Because having LASIK done is such an important, life altering decision, many people want to do their homework and know the difference between the types of lasers used.
Although LASIK has been around since the mid 1990′s the most modern lasers in use today, those that include things like wavefront technology and advanced eye tracking have only been out for a few years.
The FDA approves each laser for certain patients with certain refractive errors. Sometimes after it has been proven effective in other patients they will approve it for higher refractive errors and/or astigmatism.
Because of the way medical doctors are allowed to practice, once a medical device is approved they can use it in any way they see fit. For example a laser may only be approved to treat up to -5.00 D of myopia but a doctor can use it on anyone they want, including those with more than -5.00 D. It is this “off-label” use that helps make LASIK, as well as other surgeries better in the hands of skilled surgeons. Their experience and breakthroughs help to see what is possible.
Beyond the capability of a particular laser is the skill of the surgeon. Experience is one of the greatest factors in ensuring a good outcome from LASIK.
Eye Tracking Systems
Almost all modern excimer lasers have an eye tracking system. This allows the laser to compensate for the movements a patients eye makes during the surgery and ensures the laser doesn’t reshape the cornea in the wrong place.
Laser Types
Spot Scan Lasers – Also called “flying spot” lasers, use a small beam (from 0.8mm to 2.0mm) that scans across the entire cornea to produce the ablation. The advantage of a spot laser is the potential to create custom ablation and to treat irregular astigmatism.
Slit Scan Lasers – This type of laser uses small slits that are attached to a device that rotates and the laser beam scans across the slit. The slit gradually enlarges to produce the ablation zone. Slit scan type lasers can produce very smooth ablations when combined with an eye tracking system.
Wavefront – Most laser, whether slit, or spot scan type are connected to a device that maps the cornea, called a wavefront analyzer. This allows the laser to shape the cornea very precisely to mimic the way light travels into the eye. Outcomes ‘beyond’ 20/20 vision that correct for higher order aberrations (HOA) are achieved with wavefront technology. “Custom” LASIK uses wavefront analysis, because no two people’s corneas are exactly the same.
The following table breaks down the brand of laser, type of refractive error it is approved to correct, the treatment zone and the year it received FDA approval.
| Laser Model | Indicated to Treat | Type of Laser & Treatment Zone (TZ) | Year of FDA Approval |
|---|---|---|---|
| Alcon LADARVision 4000 & CustomCornea (laser and wavefront device to guide laser) | Alcon LADARVision 4000 & CustomCornea (laser and wavefront device to guide laser) | Scanning spot TZ: 7.5 mm | 2002 myopia with or without astigmatism 2006 hyperopia and hyperopia with astigmatism |
| Bausch + Lomb Technolas 217A and Technolas 217z Zyoptix (laser plus wavefront device to guide laser, approved 2003) Advanced Control Eyetracking (ACE) (rotational eye tracking system approved 2009 for Technolas platforms) | Myopia: up to -12.00 D with or without astigmatism (up to -3.00 D) Hyperopia: up to +4.00 D with or without astigmatism (up to +2.00 D) | Scanning spot TZ: 7.0 mm | 2000 myopia from -1.00 to -7.00 D 2002 myopia up to -11.00 D 2003 hyperopia with or without mixed astigmatism |
| Carl Zeiss Meditec MEL 80 | Myopia: up to -7.00 D with or without astigmatism (up to -3.00 D) | Scanning spot TZ: 7.7 to 8.9 mm | 2006 myopia with or without astigmatism |
| Nidek EC-5000 | Myopia: -1.00 to -14.00 D with or without astigmatism (less than 4.00 D) Hyperopia: +0.50 to +5.00 D and up to +2.00 D astigmatism | Scanning slit TZ: 7.0 mm | 2000 myopia from -1.00 to -14.00 D 2006 hyperopia and hyperopic astigmatism |
| Visx Star S4 & WaveScan WaveFront System (laser plus wavefront device to guide laser) | Myopia: up to -6.00 D with or without astigmatism (up to -3.00 D) | Variable scanning spot beam TZ: 4.5 to 9.5 mm | 2003 |
| Visx Star S4 IR & CustomVue (laser plus wavefront device to guide laser) | Myopia: up to -6.00 D with or without astigmatism (up to -3.00 D) Hyperopia: up to +3.00 D and up to +2.00 D of astigmatism Mixed astigmatism: up to 5.00 D | Variable scanning spot beam (same as above) TZ: 9.0 mm | 2005 |
| WaveLight Allegretto Wave | Myopia: up to -12.00 D with or without astigmatism (up to -6.00 D) Hyperopia: up to +6.00 D with or without astigmatism (up to +5.00 D Mixed astigmatism: up to 6.00 D | Scanning spot beam TZ: 5.2 to 8.7 mm for spherical treatments; 7.0 to 9.0 mm for cylindrical and spherico-cylindrical treatments | 2003 myopia and hyperopia 2006 mixed astigmatism |
| WaveLight Allegretto Wave with Allegro Analyzer (laser plus wavefront device to guide laser) | Myopia: up to -7.00 D with or without astigmatism (up to 3.00 D) Mixed astigmatism: up to 6.00 D | Scanning spot beam (same as above) TZ: 5.2 to 8.7 mm for spherical treatments; 7.0 to 9.0 mm for cylindrical and spherico-cylindrical treatments | 2006 myopia 2007 mixed astigmatism |