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Intrastromal corneal ring segment improves visual acuity, corneal stability at 5 years
J Cataract Refract Surg. 2009;35(10):1768-1773.
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An intrastromal corneal ring segment proved safe, effective and stable in managing keratoconus, a study showed.
The authors reported long-term results of implanting the Ferrara intrastromal corneal ring segment (ICRS, Ferrara Ophthalmics).
"Implantation of Ferrara ICRS resulted in topographic and visual stability, delayed the progression of keratoconus, and eliminated or at least postponed the need for corneal grafting surgery," the study authors said.
The retrospective study included 35 eyes of 28 patients with keratoconus; 21 patients underwent unilateral intrastromal corneal ring segment implantation and seven patients underwent bilateral implantation. Segments ranged from 0.15 mm to 0.35 mm. Indications for intrastromal corneal ring segment implantation were contact lens intolerance, progressive ectasia or both.
Follow-up examinations were performed 5 to 12 years after surgery. Primary outcome measures were uncorrected distance visual acuity, corrected distance visual acuity and keratometry values.
Study data showed that the mean uncorrected distance visual acuity improved from 0.15 before surgery to 0.31 at 5 years after surgery; the improvement was statistically significant (P = .003). Uncorrected distance visual acuity was unchanged in nine eyes. Twenty-two eyes gained one or more lines of uncorrected distance visual acuity. Four eyes lost one or two lines.
Mean corrected distance visual acuity improved from 0.41 before surgery to 0.59 at 5 years after surgery; the difference was statistically significant (P = .002). Corneal topography showed corneal flattening was achieved in all eyes. The mean minimum keratometry value decreased from 48.99 D before surgery to 44.45 D after surgery. The mean maximum keratometry value decreased from 54.07 D preoperatively to 48.09 D postoperatively. Both decreases were statistically significant (P = .000).
"Further studies with larger samples and a longer follow-up are needed to confirm these results," the authors said.
Drs. Torquetti and co-authors describe excellent results with intracorneal ring segments in this manuscript. While the Ferrara rings are not available in the U.S., they are widely used outside the U.S. They are slightly more effective at reducing corneal curvature and astigmatism than the Intacs segments available in the U.S. As in most studies, the long-term results have been stable, and yet many patients will still need contact lens correction or go on to keratoplasty. These authors state that about 5% of their patients still go on to keratoplasty despite having intracorneal ring segments. In our experience, that rate is about 15% overall, but in patients with elevation on topography in the ectatic area of over 100 µm, it approaches 50%. Still, the use of intracorneal ring segments is useful in our management of patients with keratoconus or ectasia and is important in the list of other options such as glasses, contact lenses, collagen cross-linking, and lamellar or penetrating keratoplasty.
– David R. Hardten, MD
OSN
Cornea/External Disease Section Editor