Lined Bifocal:
This has a visible line across the lens. Standard diameter of this near segment is 28 mm. There is a wider option of doing 35 mm. The distance power is in the top and the near power is in the bottom.
Lenses
Lens Designs
Single Vision: This term means the lens has a single power. This is most often your distance prescription but could be set for near or intermediate ranges.
Lined Trifocal:
This also has visible lines across the lens but now with 3 zones for distance in the top, intermediate ranges in the middle and near power at the bottom.
Progressive Lenses:
These are also referred to as no-line bifocals but they really are a multifocal. Distance vision is at the top and then there is a blend of powers down thru a channel to the near power at the bottom. The advantages go beyond not having lines in the lenses, it gives a more natural range of vision where you can find a spot in the lens that is clear for any working distance.
Computer Lenses:
These are occupational lenses for heavy computer users. They overcome an issue with progressive lenses in which the computer zone is fairly small and you may need to tip your head back to see the computer. In a computer lens they make most of the upper part of the lens set for computer distances. This allows the user to keep their head in a comfortable position and look straight ahead at the computer screen. These also give a near range at the lower part of the lens for doing paperwork or other closer distant tasks.
Relax Lenses:
These lenses provide strain relief on our eyes while doing near work. Students who are doing heavy reading and studying can benefit from these lenses. They can work well for people who feel their eyes are tired or stressed after doing extended near work. The lens gives good distance vision in the upper part of the lens and the lower part of the lens have optics that support the focusing system of the eye. This allows the muscles that focus our eyes for near stay in a more relaxed state.
Lens Options
Photochromic
This means light sensitive lenses such as Transitions and Sensity brands that go from clear to tinted. There are multiple options with these lens enhancements.
Standard photochromic lenses are activated by UV light. They work great outdoors and automatically adjust from clear to dark depending on how much UV light hits the lens. Our windshields of our cars block most of the UV so they do not get dark inside a vehicle
XTRActive photochromic lenses have two filters in them. One is activated by UV like standard photochromic but the second filter is activated by visible wavelengths of light. These can get partially dark inside a vehicle and will become fully activated outdoors.
Polarized photochromic lenses are a specialty type of light sensitive lens that is activated by UV but becomes polarized instead of just tinted. Polarization cuts down extra glare off reflected surfaces. People who like to fish can really benefit from a polarized lens.
There are a few new lenses that are faster to turn dark and to fade back to clear that are just now coming to market
There are other options such as Transitions Colors that change from clear to either Sapphire, Amethyst, Amber, or Emerald.
And for the movie star look - Transitions Mirrors. These have a full time front side flash mirror coating but the lens will transition from clear to 6 different color options.
Anti-Reflective Lenses
The technology that is put into anti-reflective coatings is quite amazing. Many layers of specific compounds are stacked on the lens front and back surface. These coatings greatly enhance your vision by cutting down on reflected light from both lens surfaces. They improve night vision and reduce strain on computers. They also allow people you are talking to see your eyes instead of the glare from reflections coming off your lenses.
The top quality anti-reflective coatings have been tested to show that they make the lenses more scratch resistant than glass.
Blue Light Protective Anti-Reflective Coatings:
Many people are using computers, tablets, cell phones for longer hours each day. These electronic devices and the modern energy efficient lighting we have in our homes produces visible wavelengths of light that are heavy in the blue end of the spectrum. There is research that shows that blue light is putting stress and possibly damaging the pigment in the back of our eyes that keep the retina and most specifically the macula healthy. By protecting our eyes from this blue light, we might be reducing our risk for macular degeneration. There is also research showing how blue light can influences our sleep - wake cycles. Protecting our eyes from blue light often makes working on computers more comfortable as well.
Sunglasses
We are exposed to higher amounts of UV light at our elevation in Colorado. Protecting our eyes from the sun not only protects our eye health it also makes us feel more comfortable when driving, exercising, working outdoors, or doing fun recreational activities.
Tinted Lenses: These have a dye embedded in the lens material to cut down the amount or certain wavelengths of light. Different tints are recommended for different activities.
Polarized Lenses:
These cut down the light intensity but have the great advantage of also cutting down glare. This is the ultimate daytime driving lens and wonderful for fishing.
Sunglasses for Kids: Protecting young eyes from the damage that UV causes needs to start early. Kids pupils are larger so they are more light sensitive and let more UV light in. The cumulative amount of UV in our lifetime has been shown to directly correlate to our risk for cataracts. Wearing sunglasses can also protect young eyes from some accidents such as flying objects hitting their eyes.
Lens Materials
There are different materials that can be used for eyeglass lenses. Here are some helpful tips for understanding the advantages of choosing a certain material for your prescription.
Basic CR39 Plastic: This is the least expensive option. It has good optical qualities but only moderate shatter resistance. Thickness becomes an issue as the prescription increases.
Polycarbonate: Is thinner and lighter than basic plastic and has excellent shatter resistance. Optical quality is lower and can easily scratch unless extra scratch protection coatings are added.
Trivex: This is the lightest weight material, has very good optical qualities, and excellent shatter resistance. It is only slightly thinner than basic plastic. Scratch protection is included in this lens.
Hi Index 1.67: If you have a higher prescription then going with higher index material will result in thinner lenses. Optical qualities are good and this is also a great lens for drilled rimless frames. Anti-reflective coatings are highly recommended on these materials as reflections increase as refractive index increases.
Ultra Hi Index 1.74: You may want to choose this material if you have a strong prescription. These are some of the thinnest lenses possible. Anti-reflective coatings are required on these materials due to the refractive index of this material.
