Chiron Vision Technolas Planoscan 217 Laser System

Overall Rating:  B

Overview:  Chiron Vision, a subsidiary of Bausch and Lomb, has developed a scanning excimer laser system. 

    Over the years Chiron has traveled an often painful and tortuous path on their course to develop a usable laser system.  The original Chiron system was merely a poor copy of the VISX platform and was rejected outright in the early 1990’s due to clear patent infringement.  However, instead of developing a truly innovative device that was superior to other conventional technology, Chiron merely attempted to develop a system that circumvented patent law.  Apparently driven by a need to retrofit their existing hardware to minimize development costs and a need to get product to the market to survive financially, Chiron felt compelled to build on existing hardware available in the early 1990’s rather than create a laser system that would be truly state-of-the-art in 2000.   

    The result is a laser platform that attempts to emulate both the VISX Star S2 and the Autonomous LADARVision platforms but comes up seriously short on two counts.  Most glaring in these deficits is Chiron’s inadequate eye tracking methodology – an essential part of an accurate scanning laser system.  Fundamentally, the acquisition time for the Chiron laser is far too long to properly track a moving eye target.  To compensate for this deficit the Chiron 217 uses a large 2 mm beam to scan the cornea.  Apparently, Chiron’s engineers came to conclude that if you cannot accurately or consistently aim the scanning beam at the correct spot, it is much easier to use a “shotgun” than a “rifle”.  In addition, the German ceramic laser head produces a beam profile that is not nearly as smooth as even older broad beam laser systems.  By creating a hybrid device that stands between the true scanning lasers and the broad beam lasers, the Chiron platform is a device that may prove to be useful for treatments in 1999 but cannot adapt to the surgeons needs into the next millennium.

    Overall, the Chiron Technolas Planoscan 217 laser platform is a 2 mm scanning laser  with a video based eye tracking system.

Advantages: 

• Scanning laser technology is “conceptually” superior to broad beam lasers.  However, it should be noted that current data presented at scientific and medical sessions for the Chiron Planoscan fails to demonstrate this superiority.  At this time this remains a potential advantage.  
• Less concern for central “islands” than with broad beam laser technology  
• Less acoustic shock wave damage than broad beam lasers resulting in a higher level of safety to the crystalline lens, retina and other delicate eye structures located deeper in the eye.  However, produces substantially more acoustic shock wave damage than the Autonomous laser platform.

 Chiron Ablation Profile

Disadvantages: 

• Accurate eye tracking is critical to properly reshaping the ocular surface when using any scanning laser system.  The Chiron laser eye tracking system is profoundly lacking in it capacity to actually track the patient’s eye.  Precise laser pulse placement only occurs in the absence of patient eye movement.  This is unacceptable.
• One of the most irregular ablation profiles in the industry (see photograph below)
• Surface profile more irregular and “rougher” than more advanced laser systems due to lack of homogeneity of the laser beam.  Surface irregularities stimulate corneal healing resulting in proportionately greater variations in refractive results, irregular healing, optical aberrations, and poorer predictability.  
• Surface profile is considerably more irregular than scanning systems with true small spot capability.  A 2 mm laser spot size requires excessive laser pulse overlap thereby creating macroscopic surface irregularities.  Surface irregularities stimulate corneal healing resulting in proportionately greater variations in refractive results, irregular healing, optical aberrations, and poorer predictability.
• More prone to create unwanted side effects such as nighttime glare or halos due to limitation of a 6.5 mm optical zone.  Treating to 8 mm or larger is ideal.
• Unable to treat farsightedness or combined farsightedness and astigmatism.  This is because it is difficult to perform farsighted corrections without a high bandwidth eye tracking system.  Farsighted laser ablation times are typically on the order of minutes.  Patient movement due to involuntary eye movement or loss of fixation on the blinking diode light can result in de-centered treatments, induced irregular astigmatism and loss of vision.

• Fails to provide the surgeon with the ability to “enhance” nearsighted over corrections especially those with residual astigmatism.  As a consequence, the Chiron Planoscan system is unable to effectively treat this surgical complication thereby leaving the patient with sub-optimal vision.  The latter patients must either wait for further FDA approval for the Chiron system or pay additional fees to have the correction on a more advanced laser system.

• Unable to compensate for rotational eye movements during the laser procedure thereby often compromising the lasers accuracy in treating astigmatism.  Ignoring rotational eye movements ultimately results in less accuracy and less predictability in the surgical outcome.

• No “hinge” protection software capabilities increasing the chance for laser damage to the hinge area of the corneal flap during LASIK surgery.

• Custom ablations are theoretically possible but in practice are limited due to the inaccurate “eye tracking system” as well as a misplaced corporate emphasis and pre-occupation with treating corneal topography.  System as designed fails to treat the eye’s optical system as an integrated unit and therefore is unable to produce custom ablations based upon wavefront methodology.

Link to Chiron Vision Web Site  - www.baushandlomb.com