accompanied by intense, blinding glare, to overcast inclement conditions, DriveWear lenses provide the wearer with the appropriate visual solution.

Note: DriveWear transitional lenses are not recommended for night driving as they do not change completely clear. There is a visible tint indoors as illustrated in the low light photo below.

Low light	Behind the windshield	Bright light outdoor

E.

Eye size:
Is the horizontal measurement of the lens on any frame. Larger eye size fits bigger heads.

F.

Flat Light:
When light is "flat," the slope looks like a white, empty canvas, and it's impossible to read the snow surface clearly. Ruts, bumps, ice, even rocks and thin patches disappear. And if you're out in an open expanse, it's hard to determine the pitch of the slope as your depth perception shrinks to nil.
 

Frame Measurements:
What do the numbers located on the bridge and temples of the frames mean?

Example:

The numbers on the frame reflect the SIZE MEASUREMENTS in millimeters (mm).

1st Number (ex.54) = the width of the lenses
2nd Number (ex.38) = the distance between the Top of the lenses to the bottom.
3rd Number (ex.59) = the diagonal distance of the lens
4th Number (ex.18) = the distance of the bridge between the lenses
5th Number (ex.140) = the length of the temple arm including the portion going behind the ear

G.

G-15:
Green-Gray lenses are the most popular general purpose lenses. Uniform absorption of colors throughout the spectrum allows colors to be seen exactly as they are with approximately 85% light absorption.

Glass lenses:
One major advantage is that it is very scratch resistant. However it is double the weight of conventional plastic. Also it is not as shatter resistant or safe as plastic. 
 

Glare:
Reflected glare by light reflected off smooth, shiny surfaces blocking vision. The number one cause of automotive accidents is glare. A polarized lens is your best defense against blinding glare.
 

Grilamid Nylon Frames:
No other material has the flexibility, remarkable toughness, and exceptional resistance to sun lotions. These elements allow our design team to combine the frame material's light weight, impact resistance, flexibility in variable temperature and overall comfort to create models that are durable and surpass all expectations.

H.

High index 1.67:
Thinner and lighter than 1.60. These lenses already come with scratch coating. Also a great choice for high prescriptions.
 

Hyperopia:
Also known as farsightedness, is usually inherited. Children are often hyperopic which may lessen as an adult. Hyperopia is a refractive error, which results from a disorder rather than from disease. A refractive error means that the shape of your eye does not bend light correctly, resulting in a blurred image.

I.

Impact Resistant:
Resistant to shattering or splintering. impact resistant plastic is made so that it will not break into small pieces. Polycarbonate is impact resistant making it a very safe lens to wear.
 

Implantable collamer lens or ICLcalled by its manufacturer Visian ICL, is a soft, flexible gel-lens used in refractive surgeries for the permanent correction of myopia (nearsightedness), made of a collagen copolymer material, named by combining "collagen" and "polymer”. The ICL procedure is a popular alternative to LASIK and PRK since it requires no removal of the corneal tissue and reportedly produces better visual results. The ICL requires no maintenance and is surgically implanted inside the eye, where it resides permanently.
 

Infrared (IR) Radiation (760 - 3000nm):
Infrared Rays are radiant energy, or heat waves, not considered harmful under normal conditions. These heat rays cannot be seen but can be felt. If you are exposed to intense sunlight for a lengthy period of time (a day at the beach, for example) without infrared protection, you may experience a burning or stinging sensation in your eyes and a sense of fatigue. Infrared rays can be especially discomforting if you wear contact lenses. If your sunglasses fail to stop infrared light, it can be absorbed by your contacts, causing them to "warm up".
 

K.

Keratoconus:
Is a malformation of the cornea, bulging it into a cone formation similar to a football. There are a few reasons that someone could experience keratoconus. It may be due to an imbalance of enzymes within the cornea, damage from UV light from not wearing sunglasses or wearing the wrong type of contact lens causing irritation and additional damage from rubbing.

L.

Lens Materials:
There are four types of lenses materials that we use.

Plastic or CR39 lenses cost much less, but are easily scratched and can not be used for sports or children.

Polycarbonate lenses are tougher than plastic and are shatterproof, making them ideal for sports and outdoor activities.

Trivex lenses are the lightest weight shatter resistant lenses available. Along with their chemical resistance and higher abbe value, it is the recommended lens if you have a lower prescription.

High index 1.67 Thinner and lighter than regular plastic good for higher prescriptions. Can easily tinted into sunglasses.

High index 1.74 is the lightest lens material we sell, although it is only available in clear.

Lens Color Guide:

	GRAY 3 reduces the maximum amount of visible light and allows for true color recognition. Good for bright sunny days and heavy glare situations. Best uses include driving, deep-water fishing and general use.		GRAY 1 is a lighter shade of the Gray C lens. Transmits colors evenly and allows for true color recognition. Good for partly sunny to bright sunny days. Can be used as a base creating custom colors.
	BROWN 3 provides excellent contrast and improves visual acuity and depth perception. Good for bright sunny and varying conditions. Reduces blue light. Best for driving, golfing and shallow water fishing.		BROWN 1 is a lighter shade of the Brown C color. Improves contrast and depth perception. Good for partly sunny to bright sunny days. Can be used as a base for creating custom colors.
	YELLOW provides the maximum light transmission of any polarized lens. Increases contrast and filters out some blue light. Used in low light conditions such as overcast or cloudy days. Popular among shooters, hunters and for night driving.		MELANIN blocks high amounts of blue light, while maintaining true color balance. Melanin provides high contrast for better visual acuity and is good for bright sunny and varying conditions. Great for golfing, driving and fishing, or any one with macular degeneration.
	ORANGE increases contrast and blocks blue light. Best in overcast or partly cloudy conditions. This is the most common lens color used for clay target shooting. Also used for hunting, biking and skiing.		VERMILLION is a vibrant color that increases contrast. Often used for fishing in early morning or late evening hours. Used in target shooting for bright sunny conditions. Also used for skiing and hunting in flat light conditions.
	VIOLET increases contrast and dampens certain backgrounds. Violet is often used by shooters in average or bright conditions. Also used for skiing, snowmobiling and golfing.		BLUE is used in partly cloudy to sunny conditions. Good for tennis, golf, snowmobiling and shooting at green targets. Blue lenses let in the maximum amount of blue light.
	GREEN has slightly better contrast than the gray colors, but is not considered a high contrast lens. Green maintains true color balance and is a good choice for varying light conditions. Used for tennis driving and golf, as well as an all-purpose color.		Clear lenses may be tinted to create custom colors for every need or request.

Lens Colors and Tints:
The color of the lens is usually a personal decision, but here are some facts to keep in mind:

Mirrored: Reduces the amount of light that reaches the eyes; good at high altitudes.

Gradient: Shaded from top to bottom. (A double-gradient lens is dark at the top and bottom, and lighter in the middle.) Driving glasses are often graduated so that you can see the dashboard clearly.

Photochromic: Automatically darkens and lightens as light conditions change. Photochromic (transitional) lenses will not get as dark as a standard sunglass - Grey 3, it will be closer to a Grey 2. They are not instantaneous like they elude to on the television commercials, they take sometime to adjust to changes in light. Heat also hinders the photochromic (transitional) lenses from getting dark. Your glasses in the winter when it is cold, will get very dark, the same pair in the hot summer will seam like they are not working as well.

Tip: Darker doesn't necessarily mean better. The darker the lenses, the more visible light they block. Brighter conditions demand darker lenses. It's important to keep in mind where you'll be wearing them most. Sunglasses designed for mountain climbing, for example, generally have lenses too dark for everyday wear.

M.

Macular Degeneration:
is a degenerative disease that robs young and old of central vision. As a result, children face a lifetime of uncertainty and elders risk the early loss of an independent life. In addition to the support of long-term efforts in the fields of Stem Cell and Genetic research for an ultimate cure, we are particularly interested in promising near-term, scientific studies designed to inhibit the progression of macular degeneration and restore a measurable amount of vision to all.
 

Mirrored Coating:
Also called Flash Coating, it is applied to the outside of the lens and can be applied over any base color. New laboratory processes have created coatings that adhere better to the surface of the lens, are less susceptible to scratching, and are available in an expanded palate of colors. Mirror coated lenses absorb anywhere from 10 percent to 60 percent more light than uncoated lenses, depending on the type and degree of coating. The light transmission is further reduced by the base tint of the lens. Due to its reflective property, any mirrored lens will appear darker since it will reflect a certain amount of light trying to reach the eye. A mirrored lens will also add an extra buffer against glare. This makes them ideal for outdoor uses such as skiing. Care and Cleaning: Because most mirror coatings are applied to the surface of the lens, extra care must be taken when cleaning a mirrored lens to prevent scratching and other damage to the surface. Lens cleaning cloths should be used rather than abrasive cotton or paper towels. Dawn dish washing soap is a good cleaner, but don't use other household cleaners such as Windex.
 

Mirror vs. Flash Mirror Coating:
Solid mirror is a heavy layer of 100% chromium on the front of the lens, Flash mirrors use 10% of the chromium used for the solid mirrors. A gray 80% lens with a solid silver mirror will reduce the light transmission by 12-15%, and a flash mirror on the same gray 80% will see 5-8% reduction of light transmission.
 

Myopia:
Also known as nearsightedness, is inherited and is often discovered in childhood. Myopia is a refractive error, which results from a disorder rather than from disease. A refractive error means that the shape of your eye does not bend light correctly, resulting in a blurred image.

Myopia often progresses throughout the teenage years, when the body is growing rapidly. People with high myopia have a higher risk of detached retina,which can be repaired with surgery, and glaucoma.

N.

Nanometers:
The measure of the length of a wave of light. One billionth (10-⁹) of a meter.
 

Nose pad:
One of a pair of pads, usually clear, that rest on either side of your nose and help to support your glasses.

O.

Ocular:
Ocular is anything of or relating to the eye.
 

O. D.:
O. D. simply means 'right eye'. It is the short form of the Latin term 'oculus dextrous'.

O. S.: 
O. S. simply means -- you guessed it -- 'left eye'. It is the short form of the Latin term 'oculus sinister'.
 

O-Seg Bifocal:
This lens is similar to the Round Seg, but uses new manufacturing techniques to allow us to put the reading area on the back of the lens, instead of the front, as was done before. This makes the lens more cosmetically appealing, and effectively increases the reading area to the wearer, as it's closer to the eye.

P.

Pantoscopic tilt:
Pantoscopic tilt is the angle between the plane of the lens and frame front and the frontal plane of the face when the superior edge of the lens is farther away from the frontal plane than the inferior edge.

Pantoscopic tilt brings the front of the frame into proper relationship with the wearer's eyebrows and cheeks. It also provides the widest field of view for reading, since the vertex distance of the lower half of the lens is minimized.

However, tilting a lens in front of the eye creates marginal astigmatism. Pantoscopic tilt changes the effective power of the lens and induces cylinder power. Additionally, pantoscopic tilt reduces vertex distance for the lower half of the lens, but increases vertex distance above the 180 degree line.
 

Patient's Own Frame (POF):
Customers who want to use their own frame are invited to do so for a $15.00 tracing fee.

Please review our policies for using a POF.

1. When a customer sends us their own frame for prescription lenses, it is at their own risk. If the frame breaks during the lens manufacturing process we will not be responsible for the broken frame, nor can we replace it.

2. In the rare case of a frame breakage, we are willing to give a 25% discount of any available frame that the customer finds from our inventory. Rudy Project and Oakley are except from the discounts due to dealer agreement policies.

3. In the event that we are unable to put your prescription in the POF, we would contact you. We will be more than happy to suggest other styles that would work with your prescription and return the POF frame to you.

Please call us with your brand and model before you send your frame. Usually we will be able to tell you if we make your prescription in your frame.
 

Photochromic:
Is the generic term used for lenses that have the ability to change lens color or darkness/density depending upon the degree of exposure to light.

The Original Transitions lenses are designed to meet the needs of the majority of those who appreciate the value of eyewear offering adaptive lens technology. With the widest variety of lens designs and materials to choose from, original Transitions lenses quickly adapt between indoor and outdoor conditions, offering a distinct advantage over ordinary clear lenses.

• Change from clear indoors to dark outdoors
• Clear as an ordinary clear lens indoors and at night
• Block 100% of the sun's harmful UVA & UVB rays
• Available in Gray or Brown

Photochromic Lenses (Day and Night or Light Adjusting)
New photochromic lenses are so smart they go from clear indoors to as dark as a light sunglasses outdoors. Their advanced technology adjusts to changing light, so you see clearly and more comfortably in virtually any light condition. These lens are sometimes referred to as Photochromic.

Indoors, photochromic lenses are as clear as your regular eyeglasses. Outdoors, they quickly darken, getting as dark as sunglasses a Sunglasses "2" if UV is present. They work so well, in a recent clinical study, four out of five eyeglass wearers preferred photochromic to their regular lenses, and photochromic provide 100% UV protection.

Ask your eye care professional about making photochromic lenses your every day lenses. And find out just how smart a lens can be.
 

Poker Mirror : 
The Poker Mirror is a hard mirror coat over a slight tint, designed to be worn indoors. The purpose is to obscure the eye while still allowing enough light to pass through the lens to see while playing poker, or engaging in similar activities. The anti-reflective coating on the back helps reduce distracting reflections from the back surface of the lens. This mirror is more reflective in lower light conditions indoors.
 

Polarized Lenses:
Light waves traveling freely can vibrate in any direction. When light strikes a horizontal reflecting surface such as water, sand or pavement, it vibrates horizontally creating glare. To the unprotected eye, glare can decrease depth perception., reduce visual acuity and create eye fatigue.

These lenses are great by the water or for driving. A good example of how these lenses work. While driving in your car you often see the glare of the dashboard or if you have a white piece of paper on the dashboard for example you see its reflection off the windshield. Having a polarized lens virtually eliminates this reflection and all of this type of glare (horizontal glare). These lenses are laminated and have a polarizing film in side the lens they are available in gray or brown. They are also available in plastic, polycarbonate or glass.

Without Polarization	With Polarization

Polished edges:
Instead of leaving the edge of the lens with the matte finish from the edger, it can be polished. This is only recommended for clear glasses. With a polished lens on sunglasses you can get chromatic aberrations within the lens from the light coming into the edge of the lens. Also lenses with polished edges are difficult to keep in a wrapped frames for sunglasses.
 

Polycarbonate:
Polycarbonate lenses or "Poly" are "impact resistant" thinner and lighter in weight than traditional plastic eyeglass lenses, they also offer ultraviolet (UV) protection and scratch resistance. In addition, they are very impact resistant. This extra toughness makes them the lenses of choice for children's glasses, sports eyewear and safety glasses.

Postural Orthostatic Tachycardia Syndrome:
Is caused by a malfunction of the patient's autonomic nervous system. Florecent lights,computers, mobile devices, Etc can cause severe pain being near unbearable. This portion of discomfort can be greatly reduced by filtering the light. The best solution we have found is manufacturerd by Live Eyewear with thier Low Vision line of Cocoons fitover eyewear.
 

Presbyopia:
Also known as "Age-Related Focus Dysfunction" is the inability of the eye lens to focus incoming light, resulting in blurred vision at a reading distance and eyestrain. Most people develop presbyopia in their 40s.
 

Prism:
This is a box on the prescription form that is rarely filled in. Occasionally, when the two eyes are not properly aligned and looking directly at the same thing, prism can be ground into the lenses in order to re-align them. This can occur with strabismus (i.e. - an eye turn) or in situations where the eyes are properly aligned but are under a tremendous amount of strain in order to keep them aligned. The value under the 'prism' heading denotes the strength of the prism.
 

Progressive lenses:
(also, progressive addition lenses or PALs) Multifocal lenses whose corrective powers change progressively throughout the lens. A wearer looks through one portion of the lens for distance vision, another for intermediate vision, and a third portion for reading or close work. Each area is blended invisibly into the next, without the lines that traditional bifocals or trifocals have.
 

Pupillary Distance (PD):
* This is a required measurement for prescription glasses. PD is not always measured when you get your prescription, you will need to get it from your local optician or local vision care center. Your last eyeglasses store needed this measurement for making your last set of glasses. If you call them they should be able to look it up for you.

The best measurement is a Mono PD or Monocular Pupillary Distance. This is a measurement from the center of the bridge of your nose to the centers of each pupil, left and right. Most people are not symmetrical so the distance usually is not the same for each eye. By having accurate number we will be able to make your prescription spot on.

PD - The distance between the center of your pupils is known as the Pupillary distance, this is measured . Before your prescription lenses are cut into the shape of your frame, the Pupillary distance needs to be measured. This measurement is then used so that the optical center of each lens can be lined up with your pupils in order to give optimal visual clarity. In general, PD measurements fall in the range of 48mm to 73mm. The most common measurements are between 58mm and 68mm.

Heavyglare.com site note - When you get a single number for your prescription you can put it in the single drop down on the Rx form. Or if you have the individual numbers check the box on our form and it will give you a second drop down for the monocular PD, right and left.

R.

Round Seg Bifocal:
Unlike the traditional "flat top" or "D" segment bifocal, this lens uses a round reading area, instead of the traditional lined segment. This allows us to rotate the lens to place the reading area in the proper position, giving us more freedom with regard to frame sizes.

S.

Selective Light Filtration:
The act of filtering a certain wave of light. An amber or yellow lens often filters the blue wave of light giving a sharper high contrast view of the world.

Sphere:
The number under the heading 'sphere' is the main part of your prescription. The number itself denotes the strength of the lens as measured in diopters. A diopter is a unit of measurement that is simply the inverse of the focal distance of the lens as measured in meters. For example, if a lens has a strength of 2 diopters, then parallel light rays that pass through this lens will focus together at a distance of 1/2 meter (50 cm) away from the lens. If you are near-sighted (i.e. - you have trouble seeing far away but can see fine up close), then you can make a rough calculation of the strength of your glasses.

T.

Temple Length:
Is the length of the "arm" of a pair of glasses, running from the ear to the lens area in Millimeters.
 

TD-2 Coating:
While the regular polycarbonate, and top-mount polycarbonate lenses have a factory-applied scratch-resistant coating, it is not as hard as the TD-2 coating. The TD-2 coating does add about 2-3 days to the turn around time on your prescription order. One thing to note, is a TD-2 coated lens cannot be tinted.
 

Trivex:
offers strength and impact-resistance, light weight and thinness, and quality optics. TRIVEX lens material lets you prescribe a single lens with the qualities of many. This revolutionary lens material combines the key lens attributes your patients are looking for while offering the superior optics you demand. Only the finest lenses provide tri-performance.

What is TRIVEX lens material?
TRIVEX is the world's first tri-performance lens material; meaning it offers a triple combination of features never before found in a single material. Superior Optics. Impact Resistance. Ultra light Weight. This breakthrough in technology is specifically designed to deliver the most comprehensive performance of any lens material, anywhere.

U.

Ultraviolet Radiation (UV):
Solar radiation is formed by visible and invisible light waves. Measured in nanometers, it has three wave lengths that reach and affect your eyes: Ultraviolet, Visible Lights, and Infrared Radiation.
 

The shorter the wavelength, the more damage to your eyes.
 

Ultraviolet Radiation (200 - 380 nm)
Studies show that long term exposure to UV rays may cause eye diseases, including cataracts. In addition, short-term exposure can cause temporary conditions such as "snow blindness", Ultraviolet radiation can be divided into three categories.
 

UVC (200 - 290 nm)
UVC is absorbed by the atmospheric ozone layer and never reaches your eyes.
 

UVB (290 - 320 nm)
UVB is a physically painful form of ultraviolet radiation. These are the sun's "tanning rays" which are absorbed by the cornea. Exposure to UVB can temporarily damage the cornea. This band of radiation causes cancer and burning of the eye and has been linked to damage of the lens inside the eye.
 

UVA (320 - 380 nm)
UVA rays are absorbed by the lens of your eye. The resulting damage heals slowly, if at all. About one percent of all UVA rays penetrate the retina, which cannot repair itself. These rays, which cause sun tanning and wrinkles, pass through the outer structure of the eye and are absorbed by your eye's lens. The resulting damage heals slowly, it at all. Extended exposure to UVA rays can lead to the formation of cataracts.
 

Protection from harmful UV radiation is becoming more and more important as the earth's ozone layer continues to be depleted. Contrary to what you might think, clouds do not block out all UV rays. Though thick, heavy clouds absorb most UV radiation, UV will pass through thin clouds, even when the sun's rays don't feel hot. And watch out for haze – it doesn't block UV radiation at all. You get higher exposure to UV radiation on snow, sand, water, or concrete, since these surfaces reflect the sun's rays. You will also get higher UV radiation levels at higher altitudes and at areas closer to the equator. To make matters worse, the damaging effects of long-term UV radiation exposure are cumulative with the consequences not immediately apparent. So beware: excessive exposure to UV radiation today can cause eye problems tomorrow. Therefore, a good pair of sunglasses is essential for enjoying the sun. The filtering qualities of the lenses must be considered so that you have the correct type of lens for your intended use. There is no point in buying lenses designed for high altitude if you use them for everyday urban life.
 

UV Filter (coating):
This coating is a filter for the harmful UV radiation. The coating is either put on the lens or is imbedded into the lens to protect your eyes for the harmful effect of the sun's UV radiation.

V.

Vertex distance:.
The effective power of lenses changes with vertex distance. Increasing vertex distance in plus lenses makes the lenses effectively stronger while making minus lenses effectively weaker. When vertex distance is shortened, minus lenses effectively get stronger, while plus lenses effectively get weaker. Therefore, making lens power compensations for changes in vertex distance is important to maintain the effective overall power of a lens in front of the eye.
 

Vertex distance also affects field of view. The shorter the vertex distance, the wider the field of view. A shorter vertex distance also enhances the cosmetic appearance of eyewear. Most progressive lenses are designed for fitting with a vertex distance of 12mm to 15mm. This distance provides wide fields of view, a cosmetically pleasing appearance, and adequate separation from the face to prevent wearer's lashes from touching the back surface of the lens.
 

Visible Light (380 - 760nm):
Visible light is that portion of the light spectrum that the eye perceives as color. In this spectrum, protective eyewear deals with glare or the brightness of the sun. Excessive amounts of visible light are irritating to unprotected eyes and can reduce your visual perception by as much as 50%. It can also hinder your eye's ability to adjust to darkness (night blindness) and cause difficulty in depth perception. The unprotected eye strains to focus (squint), which can cause wrinkles and chromatic aberration. Athletic Optics offers a variety of lens colors to enhance your vision in various lighting conditions. Blue Light (380 - 480nm): Closest to the high energy, UV portion of the visible light spectrum, it focuses in front of the retina rather than on it, which blurs vision, reduces contrast and hinders depth perception.

W.

Windless Eyewear:
will enclose and seal your eyes from the elements. Venting of the lenses allows slight airflow to keep the lenses from fogging and keeping your eyes from excessive wind irritation (great if you wear contacts). These glasses come with 100% UV protection along with diverting wind, dirt or snow. Checkout 7 Eye Sunglasses by PanOptx.

Wrap Sunglasses : Wrap sunglasses are those that curve around the curve of a person's face fitting close to the head. These wrap sunglasses are normally 6-9 Base Curve. An 8 base cure is as much wrap that you will want to keep your vision distortion free. For higher prescriptions a 6 base frame is recommended to help keep the lenses thinner and lighter while also reducing peripheral distortion.