Advantageous Phakic IOLS

Dermot McGrath reports

Posterior chamber phakic IOLs offer surgeons a safe and effective option for treating moderate to high myopia and present a viable alternative in patients where surface ablation procedures are contraindicated, according to Professor Thomas Kohnen.

“When I look at my myopic cases, I probably do two-thirds on the cornea and one-third on the lens,” he explained. “I think phakic IOLs are an underestimated procedure that offers a lot of advantages. For a start, it is the only reversible procedure, and also one where we don’t experience any prob­lems with postoperative power calculations for intraocular lenses because we are not changing the cornea.”

In a broad overview of the available phakic IOL options, Prof Kohnen said he has personally implanted more than 2,500 phakic lenses, including all three principal types: angle-supported anterior chamber lenses, iris-fixated, and sulcus-fixated IOLs.

Despite good early results, angle-supported PIOLs have not lived up to their initial promise, with the Cachet lens (Alcon) withdrawn from the market due to concerns about abnormally high endothelial cell loss, Prof Kohnen explained.

“The 10-year follow up study of more than 1,123 implanted eyes in 7 countries reported a 10% explantation rate, most because of endothelial cell loss over time in patients with a shallow anterior chamber,” he said. “I have witnessed some patients who have experienced no cell loss at all after 15 years, but all patients need to be monitored closely.”

Likewise, iris-fixated IOLs (Artisan IOL, Ophtec) have en­countered problems of long-term endothelial cell loss, despite good visual and refractive outcomes.

“A study by Rudy Nuijts’ group looked at 5- and 10-year data for the Artisan phakic lens and found a high level of endothelial cell loss over the follow-up period. So again, these anterior chamber lenses need to be monitored, as we can see problems after 10 years or even later,” he explained. “We conducted a smaller study of the same lens in high myopes and found that the endothelial cell loss was higher in patients with an anterior chamber depth (ACD) below 3.0 mm than in lenses with ACD greater than 3.4 mm.”

Prof Kohnen said his preference is to use a posterior chamber lens, either the Visian implantable collamer lens (ICL V4c, Staar Surgical) or the implantable phakic contact lens (IPCL, Care Group), for those patients outside the diop­tric range of the ICL.

“The implantation is a little bit more difficult than an anterior chamber PIOL but still only takes about four to five minutes,” he noted. “I would estimate between 50% to 75% of the ICLs I implant now are toric models so I can correct up to 0.5 D of astigmatism at the same time. There is also a cosmetic benefit to patients in that the lens is completely invisible in the eye.”

Looking at the evidence in the scientific literature, Prof Kohnen said that the lens has solid safety and efficacy data out to 10 years.

“We are currently in the process of publishing our own five-year results in 45 eyes which showed good predictabil­ity and stability over time, with a high index for safety and efficacy,” he concluded. “We found no significant change in endothelial cell count. I think it’s currently our best option for a phakic IOL.”

Prof Kohnen gave this presentation at the 27th ESCRS Winter Meeting in Vilamoura, Portugal.

Thomas Kohnen MD, PhD, FEBO is professor and chairman, Department of Oph­thalmology, Goethe University, Frankfurt, Germany. kohnen@em.uni-frankfurt.de