Where is best place for a phakic IOL? Anterior or posterior chamber?
Anterior chamber and iris-fixated phakic IOLs have been shown to produce good visual outcomes in ametropic patients. The question of which is safer for the eye was debated at the XXXV Congress of the ESCRS in Lisbon, Portugal.
Rudy MMA Nuijts MD, University Eye Clinic, Maastricht, said that he favours the iris-fixated anterior chamber lenses, the Verisyse/Veriflex (Ophtec), also coined Artisan/Artiflex (AMO) lenses.
He noted that eyes with the lens generally have a rate of endothelial cell loss well within safety limits, and unlike the posterior sulcus-positioned ICL, pose minimal risk of inducing a cataract and have no sizing issues.
In his own cohort of 379 myopic Artisan cases with up to 10 years’ follow-up, there also was annualised endothelial cell loss of only 1.4% (figure 1). That is roughly two-and-a-half times the normal physiological loss of 0.6% per year.
In terms of long-term refractive predictability, 46.2% were within half a dioptre of the attempted correction after five years, and that decreased to 23.1% after 10 years. Similarly, 68.4% were within one dioptre after five years, and that decreased to 47.9% within one dioptre after 10 years.
That translates into a loss of one line in uncorrected distance visual acuity after five years and two lines after 10 years. The myopic change in refraction probably results from nuclear sclerosis in patients’ crystalline lens.
The endothelial cell loss was a little bit higher in a cohort of 293 eyes implanted with the Artiflex lens, reaching 10.5% after five years, amounting to an annualised loss of 1.94%.
On the other hand, in this younger group of patients, postoperative refraction changed by a mean of only 0.14D at five years. In addition, two-thirds were within 0.5D of attempted refraction at five years and 88.7% were within 1.0D. That translates to a loss of only half a line of UDVA.
He noted that out of 1,196 phakic IOL implantations at his centre there were 120 explantations, a rate of roughly 10% (figure 2). Of these, 57% were due to cataract and 28% were due to endothelial cell loss.
He noted that among patients who received the Artisan for myopia, 63% of explantations were due to cataract formation and 28% were due to endothelial cell loss. However, among those who received the lens for hyperopia, explantations were due to endothelial cell loss in 67% and due to cataract in 22%.
Concerning the Visian ICL (Staar), Dr Nuijts noted that the lens has gone through many changes over the years, with an increase in the vault of the lens to prevent anterior subcapsular cataract formation and, most recently with a hole in the centre of the optic and in the haptics to prevent pupillary block and eliminate the need for laser iridotomy.
He noted that in published series of patients implanted with the V4 ICL the incidence of cataract has ranged from 0 to 18.9%. That in turn raises the risk of retinal detachment, particularly among myopic patients.
The ICL also has sizing problems. An oversized ICL can result in pupillary block due to closed iridectomies, and pigment dispersion, Dr Nuijts pointed out.
The traditional way to estimate sulcus size is to measure white-to-white diameter. However, many studies have shown that there is no correlation between the two parameters. Ultrasound echography may provide a better measure of sulcus diameter, he said.
He also pointed out that the rates of endothelial cell loss with the ICL range from 0.1 to 27.4%. In the FDA studies the rate has been about 1.5 to 2.3% per year.
IN FAVOUR OF THE ICL
Taking the opposing view, Roberto Zaldívar MD, Argentina, cited the increasing popularity of the lens as proof of its superiority. He noted that between 2006 and 2015 the use of ICL grew by 17% per year, a trend that still continues. In fact, the ICL now accounts for nine of every 10 phakic IOLs implanted.
“The reason behind the popularity of the lens is that although we have had problems with the lens we have always tried to solve them through improvements in the design,” Dr Zaldívar said.
He noted that the improvements in vaulting and the holes in the in the optic and haptics appear to have reduced the incidence of cataract and pupillary block.
He cited a study by José Alfonso MD, Spain, which showed that in 1,531 eyes implanted with the V4a ICL from 2002 to 2008, the incidence of cataract was 1.35%. However, there were no instances of cataract in 1,108 eyes implanted with the V4b from 2008 to 2011, and 1,957 eyes implanted with the V4C ICL from 2011 to 2017.
He added that in his own series of 186 eyes implanted with the V4c ICL, intraocular pressure has remained stable and endothelial cell counts have remained virtually unchanged throughout three years of follow-up.
Rudy MMA Nuijts: firstname.lastname@example.org
Roberto Zaldívar: email@example.com