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New flap dynamics with femtosecond technology
Early observations show a benefit to the inverted side-cut angle.
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Our initial experience with using the latest generation femtosecond laser on 37 LASIK eyes has been positive.
 Stephen G. Slade |
One of our first impressions of the iFS (Abbott Medical Optics) laser is the speed and precision. Most iFS-experienced physicians feel comfortable with the settings to create a 14- to 16-second flap. We also found that the iFS is easy to use, and I do not think surgeons will have much of a learning curve at all. The latest generation has a video screen rather than a microscope, which provides a clear image and is easy for the surgeon to use.
In addition to speed, the flap quality was excellent. With the expanded software, surgeons have the ability to do an inverted side-cut, which is an advantage. In patients in whom we used a 140° inverted side-cut, we noted that they were the best flaps in terms of wound approximation and appearance of all the ones we examined.
Side cut adds strength
At the time, we performed the cases and then looked at them with ultrasound and at slit lamp upon completion of the procedure. At 30-minutes postop, the cases with the inverted flaps appeared exceptionally well-sealed. The angled flap had gone underneath the edge, and they appeared like 1-week flaps. I believe that this side cut will add strength to the flap. Biomechanical studies by John Marshall, PhD, demonstrated that the thinner, inverted side-cut flap maintains the best or “strongest” part of the cornea. Theoretically, an inverted side-cut flap would be stronger than a PRK at the same ablation depths, according to Dr. Marshall.
Another early impression I have is that the ability to make inverted side-cuts would be good to hinder epithelial ingrowth. Because of the architecture of the flap, the epithelium would have to make two near 270° turns to get underneath the flap. The epithelium would literally have to grow in a z-pattern, and when it comes down the first angle of the z, it would be pressing the second angle of the z down, so it appears that it would be near impossible. As an aside, although our sample was small, we have seen no epithelial ingrowth in our iFS cases.
Customized flaps
The new femtosecond laser also provides the surgeon with the ability to adjust the parameters of the laser to customize flap formation. For example, the ability for surgeons to create an oval flap allows the possibility of opening up the optical zone and the optimization of the surface of the cornea that is being treated. Oval flaps demonstrate the potential to change flap shapes and could be used in the future in specific cases, such as for astigmatism.
In the 37 LASIK cases in which we used the iFS technology, the outcomes were excellent and certainly equal to our best LASIK patients.
- Stephen G. Slade, MD, can be reached at 3900 Essex Lane, Suite 101, Houston, TX 77027; 877-380-9560; e-mail: sgs@visiontexas.com. Dr. Slade is a consultant to AMO.