http://www.pconsupersite.com/default.asp?ID=5489

"...it will be impossible to ignore the hinge-related astigmatism, flap-induced higher-order aberrations and the minor changes of biomechanical properties seen in LASIK, all of which may make the ideal of “aberration-free” less possible."

http://archopht.ama-assn.org/cgi/content/abstract/119/6/889

"Corneal wound healing is critical to the success of topography-linked or wave front–linked excimer laser ablation to optimize visual performance. This is because of the importance of retaining subtle features of custom ablation and the tendency of epithelial hyperplasia and stromal remodeling to obscure these features following either procedure. The corneal wound healing response is exceedingly complex."

For the highly aberrated eye, treatments based on wavefront may not be as efficacious as desired if there is a large "fit error".

In and of itself, wavefront is not the total answer. It's not just a melding of wavefront and topographically-based technologies that will yield what we're after. Zernicke polynomials do not necessarily capture the whole bag of tricks.

Please see: http://surgicaleyes.atinfopop.com/4/OpenTopic?a=tpc&s=636293455&f=5434049181&m=4874054972

This isn't exactly what Broken Eyes was asking about, but it is another critical aspect in post-op retreatment assessment.

Last but not least, "the cornea is not a piece of plastic", Cynthia Roberts, PhD.

http://www.slackinc.com/eye/jrs/vol164/edit.pdf

http://jrs.slackinc.com/vol171/lett.pdf

http://jrs.slackinc.com/vol185/roberts.pdf

http://jrs.slackinc.com/vol186/alpins.pdf

http://jrs.slackinc.com/vol186/lip.pdf

http://jrs.slackinc.com/vol145/sirens.pdf

This one doesn't really belong on this thread... then again, maybe it does.

http://www.ascrs.org/publications/jcrs/editjun02.html

Good references at the bottom of the article.

I certainly agree that a wavefront solution can't fix an irregular cornea. There are just too many variables -- including flap dynamics, epithelial hyperplasia, and corneal remodelling.

I'm currently in the healing phase of the first step of a two-step topographic retreatment for a decentered ablation. What really surprised me after the first ablation was how much the back (posterior) of my cornea had changed. Of course, this biomechanical change could not have been completely predicted by the planning software. My hope is that the next procedures I have, the fine-tuning ablation, gives me 20/20 vision that is useful -- and that I don't end up with a multifocal cornea. Time will tell... Stay tuned ...

Dear Paul,

Did you see Dr. Jack Holladay from Texas for the two step?

I initally saw Dr. Holladay last August for a consultation, and he mentioned to me that his colleague Dr. Stojanovic in Norway was doing quite a few topographic retreatments, so that's where I ended up getting treated, and I'll probably go back to him.

TOP STORIES 10/31/03

Zernike fails to encompass all influences on VA, study finds


Zernike polynomials do not fully describe the surface of the cornea, a study suggests. The failure of this method to model all the features of the corneal shape that influence vision may confound clinical diagnosis and treatment with wavefront-guided correction systems, according to study authors Michael Smolek, PhD, and Stephen Klyce, PhD.

Read the rest at:

http://www.osnsupersite.com/default.asp?ID=6484

Moose posted a link to an article talking about Dr. John Kanellopoulos' results retreating LASIK patients using the Wavelight Allegretto.

http://surgicaleyes.atinfopop.com/4/OpenTopic?a=tpc&s=636293455&f=6334052921&m=9874058792


"The mean preoperative BCVA was 20/25, and this figure improved to a mean of 20/18 postoperatively. Not only did none of the patients lose any lines of BCVA, all patients gained at least one line and a maximum of three lines of BCVA. The total amount of higher-order aberrations, as measured by the parameter RMSH, decreased from an average of 0.62 to 0.25 mm. Also, patients experienced a mean improvement in low contrast sensitivity of 55%"

With the industry doing a million surgeries a year, most of them with wavefront, won't we know for sure about wavefront in just a few months, at least for virgin eyes? The number of actual results should be very large soon, and we shouldn't have to speculate any more or rely on a bunch of clinical trials. The results will be whatever they are.

Ron Link

I don't know polynomials from Polly Anna, but what we are talking about is a goodness of fit question?

What is the origin of the technology using the polynomials?

Who is the manufacturer?

http://www.osnsupersite.com/default.asp?ID=8518

TOP STORIES 7/8/2004
Coma, spherical aberration increase with age, study finds

excerpt:

“If an ideal customized ablation is possible, the perfect correction will not last because of the change of aberrations with age,” the authors said. “Patients undergoing wavefront-guided surgery should be informed of this.”

http://www.pcli.com/lasik/wavefront.html

"With the cornea being 70% water, highly customized treatment is like trying to precisely sculpt Jell-O. Even when everything is done perfectly, creating the LASIK flap and the normal effects of corneal stretching, molding or healing may negate some of the precision of the planned treatment."

PTT

I think I have been hiding my own fear of my problems after having PRK two times (96 & 98) and now my eyes are getting dryer, my corneas more irregular and my vision worse. Would wavefront help with my problems and if so, where near Toronto, Canada can I get support?