Is the Symphony IOL focus sharp enough ?

[VJWW]

The attached pic is taken from the page:

http://www.tecnisiol.com/eu/tecnis-symfony-iol.htm#

Monofocal IOL's focus seems to be much sharper than Symphony's.

Any comments ?

[SoftwareDeveloper]

The issue wasn't that the Symfony doesn't come to a sharp focus, but that rather than 1 distance coming into focus, a range of distances comes into focus. Even a monofocal has some depth of focus, the image was emphasizing that it is extended with the Symfony.

At the moment everything I've seen suggests the Symfony would still be the best fit for my needs if I were having the surgery now instead of 1.5 years ago. There is one other extended depth of focus lens that *might* potentially be a very  slight improvement on the Symfony for near, the Mini Well, but I haven't seen enough studies to know for sure since I hadn't seen all the various attributes compared nor confirmed in more than one study, so at the moment the Symfony would still seem the best bet (for my needs, people's needs vary)..

It isn't widely used (I don't know which countries it has been approved in) yet. Due to the lack of data I hadn't checked into its material and overall shape, I don't know offhand if its based on an existing lens platform. One thing that made the Symfony seem a safer bet is that the only thing that differs with it compared to the other Tecnis lenses (Tecnis monofocal and multifocals) is the optics, which can be tested well on an optical bench with only a bit of in-human testing to confirm the results and assess things like halos. The material and overall physical shape is the same so issues like biocompatibility, PCO, and inserting the lens and its stability are all the same as the widely used other Tecnis lenses.

A trifocal was my 2nd choice, and although the thought of a slight bit more near is tempting,  I wouldn't risk the crisp intermediate vision for any more near. Nor would any added near be worth risking lesser quality low light vision or problematic halos (I am one of the small minority that sees halos with the Symfony, but they aren't problematic because they are so mild/translucent, I see through/past them and my overall night vision is great).

[VJWW]

Also, I read that you have opted for symphony. However, if you were to do it all over again, would you go for Symphony (knowing what you know now)?  

I am yet to decide   between Monofocal (set for long distance)  and Symphony (set for far and intermidiate distance.)

reg

[VJWW]

Thanks for great response.

I do not have the technical background to understand those documents completely, although I have been playing around with lenses, microscopes and telescopes as a hobby.

The only reason I thought symphony's focus does not appear to be sharp enough is that as compared to monofocal, ( in the picture I attached) in the case of symphony, rays do not seem to be converging at a fine point.

But then again, Symphony corrects chromatic and spherical aberration. So  I stand corrected.

reg

[JohnHaganMD]

=

[SoftwareDeveloper]

The image isn't showing how sharp the focus it at a particular point, it is a not very clear way to try to show the differences in how the lenses work, that a multifocal provides multiple focal points while the Symfony extends depth of focus. A natural eye has a certain "depth of focus" which is the range of distances it can see clearly (without accommodating, changing focus), and each person's is different. For instance a very small minority of people with a monfocal lens set for distance can do some reading since their eye has a larger depth of focus than most people (who see things getting blurry several feet out).

The sharpness of focus of the lens is indicated by studies on visual acuity for people who have had the lens implanted. For example on the "clinical" tab on the manufacturer's site for the Symfony:

http://www.tecnisiol.com/eu/tecnis-symfony-iol.htm

they have a chart that compares the visual acuity at different distances for a Tecnis monofocal and the Symfony, and you can see that at distance the visual acuity results are essentially the same, likely within the error bars of the studies, and its focus is better closer in.

A presentation here:

http://www.efclin.com/wp-content/uploads/2016/05/3.-Dexel-Alois_New-in-IOL-_EFCLIN-2016_web.pdf

Has simulated air force target images for the Symfony and a monofocal, where at 0D (distance) you can see they are about the same (and binocular vision sharpens the image, those are monocular simulations).


The issue of MTF is too technical for people to bother with, but its one measurement of the performance of a lens:

http://www.doctor-hill.com/patients/modulation_transfer_function.htm
"The modulation transfer function (MTF) is an optical bench measurement used by engineers to evaluate the performance of a lens, or a lens system. In its most basic sense, the MTF is a way to describe the contrast sensitivity of a lens system. For the human eye, this could be though of as its “visual performance.”

The graph in Figure 1 of this next articles  shows one measure of the MTF of the Symfony being comparable to a Tecnis monofocal, and well above a spherical  monofocal and various multifocals:

http://www.healio.com/ophthalmology/journals/jrs/2016-3-32-3/%7B0aeb07b1-c5ef-46ff-b6bc-13b34f9678d3%7D/laboratory-measured-mtf-of-iols-and-clinical-performance

The discussion requires background technical knowledge most people don't have, the figure just illustrates the point.

[JohnHaganMD]

=