Wet lab experience crucial when training to implant Intacs rings

At one point, surgeons need to manipulate three instruments simultaneously.

Issue: September 1, 1999

ByVance Thompson, MD

---The Intacs implantation procedure begins with a radial incision.

With the introduction of Kera Vision Inc.’s (Fremont, Calif.) Intacs intrastromal corneal ring segments, low myopes now are offered a procedure specifically designed for them.

I was particularly enthusiastic about my first Intacs cases because patients were asking for it, some directly and some indirectly. Some patients came into my office and asked specifically about it, while there were others who were concerned about the permanency of laser procedures and asked me if there was something that I could recommend that was reversible. These patients were not specifically aware of the Intacs but sought a procedure in which they could go back to glasses or contacts if they did not achieve the visual results they were looking for. Intacs made sense for those who specifically asked for it, and also to those that wanted something that was reversible. Those are the main reasons I wanted to add it to my surgical armamentarium.

Intacs are approved for patients with between 1 D and 3 D of myopia and less than 1 D of astigmatism. The segments are made of PMMA and are implanted in the cornea to achieve a flattening effect by gently stretching tissue and eliminating excess curvature.

The implantation procedure involves the creation of a corneal pocket, two corneal tunnels and the actual placement of the segments. As a recent graduate of the KeraVision Intacs training course and as a new user, I hope to offer colleagues some helpful tips that might improve their initial experiences with these unique devices.

Training and experience

---After creation of left and right pockets, the tunneling tool is introduced.

When I made the decision to begin using the Intacs, I enrolled in the Kera Vision training course. For would-be Intacs users, the course is actually a requirement. Some of us do not like the idea of a mandatory training course, but I urge you to enter this with a good attitude, because it is so helpful.

The training course, in fact, was one of the best I have taken. There were good lectures on Intacs background, and the lectures on theory and technique also were very informative. But the wet lab instruction was most helpful. We did a number of eye bank eyes, which helped prepare me for surgery. To prepare, I did three eye bank eyes during the course and then three eye bank eyes back at my center. Generally, I would recommend surgeons who are new to Intacs perform five or six eye bank eye procedures.

I found that my experience with laser in situ keratomileusis (LASIK) was a great help with the learning curve. Similar to LASIK, an Intacs procedure involves a suction ring, but the pressure is elevated quite high and for a longer period of time than with LASIK. Also similar to LASIK, the patient’s vision blacks out, and you want to accomplish this procedure quickly because the central retinal artery is temporarily occluded.

I also found that having LASIK experience helped me with knowing how to talk with the patient and inform the patient about what they are going to experience.

Although I am purely a refractive surgeon, cataract surgeons also are likely to find that they can incorporate past experience into this new procedure, especially for the actual placement of the Intacs.

Unique marking system

---Ring segments are inserted into both tunnels and worked around into position.

In terms of the actual surgical procedure, I found draping the lashes and lid speculum routine; however, the marking system is different than anything I have used before. Prior to the creation of incisions into which the Intacs implants will be placed, the cornea must me marked. This procedure requires that markings be geometrically centered but not necessarily on the center of the pupil.

That took some getting used to, but the marking system that KeraVision has developed is straightforward and easy to use. Radial keratotomy (RK) surgeons will find this easier than some others because you have to go back to making a radial incision in the cornea, and RK experience helps with that.

Creation of the pocket also is a challenge at first. I found this a little difficult because you need to make room for the tunneling device. The pocket and tunnel are at two-thirds depth of the cornea. The pocket must be large enough to allow entry of the tunneling device. This took some getting used to, but the wet lab helped with that.

To assist in the creation of the tunnel, KeraVision has developed a guide, which helps to put one’s mind at ease, at least regarding the placement of the implants. With the guide, you know the tunnel to the left and to the right are going to fit, because you already have assessed your pocket size with the pocket guide.

The pocket guide itself is a little, flat, hockey stick-type instrument that defines how wide and how long your pocket has been made. KeraVision makes the instrument.

If it does not fit, you will have a lot of trouble introducing the tunneler tool. I always allow enough pocket space so that the pocket tester fits easily. An easy fit helps facilitate the procedure so your tunneling instrument can be introduced easily.

After the pocket and tunnels are created, we approach one of the more tricky aspects of the procedure.

Introduction of tunneler

---The ring segments are in final position. The procedure can be reversed by withdrawing the segments.

Once the suction ring is on and you have made your pocket, you are now going to introduce the tunneling device. Because you use your tunnel pocket guide to slide the tunneling device into the cornea, you are holding three instruments: a suction ring, the pocket guide and the tunneler that is supposed to fit underneath it. I find that I wish I had a third hand.

Unfortunately, no one can help you, because it would be very awkward to have someone else in there. During this stage of the surgery, the importance of the wet lab is apparent.

When practicing in the wet lab, one can develop a personal technique for handling this stage of the surgery. It is a good idea to know in advance how to position your fingers to function while working with three different instruments. It is that moment where you have three different things that you are working with that is probably the most challenging part of the procedure. I found that the wet lab helped me devise a way to position my fingers to make that maneuver easy. I was amazed how easy this step became just by doing it a few times. Ask your assistant to practice with you during web labs, making sure he or she is well trained, as well.

Because of the manipulation of the radial incision, there is more tenderness postoperatively than I would have predicted. For this reason, I treat it postoperatively like photorefractive keratectomy (PRK), with a bandage contact lens. This has helped a lot. However, you do not need the bandage lens for 3 or 4 days like following PRK. I typically use the bandage contact lens for 1 day.

Communication

---It is advisable to counsel patients that the ring can be seen in the eye cosmetically, though just barely.

Do not forget to talk with your patient the entire time, because when we do new procedures, we have a tendency to be so focused that we are not coaching our patients as much as we do during a procedure that we do routinely. Preoperative counseling is important. I also think that preoperatively it is important to warn patients that cosmetically you can see the ring. It is barely visible, but it is more visible than a soft contact, and this is something the patients should be aware of.

Also, physicians sometimes expect this to have a “wow factor” like LASIK, and I have found that it takes a little while for these patients to see well. They see much faster than if they had undergone PRK, but they do not see well as fast as with LASIK. I counsel my patients to not be upset if they are not as sharp as they wanted to be the next day. Intacs require a week or two to really settle in.

I have performed 12 cases so far, and I have been very impressed with the outcomes. The image quality has been very exciting. I have one patient who is a little undercorrected, and she is trying to figure out whether or not to keep a little bit of myopia because she is in the presbyopic age group. She may want her current implants exchanged for higher power. Otherwise, I have been very impressed with the results.

Generally, the procedure takes less time than LASIK; however, because I am still in the learning curve, I budget as much time for an Intacs procedure as I would for LASIK — about 15 minutes. Once the learning curve is complete, I have been told the procedure takes about 4 minutes, which means it can be scheduled as if it were a LASIK procedure, without disrupting the flow of patients on surgery days.

Editor’s note: This is the second in a series of articles on experiences with the Kera Vision Intacs. In this article, Vance Thompson, MD, a newer Intacs surgeon, discusses his technique and experience.

For Your Information:

Vance Thompson, MD, can be reached at 1200 S. Euclid Ave., Ste. 104, Sioux Falls, SD 57105; (605) 336-6294; fax: (605) 336-6970; e-mail: vthompson@iw.net. Dr. Thompson has no direct financial interest in any of the products mentioned in this article, nor is he a paid consultant for any companies mentioned.

For more information on Intacs intrastromal corneal ring segments, contact KeraVision Inc., 48630 Milmont Drive, Fremont, CA 94538-7353; (510) 353-3000; fax: (510) 353-3030; Web site: www.keravision.com.