REFILLABLE IOL

A refined capsular bag-refilling procedure using an accommodating-membrane IOL has been successfully tested in monkey eyes and now warrants further study for possible clinical application in humans, according to Okihiro Nishi MD, PhD. “This new procedure required 20 to 30 minutes surgical time and was found to be highly reproducible. This approach prevents leakage of the injectable silicone polymer from both anterior and posterior continuous curvilinear capsulorhexis (CCC) and some useful accommodation of the order of 2.5 D can be obtained by this refilling technique,” Dr Nishi told delegates at the XXXI ESCRS Congress in Amsterdam.

Dr Nishi noted that the accommodation attained was a consequence of the anterior curvature change of the membranous optic. He added that the new procedure goes some way towards solving two of the persistent problems that have hampered previous lens refilling techniques, namely leakage of the injectable silicone and capsular opacification. “We now need further studies to resolve some key issues associated with the procedure such as consistently achieving emmetropia and perhaps intraoperative refractometry might help in this regard. We also need to know more about how capsular opacification affects the amplitude of accommodation attained as well as the influence of YAG laser capsulotomy on the accommodative effect,” he said.

To address potential problems of silicone leakage and capsule opacification, Dr Nishi used a modified version of the foldable silicone accommodating-membrane IOL used in previous rabbit eye and pig cadaver eye experiments. Capsular opacification was eliminated by anterior and posterior CCCs at least in the visual axis in rabbit eyes, which have a much higher propensity for LEC proliferation. 8

Significant modification
The new accommodating IOL has a 9.0mm overall diameter and serves as an optic as well as a plug in order to seal the capsular opening (Figure 1). At the margin, there is an 0.8mm delivery hole for insertion of a 22-gauge needle, while more central to the optic is a 0.2mm positioning pocket through which the IOL can be positioned using a Sinskey hook. The IOL, which is thick at its margins, tapers to a 100 μm centre. The most significant modification of the original IOL is the absence of a transition zone between the optic and the haptic, with this zone now constituting a disk-shaped IOL, said Dr Nishi.

For the latest study, a central 3.0 to 4.0mm continuous curvilinear capsulorhexis was created in the monkey eyes, after which phacoemulsification was performed in the usual manner. After the accommodating-membrane IOL was implanted in the capsular bag, silicone polymers were then injected beneath the IOL into the capsular bag through the delivery hole.

Successful results
In three study groups, each with six monkey eyes, the lens capsule was refilled with 0.080ml of silicone polymers, corresponding to a 65 per cent bag volume; 0.100ml, corresponding to an 80 per cent bag volume; or 0.125ml, corresponding to a 100 per cent bag volume. To calculate the accommodation amplitudes achieved, automated refractometry was performed before and one hour after topical pilocarpine 4.0 per cent application preoperatively and four weeks postoperatively (Figure 2).

In terms of results, Dr Nishi reported that the refilling technique was successful without polymer leakage in all monkeys. Four weeks after surgery, the mean accommodation amplitudes were 2.56 D (± 0.74), 2.42 (± 1.00) and 2.71 (± 0.63) respectively, in the three study groups. “Despite the creation of a central CCC in young monkey eyes, approximately 2.5 D of accommodation amplitude was obtained independent of the volume of capsular bag filling. Furthermore, leakage of the injectable silicone polymers and anterior capsule opacification in the visual axis were avoided,” he concluded.