Modern cameras have image stabilization which can make a jittery photographer take great pictures.  Using a similar principle, modern lasers employ eye trackers to "lock on" to reference areas of the eye and makes small movements invisible to the laser which is providing the correction.  Many different types of eye trackers have been utilized but most rely on the pupil and use infrared imaging to obtain the high contrast needed for effective tracking.

Once the patient is under the laser, and in the case of LASIK, after the flap has been lifted, the eye tracker is engaged and almost instantaneously knows where the pupil is throughout the treatment.  If the patient moves their fixation too drastically, the laser will stop until fixation is within a safe range to treat.  The trick is that the eye tracker is very, very fast, and it essentially freezes any movement while the laser fires a pulse in the exact correct direction.  Again, like the photography analogy, it is like a fast shutter speed which can stop action for the instant that the picture is being taken.  Because the small spot lasers we use produce hundreds of pulses per second, the eye tracker needs to be fast enough to locate the eye and deliver the pulse before the eye can move.  In fact, even with the best efforts, most people have some fine movements of their eyes at all times but this is smoothed out by the eye tracker.  We know the eye tracker is working during the treatment because the laser tells the operator and the surgeon that it is functioning properly.  We also know from experience that when we look at the results of the treatment that they are well centered as planned.

All of this you may have known or guessed, but here is something that you may not have known.

On the Zeiss Mel 80 laser which we use regularly for our treatments, there are actually two eye trackers at work.  The first is the one which follows the pupil, but the second is defined by both the first and the border of the colored and white portion of the eye, or the limbus.  The second eye tracker is really helpful when the pupil becomes difficult to visualize due to reflections or eye movements and works like a belt and suspenders approach to keeping the laser on track.  For instance if the pupil were to begin to dilate the second tracker still knows exactly how to position the treatment.  This is one of those subtle technologies that Zeiss provides which is not marketed or readily apparent, but which clearly provides better outcomes to our patients.  We have compiled data on our results that we are happy to share with patients based on prescription ranges, and it is amazing how accurately this laser can correct a wide range of vision corrections.

Last week while flying back from the ESCRS (European Society of Cataract and Refractive Surgery) meeting in Barcelona, Spain, I was so impressed how smoothly our Airbus jet flew with barely any sensation of motion.  I have been told that there are very advanced systems on these newer jets that react to slight irregularities in the air so quickly that the passengers rarely feel the turbulence of the older airplanes.  The combination of the VisuMax femtosecond laser when paired with the Zeiss Mel 80 laser is the laser equivalent of this advanced technology which can react so quickly to changing circumstances that it can produce a smooth result even with irregular eye movements.We are the only center in Colorado, and one of the few in the nation with this advanced technology combination.

No technology is perfect, but with modern eye trackers we can get even nervous patients to have the same kind of excellent results as those who are able to be very still.  So if your concern about laser vision correction is whether you can hold your gaze for the treatment, be assured that we have got you covered.  You can relax, the eye trackers are ready.