Info everyone should know.

I’ve had big trouble purchasing glasses that provide me with what I would call normal vision.

I think all eye glass wearers should be familiar with the content in this post hopefully readers will agree.

In the old days there was never a problem, my glasses always worked well.

Today with the introduction of high index glass and plastic and all manner of expensive options and what not, optical performance has degraded. These new features seem to have all come at the expense of optical performance.

Guess what, your friendly ophthalmologist is not going to tell you this, he wants to sell you the more expensive product and can provide a plethora of reasons why the more expensive product is going to be better for you. This may be so, but you won’t be able to see as well.

Here is a nice quote from Wikipedia “Restrict the choice of lens material to the highest ABBE value at acceptable thickness. The oldest most basic commonly used lens materials also happens to have the best optical characteristics at the expense of corrective lens thickness (i.e., cosmetics). Newer materials have focused on improved cosmetics and increased impact safety, at the expense of optical quality.”

If you want thinness and lightness just get a smaller lens, forget the higher index crap.

These old and cheap materials are “Crown Glass” and “CR39″ plastic both with an Abbe number near 58. The difference between the two is that the Glass is harder and heavier and the plastic is lighter and softer. Both will produce thicker glasses than a higher index material but you will be able to see better, your choice.

I suspect that the industry has settled on 20/20 as being the desirable norm so that they can pawn of cheaper products and services. There is no reason that I know of that most people can’t get better vision without paying anymore money.

Personally I want to see better than 20/20 and I am starting from a pretty poor position, needing lots of correction on top of astigmatism. I want to be able to see at the 20/15 level which is one notch better than normal people that have 20/20. My astigmatism compounds my problems, but it is still easy to get that 20/15. Often when you go to get your eyes tested they will give you a correction for 20/20 vision. Don’t settle for that crap tell them you want 20/15. Your eyes may not have the resolution but many people I know seem to have no trouble with 20/15.

For me the difference between 20/20 and 20/15 is that at when corrected to 20/20 there is a slight blurryness to the smallest lines on the eye chart. At 20/15 there is no discernible blurriness to any line on the chart, they are all sharp even the smallest that you have no chance of reading. The reason why you can’t read the 20/10 line is that your eye does not haave enough resolution, it should still be sharp. Once your focus has been corrected by your glasses then the limiting factor is the resolution of your eyes. People with more resolution can resolve the smaller lines on the eye chart.

Now that you have a prescription for 20/15 vision you next need to purchase glasses that won’t degrade that special 20/15 vision. It is nice to be able to see better than most every body else.

To date most modern options offered at the glasses store all reduce the optical quality of the glasses you are going to buy.

An easy way to test an optician to find out if they know their business is to ask for the Abbe number of the glasses that they are trying to sell you. If he can’t answer the question go somewhere else to shop, the guy you just spoke to is a sales man and not qualified to be selling eye glasses.

The cheapest lenses have the best optical performance with an Abbe number of 58 or above. None of them are high index. All high index lenses have low Abbe numbers.

It might be nice to know where this Abbe number came from, what is it, what it is good for and why it was so named.

I can’t find a link on the net that easily tells you what the Abbe number is good for so let me paraphrase from many different sources. First we assume that your lens is properly formed. If this is the case then variations in it’s optical properties are due to the materials the lens is made from. To date no one has invented a perfect material. All materials bend different wave lengths of light (colors) by different amounts. The result is that the various colors that make up your image do not focus at the same spot and you see a blurry image (not sharp). The Abbe number tells you how good or bad the material is at getting all the colors to focus at the same spot. The higher the number the better.

Improvements to the lens can be made in various ways but as far as I know these techniques are not used in the eye glass industry. See Apochromatic lenses and Achromatic lenses

For typical eye glasses an Abbe number of 58 or higher will probably mean no noticeable problems or fuzzy stuff and you will get your 20/15 vision.

This fuzzy stuff only occurs when you are not looking right through the middle of the lens. The fuzzyness gets worse the more you look through the outside edges of the lens.

The fuzziness also gets worse the stronger your prescription and the larger the lens.

If you have a weak prescription and a small lens you may be able to get away with a lower Abbe number. Your lens will be thinner and more expensive.

To sum it all up buy the cheapest plastic lens material. This should be CR39 with various suppliers giving it their own name. If your glasses shop does not know CR39 then go some place else. The only coating you need on the CR39 is the scratch resistant coating that usually is there automatically. These lenses are cheap $30 dollars and lower for a pair. If something screws and you get a scratch, just buy another. These lens are molded in large factories where labor is cheap all your shop guy is going to do is cut the lens to fit your frame, and hopefully get the center of the lens aligned with the center of your vision.

If you drive a car then you need to be able to drive into the sun safely. To do this you need polarized sunglasses. The Polarizers not only reduce the brightness but if properly setup also eliminate glare. Polarizers can also be tinted various other colors than their native grey and setup to reduce brightness even more. As polarizers are rotated they eliminate different types of glare, thus your road glasses need to have the correct rotation to eliminate the road glare, this should be the default setup for any polarized lens, but I have some that are all over the place. So I know we can’t count on our friendly industry to do things correctly. When properly rotated the polarizers eliminate glare from water surfaces allowing fishermen to see beneath the surface, a very handy attribute.

Here is a simple chart and another showing various glass materials and Abbe number.

Here is a much more complex chart with Abbe numbers.

My current eye glasses; bifocals with integrated magnetic clip on polarizers, dedicated reading/computer glasses, normal for far use only also with integrated magnetic clip on polarizers, polarized and tinted glasses for driving and fishing. I also have a pair of bifocal safety glasses (not shown) as well as another pair of reading glasses set for use at a closer distance than normal.

In Canada you can only buy prescription lens with a prescription, so get your prescription written to include all variants that you might want such as the bifocals and closer focusing glasses.

My current eye glasses

There are two important features to get in your frames:

First, spring loaded arms so the arms will always maintain their grip on the side of your face as the hinges wear. It also makes it much easier to remove your glasses from your head. Some frames will use the arm itself as the spring. Typically the cheaper frames do not incorporate the spring feature. These cheaper frames, in my experience only work well for a couple of months, before the hinge wears and the glasses start flopping all over your face.

Second, replaceable nose pads, preferably made from silicon.

Another important note is that your glasses can be adjusted at the shop for free any time, and they should be comfortable and stay put on your face all the time even during exercise. Do not settle for anything less.

I’ve tried contact lenses many times and have never been able to get 20/15. Don’t know if it is possible or just sloppy industry practices.

Last big reminder, do not settle for anything less than 20/15 vision (better vision than most people, there has to be at least one advantage to wearing glasses).

In my own case I know I have 20/15 if everything is always sharp. Any fuzziness is not acceptable. It may take some time for you to adapt to the super sharp look as you will find your brain has to process much more information. This can take up to two weeks during which you may experience different mental capacity as your brain adapts to the new load.

Do not settle for 20/20, this is just our sloppy industry passing off a crappy product on the unwary consumer.

I just noticed that someone from Allen Town Optical Corp just dropped in. I checked out their site, and they have a nice summary of the different types of lens material. These guys might just be one of those rare vendors that tries to do a good job.