Lens refilling brings accommodation two steps closer

September 15, 2008

Ophthalmology is perhaps two steps closer to a possible clinical application of lens refilling with silicon gel for restoring ocular accommodation thanks to a refined procedure developed by Dr Okihiro Nishi, MD of the Nishi Eye Hospital, Japan.

Ophthalmology is perhaps two steps closer to a possible clinical application of lens refilling with silicon gel for restoring ocular accommodation thanks to a refined procedure developed by Dr Okihiro Nishi, MD of the Nishi Eye Hospital, Japan.

"Refilling the lens capsule while preserving capsular integrity offers the potential to restore ocular accommodation," he told a large audience at the Ridley Lecture in a presentation titled "Ridley's Legacy: An IOL refilling procedure that restores accommodation".

"The procedure may be an alternative to the multifocal and accommodating IOLs for treating presbyopia. For the past 20 years I have been modifying the clinical applications of the lens refilling technique. Today I will detail our most recent clinical adaptation," he said.

In his recent work he and his team had solved two of the most persistent problems currently impeding progress in the lens refilling technique, namely leakage of the silicon gel and capsular opacification.

The essential technique is quite simple in theory. Following phacoemulsification through a tiny Continuous Circular Capsulorhexis (CCC), a silicon gel injectable IOL is injected into the empty capsular bag replacing the biologic crystalline lens, thereby restoring ocular accommodation.

"Though simple in concept, in practice it has proven quite difficult. When liquid silicon was used as the injected material, its leakage through the capsular opening with subsequent polymerization presented a challenge that demanded a solution prior to any thought of clinical application."

Dr Nishi came up with an ingenious solution; using a very thin IOL. "Our new technique with the anterior accommodating IOL is the combined result of efforts to both prevent leakage of injected silicon polymers and to prevent capsular opacification.

"For the monkey experiments, we modified the accommodating IOL by thinning the optic. The membranous optic is 0.1 mm thick and has no refractive power. We call this the accommodating membrane IOL."

After phacoemulsification aspiration with a 3 mm CCC is performed in the usual manner, the IOL is implanted. An injectable silicon polymer is then injected beneath the IOL through the delivery hole, while the CCC edge is pulled aside slightly. The silicon polymer polymerizes within two hours in vitro.

"It is really amazing; the accommodative IOL seals such a large CCC opening and prevents leakage," he said.

Dr Nishi conducted a series of experiments with the new approach process and discovered that it solved both problems. With this technique, anterior capsule opacification can be prevented with an anterior IOL. "To prevent PCO, a posterior CCC is created, and a posterior accommodative IOL is inversely implanted to seal the posterior CCC," he said.

"Our new procedure required 20-30 minutes surgical time and was found to be highly reproducible," he said. The procedure prevents leakage of the injectable silicon polymer from both anterior CCC and posterior CCC.

It solves two of the persistent problems in lens refilling, namely leakage of the injectable silicon and capsular opacification, he noted.

"The data clearly showed that some clinically useful accommodation can be obtained by this refilling technique despite an overfilling of the lens capsule, so that overall we are two steps closer to a possible clinical application for restoring ocular accommodation."

He added that the accommodation attained was a consequence of the anterior curvature change of the membranous optic, but achieving emmetropia is an issue to be solved.

He concluded the talk with a tribute: "This research warrants further pursuit and should be viewed as a legacy to the pioneering efforts of Harold Ridley."

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