Enhanced wavefront system yields improved quality of vision, says expert
A SERIES of upgrades for the Zyoptix wavefront-guided corneal ablation system (Bausch & Lomb) has made the new system capable of delivering enhanced performance and consistently better refractive outcomes, according to Gordon Balazsi MD, who presented his findings at a B&L Satellite Symposium at the XXI Congress of the ESCRS.
The latest iteration called Zyoptix 217z 100 combines the Zywave wavefront aberrometer, Orbscan II corneal diagnostic unit, and the Technolas 217z excimer laser. It provides a one-step customised corneal ablation procedure to correct defocus and astigmatism as well as higher-order aberrations.
The improved aberrometer automatically images the limbal ring and the pupil margin in both the undilated and dilated states. It also takes a high resolution image of the iris, which is recognised by the laser software. This allows the laser to compensate for any cyclo-rotation of the eye and thereby precisely position the wavefront treatment (measured in the dilated state) with respect to the centre of the undilated pupil at the time of surgery.
The 217z laser has also undergone a number of major changes: a more efficient laser head firing at 100 Hz, the rotational eyetracker based on the iris image, a much faster infra-red tracker sampling at 240 Hz with a 6 msec response time as well as z-axis tracking, and a more efficient software mix of 2 mm and 1 mm treatment spots resulting in significantly shorter treatment time. "The results we are seeing with this new system are extremely encouraging," said Dr Balazsi. Other speakers at the ESCRS congress echoed Dr Balazsi's positive appraisal of the system.
"I think the new software upgrades and the rotational eyetracker, in particular are a great help to clinicians offering customised ablation to their patients. It gives them more options and greater control over treatment setup and delivery," said French ophthalmologist Michael Assouline MD, PhD. US surgeon Stephen Slade MD said the 217z 100 was a significant advance for customised ablation. "It will help to better position the treatment with the measurements. It will be especially important for highly aberrated eyes such as re-treatments," he said. In Dr Balazsi's study, 173 eyes were treated with pre-operative sphere up to -10.25D and cylinder up to 3.25D. The mean pre-operative refractive error was -4.46D.
At one month's follow-up, high contrast best corrected visual acuity (BCVA) improved in 50% of eyes compared to pre-operative high contrast BCVA. Low contrast BCVA improved in 42% of cases. Uncorrected visual acuity (UCVA) was 20/20 or better in 69% and 20/16 or better in 27% of patients. The UCVA was greater than or equal to the pre-operative BCVA in 73% of eyes which compares favourably to 70.3 % in the US FDA Zyoptix clinical trial. The achieved refraction was within 0.5D of intended correction in 77% of cases and within 1.0D in 97%.
A question of control
Dr Balazsi noted that while earlier versions of Zyoptix had worked well, the new version would give clinicians greater control over treatment setup and delivery. The new eyetracker, which is capable of taking a unique digital iris key' or imprint of every patient, uses this information to identify cycloduction of the eye and compensate for any eye rotation that occurs between the Zywave diagnostic measurements and the actual photoablation. It also compensates for any possible pupil centre shift between diagnostic readings when the pupil is dilated and the actual ablation when the pupil is undilated. "The iris image taken by the Zywave aberrometer is transferred to the 217z 100 laser. After the flap cut, another iris image is taken by the Rotational Eye Tracker, and the relative angle of rotation is calculated and corrected by the Zyoptix treatment. said Dr Balazsi, adding that marking of the eye is not required. The enhanced eyetracker will also be considerably faster than previous versions, with a camera sampling rate of 240 Hz, compared to 120 Hz previously, enabling the system to actively compensate for eye movements.
High myopes also candidates for Zyoptix
Dr Balazsi asserted that the Zyoptix system was capable of treating a wider range of refractive errors than competing customised ablation systems on the market. It also provided an option for treating patients who would not normally be considered good candidates for laser surgery, he said. He cited as an example the case of a patient on whom he performed Zyoptix in May of this year.
"This is someone I would never have attempted to treat with a standard laser before. She had epithelial scarring caused by chronic contact lens overuse, and an asymmetric cornea that gave her a terrible quality of vision. She is 38-years-old, could no longer wear contact lenses and was desperate to find a solution. I debated whether to treat this patient with Zyoptix because it's one of the more extreme cases I have ever encountered."
After treatment, the patient's uncorrected visual acuity was 20/20 but the real breakthrough was in the quality of vision, said Dr Balazsi.
"She was a high myope and that's another thing to consider when you look at the approval status of the other two laser systems approved for customised ablation in which the mean myopia is quite low. With Zyoptix we are routinely treating quite high myopia. After her treatment, this patient said I have never seen before like this in my life' and that's something I've been hearing a lot of since I started routinely using Zyoptix in my practice," he said.
Farewell to Halos
Dr Balazsi said that improved results for contrast sensitivity and night vision with Zyoptix had resulted in an excellent subjective quality of vision for many patients. "Here for the first time, we're seeing a major impact on contrast sensitivity results. The US FDA trial of Zyoptix demonstrated a statistically significant improvement of contrast sensitivity. That's why people are saying that they see better than ever before after they have the treatment. You might have 20/20 vision but if you have poor contrast sensitivity, your quality of vision might not be appreciably better. In the subjective questionnaires, 40% of this series said that they see better at night than they did preoperatively. This has never been seen in refractive data before," he said.
Dr Balazsi said that there was a perception among European practitioners that Zyoptix should only be used to treat highly aberrated eyes, but he believed that this approach was limiting the possibilities of the new system and needlessly consigning patients to conventional laser treatments that fall short of the results achieved by Zyoptix.
Offering the best to everyone
"Everybody, especially in Europe , is saying we have to select those patients who have higher-order aberrations so that we can reduce them. An important point about Zyoptix is that even in normal patients with very few aberrations, you induce far less postoperative aberrations compared to standard treatment with Planoscan. If that is true, then even the normal patients should be treated with Zyoptix. In our clinic, everybody who walks through the door is a Zyoptix patient unless we find a reason otherwise. Our thinking is: why not offer the best to everyone?" The widespread view that a fall-off in refractive treatments in recent years has been due to economic recession was also given short shrift by Dr Balazsi.
"I personally do not believe that the current downturn in refractive business is due to the economy. My inkling is that people are afraid of refractive surgery because of reports of poor quality of vision in a small percentage of patients operated with standard LASIK. It is precisely the kind of results that we are getting with Zyoptix that will help bring back consumer confidence and build business for refractive surgeons." Dr Balazsi noted that in his own practice in Canada , word-of-mouth from satisfied patients has resulted in a steady increase in business in recent months. "We are in a mature market in Canada refractive-wise. Some 95% of our patients come from word-of-mouth referrals. We had the fear of night-driving halos way before it occurred in Europe and the United States . And I can tell you that our volumes are now increasing because of Zyoptix," he said.
MD Montreal ,
Stephen Slade MDHouston ,
Michael Assouline, MD, PhD
Fondation Ophtalmologique A de Rothschild,
Paris , France .
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