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Wavefront Custom Lasik Laser Eye Surgery

iLasik, Allegretto, CustomVue, CustomCornea, and Zyoptix for Lasik, Bladeless Lasik PRK, LASEK, and Epi-Lasik.


wavefront custom lasik  
Wavefront-guided laser ablation for custom Lasik and other refractive eye surgery has been a significant improvement for most individuals, but not for all  
   

WaveLight Allegretto Eye-Q
Visx CustomVue iLasik
LADARVision CustomCornea
Bausch & Lomb Zyoptix

Learning if you would do fine with conventional refractive surgery or if you require wavefront custom Lasik, Bladeless Lasik, LASEK, PRK, or Epi-Lasik is much easier than it may at first appear, however it is important to understand what wavefront custom Lasik, LASEK, PRK, and Epi-Lasik is, and what it is not. As a general rule, the quality of vision with wavefront is superior to conventional laser eye surgery, but that does not mean that wavefront Lasik is best for everybody. Individual circumstances will vary.

The primary difference between conventional Lasik and wavefront custom Lasik is the mapping system that guides the laser. Wavefront can be used for virtually all laser eye surgery techniques including Bladeless Lasik, Lasik, PRK, LASEK, and Epi-Lasik.

Old Science, New Application

Wavefront is a very old technology that has only recently been applied to human vision. Wavefront has been used for years by astronomers who need to adjust the optics of their telescopes. A reflecting mirror within the telescope that can be deformed is adjusted using wavefront data to eliminate aberrations induced by the Earth's atmosphere. In wavefront custom Lasik, PRK, LASEK, and Epi-Lasik, the excimer laser uses wavefront information to change the shape of the cornea by ablating tissue.

Wavefront Diagnosis and Wavefront Treatment

Wavefront is actually used in two separate ophthalmic events. The first is a wavefront evaluation and diagnosis of existing aberrations. The second is using what is learned from the diagnosis to create a wavefront-guided ablation for Lasik, PRK, LASEK, or Epi-Lasik.

Our organization has included wavefront diagnostic as a must-do in our 50 Tough Question For Your Doctor, but we have not included it for guided ablations. A wavefront diagnostic can determine if an individual has aberrations that would be exacerbated by refractive surgery to the point of causing vision problems. No other technology can achieve this level of diagnosis. Wavefront diagnostic can determine if a wavefront guided ablation is an absolute requirement, conventional ablation would be fine, or the patient should not have surgery at all. This is why we believe wavefront diagnostic is an important evaluation.

Several Laser Options

In the United States, there are four wavefront responsive laser manufacturers. The trade names are CustomCornea using the Alcon LADARVision laser, CustomVue using the Visx S4 laser, and Zyoptix using the Bausch & Lomb Technolas 217z laser. These lasers have the ability to create an ablation customized from an individual patient's wavefront evaluation.

The Wave Light Allegretto laser used wavefront derived data in the laboratory to optimize its laser ablation pattern, but does not use an individual patient's wavefront diagnosis to create a customized ablation pattern. CustomVue, CustomCornea, and Zyoptix are all customized to the individual's eye. Visx, Alcon, and B&L refer to their systems as "custom wavefront". Allegretto is referred to as "wavefront optimized".

Square Grid In, Wavy Grid Out

During a wavefront diagnosis, light is sent into the eye in a specific pattern, then measured after it has passed through the visual system. Any difference between what goes in and what is measured is considered an aberration. Think of a square grid going in and a wavy grid coming out. The waves represent aberrations.

Higher Order Aberrations

A common eye examination and refraction evaluates low order aberrations (LOA). These are commonly called sphere (myopia, nearsighted, shortsighted or hyperopia, farsighted, longsighted) and cylinder (astigmatism). Only a wavefront diagnosis is able to measure high order aberrations (HOA), which are beyond simple sphere and cylinder. HOA are represented in mathematical calculations and are therefore infinite. The more common of these mathematical calculations are Zernike polynomials and have names like spherical aberration, coma, trefoil, and quatrefoil. Ophthalmology only deals with about the first eight levels of HOA as represented in Zernike.

Wavefront technology as a diagnostic device is unsurpassed. This technology can diagnose and measure aberrations that no other system can even see. It is important to understand that without a wavefront diagnosis, it is impossible for a doctor to accurately determine if wavefront-guided ablation is necessary for a good Lasik, PRK, or LASEK outcome. Also, without a wavefront diagnosis it is impossible for a doctor to accurately determine if a wavefront ablation is not necessary. In other words, virtually every person considering Lasik, LASEK, PRK, or Epi-Lasik should have a wavefront diagnostic evaluation.

Detailed Mapping

Think of an eye examination as a way to "map" vision limitations. A conventional eye exam can map LOA. A wavefront diagnostic can map LOA and HOA. Laser eye surgery based upon the LOA determined with a conventional eye exam is like using a map of your state to find your way around. That works pretty well if you are trying to get from Los Angeles to San Francisco. Custom wavefront could be compared to a map of your city. It can help guide you to a specific street corner. Custom wavefront-guided Lasik, LASEK, PRK, and Epi-Lasik directs the excimer laser to change the shape of the cornea using a more detailed mapping system than conventional refractive surgery.

Human vision provides some unique challenges for application of wavefront technology. The human eye is not a telescope. The eye is dynamic, with ever changing focus, pupil size, and other normal biological fluctuations. A telescope is static and once adjusted for a certain set of aberrations, never changes. A deformable mirror can be adjusted to a very precise amount. Ablating corneal tissue is not nearly so precise. Wavefront may be an excellent mapping system, but that does not necessarily mean that you can get to where you want to go.

HOA are divided into separate terms and some HOA are much more important to good quality vision than others. Spherical aberration, coma, and trefoil are examples of HOA that are very important to keep low. An HOA measurement often used is Root Mean Squared (RMS). RMS is more or less an average of all HOA. Having a low RMS is good, but if you have an elevated HOA that is one of those that is known to cause vision quality problems, a low average may not be enough. As an example, if you have low HOA RMS, but a high spherical aberration, wavefront-guided surgery may be a requirement. You will need to discuss this issue in detail with your doctor. Wavefront-guided refractive surgery is FDA approved for a wide range of correction, but this is a range that does have limits. If you are too myopic, too hyperopic, or have too much astigmatism, you may not be eligible for wavefront-guided Lasik, PRK, LASEK, or Epi-Lasik.

Ablate Deeper

Wavefront-guided ablations may remove more tissue than conventional ablations, depending upon the unique circumstances of the individual patient. If you have thin corneas, additional tissue removal may be an issue. For more information, see Thin Cornea.

The size of the fully corrected optical zone is limited for wavefront-guided ablations. If your naturally dilated pupils are unusually large, you may have an increased risk of poor vision in low light environments. See Lasik and Pupil Size

Monovision Limitations

If you are considering monovision correction, it will may be necessary to use conventional Lasik, PRK, LASEK, or Epi-Lasik rather than wavefront-guided. Current wavefront-guided lasers are very limited in their ability to undercorrect. It's full correction or nothing at this time. While the non-dominant eye will need to be undercorrected with a conventional ablation, the dominant eye may be fully corrected with a wavefront-guided ablation. Undoubtedly, each of the manufacturers will eventually allow their lasers to undercorrect in wavefront-guided mode.

Better, Not Perfect

Something very important to understand is that not all aberrations are reduced with custom wavefront or wavefront optimized Lasik, PRK, LASEK, or Epi-Lasik. In fact, in all refractive surgery procedures, wavefront or conventional, HOA tends to increase. This is one of the reasons that the FDA has approved the use of wavefront-guided ablations, but has not specifically approved any laser to actually treat and reduce HOA. Our organization distributed a special Advisory Memorandum regarding this issue. See FDA HOA Advisory.

It has been shown, however, that CustomVue, CustomCornea, and Zyoptix increase HOA less than conventional ablations. This is also true of Wave Light. HOA may increase no matter what you choose, but it will probably increase less with wavefront. Because HOA is likely to increase, if your natural HOA are already elevated, refractive surgery may elevate them farther and cause poor vision. In this situation, it may be that no corneal-based refractive surgery is appropriate.

Get Out Your Credit Card

Let's not forget cost. Many doctors charge more for wavefront-guided refractive surgery than conventional. Although no one should compromise their vision for a little cost savings, paying less for surgery is usually preferred over paying more.

If you meet all other requirements, there is nothing that indicates wavefront-guided Lasik, LASEK, PRK, or Epi-Lasik will provide an outcome that is inferior to similar conventional surgery, and there are many indications that wavefront-guided surgery will provide a superior outcome. However, there are absolutely no guarantees in surgery and refractive surgery is no exception. Any prediction of your actual outcome will be based upon past experience and reasonable evaluations, but no one will know for sure until after surgery. You may want to see Lasik Outcomes.

Wavefront Diagnostic For Every Patient

Everyone considering any corneal-based refractive surgery, such as Lasik, LASEK, PRK, or Epi-Lasik should have a wavefront diagnostic. A wavefront diagnostic will determine if critical HOA are below normal, normal, or elevated. If the HOA are elevated, either wavefront-guided surgery is required, or no surgery is appropriate. If HOA are normal, wavefront-guided surgery may be wise. If HOA are below normal, wavefront-guided continues to be an option, but not a requirement. This is assuming, of course, that you meet all other requirements for wavefront-guided Lasik, LASEK, PRK, or Epi-Lasik laser eye surgery.

Looking For Best Lasik Surgeon?

If you are ready to choose a doctor to be evaluated for conventional or custom wavefront Lasik, Bladeless Lasik, PRK, or any refractive surgery procedure, we recommend you consider a doctor who has been evaluated and certified by the USAEyes nonprofit organization. Locate a USAEyes Evaluated & Certified Lasik Doctor.

Personalized Answers

If this article did not fully answer your questions, use our free Ask Lasik Expert patient forum.


Recent Wavefront Lasik Medical Journal Articles...

[Functional Results after Implantation of an Aspheric, Aberration-Neutral Intraocular Lens.]

Klin Monbl Augenheilkd. 2014 Sep 1;

Authors: Khoramnia R, Fitting A, Rabsilber TM, Thomas BC, Auffarth GU, Holzer MP

Abstract
Purpose: The aim of this study was to perform a clinical evaluation of the functional results and quality of vision after implantation of an aspheric, aberration-neutral, monofocal intraocular lens (IOL). Patients and Methods: 47 eyes of 34 patients (median age: 68 years) with cataract were enrolled in this prospective clinical study that had Ethics Committee approval. The C-flex or Superflex aspheric IOL (Rayner, UK) was implanted after phacoemulsification. Follow-up examinations were performed two to four months after surgery including subjective refraction, ETDRS uncorrected (UDVA) and corrected distance visual acuity (CDVA), wavefront analysis, analysis of stray light (C-Quant), contrast sensitivity under different lighting conditions (F. A. C. T.) and a questionnaire. Results: Two to four months after surgery, median UDVA was 0.08 logMAR (range: 0.64 to - 0.18 logMAR, n = 41). Median CDVA increased from 0.30 logMAR (range: 1.00 to - 0.02 logMAR) preoperatively to - 0.08 logMAR (range: 0.16 to - 0.22 logMAR) postoperatively (n = 47). Median difference between achieved vs. intended (Holladay 1-formula) spherical equivalent was + 0.06 D (range: - 1.06 to + 0.87 D). Median total HOA RMS (6 mm pupil size) was 0.66 µm (range: 0.41 to 1.19 µm). The median spherical aberrations were - 0.36 µm (range: - 0.70 to - 0.17 µm). Analysis of stray light (C-Quant) revealed a median value of 1.21 log(s) (range: 0.79 to 1.57 log[s]). Conclusion: The C-flex and Superflex aspheric IOLs provide good and predictable functional results. Patients are not negatively influenced by stray light and show slightly negative spherical aberrations.

PMID: 25178043 [PubMed - as supplied by publisher]

 


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