Am i looking for trouble?

[LENNY]

Today i did a job with a SV poly lenses:

OD-8.00-0.50x180
OS-4.00 sph
PPD 31/31

I decided to decenter od lens less and made to 34mm monoculary wich gave me 2.4 prism BI
Then i cut OS to 25mm (yes it was prety small frame)
That gave me 2.4 prism BO

The job came ot greate looking but my question is am i looking for trouble even so i newtrolized the prisms?
Help!:hammer:

[Rich R]

I believe that patient vision will be compromised by o.c.'s being placed incorrectly, also this will result in more chromatic abberation, possibly bothering patient.
Rich R

[Jedi]

Yeah you used poly.
Nuf said.

[Texas Ranger]

Yes, Lenny, you're lookin' fer trouble.....

[LENNY]

Unfortunately I had to use Poly.
Otherwise i would use a different indexes of refraction to create an equal thickness look.
Am i looking for problems again?

But anyway the patient picked up the glasses loved the way they came out and ordered two other pairs.

Lets hope everything is going to be ok!

[Diane]

LENNY said:
Unfortunately I had to use Poly.
Otherwise i would use a different indexes of refraction to create an equal thickness look.
Am i looking for problems again?

But anyway the patient picked up the glasses loved the way they came out and ordered two other pairs.

Lets hope everything is going to be ok!

Lenny,

I'm going to be curious on this one. What was the patient's Best Corrected Visual Acuity with this Rx? OD, OS and OU. What was the entrance VA as well? Also, I would be curious on the age and any other type of informtion.

Diane

[Pete Hanlin]

If the lenses you used have aspheric curves, you have placed the patient's line of vision through a portion of the lens that isn't optimized for vision.

Otherwise, I don't quite understand what all this "Oh, you used polycarbonate???" stuff is all about. Is there concern because of the abbe value of poly? Well, those of you who would have fit an ultra high index lens on this patient (e.g., 1.66) might be surprised to find that the abbe value of these products is about the same as poly (low 30s)...

In the end, you've created a situation where the patient's optical axis is about 6 degrees off the optical axis of the lenses. Its an interesting concept, but it does carry other consequences (increases spherical aberration, marginal astigmatism, etc., in certain parts of the lens as the patient gazes away from the "center" of the lenses). I'd be interested to see what this decentration trick has actually done to the edge thicknesses of the lens (you can find out by crunching the numbers through OpticsLite, which is downloadable through the downloads section of OptiBoard).

When it comes time to use PALs for this patient, I certainly hope you aren't intending to have similar prism ground into the lenses!
;)

[Alan W]

Your intentions are admireable.
I am confused about something (here I go with another senior moment) . . .

Let's separate horizontal from vertical issues for a moment.

With -8.00 on one side and -4.00 on the other, seems to me the potential for vertical imbalance is as much of or more of an issue than horizontal.

My first inclination is to ask you whether the patient was, in fact, looking through OC's. I would personally resolve that issue immediately. The fact that the patient loves the glasses and ordered more speaks to the marvel of human adaptation. If that person has been looking through questionably centered lenses vertically with no complaints there is ALWAYS the risk of rocking his/her boat with the best of intentions. "Err to the side of caution!"

I have the inclination to move both centers to the best vertical position based on a simple "gaze and markup" procedure.

I have this terrible feeling that our friend may be favoring an eye. Don't know. Bet it's OD! I mean, look at the potential difference in image size. I think this persons visual quality of life is so screwed, he's happy with anything that resembles comfort and acquity. Again, theory is wonderful, but . . . "err to the side of caution!" The cure can be worse than the disease.

As far as horizontal issues is/are concerned, obviously, the disparent powers will introduce base in base out conflicts. But, again . . . Did the doctor discover convergence error? In fact, did the doctor discover a break in fusion? You may be correcting an uncorrectable. Has the doctor said anything? Helllo!

I hate poly. Full of color ab. But, it stops bullets (?). May be a bit thinner . . . maybe! There are improvements. That being said . . . a thousand and one Frenchman can't be wrong, as the saying goes.

The real culprit here is the patient. He/she should have turned in the right eye long before the warranty ran out!

Not trying to be flippant about this. But, experience has taught me that the patients optical history needs to be studied. Consistency is critical. Consultation with the doctor is essential. Clear, Comfortable, Single, Simultaneous, Binocular Vision is the goal if it doesn't kill the patient in the process.


Thanks,
ASW

[Pete Hanlin]

I hate poly. Full of color ab.
As I mentioned earlier, if chromatic aberration is that much of an issue to you I hope you aren't dispensing any ultra-high index products...

I would agree that the patient is probably favoring one eye, especially since that Rx is probably anisometropic enough to produce a difference in image size large enough to trigger aseikonic symptoms in many individuals.

How old is this patient? When presbyopia comes along, there are going to be a number of challenges. Also, did you make the patient aware of your "customization" of his/her order? If s/he happens to move to a different city and visits another Optician, it would be nice if the other LDO could know about the special design of the lenses from the get-go.

Be sure to let us know how things turn out... coincidentally, what ARE the VAs of this patient? Basically, I'd like to know the same things Diane inquired about (age, VAs, etc.).

[LENNY]

People !
You scared me!
The patient is 18 years old male.
His best corected va in the right is 20/30
In the left 20/20
So you are right he might use one eye in the glasses!
I am calling the gyu up and making the glasses right.
I probably will tell him that i found a defect in the lens.

BTW i think i will not use this for progressives
;)

[David Wilson]

I totally agree with Pete on this. Poly gets bad press because of its low Abbe number yet other low Abbe number materials seem to avoid the flack. Furthermore, the attacks are based purely on its Abbe umber, rather than the transverse chromatic aberration (the aberration related to the Abbe number). By that I mean that the Abbe number is only an issue where it creates noticeable TCA. In low power lenses it doesn't. The Polycarbonate Lens Council suggest that all powers below 4.00D are safe, and I would agree. Sure they have a bias, but clinical tests and calculations by Jalie and Torgersen (among others) have shown that TCA is not noticeable below 0.1 prism dioptre and V/A is not affected until above 0.16 prism dioptres of TCA. Good fitting, even in higher powers can avoid this problem. As for the optical centre, as Pete says, if you don't position the principal axis so that it passes through the centre of rotation of the eye both vertically and horizontally then you are introducing aberrations, notably oblique (marginal) astigmatism.
Regards
David Wilson

[Alan W]

Bad press?
When a photographer sits in front of me saying he sees a brown or orange line acros the top of a treeline, when a commercial artist says that when he does non electronic color separations, or has slight question about color matching using the Pantone Color System with is glasses on, Abbe, Jane, Paul or Samantha don't mean diddly!

As for the Polycarbonate Council . . . highly respectable.
So was the photographer from Newsweek.
So was the artist from Laguna Beach.

Yes, higher index is or can be a problem.
Compare a 1.67 Vanity from Nassau and a 1.67 from Pentax.
There is a difference.

Forgive me for taking this terrible real world attitude. 37 years doing this erodes ones sense scientific objectivity. It also teaches one that the numbers are all too often . . . bull!
It also teaches those of us who have taken care of the artist and the photographer to believe what we hear from sensitive experts.

P.S. Please read the writeup on Enigma. Perhaps it will shed some light on one that is slightly dispersed.

That's like telling someone he's crazy because, statistically, what he believes is not possible.

"Doc. It hurts when I laugh."
"That's not possible. I've given you the most powerful pain killer made."
"But, Doc, It hurts when I laugh."
"O.K. . . . Stop Laughing!"