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Intacs for keratoconus show safety, stability in the long term
Vision improved in more than 70% of patients, and the segments may have a role in stabilizing the progression of ectasia.
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ROME – Long-term evaluation of the efficacy of Addition Technologies’ Intacs intrastromal corneal ring segments as a treatment for keratoconus showed that most patients have had an improvement in their vision, and the results appear to be stable over time.
These results were presented by Joseph Colin, MD, at the Winter Refractive Meeting of the European Society of Cataract and Refractive Surgeons.
Dr. Colin’s study included 100 consecutive eyes of 82 patients with keratoconus and intolerance to contact lenses who had been referred to Bordeaux University Hospital in France for penetrating keratoplasty.
“Intacs implantation is a less invasive approach to keratoconus, which is worth trying when the cornea is still transparent,” he said. “The inserts reshape the keratoconic cornea by lifting the inferior ectasia and flattening the tissue, thus decreasing the asymmetric astigmatism. The central cornea remains untouched, and no tissue is removed. The procedure is perfectly reversible, and the Intacs can be explanted or exchanged without any problems.”
An easy procedure
In all patients, surgery was performed without any intraoperative complications, Prof. Colin said. Two segments were inserted in the cornea through a temporal incision into two manually created symmetrical channels, one superior and one inferior. The tunnels were placed at approximately two-thirds of the corneal depth. Initially, segments of different thickness were used superiorly and inferiorly in an attempt to better compensate for the irregularity of the corneas.
“The implantation procedure is fairly easy,” Prof. Colin said. “Later developments have proposed the use of femtosecond laser to perform the cannels. Although this makes dissection easier and faster, the implantation of the segments is more cumbersome, because the laser creates some bridges of tissue inside the tunnel and you have to push harder than in a manual procedure. The use of laser makes the procedure more expensive too.”
Although PMMA is not ideally suited to the metabolism of the cornea, it seems to be well tolerated after implantation, he said. White deposits are often visible along the segments, but they do not seem to produce any adverse effect, he said.
For keratoconus, the Intacs segments are placed superiorly and inferiorly in the cornea Images: Colin J | The segments are implanted at two-thirds of stromal depth. |
Encouraging results
In two eyes, the Intacs were removed after 5 and 8 months because of the extrusion of one segment at the incision site, Prof. Colin said. Fourteen eyes were lost to follow-up between the 1-year and the 2-year exams because of the long distance between the hospital and the patients’ homes. In two eyes the segments were removed due to poor visual outcome, and penetrating keratoplasty was performed.
“It is important to inform the patients that the treatment might fail in a small percentage of cases. However, they shouldn’t be discouraged from trying since the procedure is minimally invasive and easily reversible, ” he said.
In the remaining 82 eyes, results at 1 and 2 years showed a statistically significant improvement of refraction. Mean cylinder was reduced by about 1 D, and the effect of the treatment progressively continued between 1 and 2 years. The manifest refraction spherical equivalent (MRSE) improved by more than 1 D in 70% of the cases.
Almost 70% of the eyes gained one or more lines of uncorrected and best corrected visual acuity, but in some cases (5% to 12%) there was a loss of one line or more of acuity.
Post-LASIK ectasia
Another possible application of the Intacs is in the treatment of post-LASIK ectasia, “a complication that we see more and more often,” he said.
In most cases, this complication occurs when risk factors have not been properly considered before surgery, he said. He cited the example of one patient referred to Bordeaux Hospital for low vision in one eye after LASIK surgery. The preoperative topography of this patient showed features of the cornea that could have predicted the development of the ectasia, he said.
“This patient had been operated twice with LASIK in another country. The second time the LASIK enhancement addressed what was thought to be a decentration but was most probably a keratectasia,” Prof. Colin explained.
One inferior segment was implanted in this patient by creating the channel under the LASIK flap.
“There’s no problem in doing this. The LASIK flap is usually 100 µm, and the channel is performed at a depth of 300 µm to 400 µm, so there is no risk of dislocating the flap,” he said.
In this patient, Prof. Colin said, “We succeeded in improving dramatically the shape of the cornea. We couldn’t give the patient perfect vision, but at least vision that was almost normal, with a considerable decrease of spherical equivalent compared to post-LASIK results.”
For Your Information:
- Joseph Colin, MD, can be reached at Hôpital Pellegrin, Place Amélie Raba-Lèon, 33076 Bordeaux, France; 33-5-56-79-56-08; fax: 33-5-56-79-59-09.
- Michela Cimberle is an OSN Correspondent based in Asolo, Italy.