Prepare to answer patients’ questions about Intacs

May 1999

Now that Intacs from KeraVision have received Food and Drug Administration (FDA) approval, we are again reminded that it is important for the optometrist to be involved in new technology and feel comfortable with answering questions related to it. Prospective refractive surgery patients are perhaps the most informed and technologically savvy consumers you may encounter. Most patients research their decisions extensively prior to choosing a procedure and a provider.

Your participation in this process can be an important part of their successful outcome. It is very likely that your office will receive questions regarding new technology. If you and your staff can communicate the latest advances with knowledge and confidence, you will be at the forefront of optometry. Keeping up with new technology will allow your practice to stay there.

What are Intacs?

KeraVision Intacs are implantable, plastic arches almost the size of a baby’s fingernail. They are implanted within the corneal stroma near the periphery of the cornea for correcting low myopia.

• 1.00 to 3.50 D of myopia [1]
• less than 1 D of cylinder
• less than or equal to 0.50 D change in refraction within past year
• K’s between 40 and 46 D
• pupils less than 7 mm in dim illumination
• no ocular disease

They are made of PMMA, a material that has been used for nearly 50 years for contact lenses and IOLs after cataract surgery. Intacs are designed for permanent placement in the eye, but they may be removed or exchanged if necessary.

The KeraVision Intacs are currently approved for the correction of up to 3.50 D of myopia. Ideal candidates are those with less than 3.00 D. In terms of success, no other procedure to date has completed FDA studies with a greater percentage of patients better than 20/20. At Hunkeler Eye Centers in Kansas City, Mo., data from Daniel S. Durrie, MD, show that 75.6% of the patients were 20/20 or better and 53% were 20/16 or better. Intacs appeared to have the quickest visual recovery of any procedure to date.

--Fast recovery: Intacs have a faster visual recovery, with more patients achieving 20/25 and 20/20 or better visual acuity sooner than PRK or LASIK.

In the accompanying bar graph, we compare patients with this same refractive error (–1 to –4 D) for photorefractive keratectomy (PRK), laser in situ keratomileusis (LASIK) and Intacs. We see that Intacs have a faster visual recovery, with more patients achieving 20/25 and 20/20 or better visual acuity sooner than PRK or LASIK.

Implanting Intacs

---Reversible procedure: The topographic maps at the top show that the surgical treatment does not reverse the natural positive corneal asphericity. The maps on the bottom show the cornea preoperatively and 3 months after removal, indicating that the corneal topography returned to its original state.

The procedure takes about 5 to 15 minutes to perform and begins with a small (1.8 mm) incision at the 12 o’clock position outside the central optical zone. Like LASIK, the eye is held in place with a suction ring. A specially designed blunt instrument is used to separate the layers of the stroma, creating a semi-circular tunnel within the corneal stroma. First one segment is rotated into position, then the other. Once the segments are in position, the procedure is performed on the other eye. The Intacs correct myopia by flattening the central corneal curvature.

Patients may describe discomfort when suction is on during the surgical procedure just as in LASIK. Post operatively, some patients describe some burning, foreign body sensation or even photophobia that lasts for about 2 to 4 hours. Because the Intacs are placed at two-thirds depth in the corneal stroma, patients usually cannot feel the Intacs in the eye unless they rub the eye vigorously. Although some patients may initially notice a foreign body sensation after the procedure, they should be instructed that this is part of the healing process.

Because patients are usually unaware of their refractive error, to help determine if they are good candidates for refractive surgery it may be simplest to ask if they can see the big E on the eye chart (even if it is a little blurry). If they can, they are probably good can didates, although an eye examination will be necessary to verify that they are. In general, contraindications that apply to LASIK (ocular surface disease, keratoconus, herpes simplex virus keratitis, rheumatoid arthritis, etc.) are relative contraindications and also apply to Intacs. The best outcomes are with patients whose keratometry readings are between 40 and 46 D.

The procedure does not treat astigmatism, although studies show that in some patients, it may decrease astigmatism by about 0.50 D. Candidates should have less than 1 D of astigmatism.

Advantages, disadvantages

---Correcting low myopia: Intacs are implanted within the corneal stroma near the periphery of the cornea.

The fact that the procedure does not correct astigmatism or high levels of myopia is a disadvantage, although more than 50% of all myopes fit in the range for the KeraVision procedure. Furthermore, it is relatively new technology with only about 2,000 procedures performed worldwide. As an advantage, the surgical treatment is performed in the peripheral cornea, not the central visual axis. In addition, as shown in the accompanying topography, it does not reverse the natural positive corneal asphericity. Another advantage is that Intacs are removable or exchangeable. The second topography shows the cornea after removal. Refractive error returns to the original, as does the corneal topography.

With respect to time, this procedure will be as rapid to perform as current laser procedures. Patients experience rapid visual recovery and, therefore, little disturbance of their normal daily routines. Postoperative examinations will be required, similar to the schedule of appointments required after LASIK. With respect to cost, the Intacs are a completely different product. While the cost is likely to be in line with PRK and LASIK, you can expect to see more creativity in pricing and packaging.

For Your Information:

• Michael Twa, OD, director of patient care and clinical research for keratorefractive surgery at the University of California – San Diego Shiley Eye Center, can be contacted 9415 Campus Point Dr., La Jolla, CA 92093-0946; (619) 822-1805; fax: (619) 822-1514; e-mail: mtwa@ucsd.edu. Dr. Twa has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
• For more information from KeraVision about Intacs, contact Mick Taylor at (510) 353-3000.