Whether you are shopping for eyeglasses in Boise, ID or anywhere else for that matter, you should be aware of the different options available to you. This post will not discuss different optical designs such as progressives vs single vision but rather the options available to any lenses.
The first consideration is what type of material you want your glasses to be made of. In the old days glasses were made of…well…glass. While it is true that you can still get glass lenses, I don’t recommend them. First any foremost, glass can shatter. For that reason alone I feel they present an undue risk otherwise not present in other materials. Also, they will be much heavier than their resin counterparts. Keep in mind that glass is still the most scratch resistant material available, but we’ll discuss some coatings that can help with that later. The most basic “resin” type of material is called CR 39 (aka “plastic” lenses). This is the cheapest lens type, but you do get what you pay for. These lenses are easily scratched and have no UV or scratch protection inherent in the lens. However, you can add those via coating if you wish. My favorite type of material for people with low to moderate prescription power is polycarbonate. Polycarbonate costs only a little more that CR-39 but includes a basic scratch protection as well as UV protection. More importantly polycarbonate is very impact resistant and will be thinner and lighter than CR-39. A very similar lens to polycarbonate is called trivex, which is touted to be a bit more impact resistant than standard polycarbonate, is also a little more expensive than polycarbonate. We recommend polycarbonate to any patient under the age of 18 for safety considerations.
The next class of lenses is called high index lenses. This name relates to the “index of refraction” of the lens. This property defines how thick or thin a lens can be made in a given prescription. Basically, the higher the number, the thinner the lens. Also, the higher the number, the higher the price as well. The index values are defined as ,1.6, 1.67, 1.70, and 1.74. There are higher index lenses available but cost becomes a limiting factor. The primary benefit of these lenses is the ability to thin and lighten the lenses as much as possible for those who have higher prescriptions. I, myself wear the 1.74 index lenses and I love them.
Another option available from the polycarbonate level and above is called the aspheric cut. Aspheric is a different way of making the lenses which reduces some distortions in the lenses and allows the lenses to be thinner in the center. However, we really only recommend this on a case by case basis, as not everyone will notice improvement from a non-aspheric lens to an aspheric one.
Coatings are varied and can function to add scratch resistance, UV protection, or tinting to a lens. I personally love an anti-reflection coating. The coatings (AKA A.R., or glare coatings) basically improve the efficiency of light travel through the lenses hence decrease the amount of scatter on the lens surface. This causes much less glare. This coating is especially useful for those who work on computers, in office environments, or those who are distracted by oncoming headlights while night driving. They also help reduce a phenomenon known a “total internal reflection” which occurs on high prescription lenses. AR coating are priced at different levels. The thing to remember is that the more you pay for the coating, the better the scratch resistance (and the warranty), the more smudge protection, and water resistance. Besides tinting a lens darker, you can alternatively opt to have a polarized lens. A polarized lens filters light differently than a tinted one and hence with polarized lenses you get vastly better glare reduction than a tint, however, it is more expenses as well.
My last topic concerns transition lenses (aka photochromics). These lenses are designed to darken when you go outside, and clear when you come indoors. They are useful in some, but not all cases. The biggest downfall of these lenses is that the require direct UV light in order to transition. Since most car windshields contain UV blocker, then these lenses don’t function well for driving. They do however work very well for those who work outside or enjoy outdoor activities.
Clearview Family Eyecare has an optical in Boise Idaho.