plastic vs. glass and the burden of prism affects

[beta chem]

What glass would give the least prism affect? Is there any special glass that would give the least prism affects? I had hi-index plastic lenses and they through prisms off 85% of my area of view. The glass lenses I went to are better but still give a prism affect in the area of 35% of my field of view. This is with a small lense size around 40mm by 55mm. I have found sites that offer optical lenses for lasers and other projects that have very little distortion and ultra high transmittance. If a person aquired some of these lenses or glass blanks, could a OD lab grind them into a lens of a specified power.

[John R]

What glass would give the least prism affect?
Not to sure what you mean by this?
Are these lenses for lazers etc made from a pyrex type of glass if they are then yes they can be worked but they sure aint cheap.
I think you find for lazers etc that they will measure distortion in the reflected light aka as in a mirror.
as we have made this type of lens and they are always mirror coated to reflect the light.

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Every day a grind
Every week a bind
www.iooi.co.uk

[Pete Hanlin]

Beta Chem,
Could you specify what you mean when you are referring to "prism effects?" Do you mean chromatic aberration? If so, good old CR-39 plastic and/or crown glass are your best bet- as their abbe values are the highest of the materials commonly used for spectacle lenses.

Also, what Rx power are you working with? It is difficult to imagine a prescription where 85% of the lens is unacceptably distorted because of chromatic aberration.

If you are speaking of the effects of actual prism (i.e. the decentration of an object's image towards the apex of the prism), I'm afraid you are out of luck. Prism away from center is a given with any lens that has focal power.

Pete

[Jeff Trail]

Pete,

He could be talking about oblique power as well.. probably a combination of off axis oblique power and chromatic abberations.. but 85%?.. thats a little extreme.. that would leave only a viable area of less then a 15 degree arc ..
Pete started a thread in the ophthalmic optics forum where we discussed chromatic abberation.. you might want to check it out Beta.. I think the heading was 1.74 index something or another :)

As for the question about the "laser sight" lens and scopes... you have to remember they are interested only in the geometric center and the clarity of tranmission at that apex.. as well as the magnification in a scope lens is far different then corrective lens on the ophthalmic side, we have to tend for a variety of focal problems and have to deal with the possibilty of upto 4 surface angles in one single lens! Decentration,sherical power, cylidrical power, toss in reading power if you are a presbyop etc.,etc. Working with just a set power in an atoric or aspherical surface in an convex or concave or equiconvex is far different then the problems we have to deal with.
You try to take all aspects of the RX into consideration, as well as YOUR desire in cosmetics you request, lens design expectation and then find the best combination of curvature design, material and actual lens design (SV,FT,Mutli-focal) to best meet all your requirments.
Since we have to answer to those pesky "laws of physics" as we do one thing another portion may get worse..i.e. as you increase index you lose abbe value.
That is why we have a multitude of choices out there to help nullify some of the problems you run into, such as lens curvature (spherical,aspherical,atoric,semi-aspherical) then you have coatings to help with some of the problems i.e. as you increase index you ALSO lose light transmission due to reflection (Fresnal's equation)
You might want to post you actual RX, pupilary distance, lens type (SV,FT,PAL etc. etc.) exact frame measurements would also be helpful as well :) You'll get a whole range of lens choices from people on this "sight" :) just let them explain the high points as well as the low points of each ... Plus you might want to post exactly what YOU expect out of the lens and the possible conditions you would be using them most often.. I'm sure you'll see a ton of postings then
You might be amazed how small things like reducing vertex fitting distance will help improve the optical performence of the lens by reducing the actual physical lens surface you use to still have the same amount of visual field :) pushing that oblique area's out of you natural field of vision.

Jeff "optics are a real pain in the eye at times" Trail

[beta chem]

Hello Jeff, Pete, and Tom,

I wish the UBB code was working right then I could show you what I am speaking of. I will try to put it into words.

When I am looking through my glasses straight ahead everything is fine but when I turn my eye I see a spectrum of colors out the side or thickest part of the glasses.In the case of the plastic lenses, I couldn't turn my eye at all with out getting the distortion(prism) affect. The spectrum I see is enhanced around corners of papers and objects. On one side of the paper I see the blue and green end of the spectrum on the other I see the red and yellow. Everyhting is blurry when looking through the sides also. I assume this is because the edge of the lenses is similar to a prism. I know that there are a few things like quartz that can magnify things with out being made into a lens. These peices of quartz were cut flat.

My prescription is -8.5-75.X020
-8.75-75.X160 at one doctor
at another it is -8.25,-8.5
both doctors gave me different base curves on my contacts, one was 8.4 and the other 8.6 and it hadn't changed for 5 years from 8.8. I am in my mid 20's and when I first acquired glasses my prescription was around -2.5. When I first got contacts it was around -5.5.

When I told the first doctor I wasn't happy with the glasses he told me I was stuck paying for them anyway. That is when I went to a different doctor, actually two different ones. Each different doctor I went to gave me a different prescription.

Thanks for your response.

beta chem

[chip anderson]

Suspect your problem is simply the vertical centers off. Will give red and blue outlines to distant objects. Check vertical centers on glasses before proceeding further. Also note that you will have chromatic and other aberrations when moving eye from center of glasses. You would not be conscious of this if you had always been a spectacle wearer. But as these are not present in the contact lens wearer, they seem to be overwhelming when you first go from contacts to glasses. Other problems, spectacle image is smaller and will give effect of curving straight lines not present when contact lenses worn. Aspheric lenses will help but not eliminate problem.

[beta chem]

Hello Chip,


What are aspheric lenses.Also I see these prism outlines when I look at things that are near also.

Jeff, also to answer your question about what I would expect about the glasses. The glasses would be used for school. Basically what I want is a pair of glasses that have the least amount of chromatic abberation and highest transmission of all wavelenghts of light. They don't have to be cosmetic, I want a pair of glasses that show an extreme field of view. They need to be closest to the unaided eye as possible. I know that is going to be a tall order. If you had UBB on I could show you my prescription. I have tried and I can not send a picture(gif) from a website to be shown on here.
thanks,
beta chem

[This message has been edited by beta chem (edited 09-06-2000).]

[Jeff Trail]

Originally posted by beta chem:
Hello Jeff, Pete, and Tom,


When I am looking through my glasses straight ahead everything is fine but when I turn my eye I see a spectrum of colors out the side or thickest part of the glasses.In the case of the plastic lenses, I couldn't turn my eye at all with out getting the distortion(prism) affect. The spectrum I see is enhanced around corners of papers and objects. On one side of the paper I see the blue and green end of the spectrum on the other I see the red and yellow. Everyhting is blurry when looking through the sides also. I assume this is because the edge of the lenses is similar to a prism.

What you are talking about is "chromatic abberation" .. the lens material is breaking the "white light" down into the different wave lengths (I guess this is where you picked up the "prism" phrase) It is acting like a "prism" breaking down the light and the greater the index the worse the abberation.. check out that thread listed under the ophthalmic optics forum and you will get a fairly detailed explanation about chromatisism.

I know that there are a few things like quartz that can magnify things with out being made into a lens. These peices of quartz were cut flat.

My prescription is -8.5-75.X020
-8.75-75.X160 at one doctor
at another it is -8.25,-8.5
both doctors gave me different base curves on my contacts, one was 8.4 and the other 8.6 and it hadn't changed for 5 years from 8.8. I am in my mid 20's and when I first acquired glasses my prescription was around -2.5. When I first got contacts it was around -5.5.
beta chem[/I]

The "base curve" of a contact has NO bearing on what base curve you would get in a pair of lens in a frame...in a myopic RX the higher the number (-sphere) the flatter the front curve of the lens, your lens (in the frame) are probably around a .50 base curve.
The thing to remember is that to have the least amount of distortion the optimum ocular curvature should be around a 6^ curve,
this is why we have such a large selection of "base curves" to work from when we grind power into a lens, down in minus power flatter the front surface, because the ocular surface where the power is being ground is going up in curve amount. while if you go up in plus power it's the opposite, you increase front curvature because the ocular surface gets flatter to get the corrective power.. having base curve selection cuts down on all the oblique problems that you might get (distortion, off axis power, axial fluxuation etc. etc.)
Take (I'm rounding off here to make it easy to explain) your RX -8.25 (od) -8.50 (os) on a .51 base in CR39 you would have a (fairly) flat front surface and the back surface (ocular)would be -9.25 (od) -9.50 (os) ..while that SAME exact RX in a 1.60 index lens the ocular curves would drop to -7.75 (os) -8.00 (od)..in going further to a 1.66 indexed lens -7.12(os) -7.37(od)
Now we are fighting battles on a couple of fronts here, as you increase the index of refraction of the lens then your abbe value DECREASES. the result is a higher degree of chromatisism as you go up in index, you also start to experience off axis problems on an oblique angle (distortion) There are things that can help in this area such as curve design. While on the other hand you get to decrease the amount of curvature and STILL get the same amount of refractive power (so the lens is thinner and lighter) AGAIN if you read the postings in that other forum you'll really be able to get a better grasp of what we are talking about.
Now even though the amount of curve is decreasing the other problems are increasing, because the higher index material are more dense and slow light more you lose in two places, the amount of light being transmitted through the lens (fresnal's equation) and the lens acting like a "prism" and breaking the different legthes of light down into it's natural wave lengths (chromatic abberation)
Looking at it from the other end of the spectrum (no pun intended :) ) if you choose a lower index of material and get far less chromatic effect then the amount of curve will make the actual amount of usuable physical lens surface decrease, do to the refractive error of the "steep" curve needed to get the correction of power. That's physic's for ya
To get around all the problems we try to use curve shape (aspherical,atoric etc.) as well as coatings to help with the loss of light transmission due to the refractive index of the material...
Some of the key things to do is make sure you get a mono fitting(PD) fitting of the optical center (EVEN in sv) to ensure that the optical center falls in the correct place..a frame that allows for the shortest vertex fitting ditance will also improve the lens performence, it effectively removes the peripharel area from your "line" of sight. Which isn't really all that useful to a high myop. try to pick a frame that is the smallest you can get that will still look "right" for you, roundish or oval shaped is best. AND get the frame that will need the LEAST amount of decentration to get the correct PD ...
Decide if the cosmetics are more important then the optical quality (which some people waiver on.

As for the "refraction" and going from OD to OD, you have to remember a refraction is subjective, you are more or less refracting yourself when it comes to sitting in the chair and having them "flip" the dials.. you get a refraction in the morning and you'll probably get a different one in the evening (power) .. if they all were in a .25 with the amount of power you have then it's really no big deal.. now if they moved your axis 15 or 20 degree's WELL... :) ..
A slight power change going from one OD to the next is nothing to be concerned about..
Read that other thread (1.74 index) and get a feel for what we are discussing and by then I'm sure others will have added to this thread.. or post some questions here where I might have went off in a tangent and you need some further details.. I'm sure everyone will be willing to jump into the posting.. right now my fingers are tired :)



Jeff" hope some of this was helpful" Trail



[This message has been edited by Jeff Trail (edited 09-06-2000).]

[Steve Machol]

Originally posted by beta chem:
<FONT COLOR=#FF0000>If you had UBB on I could show you my prescription. I have tried and I can not send a picture(gif) from a website to be shown on here.</FONT>

Uh, UBB code is on. Here's an example for instance,



Also my signature uses the UBB [img] tag.


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OptiBoard Administrator

[beta chem]

http://antwrp.gsfc.nasa.gov/apod/ima...cena_wfpc2.jpg

okay, good then!

beta chem

[This message has been edited by beta chem (edited 09-06-2000).]

[This message has been edited by beta chem (edited 09-25-2000).]

[Jeff Trail]

Originally posted by beta chem:

What are aspheric lenses.Also I see these prism outlines when I look at things that are near also.
[/I]

In high index, as well as other materials you have (mainly) three choices of surface curvature
1. spherical- a curve with uniform radius of curvature in all meridians

2. aspherical- nonuniform surface curvature, helps with magnification and minification on the higher indexed lens and more powerful powers, also helps with peripheral distortion.

3 toric- different curvature in the two principal meridians

Basically what I want is a pair of glasses that have the least amount of chromatic aberration and highest transmission of all wavelengths of light. They don't have to be cosmetic, I want a pair of glasses that show an extreme field of view. They need to be closest to the unaided eye as possible. I know that is going to be a tall order. If [/I]

As of right now (our technology today) you are not going to get what you are looking for with a lens in frame combination, we can reduce it somewhat but as long as you have that vertex distance and not in a contact you are going to experience off axis aberration and some chromatic aberration in any material you choose with your RX.. Just physics...
If I understand you are wanting a lens that will let you sweep the full surface from nasal to temple and have NO distortion. Not with your RX, sorry..
If you want the best, optically speaking, then get crown glass with a high quality anti- reflective coating.. this will almost eliminate the chromatic problem but you still will have the peripheral distortion starting at around 12 degree's either way from the G.M.C. .. you can even take a flat pc. of glass with NO power at all but if you tilt it on it's optical axis you'll get distortion.. that's just the nature of the game when you are "bending" light at oblique angles..
If you don't mind the weight and keep the frame SMALL and round as possible and get the optical center out there where you have as little decentration as possible (none would be best) then that's about the best (optically speaking) you're going to get.. also keep the vertex as SHORT as possible...of course you won't have the same unobstructed view as if you were not wearing any glasses or contacts but it is going to be your best bet...
Some times we just can't do what you want or expect.. no matter how many ways we try to do it :)

Jeff" who ever said we could solve all the optical problems" Trail

[This message has been edited by Jeff Trail (edited 09-06-2000).]

[This message has been edited by Jeff Trail (edited 09-06-2000).]

[Steve Machol]

beta chem,

Er, what is that a picture of exactly? I tried to email you, but the email address you registered with is invalid. Please note that as per the FAQ, you must have a valid email address in order to post on OptiBoard (although you don't have to make that address visible to other users.) Please fix this by going to 'preferences' and putting in your valid email address. Thanks.

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OptiBoard Administrator

[beta chem]

Hello Steve,
This is the Center of Centaurus A
Credit: E.J. Schreier (STScI) et al., NASA
Explanation: A fantastic jumble of young blue star clusters, gigantic glowing gas clouds, and imposing dark dust lanes surrounds the central region of the active galaxy Centaurus A. This mosaic of Hubble Space Telescope images taken in blue, green, and red light has been processed to present a natural color picture of this cosmic maelstrom. Infrared images from the Hubble have also shown that hidden at the center of this activity are what seem to be disks of matter spiraling into a black hole with a billion times the mass of the Sun! Centaurus A itself is apparently the result of a collision of two galaxies and the left over debris is steadily being consumed by the black hole. Astronomers believe that such black hole "central engines" generate the radio, X-ray, and gamma-ray energy radiated by Centaurus A and other active galaxies. But for an active galaxy Centaurus A is close, a mere 10 million light-years away, and is a relatively convenient laboratory for exploring these powerful sources of energy.

My e-mail address was canceled because of low activity and the new one has been added.

[Steve Machol]

Thanks beta chem!

I asked my wife what she thought the picture was and she said it looked like an 'open sore'. It wasn't until I looked at the source of your message that I discovered all the astronomical pictures. Pretty interesting stuff!

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OptiBoard Administrator

[This message has been edited by Steve Machol (edited 09-07-2000).]

[chip anderson]

Beta:

Aspheric lenses have one or more surfaces that become longer or shorter as they deviate from the center. Properly used they can reduce distortion as the gaze moves from the optical center of the lens. i.e. chromatic and other distortions. Improperly used they can induce more problems.

Your illustration may show this but I can't see that it does. This could be due to low quality of curved lines being shown on computer generated drawings.

[Jeff Trail]

Beta,

Maybe we should go back a couple of steps and start at the beginning....
The terms of aspheric and spherical seems like a good starting point. A spherical lens surface is "regular" like the surface of a ball (or sphere) An aspheric lens surface "changes shape," it does NOT have the same radius of curvature over the entire surface.
You use an Aspheric design for a number of reasons, it can be manipulated to "correct" certain lens aberrations you can use a "flatter" surface, which in your case (myop)reduce some of the problems inherent with your RX which is depth perception problems and or image distortion and power error.
When looking through a lens the optics of that lens (beside correcting acuity) does have certain properties, such as in your case a myopic lens will "distort" objects (appear "bulged" [barrel distortion)) an aspherical surface does help with these types of problems.
The next problem would be due to the "amount" of ocular (backside) of curve needed to get your corrected vision. The nature of the game is you increase in minus power you decrease front surface curvature, there by decreasing the amount of curvature needed to be placed on the backside to get the corrective power. As you increase in index of material as well then you can get an even less curve on the back and still get the same amount of corrective power.
Sounds good so far? Well, here comes the "bad" part, as you increase index you go down in abbe value, the lens will show the chromatic effects more as you go up in index.
Sorry to say but having an Aspherical design does NOT help with chromatic aberration. The chromatic aberration is due to the way the material is "bending" light and the "speed" that it is traveling through the lens surface(s).. the higher the index the more the lens will break down white light into the natural wave lengths (that "nasty" rainbow) As you move from the geometric center and optical center (both in the same place on an aspherical design) you have curvature of field aberration, the light enters the peripheral area of the lens does NOT focus where it should. Not much we can do about it, even if we did delete the oblique astigmatism you still will experience curvature of field or power error, if you would rather call it that. The power error describes the aberration of that edge spherical power being different at the OC then at that "thicker" edge. This is one of the MAIN reasons selecting the BEST base curve for the ground power, that way we can atleast keep it as low or at least as error free as possible.
That is just the nature of a myopic RX you are going to have a "thin" center and "thick" edge. If you go to flat, or into bi-convex side, then you are going to increase off axis distortion as well.
Even though this is acceptable to some people, from your posting it does not seem to be what you want :)
No matter WHAT material you chose you would have power error with your RX, of course it can be helped somewhat with proper base curve selection, PROPER fitting procedure. (mono PD's, vertical OC fitting, shortest possible vertex fitting, small as frame that you are comfortable wearing (roundish or oval is best) the LEAST amount of decentration)
I would definitely invest in an antireflective coating if I were you, besides the loss of transmission due to index( Fresnel's equation)you also seem to be interested in astronomy, the last thing you would want is front side as well as backside reflections (especially in low ambient light situations)
This is as far as I go.. let some one else carry the torch :)..other then if you want the best "optical" quality and don't mind the weight then crown glass is probably your best choice. You could always get a second pair of the thinner higher indexed lens for "casual" use (social settings) where a little chromaticism isn't really a bother.. try an aspheric or atoric surface to help with the other problem I went over.
(and the AR coat)

Darris, Darryl..Pete..anyone? Any other suggestions? ANYONE?.. my fingers are tired and it's late and I'm grumpy

Jeff "to tired to even think of something to say here :)" Trail


[This message has been edited by Jeff Trail (edited 09-08-2000).]

[Darris Chambless]

Hello beta chem,

With all due respect I think I'm beginning to understand why doctors weren't giving any straight answers to your questions. Your question are starting to make less or no sense at all. The picture you posted (The lenses pic) is ambiguous and has no baring on anything without an explanation of its relevance.

I liked the celestial picture though. At first I too thought it to be an open wound of some soft tissue, but then realized that you could see other stars in the background. I also visited the site that the picture came from (Good stuff. Even added it to my "favorites" list for reference material.)

This isn't an attack on you, but I am saying that you may want to reword your questions in a manner that would make them a little more to the point. We seem to be playing a lot of hit and miss on your questions mainly because what we think you're asking isn't what you want to know.

Example: Your question about UV and melitonin production due to blocking of UV light. First I will say definitive that this isn't your problem, but if getting non-UV blocking lenses helps your psyche then more power to you (It's still not your problem) What I'm still unsure about is whether you wanted information on the properties of UV, its effect on melitonin and narcolepsy, if you wanted to know what lenses don't block UV or if you were wanting to know about any studies linking these combination. Not to mention it is a very broad subject and would take years of research for us to even be able to answer you (whichever question you may have been asking)

You think in terms of chemistry and astronomy, so let me ask you a question not unlike the questions you've asked. What stars are really there and what stars are just the light images of themselves from the past? Much like ours on occasion, I think your intellect is causing problems in conveying what you want to know. You are asking in chemistry terms and we are trying to translate them into opticianry terms and then answer them in opticianry terms at which point I think you are trying to translate them back into chemistry terms. Basically it's losing something in the translation ;-)

In your questioning you are wanting to know how to solve problem A by using the means provided in problem B and problem B only. Therein lies the problem you may not be able to solve problem A with the means provided by problem B, in fact it may be impossible. (Hypothetically) If you use the means from problem F combined with the extremes of problem Q and take the coefficient of problem K you may have a more viable solution. It seems you have made your conclusions and won't let any conflicting information steer you in a new and or better direction and seem convinced that the direction you have chosen to solve these problems is the correct one.

I will go back to the deepest darkest recesses of my mind and try to dig up my "chemistry think" (that's scary ;-) I'm just trying to make your stay here more productive not attacking you in any way, but I don't know how else to word it. If it comes across as combative then I apologize. It's not intended that way.

Thanks,

Darris C.

[beta chem]

Hello Darris,
The topic of this discussion was "plastic vs. glass and the burden of prism affects" so you are a little of the topic. I will leave a little note for you at the other thread pertaining to what you have said and about your knowledge of chemistry.

As for the above pictures I guess I will just start having to do my homework. They probably have a opticians dictionary around someplace. Maybe you could steer me in the right direction to find one online so I could understand your terms with out making a complete "JACKASS" out of my self. I realize know this was a stupid question and should have just found the answer out myself
which I am very good at.


beta chem

[Jeff Trail]

Beta,

Your best bet is just read my posting above Darris, pick out the parts you want further explanation on and post it.
I think I pretty well covered about every aspect of an RX (ground form)that you'll see dealing with your RX..
I'm through with this thread.. I might have mentioned a few things other people could use or file away in the "hmmm" file, but you do not seem to be really wanting any answer.
I thought I covered just about every point I could think of and you just skipped right over it.. so let these other guys try to figure out what ya want.. stick a fork in me I'm done :)

Jeff "thought I made it pretty plain but guess not..no wonder I'm back in school, I must be "dumb" " Trail :)

[John R]

Originally posted by beta chem:
What glass would give the least prism affect? .

The higher the glass index the more noticable the prism affect is. (That is if by prism affect you mean white light passing through a prism and coming out in a rainbow aka pink floyd's cover on "dark side of the moon")
so i would stick to std? 1.523 index glass then. And probley put an ar coat on it.


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Every day a grind
Every week a bind
www.iooi.co.uk

[Pete Hanlin]

Beta Chem,
In your illustration, you show a lens with a curved front surface and one with a flat (aka, "plano") front surface. Unfortunately, lens design has less influence on the amount of chromatic aberration produced by a lens than does the lenses material. In other words, your initial question ("which material should I use for my lenses to reduce chromatic aberration") was the right question to be asking.

As I mentioned in my first posting in this string, the answer is to either use "crown glass" or CR-39 (aka, "plastic"). The key to your query regards the abbe value of each material (i.e., the measurement of the material's tendency to refract varying colors unevenly).

Crown glass and plastic both have abbe values approaching "60." High index materials (like those you have tried) have significantly lower abbe values (some approaching as low as 30). Why is abbe value important? The formula for determining the amount of chromatic aberration at any given point in a lens demonstrates this rather well. Rounding your Rx off to -8.00, when you look 5mm away from the center of the lens, you experience 4 diopters of prism (regardless of what material or lens design you choose). This means that light from an object viewed through this portion of the lens will be displaced 4/100 of the distance from the lens from its original path.

Now enter the consideration of chromatic aberration. To determine the dioptric power of chromatic aberration, divide the regular prism (in our example, 4 diopters) by the abbe value. If your lens is made of polycarbonate, you will have around 0.13 diopters of chromatic aberration (i.e., light from one end of the spectrum will be deviated 13/10000 differently than light on the other end of the spectrum). Through a crown glass lens, this deviation is only 7/10000.

Although any explanation of chromatic aberration apparently becomes complex, the result is simple: lenses with higher abbe values display less of a tendency to refract differing colors unevenly (i.e. have less chromatic aberration). If you want to get rid of color fringes, you have to use a material with a relatively high abbe value (i.e., crown glass or plastic).

Pete "use crown glass or CR-39, my friend" Hanlin

PS- While you will be reducing chromatic aberration, however, you will find the lens is also thicker and/or heavier than the previous high index lenses you have had.

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[This message has been edited by Pete Hanlin (edited 09-08-2000).]

[beta chem]

Hello Jeff, John, Darris and Pete

You have been very helpful and I thank you for your posts. I assumed that my problems with corrective lenses,"especially glasses" had been encountered before. I'm just going to have to learn the lingo. Below is a picture of my glasses and prescription.The glasses possibly have a problem, check it out.Maybe someone could explain all the numbers on my prescription.
http://www.angelfire.com/scifi/HIFI4/_LWF0014.gif
http://www.angelfire.com/scifi/HIFI4/_LWF0015.gif


[This message has been edited by beta chem (edited 09-08-2000).]

[This message has been edited by beta chem (edited 09-25-2000).]

[Darris Chambless]

Originally posted by beta chem:
Hello Darris,
The topic of this discussion was "plastic vs. glass and the burden of prism affects" so you are a little of the topic. I will leave a little note for you at the other thread pertaining to what you have said and about your knowledge of chemistry.

As for the above pictures I guess I will just start having to do my homework. They probably have a opticians dictionary around someplace. Maybe you could steer me in the right direction to find one online so I could understand your terms with out making a complete "JACKASS" out of my self. I realize know this was a stupid question and should have just found the answer out myself
which I am very good at.


beta chem

Hello once again beta chem,

First let me say that I don't recall saying that you were "making a 'JACKASS'" out of yourself. I was merely saying that your questions are not coming across in a manner that can be easily defined in optics and are somewhat vague or too broad to give you an answer to without writing an entire book for you (e.g. Jeff's posting :-)

I will leave you with a question that is not unlike any of yours have been thus far and perhaps it will shed some light on what I've been trying to say to you.

How much is a car?

Darris C.

[Jeff Trail]

Beta,

From the pic you posted of your frame.. two things are happening, first since you are a myop by mounting the lens "titlted" nasal side sticking out you are get some base in prism (deviatation) how much? hard to be exact without having the glasses in our hands :) .. second thing, if you wear a lens "tilted" you also increase the amount of spherical and cylindrical power across the axis plane..
Also, how much? can't tell without having the frame in hand.. if you want to see if it makes a difference (and you want to take the chance)and not let the optician dot it, just "bend the frame outwards on one side so both lens are setting at the same angle (in this case fairly flat)you want to hold the frame at the bridge (that "bar"in the between the lens) "bend that right side outwards on the TEMPERAL side (the side where the lens is sticking "out" on the nasal side) .. if you havn't broken the frame yet, pop it on and see if it cleared up any :) .. it should make some difference, how much? don't know (again) unless we had your frame on hand to check
I'm stopping here before Darris wants to become my agent and start publishing my "book" :)
BTW, Darris havn't seen Chad posting for awhile.. did you give him your "depression bug"

Jeff "keeping it short and sweet" Trail

[This message has been edited by Jeff Trail (edited 09-08-2000).]

[beta chem]

Jeff,

Could something like this contribute to headaches.

beta chem