I need to create a thinnest +10.00 job possible
Pd is 56mm going into 48-18 30 49 frame
I cant use a smaller frame!
I surfaced CR39 --got 2 Bricks!
What is the best material?
I understand that 1.66 or 1.67 does not have a high enough base.
So my choises are 1.56 aspheric or 1.6 spherical ( is there 1.60 asph?)
What else ?
What will look thinner?
Lenny,
Who told you that you could not get a base curve to handle a +10 in 1.67? That's not correct... even though you can only get an 8 the index of refraction makes up for it and for once you can use less base curve than power and STILL not end up with a bi-convex...
I just did a +10.75 or 10.50 (I forget) on a 1.67 and the tool was still in the minus range...it was like a -.12/-1.75 ..all right it was almost "plano" but still it was not bi-convex... I think I ended up doing it on a -.25/ tool..
You can carry off putting a +10 on a 1.67 or 1.71 ..unless I'm dreaming and the times I did do it I really didn't...oh gee I hope this isn't a "dream" thing and I wake up and find out I was never in optics but am some 15 year old kid working at burger king..
Jeff "you want fries with that whopper" Trail
I just run the numbers Using a 8.25 base Seiko
1.67 index you end up with a -0.37 curve
Bill
+10.00D in 1.67 = 7.41D
The diffrence in subs between a 1.60 and 1.67 is going to be approx 1 m/m.
Finish your sentence
I think you meant: a curve that produces 10 diopters in index 1.67 produces 7.43 diopters in index 1.498.John R said:
+10.00D in 1.67 = 7.41D
Or, perhaps more importantly for Lenny's purpose, a lens of index 1.67 with a "true front curve" of 8.54 diopters calculated in shop index (which is certainly the convention hereabouts) has an actual front curve power of 10.79 diopters. The effective power of the front at the back surface will of course be greater than that, depending on the thickness required.
Well, technically if you wanted the thinnest possible in the power you can go with an ultra high index glass and the smallest blank possible, but of course nobody would do that.;)
ViZio makes a very thin plus powered lens. They are atoric and come in all sorts of specified base curves. They are also UTC AR Coated right from the factory.
Harry,
The ViZio comes in "finished" version only and a plus 10 is beyond the power range available..
Jeff
What about 1.56 aspheric?
Will the asphericity make lens thinner or thicker than spherical high index?
What is the size of the spherical portion on an aspheric lens?
BTW I dont know what i would do without Optiboard comunity help
Thanks to everybody!
Now why didn't i say that...shanbaum said:
I think you meant: a curve that produces 10 diopters in index 1.67 produces 7.43 diopters in index 1.498.
:hammer:
Its what you get for posting so early in the morning before 2 mugs of tea..:cheers:
has anyone here considered a lenticular???
obviously contacts and laser are out, other wise you wouldn't of asked!!
how about a nice 1.6 finalite/microlite(sola), i did one for a +8.00Ds - nice jobby, requested an et of 2mm to create a small overlap, in a very similar frame...
if you wanted a less bulbess look, wouldn't you want a bigger frame?? ohterwise you need a huge front curve!!! very ugly!!
whatever the case don't forget your aspheric front curve!!
James
Jimbob said:
has anyone here considered a lenticular???
obviously contacts and laser are out, other wise you wouldn't of asked!!
how about a nice 1.6 finalite/microlite(sola), i did one for a +8.00Ds - nice jobby, requested an et of 2mm to create a small overlap, in a very similar frame...
if you wanted a less bulbess look, wouldn't you want a bigger frame?? ohterwise you need a huge front curve!!! very ugly!!
whatever the case don't forget your aspheric front curve!!
James
James,
chances are if the person Lenny was dealing with wanted the "thinnest" they are going for a job for cosmetic reasons more so than for any reason, which an aspheric lenticular is anything but pretty :-) ....The reason a 1.67 or 1.71 or 1.74 would work better than a 1.60 is the total power vs. total lens power, because of the index of refraction we can actually put more power into than lens than you have base curve and still have a concave ocular surface, while a 1.60 you could not have as much curve, the highest blank curve we can get is a 10.25 in 1.60 (actual curve 9.05)..so taking into account the curvature and index you would go with the higher index.. I try to stay away from an aphakic lens as long as possible especially if someone is looking for the cosmetic answer...
We yanks are a little picky when it comes to how great we look, even when we can't see two inches in front of our face :-) ..plus if the patient is willing to spend the bucks the sky is the limit..
It is pretty weird the prices as well, just went through this problem, had 3 pair of +11.75-.50 and the optician charged for lenticulars since the guy had a cow when he heard the prices for a 1.67 or 1.71 design... than they decided to at least up grade it to super modulars..they putthe lens into to small of a frame where we had to cut to much into the bowl so it looked pretty bad..ended up going back to the 1.67 and everyone was mad :-) WEELL except me (the lab), hey I did my part in warning that the frame was to small and I had to edge away all the carrier and was into the bowl...
Lenny,
You wouldn't want to try to use a 1.56, not enough index to really help with getting the curves you would want and if you end up having to put a biconvex lens in the extra charges by the lab (hey a biconvex is a tough cut) would make it just as cheap to go with the higher index material... when you are dealing with an aspherical or spherical, your total surface design is going to be one or the other unless using a few of the companies that give you a mix (only in finished version stock lens) Seiko "luscious" etc., etc..your RX is past that stock range..
Jeff "we lab guys usually get ingnored" Trail
I have been reading all the posting on this subject of +10/ going for the thin and lite lens. Since I am a +10. this is a problem I have been trying to resolve for myself. The best that I have come up with is a aspherical 1.60 in about a 52 eye size. Power is not the best, within +-.25 to .50. This ok because the best vison that I get is about 20/30 any way. A must for me is a/r. This is my back up pair. I have tried the lenticular, did it in oversize then cut down to small frame size. This was ok, but I like the pair that was the 1.60 better. I do wear contacts G_Ps about 90% of the time/ must have the bifocal/ Just some personal thoughts on the subject.
Dave
Thanks Dave
Nice to get the views of someone wearing what is being talked about rather than all the expert views.
Seiko makes an aspheric single vision in 1.67 index with a nominal base curve of 11.25 (true base curve 8.15). I ran it through my Rx computer and compared it with a Silor SV Cr-39 10.50 base (true curve 10.34) and here are the results:
CR-39 1.67 Aspheric
--------- ----------------
true base curve 10.50 8.15
back curve (tool) -0.37 -0.75
finished edge thickness .50 .50
finished center thickness 9.30 6.60
I know you said you can't change the frame, but I can't resist pointing out that you could reduce that 6.6 to 4.8 by getting rid of the decentration altogether (ie: DBL=8 ?)
Terry
:)
Yes, Yes, Yes The FRAME!!!
I wish icould do that!
The customer has a watermelon instead of the head.
Even this frame looks and fits her small.
BTW She picked up the 2 jobs i made for her and she were extatic!
She said this were the thinnest and the lightest pair she ever had!
I forgot to mention that she was wearing a PBX in 58 eye frame!
So i guess anything would be better!
I ended up using 1.56 kodak aspheric. I was tired of fighting with my lab. They were to much afraid to do 1.66 because according to them it may not cut out:bbg: !
It was an inexpensive choice and she was happy.
Just out of curiosity, what base curve, back curve and thickness did you end up with?LENNY said:
I ended up using 1.56 kodak aspheric.
Terry
I dont remember of hand but the base was prety high , probably the steepes they have 10?. PD came out ok . I also dropped the OCs 3 mm so the top came out a litle thinner (nobody looks at the buttom of the frame)
Question (from a NON-optician): Would you have to make the frame ride a little higher by adjusting the nose pads so the OCs would be in the correct location or would 3 below the datum work OK without any adjustments? It just seems to me this might be problematic for the patient especially considering the strength of the RX and the fact the lens is aspheric.LENNY said:
I dont remember of hand but the base was prety high , probably the steepes they have 10?. PD came out ok . I also dropped the OCs 3 mm so the top came out a litle thinner (nobody looks at the buttom of the frame)
BTW, I ran the KODAK 1.56 through my computer and it picked a 9.75 base (tc=9.47) and computed 8.1 center thickness on the datum line and 8.7 at 3 below the datum line, which is roughly 1.4 thinner than the CR-39 and 1.6 thicker than the 1.67 lens. Does this sound about right?
Terry
:)
By lowering both centers i did not create any vertical imbalance.
The lens is still spherical in the center so i dont think that the asphericity would make any difference.
The patient was more than happy with their vision.
If you think how many patients wear their glasses in different positions after the glasses were manufactured and dispensed (even if we did take a height on SV lenses) this number is going to be very high.
Teoretecaly it might affect the vision.
About the thickness!
I did not measure it but htere was a Significant difference between a CR-39 and 1.56 ( I made it first in CR-39 and got 2 bricks)
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