NEW HYDROPHILIC MATERIAL

A new hydrophilic acrylic micro-incision IOL is easily implanted though a sub-2.0mm incision and provides good predictable visual outcomes with good centration and possibly better protection against PCO than other hydrophilic acrylic lenses, according to a series of presentations at the XXXI Congress of the ESCRS in Amsterdam.

The new lens, called the InciseR (Bausch + Lomb) is a customised version of the Akreos MI60 IOL and, like the older lens, is a one-piece aberration-neutral aspheric IOL with four angulated haptics. However, unlike the Akreos, it is composed of a new, stiffer material with 22 per cent water content and it has an optic edge that is sharper than that of many hydrophobic IOLs.

“There is some evidence that the poorer posterior edge characteristics of hydrophilic IOLs is to blame for their poorer PCO performance in comparison to hydrophobic IOLs. The Incise IOL is designed to have enhanced PCO prevention performance,” said David Spalton FRCS, FRCP, FRCOphth, St Thomas' Hospital, London, UK.

He noted that environmental scanning electron microscopy imaging of the IOL's profile at the optic edge and optic-haptic junction revealed that the IOL has an extremely sharp high-quality edge profile with a local radius of curvature of 5.0 microns throughout its periphery. “That is a really high-quality edge which would be expected to confer excellent PCO prevention. Clinical studies are required now to confirm this,” Dr Spalton added.

Good preliminary results

In a prospective clinical trial carried out in five European centres, implantation of the lens through a sub-2.0mm incision resulted in very satisfactory visual and refractive outcomes, said Burkhard Dick MD, Ruhr University Eye Hospital Bochum, Germany. Among 70 eyes with four to six months of follow-up in the trial, mean uncorrected visual acuity was 0.13 LogMAR (20/25) and mean corrected distance visual acuity was -0.03 LogMAR (20/20) and 97.1 per cent were 20/25 or better. In addition, mean manifest refraction spherical equivalent was -0.22 D, compared to a target refraction of -0.25 D. Furthermore, 57 per cent were within 0.50 D of target refraction, 90 per cent were within 0.5 D and all were within 1.0 D.

Dr Dick noted that patients in the study underwent either coaxial MICS with a 1.8mm incision or biaxial MICS with a 1.4mm incision and a wound-assisted implantation technique. In an additional investigation of patients in the study, digital slit-lamp biomicrosopy imaging after seven to 15 days postoperatively, after one to two months and four to six months postoperatively showed that centration was predictable and stable, said Gilles Lesieur MD, Albi, France.

The absolute mean decentration was 0.31mm after seven to 15 days and 0.35mm, after one to two months and four to six months. That compares to mean decentrations of 0.2mm to 0.6mm for conventional one-piece and threepiece IOLs, he said.

Another study (carried out at St Eriks Eye Hospital, Stockholm) involving 60 of the 100 patients in the prospective trial examined the size of the incision used for implantation of the IOL with the injector tip inside the eye in coaxial MICS procedures. After insertion of the lens the incision size increased on average by 0.08mm, said Bjorn Johansson MD, PhD, Sweden.