Safety a Key Benefit of Laser-assisted Cataract Surgery
Article featured in Ocular Surgery News by Dr. Johnny Gayton
Expanding the margin of safety is an important reason to consider femtosecond laser-assisted cataract surgery.
Ocular Surgery News U.S. Edition, July 10, 2014 Johnny L. Gayton, MD
Increasing precision and improving refractive outcomes in cataract surgery are important goals, but I am most interested in new tools and techniques that make the procedure safer.
Today, I am confident that femtosecond laser-assisted cataract surgery (LACS) is incrementally safer, in my hands, than manual surgery. It is important for surgeons to research laser platforms carefully, however.
Protecting the endothelium
I have found that LACS reduces or eliminates ultrasound time and total phaco energy. Femtosecond laser and ultrasound phacoemulsification both use cavitation to disrupt tissue, but the laser delivers energy more efficiently, with less heat and less collateral damage than ultrasound.
I explain the difference between light energy and sonic energy to patients like this: If I shine a flashlight at you in a room full of people, you can tell exactly where I am aiming the beam. If I clap, everyone in the room hears the clap. Like that clap, ultrasonic phaco energy is dispersed throughout the eye, while the laser light energy is more focused.
In my hands, this reduction in ultrasound results in less corneal edema and inflammation. On the first postoperative day the eyes are quieter. I am much less concerned about endothelial cell loss in compromised eyes, such as those with Fuch’s dystrophy.
Perfecting the capsular opening
Femtosecond laser capsulotomies can be customized to the patient and are accurate to within 30 µm. We have all seen pictures of perfectly uniform LACS capsulotomies. Achieving more precise sizing and circularity is more than just aesthetically pleasing, though. In my hands, a laser capsulotomy is less likely to extend radially, even in challenging cases.
I am also more likely to achieve 360˚ optic coverage, which increases the predictability of the effective lens position and the accuracy of the predicted refractive error. With a manual capsulorrhexis that is a little too big, the IOL may shift anteriorly or a haptic may come out of the capsular bag. If the capsular opening is too small, it is more likely to phimose and push the lens posteriorly. These subtle changes to the effective lens position can have a big impact on the visual outcome and the potential decentration.
Making complex cases routine
What is perhaps most impressive about LACS is the degree to which it can transform a complex case. Using the Catalys laser (Abbott Medical Optics), I have now successfully operated on five hypermature black cataracts (Figures 1 to 3). In each case, I imagined the eye without difficulty, achieved a perfect capsular opening, gained significant nucleofracture without hydrodissection and removed the cataract through a 2.2-mm incision.
Figure 1. Femtosecond laser OCT imaging of a black cataract.
Figure 2. One advantage of the Catalys femtosecond laser in the automatic placement of the anterior and posterior ‘gates” for the nucleofracture, as seen in this image of a black cataract. Images: Gayton JL
Figure 3. Nucleofracture of a dense black cataract was achieved with quadrant segmentation and lens softening with 100-µm grid spacing.The laser made it possible to perform small-incision cataract surgery in these challenging eyes without having to convert to an extracapsular procedure, as I likely would have needed to do in a traditional case. For these black cataracts, I was aggressive with the lens softening, reducing the grid spacing to 50 µm to 100 µm. Softening the lens peripheral to the capsular opening is also particularly helpful in dense nuclei.
Other cases in which LACS helps the surgeon achieve a perfect capsular opening with much less difficulty and risk include eyes with prior trauma, capsular issues, zonular dehiscence and pseudoexfoliation.
The population where I practice in Georgia has a high rate of nanophthalmos. These small hyperopic eyes typically have narrow angles that make a manual capsulorrhexis more likely to run peripherally. With LACS, a radial tar is unlikely, and because of the laser nucleofracture, there is less need to establish working space. The femtosecond laser essentially turns a narrow-angle eye into a more routine cataract case.
Other safety features
In evaluating how a particular LACS device will enhance safety during cataract surgery, here are some features that I found essential.
IOP impact. Lower pressure during docking with a liquid interface enhances the safety of the procedure because one does not need to worry about increasing IOP in eyes with glaucoma, opening old RK incisions or affecting the microcirculation.
Automation. By automatically setting the parameters for the capsular opening and anterior and posterior ”gates” for the nucleofracture, there is less room for error, and the chance of accidentally cutting the posterior capsule with the laser is reduced.
Advanced imaging. Integrated imaging provides more information than we have had before. For example, in several of my cases, laser imaging confirmed a posterior capsular defect before surgery (Figure 4), thus reducing the chances of dropping the nucleus.
Figure 4. Polar catracat seen on laser OCT. Laser OCT imaging confirmed a posterior capsular defect before surgery. Figure 4. Polar catracat seen on laser OCT. Laser OCT imaging confirmed a posterior capsular defect before surgery.Tilt compensation. Automatic compensation for any tilt due to a positioning problem or anatomic abnormality reduces the chance of a malpositioned capsular opening or a posterior capsule rent, thus improving safety.
Speed. Shortening phaco time by pre-softening and fragmenting the lens reduces the chance of an intraoperative complication due to patient movement for any reason. If the patient is in the operating room for less time, there is less time to have a complication.
I suspect that most practices will find, as I did, that staff perceptions of efficacy and safety have a major impact on conversion rates. The staff’s and my conviction that LACS is safer is what resonates so strongly with our patients.