It is a common misconception that lasers alone are used to remove a cataract. Lasers basically cut tissue by creating heat, or cut tissue by a series of very tiny bursts of energy without heat, creating perforations like a postage stamp. The femtosecond laser is for both LASIK and cataract surgery. The femtosecond laser uses bursts of energy that last one millionth of a billionth of a second. That is extremely fast! No laser alone will ever be able to do a cataract procedure because you are getting an incision in the eye, taking the human lens out, and replacing it with a new lens. However, one can use a laser to make certain incisions.
YAG LASER FOR SECONDARY CATARACT
A common question is; Can a cataract grow back? The answer is no, but a secondary cataract, called posterior capsule opacification, is very common. This occurs typically 3 to 5 years after the original procedure, although it can occur weeks or decades later. Fortunately it’s correctable using a YAG laser.
A YAG laser has been used for almost 30 years now to create an opening in the capsule of the lens, if after surgery the capsule that enclosed the lens implant becomes cloudy. In modern cataract surgery, the skin of the human lens (called the capsule) is used to support the new lens in the eye. The human lens is like a grape…a hard skin (capsule), a juicy middle (cortex), and a hard seed (nucleus). The lens is removed by making a circular opening in the skin or capsule, removing the juicy middle (cortex), and breaking the seed (nucleus) into fine particles by a rapidly pulsing ultrasound (phacoemulsification), then irrigating those bits out of the eye. The net effect is the capsule of the lens is left intact, resembling a clear cellophane bag with a hole in it. The new lens, called an intra ocular lens (IOL), is placed inside the skin of the human lens which shrink wraps it into place. The capsule is normally clear, like cellophane, but over time it turns into the appearance of wax paper or bubble wrap, which blurs vision.
The YAG laser creates an opening into the middle of the skin of the lens to allow clear vision again. It produces no heat and no scarring. It is painless, takes only a few seconds to do, and requires no post-operative care or drops. Complications with this are very few. When I started my training, we had to insert a needle in the eye itself, so this is a BIG advancement!
A few problems can occur after this on the whole. The most common issue is some mild irritation of the surface of the eye for a little while after. Typically, a special contact lens is used to keep the eye open and to focus the laser. About 10% experience some scratchy or irritation sensation once the numbing drop used for the procedure itself wears off. Keeping one’s eye closed for 15 minutes or so helps avoid this. The vision is a little blurry that day, though most notice improved vision in a few minutes and is typically normal after dilation wears off. The optical correction may be a little different, though most do not need a change in glasses. Rarely, the pressure in the eye can be elevated either short or long term, but this can be managed with eye drops.
The only long term issue of possible significance is a possible slight change in the risk of retinal detachment. It is important to remember it is cataract surgery itself that puts one at risk for retinal detachment (especially in near sighted males), that can occur months or even years after the original surgery. YAG capsulotomy may increase that risk even a little more. The timing of a detachment after a YAG laser capsulotomy is not right away, typically occurring months or years later. We typically look at the eye a week or two after a YAG laser with a dilated exam to look for a pre-disposing factor for a retinal detachment, specifically a peripheral retinal hole. If one is found, it is a relatively safe office procedure that can seal a hole before a detachment can occur. The issue of retinal detachment is fortunately very uncommon, but it is a serious issue if one develops. It is treatable if one occurs, but some patients can have permanent visual loss after a retinal detachment, despite good treatment. I have had some patients get more nervous about YAG laser than the original cataract procedure itself. This anxiety is misplaced in my opinion, as the original surgery procedure, although low risk to begin with, is many, many times riskier than a YAG laser capsulotomy.
FEMTOSECOND LASER ASSIST CATARACT SURGERY
This topic has created a big buzz in the field of eye surgery. When I first heard about it, I thought “Gee, this should make the procedure easier to do”. Turns out, after three years of doing some of my cases with this technique, I now believe it makes things different, not easier, for the surgeon. It is being used to improve the optical accuracy of cataract surgery. The FDA approves the laser to be used for astigmatism correction and in the use of multifocal lens implants.
This portion of the blog is going to go into great detail about femtosecond laser assist technology; how it works, what it does for us, what it doesn’t do, published results to date, etc. There are different opinions about this especially given the added cost. However, it is controversial in that some feel the possible benefits are not worth the extra cost. I am going to hopefully try to give you, the reader, enough information to make up your own mind, but I do think it is worth the extra cost for some (but not all) of our patients. In our practice, we offer it for those who we think it would benefit.
The holy grail of cataract surgery is to get people to the best possible vision for distance with no surgical complications. Femtosecond laser assist surgery is an attempt to get us closer to that goal. In theory it should help, but the published medical literature to date on the subject is not clear. Most surgeons using the technology find it does improve the odds of glasses independence for distance vision, but is difficult to prove it in large studies done so far. Some studies have shown some mild improvement in post-op uncorrected vision, while others have shown no difference compared to manual surgery. Many studies to date are small, use different criteria, and different other modalities, such as intraoperative aberrometry, etc. Larger studies have not shown a significant difference in results. So, what is the truth? This will be my opinion, and you may find very conscientious surgeons who will agree with me in some points and disagree in others. But I am going to call it as I see it……and the bottom line is I believe it is useful for some patients (but not all) to have the procedure done with femtosecond technology. I know if I had a procedure done on me, it would be with the femtosecond platform.
WHAT DOES FEMTOSECOND LASER ASSIST SURGERY DO?
A femto is a millionth of a billionth of a second…that’s pretty fast. The laser fires in multiple bursts in line that cuts tissue without producing heat. This assists with 4 parts of the procedure. The incisions into the eye, the opening of the skin of the lens (the capsulotomy), the breaking up of the seed-like portion of the lens (nucleus), and when needed, partial thickness incisions in the cornea. This is designed to relax and reduce pre-existing astigmatism, called limbal relaxing incisions. The surgeon still has to remove the lens and put in a new one, and the complexity of the procedure overall from the surgeon’s perspective is not much different. It is a challenging procedure that we do so commonly that we are very good at it, and the overall difficulty is similar with or without the femtosecond component.
In my mind, two of these components I like….and the other two are nice but not as big a deal. The nice parts are the capsulotomy and the relaxing incisions of the cornea. The breaking up the nucleus part is nice, in that is reduces the overall energy used to remove the lens by about 40%, which helps protect the back of the cornea (the endothelium). However, in the typical patient, the power required is so low it makes little practical difference. However, if the patient has a pre-existing disease of the cornea, such as an endothelial dystrophy (trust me on this, I am not going into detail about this one), then I may recommend the femtosecond platform in order to protect the cornea. The other element of laser assist procedure regards the initial incisions into the eye. Although appealing in theory, I haven’t found this aspect as helpful as one might think. I still use manual incisions. As for my hands, my incisions are more water tight than those created by the laser.
FEMTO INCISIONS INTO THE EYE
As for the incisions into the eye, most surgeons make two incisions. The main cataract incision, and a “side-port” incision that we use as a second entry into the eye to put in instruments to help, while we remove the lens material through the main incision. It turns out that manually made incisions, in my hands at least, seem more stable if done manually than by the laser. Although the laser can be used to do this, I actually like my own better. I am not alone in this, as anecdotal conversations with other surgeons have supported. Obviously, some surgeons will prefer the laser to make both incisions. Some use the main incision by the laser and manually do the side-port, others do both manually. Why? Because our goal is a water tight incision without sutures being needed at the completion of the procedure.
The femtosecond laser cannot cut though any tissue that is not perfectly clear, therefore, its incisions have to be in the clear portions of the cornea. It turns out that incisions made more peripherally into the white part of the eye (sclera) induce less astigmatism and tend to be watertight more frequently. If a wound is not self-sealing, a suture is used to insure a watertight status, or a devastating infection into the eye becomes a distinct possibility. Although the laser incisions are “perfect ” in theory, in practice, little bubbles can cause the incision to be degraded, and the clearer parts of the cornea are more susceptible to stretching. Net result is, I am less likely to need a suture in my manual incisions and I feel my induction of astigmatism is less, hence I still make both entries into the eye manually.
This is the second part of a laser assist procedure. This is one portion of femto that I like. One thing is the capsulotomy, or opening into the skin of the lens, is like a cookie cutter…perfectly round and sized…all the time. I aim for an opening that is about 5 mm in size, and my manual opening can vary a little, both in size and shape. No surgeon can do a reproducible 5.0 mm opening as reliably as a femtosecond capsulotomy. Question is; Does it matter if the opening is a little oval or differently sized in regard to the post-operative vision correction? Answer is; We don’t know. However, a significantly different size than average probably does influence the post-op glasses requirement. In theory, a big deviation is size could influence where in the eye the IOL centers. An opening that is too large may allow the lens to push forward, making the post-op optics more myopic, while too small may have the opposite effect. My feeling is there may not be a significant difference in most manual capsulotomies to make a clinically significant difference, but it probably does matter in a few patients.
If a patient moves or coughs at the wrong time, or for other reasons, sometimes the opening in the capsule can extend peripherally. If the tear goes to the back of the lens, such that the gel-like material behind the lens (called the vitreous humor) can then be more forward to be in contact with tissues in the front of the eye. This is a complication called vitreous loss. This problem increases the risk of retinal complications related to cataract surgery, such as retinal detachments, by 10 times or more. One of the main goals of all cataract surgeons is to avoid vitreous loss. Unfortunately, all surgeons will get an occasional case of vitreous loss. The laser making the capsulotomy in theory may reduce this complication, although tears in the capsule can still occur, data from studies have not proven this conclusively.
Fortunately, the rate of vitreous loss at the Surgery Center of Farmington is at or below the national average, as compared to over 300 centers nationally. But it is not zero anywhere, so does laser assist help reduce this risk? A couple of studies from training institutions saw a lower vitreous loss rate in surgeons in training with femtosecond compared to manual procedure, which is not a surprising finding. We do not have good data about experienced surgeons. A few international studies have shown an actual increase in this complication, but this may have occurred in the “learning curve” phase and in earlier versions of the laser platforms. Our current laser had 8 software upgrades to-date, and improvement continues, so it is hard to say. My feeling is that femtosecond capsulotomy compared to an experienced surgeon may have a little lower risk, but the number is going to be so low it may not matter much clinically. When this technology was first introduced, I thought this would greatly lower this complication. Turns out, I think this technology has allowed a below average surgeon to become above average, but the vitreous loss rate compared to a good and experienced surgeon is probably not much different.
In Summary, I like the femtosecond capsulotomy. This makes the effective lens position more reliable, which helps with overall predictability of the glasses requirement after surgery. It probably improves safety slightly as well.
FEMTOSECOND NUCLEUS FRAGMENTATION
The third aspect of femto assist regards to help breaking up the cataract itself. One of the steps of the cataract procedure is the fragment of the seed, or nucleus as we call it, into microscopic pieces that are then suctioned out of the eye. The femtosecond laser creates cuts in the nucleus that aides in removing the lens, reducing the power of the ultrasound (phacoemulsification) required for this stage of the surgery. Phacoemulsification energy can damage the back of the cornea, so reduced energy may lessen damage. For the vast majority of patients, our corneas are healthy enough that this is not a clinically practical issue. However, if the cataract is particularly dense and especially if the cornea is not healthy to begin with, this aspect of femto laser assist procedure I appreciate. The disease of the cornea that makes us want to reduce corneal trauma is called Fuch’s Endothelial Dystrophy. I will not get into that topic here (maybe a future blog topic), suffice to say for most patients this is not a big deal, but for some patients this is a clinically significant advantage.
FEMTOSECOND CORNEAL ASTIGMATISM REDUCING INCISIONS
This is the fourth element of the laser assist procedure. As mentioned earlier, astigmatism reduces uncorrected vision. Glasses or contacts correct it, but if you want to see well most of the time without glasses, this must be corrected with prescription lenses. If you have no astigmatism of significance and you are mid 40’s or older, your distance uncorrected vision may still be good, but you can’t see up close. Non-prescription reading glasses are made for these individuals. This means if you want to correct astigmatism for distance, you can use “dimestore” readers, whereas if you have uncorrected astigmatism, you will need glasses for both distance and near.
Every human being has some astigmatism. The question is: Where and how much? Remember, astigmatism means the cornea has a shape resembling a football cut in half, not a basketball cut in half. The direction of the fold is called the axis of astigmatism. The fold can be at 12 o’clock to 6 o’clock orientation (90 degrees); or it may be in any other direction as well. Correcting astigmatism is done with glasses, by the lens in the glasses having a fold in the opposite direction than is on the cornea, whereas a hard type contact corrects it by smoothing the fold of the cornea itself. If the amount of astigmatism is small, it doesn’t matter where the fold is if it doesn’t have much optical significance, so humans can tolerate a small amount well.
Femtoscecond lasers can relax the fold in the cornea to reduce the amount of astigmatism to be not very optically significant. These incisions are therefore called corneal relaxing incisions. They are also called limbal relaxing incisions, as they are done in the periphery of the cornea near the part of the eye called the limbus. It can correct any direction of the fold. However, the magnitude of the fold can only be corrected to a certain degree. The unit of measurement we use in the Eye Doctor world is called a diopter. A 1 diopter lens bends light to be focused 1 meter away; 2 diopters is 1/2 meter, 3 diopters 1/3 meter, etc. Astigmatism is noticeable in most people if it is more than 1/2 diopter in power. The femtosecond laser corneal incisions correct up to 1.5 diopters or less. If there is more astigmatism than can be corrected on the cornea, the patient needs a lens in the eye that can generate more power, called a toric lens. Some patients need both a corneal relaxing incision and a toric implant.
These same incisions can be made manually and some surgeons do this pretty well. The cornea is ½ millimeter thick and getting an 80% depth incision the perfect length and location is difficult. The femtosecond laser does this incision more accurately than any human can do. Even with the laser the results can vary, but the majority of patients who receive these incisions will have enough relief as to make the residual astigmatism not optically significant. However, no human being can be nearly as precise as the laser in creating this incision. In fact, it is for the treatment of astigmatism that the Food and Drug Administration (FDA) allowed these lasers on the market.
In summary, it is the treatment of astigmatism that is the primary benefit of laser assist surgery. Not surprisingly, it is my favorite feature of this technique. True, it doesn’t eliminate all astigmatism, but the residual amount is usually optically insignificant. About 5 to 10% of patients may still have residual astigmatism and/or far or near sightedness to be optically significant (although much less than they would have otherwise), and that can be corrected with glasses or LASIK/PRK. Most surgeons, including our practice, doing a touch up on residual refractive error is done at no charge as part of the original fee. This is needed in less than 5% of our patients.
HOW FEMTO IS DIFFERENT FOR THE SURGEON
As mentioned earlier, when we started to offer this to patients 3 years ago, I thought “Gee, this is going to make the surgery much easier”. Well, I was wrong. It is different, and I do think it gets a better optical result than manual surgery, but it did not make things easier. For starters, these patients are paying more money out of pocket and therefore tend to have higher expectations. As a result, the stakes seem a bit higher to get a good outcome. Since optical results are never perfect in 100% of our patients, I will have a less than pleasant discussion to explain all that. We try to educate prior to as much as possible, but those who need an “enhancement” are never thrilled with that.
These expectations may exceed what any surgeon can deliver in all patients. There is much more discussion time needed to discuss these options, particularly when extra money is involved. We have to discuss laser options with all our patients in fact, whether they want it or not, so people are aware of their choices.
In overall surgical complexity, it does make the removal of the center of the lens, the nucleus, easier…or perhaps, different is a better word….it makes it quicker. But I did have to modify my technique and use a new instrument to aid in this, which took a while to figure out. The so-called “learning curve ” and the initial opening of the lens is nice as well. However, I was not thrilled with the laser induced incisions, and in fact now use my manual ones which were part of “the learning curve”.
The removal of the cortex, the juicy middle part of the lens, is actually harder with the laser assist technique. The cortex is stickier and the laser induces gas bubbles that sometimes blocks my view. Therefore, although the removal of the nucleus is quicker, the cortex is slower so the surgery time itself was no different. In fact, the whole thing is definitely more time consuming, as we do the laser portion before the actual surgery itself. Not a big deal, but not a time saver. Of course, surgical complications can occur with any technique and are fortunately very low even with manual surgery. I thought they might be dramatically lower, but in my hands it did not change much. That is good, I suppose, because that implies I am in the better than average category for manual surgery. Still, I thought the laser might make it dramatically better, which it does not.
To sum all this up, femtosecond laser assist cataract surgery doesn’t make it easier for a surgeon to do. It does add more cost to the patient and it does improve the optical results after surgery for some patients. However, the amount of improvement is relatively small. In other patients without much astigmatism, the manual surgery results are close to that of femtosecond surgery. However, it is recommended for the correction of astigmatism in some patients and to improve the optics in patients receiving multifocal implants. At Precision Eye Care we recommend this for people with moderate astigmatism. In patients who have smaller amounts of astigmatism, the benefit may not be worth the cost, but for others with more astigmatism it can be worth it if the patient is financially able.