The Toric Visian ICL
The toric Visian is made of Staar's collamer material with an astigmatic correction, and therefore a little extra thickness, built into one axis of the lens. Here is a look at various aspects of the Visian's implantation and performance:
• Patient selection. Steven Schallhorn, MD, who took part in the U.S. toric Visian trial, notes that it's not indicated for all patients with astigmatism. "There are significant risks with a phakic lens that are completely different from those associated with LASIK and PRK," he says. "These risks include corneal decompensation, glaucoma and cataracts." He says a patient with cataract, corneal dystrophy, a history of uveitis or who won't be able to tolerate the more intense, invasive intraocular procedure necessary to implant the lens shouldn't undergo implantation.
• Surgical nuances. "Implanting the toric ICL isn't at all different from implanting the myopic lens," says John Vukich, MD, medical monitor for Staar's U.S. Visian ICL trial. "The only thing that's slightly different is we have to mark the cornea to make sure the lens goes in at the appropriate axis. We mark the cornea at the 3 and 9 o'clock positions so that when the patient goes from a sitting to a lying position he doesn't have rotational issues that would impact the axis of astigmatism." The optic-haptic junction is marked as a reference point for the 3 and 9 o'clock horizontal axis.
 |
| The diamond marks on the optic-haptic junctions of the toric ICL help with alignment. |
Also on the implant's packaging is an adjustment for precise axis location to account for any small axis deviation that can occur when a particular lens is rehydrated after manufacturing.
"So for that specific lens, for that serial number, for that patient to get a perfect end result, the surgeon may be instructed to rotate the lens a few degrees, never more than 10, either clockwise or counterclockwise," explains Dr. Vukich. "We're not talking about huge rotations here, but rather tweaks one way or the other. You just need to be meticulous about where you put the implant, but that's already second nature to cataract surgeons. This is just one more thing to pay attention to."
The lens design has certain elements to help prevent rotation once it's in the eye, as well.
"The toric ICL is fundamentally different from toric IOLs in that it's not subject to contraction of the capsular bag," says Dr. Vukich. "Also, its geometry is such that it's made to custom fit the eye. The soft footplates will conform to the undulations or the normal topography of the contours of the ciliary sulcus. It's not a perfectly smooth, flat shelf that it sits on. The ciliary sulcus has some anatomic features to it, minor elevations and the like. So, in essence you get a kind of lock-and-key situation where the footplates will drape over and into the tiny irregular features of the sulcus. That helps prevent the lens from rotating."
The amount of cylinder that a particular Visian ICL can correct varies based on the amount of myopic correction, with a theoretical maximum of 6 D.
"It can always correct up to 4 D of cylinder," says Dr. Vukich. "However, the cylinder can't exceed the base myopia amount because of manufacturing-related issues."
Surgeons may need to rotate the toric ICL a few degrees for the best axis alignment.
Steven Schallhorn, MD
• Outcomes. In the U.S. trial of the toric Visian ICL, surgeons at five centers implanted 186 lenses in the eyes of 119 patients. The average preoperative spherical equivalent was -9.25 D (range: -2.4 to -19 D). The refractive cylinder ranged from 1 to 4 D, with an average of 1.9 D.
Preoperatively, 85 percent of patients saw 20/20 best-corrected. Postop, though, 84 percent achieved 20/20 or better without correction. Ninety-five percent of patients could see 20/25 best-corrected preop, while 95 percent saw 20/25 or better uncorrected after surgery. Seventy-three percent of all patients gained one or more lines of best-corrected acuity, compared to 4 percent who lost one line. No one lost more than one line of acuity.
Dr. Schallhorn analyzed the residual astigmatism and incidence of lens rotation over the first six months of the study, and found that about half the patients had less than 0.5 D of residual astigmatism. Of the remaining patients, 75 percent had a 15-degree axis shift or less, and "very few patients had greater than a 30-degree shift in their axis," Dr. Schallhorn says. "So there's not a great shift in the manifest axis of cylinder over time."
 |
| Most toric ICLs in eyes with 0.5 D of cylinder or more rotated only 15 degrees or less by the six month follow-up point. Steven Schallhorn, MD |
The overall refraction has remained stable for the one year follow-up period.
• Complications. Dr. Vukich reports that there have been no cataracts in the study, no induced glaucoma and no loss of best-corrected visual acuity. Two of the lenses had to be explanted. "Glare hasn't been an issue, and the glare scores tend to be equal to or better than the preop glare scores," says Dr. Vukich. He says they don't exclude patients based on their pupil size.
As far as approval goes, the next step is, of course, first gaining approval for the myopic Visian ICL. The toric data is currently being prepared for submission to the U.S. Food and Drug Administration, and Dr. Vukich hopes its approval comes soon after that of the myopic lens.
Dr. Vukich thinks that toric phakic lenses will bring about a sweeping change in the way refractive surgeons approach refractive errors. "It's quite analogous to the difference we saw when LASIK went from myopia only to myopia with astigmatism," says Dr. Vukich. "When that occurred, all of a sudden we didn't have to choose certain patients, compromise with final acuities or do astigmatic keratectomies; we weren't using stone knives to supplement computer-driven lasers."
The Artisan Toric
The toric version of the Artisan phakic lens is currently available outside the United States for the correction of astigmatism from 2 D to 7 D. The Artisan is an anterior-chamber phakic lens that is fixated by tucking two small knuckles of iris through two openings on the lens's haptics, one on each side. The toric Artisan has a 5-mm optic that goes through a large incision that's then sutured postoperatively.
Here are the toric Artisan's key features:
• Lens design. Camille Budo, MD, of Sint-Truiden, Belgium, has been implanting the original Artisan lenses for 18 years, and has implanted 150 toric Artisan lenses over the past eight years. He explains that there are two types of Artisan torics, depending on the axis of astigmatism.
"Version A is for the correction of astigmatism that's in the axis of the lens's claws," he explains. "With version B, we have the correction of astigmatism perpendicular to the axis of the claws. So, if you use a superior surgical approach and you have to correct preoperative astigmatism between 0 degrees and 45 degrees, or between 135 degrees and 180 degrees, we recommend model A. If the preop astigmatism is between 45 and 135 degrees, then the model B is recommended."
• Patient selection. Dr. Budo says the anterior chamber depth dictates how much myopia the lens can correct, since thicker lenses are necessary to treat higher degrees of myopia. "The shortest clearance in the eye with the Artisan lens is the distance between the rim of the lens and the corneal endothelium," he says. "The minimum distance you must have between these structures is 1.5 mm. So, for example, if you have a preop sphere of -6 D and astigmatism of -4, I think you could correct this error with the Artisan in almost all cases. However, if it's a -15 D sphere with
-7 D of cylinder, whether you can implant the lens or not depends on the anterior chamber depth."
Dr. Budo says that, to receive an Artisan lens, a patient's anterior chamber must be at least 2.8-mm deep. Other criteria are a normal mesopic pupil, a normal endothelial cell count and a flat iris. Dr. Budo says that the last criterion is important, since it avoids pigment dispersion.
 |
| The toric Artisan. Note the YAG laser iris marks on either side of the lens. Camille Budo, MD |
To ensure the lens is implanted on the correct axis, Dr. Budo prefers to mark the iris preoperatively with an argon or YAG laser with the patient sitting up (to avoid cyclorotation error). He says surgeons can also mark the correct axis on the limbus instead, if they desire.
• Clinical results. In a prospective, multicenter study in which Dr. Budo took part, surgeons implanted toric Artisan lenses in 70 eyes of 53 patients. Their preop spherical equivalent refractions ranged from +6.5 D to -21.25 D, and their cylinder amounts ranged from 1.5 D to 7.25 D. In the myopic group (48 eyes), the average refractive error was -8.9 D. In the hyperopic group (22 eyes), it was +3.25 D.
At six months, no eyes in either group lost any best-corrected vision, and 46 gained one or more lines. Eighty-nine percent of eyes saw 20/40 or better uncorrected. All eyes were within ±1 D of the target refraction, and 73 percent were within ±0.5 D. There was a 4.5 percent average total loss of endothelial cells. There were no other significant complications and the refractive effect remained stable.
Dr. Budo says that, though endothelial cell loss over time appears to be within safe parameters, the two complications that commonly crop up when he discusses the Artisan procedure with other surgeons are spontaneous subluxation of the lens due to an inadequate amount of iris tissue within the enclavation holes in the haptics, and pigment dispersion and synechiae that occur with a convex iris. He says the incidence of each of these is about 5 percent. About 5 to 7 percent of his patients mention glare or halo symptoms, but Dr. Budo says none have been unable to drive at night or work because of the aberrations.
In 95 percent of Dr. Budo's cases, there is less than 1.5 D of induced astigmatism from the large entry incision, which he makes at the limbus and closes with a running suture. In about 5 percent of cases, he has to remove the sutures at five weeks postop because of the astigmatism. He's not had to explant any toric Artisans, but he did have to recenter four of them that were implanted on slightly incorrect axes.
Though the toric 5-mm Artisan is the version currently being used overseas, Dr. Budo predicts that the one U.S. surgeons will eventually get to use will probably be the 6-mm toric Artiflex lens. This is a foldable version of the Artisan that goes through a small 3-mm incision, avoiding any concerns of induced astigmatism.
