Florence Cabot MD
After many disappointments in the past, a new generation of IOLs offers hope of at last achieving the holy grail of accommodation restoration, Florence Cabot MD told the 37th Congress of the ESCRS in Paris, France.
“Restoring accommodation means creating a device that has a continuously variable, adjustable, active, near-focusing ability. Ideally, we need to restore three-to-five dioptres,” said Florence Cabot MD, Assistant Professor of Clinical Ophthalmology, Bascom Palmer Eye Institute, Miami, Florida USA.
She noted that the first generation of accommodating IOLs supposedly provided accommodation by a forward movement in the axial position of the IOL’s optic in response to ciliary muscle contraction. However, this change in focus was slight and studies have shown that the apparent improvements in near vision might have been partially due to an increase of optical aberrations that provide a better depth of field. Furthermore, studies using optical coherence tomography (OCT) have shown that not only was there no forward movement of the optic in response to accommodative stimulus, the optics sometimes move backwards instead.
The new generation of accommodative IOLS uses a variety of mechanisms to achieve a more physiological form of accommodation. They include in-the-bag and sulcus-implanted IOLs and rely on ciliary muscle movements or pupillary changes to stimulate a change in shape or alteration of the optic’s refractive properties.
Among the first of the new lenses is the Juvene (LensGen). It is a single-piece IOL with two fluid reservoir haptics, two optics attached by a flexible actuator and active and passive fluid chambers. The capsular forces exerted on the haptics during accommodation cause the fluid to be pumped centrally into the optic resulting in a shape change and increased refractive power without splitting the light like multifocal IOLs. The lens is designed for implantation in the capsular bag through a sub-4mm incision. A clinical trial, the "Grail Trial", is now under way in Mexico and the Dominican Republic. So far, the lens has been implanted in 44 eyes with very good results, Dr Cabot said.
“One of the drawbacks of this IOL is its bulkiness and the difficulty of injecting it through a small incision. On the other hand, because of its shape, the early trials have not shown much PCO, besides which there is none of the glare that is common with multifocal IOLs.”
Another of the new accommodative lens concepts, still in the experimental stages, is the Sapphire autofocus IOL, (Elenza, USA). It ticks all the boxes of modern technology. It is electronically controlled and utilises nanotechnology, artificial intelligence and advanced electronics to auto-adjust focus in response to pupillary changes. It uses pupillary responses to stimulate changes in the liquid crystal within the lens that alter its refraction. The speed and amplitude of pupil response are used to differentiate between light and accommodative stimuli.
The lens has a power-cell that requires recharging every three-to-four days. It has a hibernation mode and a fail-safe mechanism that converts it to monofocal status till recharged.
It also allows the physician to remotely adjust the sensitivity and magnitude of the switching point of the add power in the IOL, based on the needs of patient.
The Dynacurve (Nulens) is an out-of-the-bag IOL in which the PMMA haptics are secured by internal scleral fixation to the sulcus without sutures. Its optic changes curvature in response to accommodation by using the collapsed bag-zonular complex as a mobile diaphragm, which activates a piston that modifies a flexible membrane to provide spherical or aspherical dynamic surface.
The Lumina IOL (AkkoLens) out-of-the-bag/sulcus IOL has two optical elements shifting in a plane perpendicular to the optical axis producing accommodation. The dual-optic, hydrophilic acrylic lens has two complementary refractive plates, which, translated laterally, produce a progressive change in optical power.
“There are lots of options and interesting concepts in the pipeline with good results in both in vitro and animal studies, with some lenses still awaiting clinical trials. True accommodative IOLs remain the holy grail of ophthalmic surgery,” Dr Cabot concluded.
Florence Cabot: fcabot@med.miami.edu
