Intacs placement in contact lens-intolerant keratoconus patients now at 2-year follow-up

The procedure improves the shape of the cornea, potentially delaying or even eliminating the need for corneal transplants.

CANNES, France — Positive results obtained on an increasing number of cases indicate that Intacs micro-thin prescription inserts may be an effective method for treating keratoconus patients with contact lens intolerance, according to a report on 2-year results with this technique.

“In almost all patients, spherical equivalent error and refractive astigmatism were significantly reduced, topographies appeared more regular and uncorrected visual acuity (UCVA) improved,” said Joseph Colin, MD, speaking at the winter meeting of the European Society of Cataract and Refractive Surgery here.

“There are reasons to be confident that these patients will not need corneal transplantation for a long time, and might even avoid it altogether.”

Penetrating keratoplasty (PK) has a good rate of success regarding visual acuity but should always be delayed as long as possible, especially in young patients, Prof. Colin said. When the cornea has become opaque and irregular astigmatism has become severe, there is no option other than keratoplasty. However, patients with clear cornea but who are contact lens-intolerant should always be offered some form of alternative treatment.

The photorefractive option, which has been experimented by a number of surgeons, is not a technique favored by Prof. Colin.

“It seems unreasonable to treat an already weak and thin cornea by making it even weaker and thinner. It seems far more logical to reinforce the cornea, as we do with Intacs,” he said.

The procedure

Eye Analyser system photos of a keratoconic eye before placement of Intacs micro-thin prescription inserts (above). The same eye after placement of Intacs inserts; the thicker insert has been placed inferiorly and the thinner insert superiorly (below).

Prof. Colin’s method for Intacs placement consists of the insertion of two segments of different thickness into the corneal periphery to reduce surface irregularities and decrease the asymmetrical astigmatism induced by keratoconus. An internal segment lifts the cone and a superior segment stretches and flattens the center of the cornea.

“The procedure is minimally invasive, reversible and also allows for refractive adjustments. In case of under-correction or overcorrection, or when unexpected corneal shape changes occur, the segments can be removed and/or exchanged with segments of different thickness,” Prof. Colin said.

His results referred to 23 eyes. All patients were affected by keratoconus with clear central cornea and were intolerant to contact lenses. Mean age was 30.9± 6.1 years. Best corrected visual acuity (BCVA) was 20/100 or better in all cases and corneal thickness was 400 µm or more at the location where Intacs inserts were to be placed. Pre- and postoperative evaluation included slit lamp examination, refraction measurement, UCVA, BCVA and videokeratography. Central and peripheral corneal thickness was measured using ultrasonic pachymetry.

Patients were operated under topical anesthesia. A small corneal incision (~1.8 mm in length) was made temporally. Two intrastromal tunnels (clockwise and counterclockwise) were created. Special care was taken when making the inferior tunnel, where the cornea is thinner. A 0.45-mm Intacs insert was placed inferiorly to lift the conus and a 0.35-mm Intacs was placed superiorly, to flatten the cornea back to its natural prolate shape. The incision was then closed with one 11-0 nylon suture, which was removed 1 to 4 weeks postoperatively.

Follow-up examinations were carried out at 1 month, 3 and 6 months, and at years 1 and 2.

“At present, most patients have achieved 6 months of follow-up, and nearly 50% have been carrying the implants for at least a year,” Prof. Colin said.

Results

Mean pre- and postoperative UCVA are shown in figure 1. “Mean preoperative UCVA was approximately 20/400. Postoperatively, at all time points, it improved significantly over baseline (P<0.05),” Prof. Colin said. As shown in figure 2, “average preoperative BCVA approximated 20/50. Postoperative values improved progressively in time, and at months 6, 12 and 24 mean values were about two lines better than baseline.”

Average spherical equivalent error, sphere and cylinder values decreased over time. Mean values for all three parameters were significantly improved over baseline at postoperative month 12. Average postoperative mean keratometry was reduced by approximately 3 D and mean keratometric astigmatism decreased steadily.

“Preliminary results are encouraging, but unanswered questions still remain,” said Prof. Colin.

“Future studies should aim at determining the best candidates for Intacs placement and to refine some aspects of the technique. We need to find a more reliable method of sizing the Intacs and also find the best combination of thicknesses for treating the various keratoconic deformations. We must also determine whether two inserts are always needed,” he said.

“Long term studies will also evaluate the effects of the implants on the natural progression of the disease. At the moment, we cannot say whether Intacs inhibit or accelerate progression or have no effect at all. Finally, we must evaluate if Intacs placement may affect the clinical outcome of penetrating keratoplasty,” Prof. Colin said.

For Your Information:

• Joseph Colin, MD, can be reached at Bordeaux University Hospital, Hopital Pellegrin, Place Amèlie Raba-Lèon, 33000 Bordeaux, France; (33) 55 6795608; fax: (33) 55 6795909. Dr. Colin 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 about Intacs, contact KeraVision at 48360 Milmont Dr., Fremont, CA 94538; (510) 353-3000; fax: (510) 353-3030.