IOLS GIVE HOPE

Gerd U Auffarth MD, PhD, FEBO

Intraocular lenses (IOLs) designed to produce an accommodative effect have as yet come short of their goal, but new IOLs that are now in early trials or still under development may yet prove to be the Holy Grail of presbyopia treatment, said Gerd U Auffarth MD, PhD, FEBO at the XXXIII Congress of the ESCRS in Barcelona, Spain.

“People have been looking for the Holy Grail for centuries and nobody has found it, and I hope that will not be the fate of accommodating lenses,” said Dr Auffarth, University of Heidelberg, Germany.

He noted that the two principal approaches to restoring physiological accommodation with an IOL are those based on the forward movement of the optic and those based on a change of curvature of the optic.

LIMITED RESULTS

Lenses in the first category include single optic IOLs such as the Crystalens and dual-optic IOLs such as the Synchrony (AMO). The single-optic accommodating IOLs have not functioned as designed, showing little forward movement and at most half a dioptre of true accommodation, a small amount of pseudoaccommodation and perhaps some mini-monovision, Dr Auffarth said.

He cited a prospective randomised trial involving 31 patients which showed that patients who received one of three types of single-optic accommodating IOL had no significant advantage in terms of near visual acuity compared to patients targeted for mini-monovision using monofocal IOLs, where there is only a slight disparity between the postoperative refraction of the two eyes.

The Synchrony dual-optic IOL is a more sophisticated movement-based lens, combining a high-power optic and a low-power minus lens so that it requires much less forward movement of the anterior optic to achieve an accommodative effect.

Dr Auffarth noted that, in his experience, the lens provides patients with fair intermediate vision and a near visual acuity ranging from 0.8 logMAR to 0.4 logMAR. Measurements with aberrometry show about 1.0D of accommodation. Yet defocus curves show that patients can achieve 2.5D of combined real accommodation and pseudoaccommodation.

On the other hand, another trial found no significant difference between 27 patients implanted with the single-optic Crystalens and 26 eyes implanted with the dual-optic Synchrony lens, in terms of near or intermediate visual acuity, he added.

Recent years have seen the introduction of a couple of lenses that emulate natural accommodation through a change of curvature in response to the action of the ciliary muscle. The advantage of this approach is that the amount of increase in curvature necessary for a lens to achieve an accommodative effect is small compared to the amount of optic movement required to achieve the same effect.

Two shape-shifting IOLs that have made it into clinical trials are the NuLens (NuLens) and the FluidVision IOLs (PowerVision). The NuLens consists of two parts, one placed on top of the bag and the other in the sulcus. It operates on the principle of reverse accommodation. Early trials with the NuLens have shown that it can improve distance and near visual acuity of low-vision patients.

The FluidVision lens is a silicone oil-filled IOL which pushes fluid from an outer reservoir through small channels into the optic, in response to the relaxation of the zonules that occurs with contraction of the ciliary muscle. That in turn changes the curvature which translates into a change in refraction.

In a study Dr Auffarth and his associates conducted involving six patients implanted with the FluidVision IOL, mean uncorrected visual acuity at six months was 20/20 for distance and intermediate, and 20/23 for near.

Gerd U Auffarth:

gerd.auffarth@med.uni-heidelberg.de

Dr Auffarth has received research grants from PowerVision, AMO and Alcon