Custom Ablation

Anatomy of a Better Visual Result  

Over the past few years there has been a concerted effort on the part of Refractive Surgeons and researchers to increase the number of people achieving 20/20 vision, attempt to get a significant number of these people to get 20/15 (significantly better than 20/20) vision, to decrease or eliminate night glare and halos, and to decrease or eliminate contrast sensitivity loss. This branch of work has been called Custom Ablation, or having a different ablation patterns dependant on the patient's prescription and eyes.  There have been several directions of research in the custom ablation area, but they have come down to two camps of thought.

The first school of thought is of wavefont guided ablation.. This theorizes that there are microscopic flaws that exist in the human eye as a whole that prevent an eye from seeing better than 20/20.  If these flaws could be detected by a wavefront analyzer, a theoretical "fingerprint" of the eye could be created. If these flaws were removed by selective laser ablation, an eye could theoretically make everyone see 20/10, which is close to the absolute possible resolution of the human eye.  Unfortunately, this theory never worked out, for several reasons

1. Wavefront detection analyzers just aren't sensitive enough to provide the information needed

2. There is an enormous amount of "chatter" giving inaccurate "garbage" information

3. It is dependant on the technical operation for a good reading, and the readings are difficult to reproduce over multiple measurements

4. The reading can be thrown off by an eye that dries out, has a tear film abnormality, or has, any epithelial breakdown.

5. No one has ever come up with a good way to line up the wavefront analyzer information to the eye under the laser, so the wrong pattern can actually be carved on to the cornea.  The current state of the art is to use a magic marker marking on the patient eye while they are sitting up to line up the "fingerprint" map under the laser.

6. Only about 10% of the population has significant abnormalities in their cornea, or what are called higher order aberrations.  That would indicate that wavefront ablation is not useful for the other 90%.  

The wavefront guided school of thought has been championed by the VISX system, which received its FDA approval for wavefront guided ablation on the basis of the fact that it was as good as regular non-custom ablation, and NOTHING IN THE APPROVAL SAYS THAT THE WAVEFRONT GUIDED ABLATION SYSTEM GIVES BETTER VISUAL RESULTS THAN THEIR REGULAR LASER ABLATION.  Other laser systems have virtually abandoned the idea of wavefront guided ablation as being effective. 

Although Dr. Motwani continues to use a wavefront analyzer to measure wavefront aberrations as part of his clinical analysis, the use of such information is limited at this time.            

The second school of thought focuses on the actual shape of the laser re-shaping, and is sometimes called Wavefront Optimized.  This theorizes that the laser re-shaping of the cornea should leave behind a shape that is more similar to the natural cornea, or what is called a "prolate" shape.  When done properly, this results in a virtual elimination of any added night/glare or halos from laser re-shaping, almost no change in contrast sensitivity, and also a significant jump in better than 20/20 results.  This corneal re-shaping is also called aspheric ablation.  This approach has been used by both Allegretto and the Nidek systems.  The Nidek system has a patent on the proportional transition zone which can be used to perform aspheric ablation, and allows for a different "customized" profile for every prescription treated.  The Allegretto system also focuses on aspheric corneas by increasing the number of laser spots in the periphery to create a more prolate cornea.  In fact, most Allegretto laser physicians do not even use the wavefront analyzer anymore, finding wavefront guided ablation to not be as effective as aspheric "wavefront optimized" ablation.            

Currently approximately half the procedures in the U.S. are done as wavefront-guided procedures, and about half are done as aspheric or "wavefront optimized."  Both systems have good results, but aspheric results show consistently better "better than 20-20" results.            

Dr. Motwani did some of the early clinical work on aspheric ablation in the United States using the Nidek system.  This work was performed under the FDA guidelines that allow a physician to change a procedure on an FDA approved machine to improve the results.  This work has been documented for several years by Motwani LASIK Institute, and has allowed Dr. Motwani to achieve a 20/20 rate of 98-99%, and a 20/15 rate of about 68% for all myopic and myopic astigmatism patients.  It is important to remember that this is PER EYE, and not with both eyes open.  That is a more critical standard.  This percentage rate is for all people with nearsighted or nearsighted with astigmatism patients, and not just limited to -7.00 of myopia and -3.00 of astigmatism like many other studies.

Dr. Motwani has been a strong and early advocate of aspheric ablation/prolate corneal creation since 2003, and has pioneered these techniques to create vision that can be as clear, with the highest resolution possible.  Dr. Motwani was the first physician in San Diego to perform aspheric ablations, and the first to do so routinely.