EyeWorld India March 2012 Issue

March 2012 10 EW FEATURE EyeWorld - from page 9 corneal plane. However, incisional techniques on the cornea are not that predictable, and I have a feeling it’s inherent to corneal remodeling. Additionally, it’s a trauma to the eye, whether you make the incision with a blade or a femtosecond laser. CE: My stand would still be to correct the astigmatism with a lens. I wouldn’t approach the patient with more than 1.25 or 1.5 diopters of cylinder with an arcuate cut, even using the femtosecond laser. If it was 1 diopter or less I might consider using the femto, but for more than 1.25 or 1.5, I would rather use a toric lens. GB: I suspect that toric IOLs are still going to be our primary tool for correcting astigmatism. CSP: Going back to the incision, I’ve not done any incisions using the femtosecond laser, but as you said I think they are very important as the safety part of the surgery. If the incisions leak postoperatively, they may place the patient at risk of endophthalmitis. However, I do not thing it is just the length and the proportion, but also the angle of that incision. I did an observational study and I found, to my surprise, that there was a sideport incision leak in 31% of the eyes on the operating table— and even though hydrated, they had still leaked. In these eyes, the anterior chamber was nice, deep and stable, the pressure was good, yet there was still a very slow ooze from the sideport incision. What I did then was to change the direction of the incision, making it more like the direction of my main incisions—even slightly upward instead of going straight down—which happens to also make it easier to access the nucleus with the second instrument. Thus, I think that the direction of the incision is also a very important safety factor that can be precisely controlled and reproduced using the femtosecond laser. Furthermore, I think when we get to making smaller and smaller incisions, there’s a tendency— especially with a square incision, which we believe is more stable— to develop oar-locking of our instruments. What I do in my practice, especially when I deal with a high myope, is to widen the inner lip of the main incision to allow me to yaw the phaco needle downwards without creating corneal striae. When we do that, there’s the concern that we may end up widening the incision instead of just the inner lip, and you can’t create a blade to do that, really. So the femtosecond laser will help us to actually design a tunnel that’s wider on the inside and narrower on the outside. GB: Yes, that may allow us to design specific incision architectures that we haven’t thought about, which we may not be able to do with blades. Lasing the nucleus GB: There have been attempts at softening the nucleus using technology such as Aqualase or NeoSoniX [both Alcon] and many other ways to reduce phaco time and energy; most have come and gone. What is your experience with the femtosecond laser in this respect? KPR: We initially tried different patterns. Having tried all these different patterns, now we have settled. In grade 1 and 2, we use rings. Grade 1 is like a clear lens extraction—concentric ring cuts definitely help and there’s no point in doing a crosscut. Whereas in grades 3, 4, and 5, we always use a crosscut. I’ve tried different patterns, but I find that most effective. Now our routine is to use rings for grades 1 and 2, and crosscuts for grades 3, 4, and 5. And you don’t need to do a hydrodissection. GB: What about rotating the nucleus? KPR: We start lasering about 1,000 microns away from the posterior capsule, so by doing that there is that pinch of energy dissipation all over, and I think it eases epinucleus separation, so I have not had any issues there. We can rotate the nucleus. The only thing is I found that by doing this, when I come to the step of irrigation and aspiration, I found that it was a little adherent to the capsule. GB: With cortical cleaving hydrodissection, it’s easy to remove the cortex, but you often get tiny strands that are left behind. It may be a little more adherent, but you could end up with a cleaner bag. CE: We use the same pattern for softer nuclei. Being a refractive center, we’ve done quite a number of refractive lens exchanges, and I was just using a big bore needle to aspirate the soft lens material. With the femtosecond laser, the concentric ring pattern would be best for these cases. For 3 to 4, we observed that the Maltese cross is actually the best. We combine this with a central ring at around the 2- to 3-mm zone. Being involved in teaching residents, we found that the hardest part of the learning curve is to hold on to the nucleus and chop it. One of our partners, Richard Kho [MD], developed this technique that he calls the ‘pothole technique’, where a 2-mm diameter central crater is created that fits like a lock-and-key to the bevel of the phaco tip. Fixation of the nucleus is achieved even without burying the tip and cracking is achieved with a horizontal chopping maneuver. We’ve also had experience with dense cataracts—grades 5, 6—and the pattern that we find really helps is creating the cross, and then creating two concentric ring cuts at the 2.5-mm zone and at the 4.5- mm zone. That weakens the central, hardest portion of a hard, dense cataract, so it’s easier for us to break it down and to sculpt it or to crater it. And then, beyond the 4.5-mm ring, you now have a nice, softer peripheral rim that you can easily chop or crack to complete your phaco. We’ve cut down our CDEs [cummulative dissipated energy] by as much as 30% in brunescent cataracts. CSP: The cases I did in Hyderabad, I chose the harder ones, because I thought that those were the cases that would be more challenging to the cataract surgeon. I asked for the Maltese cross in both cases. It didn’t make that much of a difference, because for me chopping is simple enough. But it did help in that it was already there—I didn’t have to use that much effort in order to separate the fragments. CE: If I may add, on the issue of hydrodissection: Ever since I’ve started using the femto laser, I’ve only hydrodissected twice and have totally given it up. I believe that the phenomenon of the bubbles produced during the treatment actually dissects the layers of the lens such that this step [hydrodissection] becomes superfluous. When you do the harder types of cataract, you’ll first see the nucleus turning yellow orange. Then a bubble layer forms and spreads peripherally underneath the nucleus. We’ve started to call it ‘pneumodissection’. Having observed that, we tried not doing hydrodissection—partly because Michael Lawless [MD] reported posterior capsule ruptures with vigorous hydrodissection without having the air bubbles come out first. Despite not hydrodissecting, we’ve consistently observed the nucleus to be quite mobile. Trouble with lasers? GB: Although the experience worldwide is limited, it’s somewhat surprising to note a significant number of complications being reported. These include rhexis tears and even cases of nuclear prolapse. For surgeons considering the purchase of such an expensive machine, hearing these reports of complications might make them wonder, why purchase technology that could increase their complication rates? Perhaps it’s just the learning curve as we saw in the early days of phaco? KPR: I think that like most techniques, if it is not practiced properly and you discredit the technique, I don’t think it’s fair, because man/machine variables are involved. When I first got this machine, I was told to keep stay 500 microns from the posterior capsule, as recommended in Germany. I asked whether it was okay to keep it at 1,000 microns and I was told it was up to me as surgeon. I think that the reason I’ve never had any complications at all is because I stay away from the posterior capsule. Yes, there were some difficulties in the rhexis part initially in the first 15 cases, but never any issues such as drops or prolapses because we stay away from the posterior capsule. And since the capsulotomy