Mixing Lense Designs

**Mike Fretto** · 08-13-2001, 07:13 PM

We had an order come down today as a doctors remake for an increase in add power. They wanted OD only ASL ST28 requesting a 3.50 Add. I didnt think there was an aspheric st 28 available with a 3.50 add, so I am curious to see your opinion on using aspheric in one eye and spherical in the other, is it acceptable? The only other option I could see was to make both lenses in another material, seeing how the patients distant RX was only -1.00 I couldnt see selling ASL to begin with but dont get me started on that. Rx on the OS was plano.

**hcjilson** · 08-13-2001, 07:40 PM

Mike, I shudder to post this!!!!!!!!!!!!

Correct me if I'm wrong, anyone. ( and I'm Sure someone will......It is my belief that the only aspheric available in a +3.50 add is a curved top 28 by Rodenstock.Its been a while...but I think that is correct.........God help me if Darryl reads this.......
hj
PS I wouldn't mix and match.I'd sell both lenses....... after a call to the refracting Dr of course!

**Cindy Hamlin** · 08-13-2001, 08:23 PM

Harry,
I believe the aspheric is a FT22, not the 28.

I agree with you. Why put an aspheric lens on a patient whose RX is a -1.00 and a plano?????????? One of the things that make me go HMMMMMMMMM.............
~Cindy

**LaurieC** · 08-13-2001, 10:43 PM

In a word: don't

**chip anderson** · 08-14-2001, 05:30 AM

I do this occasionally as well as mix indices in high imballances, hasn't come back to haunt me yet. Have also been known to use an ST on one eye and a round seg. on the other in plus minus mis~matches, works great! Wouldn't do it if the R & L where highly similar though.

Of course you have to live with the lab calling you up a lot and saying: "Are you sure you want this?"

Chip

P.S. I used to know an old experienced opthalmologist who often Rx'd plus cyl on one eye and minus on the other (both before and after "all cylinder was ground on the posterior") never did find out just what his objective was.

**Alan W** · 08-14-2001, 06:08 AM

don't!
You're inviting disaster.

a, 5mm or so from any direction off the distance OC things change rapidly on an aspheric. So, one eye may easily have a different visual experience than the other.

b, It would be a disservice to the patient if for any reason there was a lens replacement made by anyone other than you, and that provider didn't know there was an aspheric lens just on one side.

The periphery of a plano lens is also subject to some aberrative characteristics given thickness, curvature, etc. I would hate to tempt fate by underestimating the inluences mentioned when compared to the advantages that might be derived from an aspheric lens . . . then put that whole hodge podge in one pair of glasses. . . . eek!

**Alan W** · 08-14-2001, 06:16 AM

that ophthalmologist didn't also have an office in Omaha?
The guy was nutz-a-roony!

This guy was so exotic his minimum age was 18 to get an eye exam!

d' dum, dum!

**Texas Ranger** · 08-14-2001, 09:45 AM

Mike, you said it was a doctor's remake, so I can only tell you how I would handle it (of course let me *** u me that the original lens was not asl or over a three add). Time frame is a consideration, nut suppose it was with a couple weeks, First , things that cost a lot more, I would charge the difference above the original, tell the pt that the asl lens is about $40 more than the regular material, of course there will be a fee of $25 for the 3.50 add, so does he wish to pay $25 or $65, doesn't matter to me, but I don't understand the need for the asl. there is no induced aneisokoia, probably less than 0.5% mag. difference. And do trial lenses come asl now? Is there a medical problem that we need to be aware of that requires a 3.50 add?, or does the person do needlepoint or work on pc boards? interesting problem.

**Homer** · 08-14-2001, 09:52 AM

My guess is that this person is over 70 and has some macular degeneration. Has the person had cataract surgery? In either case, again a guess, the visual acuity is probably just bearly 20-/40; perhaps a bit better. In this case it would probably make very little difference what you did.

One of the things that might be most appreciated in this case is giving the patient some intermediate options; perhaps a wide bifocal with a +.75 upper and a 1.75 add or perhaps a trifocal.

What I would like to see on all RX's is the visual accuity for each eye. That would really help us make these decisions.

The mixing of lens designs can work because in 90% of the cases where we might consider it, one eye has an accuity of 20/40 or less and all of those technical / optical calculations assume both eyes have the same visual ability.

Homer