By Roibeard O'hEineachain

BRUSSELS-A new toric iris-claw phakic IOL (Toric Artisan Phakic™) has yielded good early results in the treatment of astigmatic ametropia according to the results of studies conducted in Spain, Belgium and Germany which were presented here at the xviii Congress of the ESCRS.

In one study involving eight eyes of five patients receiving the new phakic IOL, all eyes gained at least five lines of un-corrected visual acuity, all but one gained lines of BCVA and none lost any lines. Furthermore, astigmatic correction remained stable throughout six months follow-up and there was no evidence of progressive endothelial cell loss, said Burkhard Dick, MD, Department of Ophthalmology, Johannes Gutenberg-University, Mainz, Germany.

"The implantation of the toric Artisan phakic IOL is a promising new option in refractive implant surgery which guarantees a precise prediction of the post-operative refractive result and stable fixation of the implant without the danger of rotation over time."

The patients in the study ranged in age from 30-49 years of age and all had high ametropia with corneal astigmatism. Three of the eyes receiving the implants had hyperopic astigmatism with a mean spherical equivalent of 3.2 D (range 2-4D), and five eyes had myopic astigmatism with a mean spherical equivalent of 4.3 D (range -3 to -5D). All underwent uncomplicated implantation of the toric phakic IOL through a short scleral tunnel incision.

After a mean follow-up of six months, three eyes gained 5-10 lines of UCVA, four gained 11-15 lines, and one eye gained more than 15 lines. As regards, BCVA, two eyes remained unchanged, four gained one line, one gained two lines, and one eye gained more than two lines. In addition, all eyes were within one dioptre of intended correction, six were within half a dioptre, and five were within 0.25 D, Dr Dick noted, adding:

"The efficacy index, which is the ratio of the post-operative UCVA to the pre-operative BCVA, was 0.88, and that is better than I have ever seen with any other refractive procedure."

No Progressive Cell Loss
Furthermore, in four eyes that had reached six months of follow-up, fixation of the lens remained stable.

Moreover, there were no intra-operative or post-operative complications, and examination of the corneal endothelium by specular microscopy showed no signs of progressive cell loss, he pointed out.

The new IOL is similar in design to the conventional non-toric iris-claw Artisan lens. It has an optic diameter of 5.0 mm and an overall diameter of 8.5 mm. It has a spherical anterior surface and a toric posterior surface. It can correct myopia from -3 to -20 D and hyperopia from +2 to +12 D. It can also correct 2-7 D of astigmatism and since March 2000 has been available in half dioptre steps.

The IOLs come in two designs; model A, which has its cylinder axis at zero degrees and is used to correct against the rule astigmatism, and model B which has its cylinder axis at 90 degrees and is used to correct with-the-rule astigmatism.

"Due to the small number of eyes and short follow-up we can draw no final conclusion from this study. However our early results suggest that the Artisan™ toric IOL is a safe and efficacious new option for astigmatic eyes. The visual outcome with the new lens appears to be highly predictable in terms of both spherical equivalent and astigmatic correction. Long-term outcome and stability remains to be investigated," Dr. Dick added.

His co-author was Oliver Schwenn, MD, also at Johannes Gutenberg-University. Neither author has any financial interest in the IOL.

Preliminary results from a Spanish study supported the findings of the German investigators.

In seven eyes of seven patients with ametropic astigmatism implanted with the lenses, six eyes were within 1.0 D of emmetropia at six months follow-up and all had an uncorrected visual acuity of 20/25 or better. In addition, no eyes lost any lines of best corrected visual acuity, said Josep Guell, MD, Institute of Ocular Microsurgery (IMO), Autonomous University, Barcelona, Spain.

The patients in the study had a mean pre-operative spherical equivalent of -5.25 D (range +2.25 D to -10.8 D). Their pre-operative mean best corrected visual acuity was 20/40 (range 20/50-20/20) and their cylinder ranged from 2.25 - 6.5 D. All underwent implantation of the toric phakic IOL through a posterior corneal incision.

"The rationale to use the Artisan toric in astigmatic eyes is to take advantage of the fixation system of this IOL and personally I think that without any doubt this is the best toric lens to use because you are sure it will stay in the same place over time and has a clear advantage over angle or sulcus-fixated IOLs because of their tendency to rotate."

Dr. Guell noted that one of the eyes needed a surgical position adjustment because of a 25-degree mis-alignment of the IOL. However, there have been no other clinical complication so far, he said, concluding:

"These are preliminary results but they are extremely encouraging. With this lens, surgical technique is the single most important factor because you need to position the lens in the perfect place. Longer follow-up is necessary to fully assess its safety, and efficacy, particularly with regard to cylindrical stability and endothelial cell count."

Dr. Guell's co-authors were Camille Budo, MD, Sint Truiden, Belgium and Jorg Krumeich, MD, Marien Hospital, Bochum, Germany.