Phakic IOL update
Phakic IOLs remain an option, but problems remain with endothelial cell loss and cataract.
Rudy Nuijts MD,PhD
Iris-fixated and sulcus-fixated phakic intraocular lenses can provide high ametropes with corrections beyond the range of corneal refractive procedures, but eyes with the implants have an accelerated endothelial cell loss and remain prone to changes in refraction as the natural lens ages, according to review on the literature presented by Rudy Nuijts MD,PhD, Maastricht University Eye Clinic, Maastricht, the Netherlands.
The original phakic IOLs were introduced in the early 1990s. They included the iris-fixated Artisan (Ophtec) lens, the sulcus-fixated implantable collamer lens (Visian® ICL, Staar Surgical) and a series of anterior chamber lenses. Over the years all of the angle-supported anterior chamber IOLs have been withdrawn from market because of endothelial cell loss, leaving only the iris-fixated and sulcus options, Dr Nuijts told the 23rd Winter Meeting in Athens, Greece.
Dr Nuijts and associates have followed a cohort of 379 eyes implanted with the Artisan Myopia lens and 293 eyes implanted with the Artiflex Myopia lens at the Maastricht University Eye Clinic from 1998 to 2016. The Artisan/Verisyse IOL, introduced in 1991, has a PMMA optic of 5.0mm or 6.0mm in diameter, depending on the amount of correction required and provides correction for -1.0D to -23.5D of myopia. The Artiflex/Veriflex, introduced in 2004, has PMMA haptics and a polysiloxane optic of 6.0mm in diameter, and is designed to correct -2.0D to -14.5D.
The research shows that at 10 years’ follow-up 95% of eyes had uncorrected visual acuity (UCVA) of 20/40 or better and 46% had a UCVA of 20/20 or better. In addition, 39% gained two or more lines of best-corrected visual acuity (BCVA), but 11.0% lost more than two lines.
In terms of stability, owing to the naturally occurring thickening of the crystalline lens and continued increase in axial length, there was a myopisation of around -0.4D over five years (p <0.01) and -0.82D over 10 years. Correspondingly, in terms of predictability, after five years 68.4% were within 1.0D of target refraction and 46.2% were within 0.5D. At 10 years only 47.9% within 1.0D and 23.1% were within 0.5D.
Furthermore, over 10 years of follow-up, the mean corrected distance visual acuity (CDVA) decreased by +0.06 logMAR, or roughly half a line (p<0.01), and UDVA decreased by +0.16 logMAR, a whole line.
Endothelial cell loss
Dr Nuijts reviewed a prospective, clinical cohort study designed to evaluate the long-term change in endothelial cell density (ECD) in a total of 507 eyes of 289 patients implanted with the Artisan Myopia or Artisan toric phakic IOL.1
The researchers found that from six months to 10 years postoperatively, mean ECD decreased by -16.6% in eyes with the myopic implant and by 21.5% in eyes with the toric implant. That is equivalent to an additional 10.9% decrease in ECD in the myopic group and 15.8% in the toric group, when corrected for physiological loss of 0.6% per year, he noted.
Among eyes with 10 years of follow-up, the proportion requiring explantation because of endothelial cell loss was 1.0% in the myopic group and 3.8%, in the toric group. The total explantation rate among all eyes over the complete follow-up was 6.0% in the myopic group and 4.8% in the toric group. Mean time to explantation was 11.97 years in the myopic group and 7.4 years in the toric IOL group.
Posterior chamber PIOLs
The remaining phakic IOL is the sulcus-fixated Implantable Collamer Lens (ICL). Approved in 1991, the lens is composed of pig collamer and has a 5.8mm optic and overall diameters ranging from 12.1mm to 13.7mm. It is designed to correct up to -18.0D of myopia and up to +10.0D of hyperopia, and -0.5D to -6.0 D of astigmatism.
Dr Nuijts noted that although he has no personal experience with the ICL, studies conducted to date with the latest version of the lens show 68-to-95% achieving visual acuity and 0-7% losing two or more lines of BCVA.
In studies with up to five years’ follow-up, the mean loss in ECD has ranged from 0.5-to-9.5% with V4 ICLs. Research where patients were followed very meticulously suggests that the annualised endothelial cell loss was three-fold higher than natural physiological loss.
The percentage of patients developing cataract reported in the literature ranges from 0-to-9.4%. Studies with longer follow-up tend to show a higher incidence of the complication. That corresponds to the continuous decrease in vaulting that occurs as a result of the growth of the crystalline lens.
“Although there are no randomised trials comparing the two lenses, cohort studies show slight advantage of refractive and visual outcomes with the ICL compared to the Artisan. Endothelial cell loss is variable, but in both IOL types an annualised loss of two-to-three times the physiological loss of 0.6% per year was shown. ICL history has shown an increased rate of anterior subcapsular cataract,” Dr Nuijts concluded.
1. Jonker SMR, Berendschot TTJM, Ronden AE, Saelens IEY, Bauer NJC, Nuijts RMMA. Long-Term Endothelial Cell Loss in Patients with Artisan Myopia and Artisan Toric Phakic Intraocular Lenses: 5- and 10-Year Results. Ophthalmology. 2018 Apr;125(4):486-494.
Rudy Nuijts: firstname.lastname@example.org