INTRACORNEAL RING SEGMENTS

Implantation of intracorneal ring segments (ICS) using channels created with a femtosecond laser can provide keratoconus patients with improvements in uncorrected and best-corrected visual acuity, and could delay or avoid keratoplasty, according to Beatrice Cochener MD, PHD, CHU Brest, France.

“The femtosecond laser has become an essential tool for intracorneal ring segment implantation, offering perfect customisation of channels for placement of any model of ring segment on one single platform providing perfect control of total size and depth with better safety,” she said at Femto 2013, an international meeting on anterior segment surgery.

Prof Cochener presented the results she and her associates achieved in 94 eyes implanted with INTACS or INTACS SK (Addition Technology) and 194 eyes implanted with Kerarings (Mediphacos) using femtosecond laser-created channels.

Among 54 patients who received the INTACS of the original design for ectasia and for myopia with a risk for ectasia, uncorrected visual acuity and best corrected visual acuity improved in 57 per cent. In addition, aberrometry showed a significant reduction in higher order aberrations.

There were complications in four per cent of eyes, which included one case of infection (to an atopic patient with MGD) and two case of extrusion (induced by too superficial channel). In addition, there was loss of two lines in nine per cent of eyes.

INTACS SK a step forward
Results were somewhat better among 40 eyes which underwent implantation of the newer INTACS SK implants. Some 48 per cent were 20/40 or better and 72 per cent gained one or two lines of vision. A majority, 79 per cent, had improvements in both UCVA and BCVA.

She noted that the INTACS SK are different from the original INTACS design in a few essential ways. The newer model has a 6.0mm inner diameter to provide a better flattening of the central cornea than that achieved with the 6.8mm inner diameter of the older design.

In addition, the INTACS SK has an ellipse-shaped rather than hexagonal cross-section to further enhance central corneal effects and reduce haloes. The INTACS SK ring segments range in thickness from 0.21mm to 0.45mm. At present they are only available with 150-degree arcs. However, Addition Technologies have announced that they are planning to launch INTACS with arc lengths ranging from 90 degrees to 230 degrees.

Kerarings with femto            
The Kerarings are already available in several different arc lengths, ranging at present from 90 degrees to 210 degrees. They are triangular in cross- section and have an inner diameter of 5.0 and more recently 6.0mm and range in thickness from 0.15mm to 0.35mm.

In 47 eyes that were implanted with the 5.0mm Keraring with femtosecond laser-created channels, mean visual acuity improved from 0.05 to 0.4 and best corrected visual acuity improved from 0.54 to 0.71. In addition, keratometry was reduced by 2.24 D and higher order aberrations decreased by mean of 62 per cent. The results achieved with the 6.0mm model in 147 eyes were statically identical with the benefit of a better quality of vision thanks to a larger optical zone, although Prof Cochener said that it has become her first choice among the Kerarings.