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Different Lasers Used In Laser Eye Surgery

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Excimer lasers, used in both LASIK and LASEK procedures, produce energy in the UV spectrum (invisible light) to reshape the surface of the eye. The earliest versions were developed in the 1970′s, when researchers found that IBM’s new Excimer Laser, initially created for etching computer chips, had medical applications as well. Now in its third decade of use, the technologically-advanced Excimer Laser has added a tremendous amount of precision, control and safety to treating short sightedness, long sightedness and astigmatism.

 

Types of Modern Excimer Lasers and Wavefront Treatment

Slit scanning lasers - Slit scanning lasers use relatively small beams, linked to a rotational device, with slit holes that enlarge. The laser beams scan across these holes during surgery, producing a gradually enlarging treatment zone. The approach provides a uniform beam and potentially smoother treatment than obsolete broad-beam lasers.

Spot scanning lasers - Spot scanning (or “flying-spot”) lasers are the most commonly used lasers, and use small-diameter laser beams scanned across the surface to deliver treatment. This approach has the potential to produce the smoothest surface, to more readily allow customised treatments, and to better treat complex prescriptions.

Wavefront-guided treatment - Many Excimer Lasers (both slit and spot scanning) are connected to a device that detects and “maps” imperfections in the eye’s optical system, based on how lightwaves travel through the eye. These Wavefront devices individually guide the way the surface of the eye is reshaped. Such technology captures unique imperfections in each individual’s vision that could not have been measured before. This new level of measurement provides 25-times more precision than measurements using standard methods for glasses and contact lenses. The majority of laser machines rely upon traditional Hartmann-Shack or Zernicke calculations to interpret these “maps”. Only one system has switched to the latest Fourier calculation method – an approach which significantly improves the interpretation of these “maps”.

 

 The Lasers

Several characteristics are important when considering the abilities of the latest lasers used in refractive laser eye surgery today. Type of laser, size of beam vs. frequency, Wavefront interpretation technique and safety checks in the form of Iris recognition, eye tracking devices and other systems contribute to the overall performance of laser treatment. Generally, a smaller beam size is advantageous if it is coupled with high frequency of delivery. However, too high a frequency can disrupt hydration during treatment and so a balance is to be maintained. Nevertheless, it must be stressed that the skill of the treating surgeon and post-operative aftercare are paramount factors.

All Laser machines below are Argon Fluoride 193nm Excimer Lasers and FDA approved.

 

 Manufacturer: AMO

VisX STAR S4 IR - is a variable spot-scanning system. This is the only platform which can vary laser beam sizes from 0.65 to 6.5mm. The system can deliver treatment at Varying Repetition Rates (frequencies) optimizing treatment time to at least 15 seconds and avoiding disruption to hydration during treatment. This technology is exclusive and proprietary to AMO.

An Iris Recognition System interprets 24 unique reference points. An ActiveTrak 3D Eye Tracker captures movement of the eye 60 times per second during the procedure. An ActiveTrak Automatic Centring programme locates and automatically sets the central area of treatment to the centre of the pupil.

Wavefront results calculated via latest generation Fourier-based algorithms “WaveScan”

The VisX STAR S4 IR currently treats over 60% of patients in the USA and is proven to deliver exceptional results.

The VisX STAR platform’s heritage of dependability and performance is well known. This latest Excimer Laser system represents the most advanced laser technology platform available today.

 

 Manufacturer: ALCON

LADARVision System - The LADARVision Escimer Laser is a small-spot scanning laser with a radar eye-tracker speed of 4000 times per second. A Gaussian laser beam (0.8mm in diameter) is used at a frequency of 60Hz, which can prolong treatment time. Wavefront maps calculated by Hartmann-Shack Technique “CustomCornea”

 

 Manufacturer: Bausch and Lomb

Technolas 217 Zyoptix - This is a flying-spot scanning system. This system employs a combination of 2 Gaussian beam sizes (1mm and 2mm) at a frequency of 50Hz to provide treatment. Iris Recognition Zywave measures and maps the iris. An Active Infra-red Eye Tracker – 120 times per second monitor interrupts the laser beam only if the eye moves considerably (in excess of 3mm). Wavefront results calculated via Zernicke-based algorithms “Orbscan”

 

 Manufacturer: Nidek

EC-5000 CX - This is a slit-scanning system. The scanning beam is a rectangular slit which scans, dynamically rotates and overlaps at a frequency of 10-15Hz. The rotation of the scan may increase the smoothness of treatment. This system mimics retinoscopy – a test readily used by optometrists when calculating a prescription for glasses.

Iris Recognition technology detects and follows involuntary eye movements during the procedure, and an Eye Tracker System monitors the eye 200 times per second. Wavefront results calculated based upon time-based retinoscope measurements “Optical Path Difference”

The system can be integrated into NAVEX Quest – Nidek’s Advanced Vision Excimer Laser System (not currently approved by FDA).

 

 Manufacturer: Carl Zeiss

MEL 80 - This is an Excimer Laser and has a Gaussian beam spot size of 0.7mm. The Eye Tracker samples pictures of the eye 250 times a second and is synchronized with the speed of the laser, which also runs at 250 times a second. MEL 80 integrates the Wavefront, topography (shape of surface), prescription, curvature and thickness of the surface of the eye, all into a complex calculation. This is designed to produce a correction to reduce the imperfections that are inherent in the eye before treatment. Wavefront-Topography Optimized results calculated via “CRS Master”.

 

 

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