Eyeglasses.com keeps the highest lens quality standards for our lens products and lens services. Maintaining high lens quality involves quality control at many stages. To learn how we manage to maintain a high level of lens quality, read on.
What is an eyeglass lens?
Eyeglass lenses are nothing more than a carefully carved block of clear plastic. Lens quality is determined by four factors: 1) The clarity of the plastic, 2) the precision of the carving, 3) the accuracy of the prescription and PD measurement, and 4) the accuracy of the cutting of the lens to fit your frames.
Who makes the lens?
Several groups are involved in the making of lens. A problem in any one of these steps can lead to less effective vision correction by the lens. A good provider of eyeglass lenses will have relationships with the best lens quality providers, but will also check and re-check every lens before dispensing it. The store you choose to make your lenses must insist on quality at every level in order for you to receive the best quality product. This kind of quality control is essential in order to ensure consistent results.
Who is involved?
What they do
|The maker of the plastic||Determines the clarity of the plastic.||Essilor, Zeiss, Pentax, Seiko, many others.|
|The cutter of the plastic||Determines the precision of the carving.||The plastic maker does the surfacing for stock lenses. The lens laboratory does the carving for surfaced lenses.|
|The issuer of the prescription and pupillary distance measurement.||Determines the optics for the lens such that it will work best for your eyes’ condition.||An optometrist or ophthalmologist issues the prescription. An eyewear store employee measures the pupillary distance.|
|The person that cuts (“edges”) the lens for your frame.||Installs lenses so that the optical centers match the pupillary distance measurement.||An eyewear store employee, or lens laboratory.|
About the plastic manufacturers
Nowadays most quality lens plastic in made in the Far East. It is made in large pieces called blanks which are round about four inches in diameter and about half an inch thick. There are different types and qualities of blanks. The quality is determined by the clarity, meaning the absence of miasms (small bubbles or inconsistencies which can only be seen with a microscope). The lower lens quality and less expensive plastics have more miasms which, although you cannot see them with the naked eye, can still add up to decreased visual acuity.
At eyeglasses.com, we only use better or best quality lens plastic made by well-known plastic suppliers. It is very easy for any eyewear retailer to cut their lens costs by 50% by switching to lower quality lens suppliers. We inspect every lens that we receive at least three times to ensure that it meets our standards. All of our suppliers have unconditional return policies for defects in lens quality.
About Lens Laboratories
There are two basic ways of cutting lenses, depending on the prescription. Most prescriptions fall within a standard range, called the stock range (on average the range is +/-8.00 sphere and up to +2.00 cylinder). Single vision lenses that are in the stock range are usually surfaced by the plastic makers in bulk by huge computerized machines. These lenses are then shipped to optical stores so that the store employees can edge the lenses into the frame.
Most multifocal lenses, and all lenses that fall outside of the stock prescription range, must be fashioned custom for each prescription. In these cases, plastic blanks (chunks of plastic) are shipped to lens laboratories where they are carved (surfaced) for each individual prescription. There are hundreds of lens laboratories around the country, several in each state. A typical lens laboratory will do a minimum of a few hundred lenses a day with a large staff of highly trained and experienced technicians. A few optical stores (like Lenscrafters) have small surfacing facilities in each of their stores doing much smaller lens volume.
To surface a lens, the lens laboratory takes the blank and puts it through a series of grinding machines, which grinds the surface the lens and shapes it exactly to the specifications of the prescription. Lens laboratories also provide other services like edging and mounting, which optical stores can choose to use or not, depending on whether they want to do that work themselves.
As with any custom service, the quality of the surfacingand any other services that the lab provides-- is determined by the experience and the expertise of the laboratory, its personnel, and the equipment it uses. We only use labs that employ a large staff of highly trained technicians, doing a large volume of lenses every day.
At eyeglasses.com, we do some of our edging services ourselves, and some of it is done by our lens laboratories. Any edging that we do in-house is performed by a licensed optician with more than 30 years of experience. His work is checked by a quality control expert before we send it out. Most of our orders require stock lenses; all of our custom surfacing work is done by lens laboratories. The laboratories that we use each have many years of experience and do thousands of lenses each week. Each lab that we use inspects each lens several times during the manufacturing process. When we receive the finished product from the lab, we do our own final inspection.
Eye doctors: they can make mistakes
The optometrist (OD) or ophthalmologist (MD) that issues the prescription is not involved in the fashioning of the lens, but the prescription they issue is crucial to the overall effectiveness of the lens. Occasionally the OD or MD can issue a prescription that is not quite right. Also, it is possible for your eyes, and your prescription, to change rapidly during some stages of your life.
Pupillary distance PD measurement: who measures it?
Normally an optical store employee will take your PD measurement when you go to buy glasses. If you want more freedom to choose where to buy your eyeglasses, you should ask your optometrist or ophthalmologist to measure the PD during your exam. Usually they will not measure the PD unless you ask them to.
If you have your PD measurement and your prescription when you leave your eye doctors office, then you can buy glasses and lenses at any eyewear store. With your PD and your prescription, you will not be forced to go to an optical store to get your PD measurement, and then feel obliged to buy glasses from that store.
Edging lenses: Who does that?
Edging is performed in a number of different ways. It can be done at the lens laboratory, or in the optical store. Either way, it is not required in any state that the edging be done by a licensed person. About one-half of the states in the United States have opticianry laws. In those licensed states, edging can be done by an unlicensed person that is “overseen” by a licensed person. The edging for most glasses made in this country is not performed by a licensed professional. However, all of the edging that is done for eyeglasses.com is done by a licensed professional. Or, if we ask our laboratory to do the edging, it is done by an employee/tradesman that does at least 30 jobs per day. That person has a very high skill and accuracy level that we have found to deliver very high quality.