By Roibeard O'hEineachain

BRUSSELS-The Artisan™ phakic IOL (Ophtec) is effective and well tolerated in the eye over the long and short term in highly myopic eyes and can achieve uncorrected vision to better than pre-operative corrected values. In addition, it shows no loss of contrast sensitivity or significant endothelial loss with time, according to studies carried out in Portugal and the United States.

The Portuguese study showed that in 146 eyes implanted with artisan phakic IOL for myopia ranging from -6.75 D to -28 D and which were followed for up to three years, 66% were within half-a-dioptre of emmetropia, 78% were within one dioptre, and 95% were within two dioptres. The remaining five percent who were more than 2.0 D outside of emmetropia, were patients with a pre-operative myopia above -25 D, said Fernando Vaz, MD, Hospital Santo Antonio, Porto, Portugal.

Post-op UCVA Better Than Pre-op BCVA
Furthermore, in 45% of eyes post-operative un-corrected visual acuity was better than pre-operative BCVA and 80% gained lines of BCVA while one patient lost one line. The overall efficacy index of the lens, comparing pre-operative UCVA to post-operative BCVA, was 113%. In addition, there were no cases of significant endothelial cell loss and flare results were within normal limits, Dr. Vaz said, adding:

"We found that that the Artisan is very accurate for myopia up to -22D. Overall, we have almost 80% of patients within a dioptre of emmetropia and we have important gains of BCVA with an efficacy index higher than 100% with no damage to the corneal endothelium and with an IOL that is not size -dependent."

Dr. Vaz and his associates implanted two different designs of the ArtisanTM Phakic IOLs in two separate groups of patients. In 114 eyes with myopia ranging from -6.75 to -16 D they implanted the 5 mm-optic version of the lens. In 32 with myopia ranging from -8 D to -28 D they implanted the 6 mm-optic version. The patients in the study all had anterior chamber depth above 2.60 mm, anterior chamber angle greater than 30 degrees, and endothelial cell count greater than 2200 cells/mm2.

Complications included two cases of traumatic hyphaema, two cases of traumatic dis-enclavation due to weak grasp, five cases of mild de-centration and four cases of sub-clinical inflammation. Dr. Vaz noted that the increase of flare that occurs with surgery returns to normal in almost all cases.

However, three eyes had chronic sub-clinical inflammation (flare 12-80 photons per millisecond) which persisted for three months.

"We don't know why this happened. It was probably because of pigment deposition on the IOL but all these cases were cases with incorrect grasp so it might have resulted from surgical error. That underlines the learning curve required in the use of this lens. In order to prevent weak grasp we think it's important to use the needle technique. In the two cases of traumatic dis-enclavation we were able to re-position the lens under topical anaesthesia through a clear corneal incision."

Dr. Vaz noted that patients with the 6.0mm-optic implant had significantly less glare and better quality of vision when compared with the 5.0mm-optic implant. There was no statistical difference between the lenses regarding the contrast sensitivity although results were generally better with the 6mm lens than with the 5mm lens, he said. Furthermore, there was no important loss of corneal endothelial cells with either lens between four months and 12 months, and digital Scheimpflug photography showed that eyes with the two lens-types had almost identical anterior chamber depths.

The US study-presented by David Hardten, MD, Minnesota Eye Laser and Surgery Center, Minneapolis, Minnesota, supported the Portuguese findings and confirmed that the implantation of the iris claw lens in highly myopic patients has little detrimental effect on contrast sensitivity.

Dr. Hardten said that in 41 eyes with a mean pre-operative spherical equivalent of -14.07 (range -8 to -20), the mean post-operative spherical equivalent was -0.80 D at 12 months. Furthermore, 96% of eyes achieved a UCVA of 20/40 or better, and around half gained one or more lines of BCVA. One eye lost a line of BCVA.

Contrast Sensitivity Improves in Some Cases
Furthermore, extensive testing indicated that there was no significant difference between pre- and post-operative contrast sensitivity with and without glare among all patients with 4-6 month's follow-up.

"We measured contrast sensitivity pre-operatively and at the 4-6 months post-operative visit using the Vistech VCTS test under both photopic conditions (25 Foot Lamberts) as well as mesopic Conditions (0.8 Foot Lamberts). We also used a glare source, which for the photopic glare was the medium BAT setting and for the mesopic glare was a 5 ft. candle, and we used side glare setting from two different sides. We looked at five different test spatial frequencies ranging from 1.5 cycles/degree to 18 cycles/degree to look at the various different aspects of the contrast sensitivity.

"For the most part contrast sensitivity is unchanged but there is some statistically significant loss of contrast sensitivity at some of the higher level frequencies, particularly the photopic frequency of 18 cycles /degree as well as photopic with glare. Yet, you see the opposite when you look at patients with their spectacle correction in place for that small residual, (about 0.75 D), of post-operative myopia. In fact, there is actually a statistically significant increase in contrast sensitivity in the photopic with glare situation at the lower frequencies.

"The study clearly shows that at most frequencies at which we tested this phakic IOL there was no change in contrast sensitivity. There is some loss of contrast at higher spatial frequencies without spectacle correction, which we would expect anyway in eyes with residual myopia. With spectacle correction there was some gain in contrast in photopic with glare situations, and overall the phakic IOLs provided excellent visual outcomes," Dr. Hardten concluded.