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Sep
2006

Ivy League Vision

It’s said that the journey of 1,000 miles begins with a single step, and many surgeons will soon embark on their journey into the world of phakic IOLs by taking their first steps in instructional courses and wet labs. To help ensure they don’t stumble at this crucial learning period, here are several experts’ tips for maximizing outcomes, minimizing complications and getting the most out of this exciting new technology.

The Verisyse Lens
Patient selection and biometry. For this anterior chamber IOL, experts say that it may be better to start out with the higher myopes, who usually enjoy better improvement in their quality of vision with lenses than with LASIK.
“With -12 D and up, it’s almost a slam dunk, with outcomes data generally favoring phakic IOLs over LASIK,” says Richard Lindstrom, MD. “I recommend surgeons start with the slam dunks.”

To ensure the safety of the corneal endothelium, the Verisyse needs at least 1.5 mm of clearance from the edge of the optic to the endothelium. “A rough guideline is that if the anterior chamber depth is 3.5 mm or deeper, you’ll have enough room,” explains Dr. Lindstrom.

Astigmatism is also a consideration, because a toric Verisyse isn’t yet available for sale.

“You can do limbal relaxing incisions or LASIK enhancement with bioptics, but it’s nice to start out with someone with reasonable astigmatism,” says Dr. Lindstrom. “If the patient has more than 1 D to 1.5 D of cylinder, you’re going to have to deal with the astigmatism surgically. Since this just adds another variable to a new procedure, I’d recommend starting with patients with 1.5 D of cylinder or less.” He also recommends that the beginning Verisyse surgeon start with someone who’s pre-presbyopic, to avoid having to deal with presbyopia issues.

The procedure. To help avoid postop pupillary block that can occur if there’s shallowing of the chamber and the iris comes forward to touch the back of the lens optic, one or two peripheral iridotomies are essential. Many surgeons perform these with the YAG laser about a week preop, placing them superiorly, with one at the 10:30 or 11:00 position and the other at 1:00 or 1:30.

A superior Verisyse insertion can be preferable for patients with with-the-rule astigmatism.

“Do two of them if you’re going to do them with the YAG,” advises Dr. Lindstrom. “Because they tend to be smaller, and some of these young patients are aggressive healers and can sometimes heal them closed.” Though the YAG iridotomies are smaller than surgical ones, which reduces the risk of glare postop, it also puts the onus on the surgeon to make sure they’re patent. “Watch for iris pigment epithelium to come streaming through the iridotomy once it’s created,” says Santa Monica surgeon and Verisyse investigator Kerry Assil. “That tells you it’s fully patent.”

On the day of surgery, patient preparation is similar to cataract surgery, with some new considerations.

“I’d encourage surgeons not to use topical anesthesia with their first Verisyse cases,” says Dr. Lindstrom. “I’ve been doing these cases for five years now, and I still use a peribulbar injection and a facial nerve block to prevent the patients from squeezing hard and to reduce the positive pressure, since these eyes tend to collapse and have a low scleral rigidity. If you have a nervous, 25-year-old, extreme axial myope, he may have low scleral rigidity and may squeeze hard. This combination leads to a lot of positive pressure, meaning things in the eye press forward, making surgery more difficult.” He notes, though, that, once you are more experienced, these cases can be performed under topical. He advises that, if a surgeon were to use topical for one of these cases, that he also instill intracameral xylocaine, since iris enclavation can create more patient discomfort without it.

You use a miotic to constrict the pupil preoperatively, usually 1% pilocarpine twice before surgery, followed by Carbostat or Myostat at the time of surgery. Dr. Lindstrom also pretreats the eye with a current generation fluoroquinolone t.i.d. or q.i.d. on the day of surgery, and tries to head off any inflammation with preop steroid drop and an NSAID.

You then make three incisions: a 6-mm or 5-mm primary wound (depending on the lens size) for lens insertion, and two stab incisions that will enable you to use instruments intraocularly to fixate the lens. The primary incision can be scleral, limbal or corneal.

Dr. Assil says that, for a patient with with-the-rule astigmatism, inserting the lens through a superior incision is preferable. For large amounts of against-the-rule cylinder, he says a temporal wound is better. The stab incisions are also superior, at approximately 1:30 and 11:30, about 10.5 mm apart. “The paracentesis ports should be pointed inferiorly, not radially,” says Dr. Assil. “Nor should they be exceptionally long, in order to avoid oar-locking the instruments. A good way to avoid them being too long is to put some viscoelastic in the eye after you make the first one.”

After the incisions are made, you inject a cohesive viscoelastic into the anterior chamber to form it. Verisyse users say a cohesive viscoelastic, as opposed to a dispersive one, allows easier removal at the end of the case, and its viscosity is satisfactory in maintaining the chamber.

“Then, you just slide the lens in,” says Dr. Lindstrom. “You’re simply using the viscoelastic in this case to maintain the chamber and protect the endothelium. Once the lens is inserted, you rotate it with a Sinskey hook to get it where you want it, and then you put a bit of viscoelastic right over the optic to push it a little posteriorly. If you inject viscoelastic behind the implant, however, you can float the implant off of the iris, making it difficult to enclavate it later.”

Enclavation. This is the surgical maneuver unique to the Verisyse lens, and the one which experts say will take the most getting used to.

The idea behind the iris enclavation is to pull up a small knuckle of iris into each of the fixation holes on either side of the lens. To get a feel for it, Dr. Lindstrom recommends practicing with cadaver or pig eyes.

“We clinical investigators flew off to Holland and did it under the tutelage of Jan Worst,” says Dr. Lindstrom. “Before my first cases, though, I did the maneuver with some cadaver eyes with the corneas off, to allow me to see well. Even one cadaver eye can be enough, because you can keep rotating the lens and using different points on the iris. The other issue with this maneuver is that it’s a bimanual one, so the surgeon needs to be able to use both hands, one to stabilize the lens, and one to enclavate the iris.”
It may take two or three attempts to get the proper iris enclavation with the Verisyse lens, surgeons say.

Assuming he or she is right handed, the surgeon needs an instrument in the left hand that will fixate the implant, such as the Budo forceps. The other hand holds the Worst enclavation needle. “What I find works the best is to enclavate using the side of my dominant hand first,” instructs Dr. Lindstrom. “When I grasp the optic, and I’m getting ready to enclavate the iris, I just tilt or rotate my hand a tiny bit, maybe 5 degrees, which tilts the end of the optic right against the iris. The other trick is to take advantage of an iris crypt, or small valley in the iris, for enclavation. You take your enclavation needle and slide it into one of the little valleys of the iris, which makes a nice place to start creating the little wrinkle of iris that you’re going to pop up through the enclavation opening.”

Dr. Assil recommends performing the temporal enclavation first, because there’s more excess iris temporally. Then, when the surgeon performs the nasal enclavation, any tugging he has to do on the already enclavated side won’t overly traumatize the iris.

“Also, enclavation should be started about 0.5 mm below the midline of eye,” says Dr. Assil. “Because, as you start feeding iris through the haptic during enclavation, the lens will ultimately end up at the midline.”
Dr. Lindstrom also advises not to let the term enclavation “needle” fool you, as the tip doesn’t catch the iris.

“Enclavation is similar to taking your finger, bending it 90 degrees, and pressing on a piece of fabric; you create a little wrinkle with it. That’s exactly what you’re trying to do with the enclavation needle,” he explains. He adds that you will usually get a small amount of iris at first, and usually need to repeat the maneuver until you get the right amount; too much and you end up with an oval pupil, too little and you get poor fixation.

“When you go to enclavate the other side,” continues Dr. Lindstrom, “you have to stop for a moment and put in a little more viscoelastic and make sure the optic is still centered over the pupil, because it’s possible to rotate the lens so that it’s decentered.”

Once the lens is fixated by its two knuckles of iris, you can close the case. Dr. Lindstrom actually sutures the wound first with interrupted 10-0 vicryl sutures, then removes the remaining viscoelastic with bimanual I/A, either through the two sideport stab incisions if they’re large enough, or infusion through a sideport and aspiration through the larger primary incision. Postop, he treats the patient as a cataract patient, prescribing a steroid, NSAID and antibiotic drop.

By following these techniques, Dr. Lindstrom believes users will be happy with the Verisyse. “It turns out that this procedure has had the most significant ‘wow factor’ of any of the refractive procedures I do,” he says.

The Visian ICL
The Staar Visian Implantable Contact Lens has patient selection criteria similar to the Verisyse.

“Typical patients might be those with thin corneas, high myopia, a bias against LASIK, lid problems, or someone who has had corneal surgery in the past on whom you wouldn’t want to operate again,” explains ICL investigator Stephen Slade, MD, of Houston.

“The main criteria with the myopic ICL is that the patient have a deep enough anterior chamber,” says fellow ICL investigator Stephen Bylsma, MD, of Santa Maria, Calif. “The distance from the endothelium to the anterior capsule needs to be 2.8 mm or greater; that’s been the FDA protocol. A deeper anterior chamber makes it easier to implant. So, a good pearl for surgeons embarking on their first few cases is to select patients with anterior chambers 3 mm or deeper.”

“In contrast to using the Verisyse, implanting the ICL is an astigmatically neutral procedure, so surgeons should be aware of high preop astigmatism,” says Dr. Bylsma. “The Verisyse, since it’s not foldable like the ICL, involves a larger incision by which the patient’s astigmatism may be changed,” he says. “Preop astigmatism with the ICL may be managed with limbal relaxing incisions, though this option wasn’t available in the FDA study. Until the toric ICL becomes available, it’s currently under FDA review, the best pearl for new surgeons is to limit preop cylinder to 1 D or less, or to use LRIs.”

When selecting a lens, the white-to-white measurement is key to ensuring the correct vault of the ICL over the crystalline lens.

“It appears that calipers, ultrasound and the Orbscan yield similar results,” says Dr. Bylsma. “If the surgeon uses calipers, it’s important to calibrate them against a metal ruler to ensure they’re accurate. There was an international ICL site where a surgeon was getting the wrong size lenses. When a site visit was done to investigate, it was revealed that his calipers were off by 0.5 mm.” Surgeons will have to get used to routinely doing the anterior chamber depth, as well. Axial length and K readings factor in, too.

“Anterior chamber depth may be measured with an IOLMaster, standard ultrasound, or an Orbscan,” says Dr. Bylsma. “Standard ultrasound and IOLMaster users must remember to subtract corneal thickness (pachymetry), whereas measurements with high-speed ultrasound or the Orbscan give direct endothelium-to-anterior capsule distance.

Preop patient care, all the way up to draping the patient, is identical to clear corneal cataract surgery, notes Dr. Bylsma. “The one difference is that some doctors use Voltaren starting three days preop to help prevent constriction of the pupil intraoperatively.” Along these lines, the eye has to be sufficiently dilated preop.

Peripheral iridectomy. “Probably one of the biggest pearls I can provide surgeons is to make the preoperative peripheral YAG iridectomies quite large (at least 0.8 mm), and at the 10:30 and 1:30 positions,” says Dr. Bylsma. “Retroillumination isn’t sufficient to determine patency. The PIs need to be visualized as patent to the posterior chamber to be considered patent.” It’s recommended the PIs be made a week preop. “Of all the things that are most likely to cause problems postop, it’s the inadequate PI, which will lead to pupillary block,” Dr. Bylsma says. While he has used surgical PIs rather than laser PIs, he feels that surgical iridectomies add another layer of complexity to a new procedure that already has it’s own nuances.

Lens insertion. Loading the ICL injector before insertion is “half the battle,” says Dr. Slade. “If you have a good loading, you’re pretty much home free. It’s important to make sure the lens is lined up before you start pushing it through. Make sure it’s not folded. Instill a mixture of BSS and viscoelastic so it’s loose but lubricated in the cartridge.”

The lens is inserted through a temporal, clear-corneal incision. This, in itself, will be a change for some surgeons. “If a surgeon isn’t currently using temporal, clear-corneal incisions, he should begin transitioning to these with his regular cataract procedures,” advises Dr. Bylsma. “If people are doing superior scleral tunnel, they should move temporal and do scleral tunnel there. Don’t immediately go to a temporal, clear corneal ICL technique, because that’s changing too many things at once for those unfamiliar with the temporal position.” Some of Dr. Bylsma’s considerations when making the transition include:

In the temporal position, you must use a wrist rest, because there’s nowhere to stabilize the hands compared to operating superiorly, where a doctor can use the patient’s forehead.

Do your knees fit under the table? Your legs can go on the side of the table when operating at 12 o’clock, but when a surgeon operates temporally, depending on the type of OR table and how tall the surgeon is, sometimes the knees don’t fit.

Most ICL surgeons use topical anesthesia, “but if you don’t use it normally, and want to use it with the ICL, you don’t want your first topical case to also be your first ICL,” says Dr. Bylsma. “So, you need to convert to doing cataract surgery with topical with unpreserved 1% intracameral lidocaine a couple of months before you’ll be comfortable doing it with the ICL.” Dr. Bylsma, however, prefers a peribulbar block because it ensures the eye won’t move.

The temporal ICL incision is about 3- to 3.2-mm wide, and there are also two paracenteses, one at 12 o’clock and one at 9 o’clock. The surgeon then injects viscoelastic to help form the chamber. Surgeons should avoid cohesive viscoelastics, though, because the ICL won’t open into them.

When injecting the ICL, it’s important to do so in a slow, controlled fashion. “One helpful pearl is that, when the ICL starts to come out of the injector and it enters the anterior chamber, drop your wrist toward the floor,” says Dr. Bylsma. “This raises the front end of the injector in the eye and allows the ICL to unfold more easily.” He adds that, if the lens is injected upside down, it’s critical not to try to flip it in the eye, because this can damage endothelium and/or the anterior capsule. It must be removed and re-inserted.
Once the ICL is in the anterior chamber, surgeons recommend putting a little viscoelastic above it to act as a cushion for the endothelium. After that, Dr. Bylsma prefers to put the distal haptics into the posterior chamber first. This way, he explains, if something happens and the surgery needs to be aborted, it’s a simple matter of grabbing the proximal haptics to pull out the lens. ICL surgeons must also make a habit of never crossing the visual axis or the pupil with an instrument, avoiding anterior-capsule touch.

Iris prolapse rarely occurs in ICL surgery, but if it does, Dr. Bylsma says it must be managed precisely, because refractive patients won’t tolerate a transillumination defect of the peripheral iris. “It’s important for all surgeons to review how to manage iris-to-the-wound intraoperatively,” he says. If the iris prolapses through the incision, the anterior chamber needs to be decompressed through the paracentesis. “The reason the iris prolapses is that the intraocular pressure is higher than atmospheric, so the iris is moving,” he explains. “If we try to reposit the iris first, it will only lead to pigment dispersion and a transillumination defect. The maneuver to remember is to decompress the anterior chamber through the paracentesis before doing anything else. This eliminates the high IOP and will allow the iris to be reposited with viscoelastic.”

Closing the case. Once the haptics are placed, it’s time to evacuate visco. Dr. Slade prefers to irrigate it out with a cannula inserted in the primary incision.
Dr. Bylsma advises that, if you use I/A, it’s important not to bounce on the ICL as is done with IOLs in cataract surgery in order to evacuate viscoelastic behind the IOL, “but you want to get as much viscoelastic from under the ICL as possible,” he says. Once the viscoelastic has been evacuated, the clinical trial protocol involves constricting the pupil with Miochol. The case is then finished.

“The beauty of the ICL is that even patients with very high amounts of myopia do wonderfully,” says Dr. Bylsma. “Just as with LASIK, the first postop day is a thrill for both patient and surgeon.” 

 

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