Posterior chamber implantation offers novel use for IOL

"The advantages of aphakic IOLs are the ease with which they are inserted and low cost," said Dr. Neuhann, clinical director of the AAM Augenklinik am Marienplatz, Munich, Germany. "The disadvantages are the dependence on the white-to-white measurement, the need for an iridectomy, and possible complications with the corneal endothelium.

"Chamber angle fixation, pupil ovalization with iris stromal defects, decentration, and the development of a hazy cornea also can be problematic," he continued. "Iris-fixated aphakic IOLs can develop fixation problems or rupture the iris, and sulcus-fixation lenses can decentrate.

The answer to these challenges at present, Dr. Neuhann pointed out, is the posterior chamber Verisyse aphakic IOL.

"This lens is now implanted through a 6-mm incision with the surface upside down in the posterior chamber. The lens initially is implanted into the anterior chamber, the incision is sutured, and then the lens is guided through the pupil into the posterior chamber. This is only possible if a core vitrectomy has been performed," he explained.

Dr. Neuhann went on to explain that the next step in the procedure is to lift the lens against the iris. The lens claws are then fixated into the iris. The lens is then released, with a resultant round pupil. Iridectomy is needed because aqueous humor can proceed from the posterior chamber to the anterior chamber in the presence of the vaulted lens.

Dr. Neuhann discussed the rationale for such a procedure, which uses the same IOL as for anterior chamber implantation.

"This lens behaves like a posterior chamber IOL," Dr. Neuhann continued. "There is pure uveal fixation without sutures. The IOL centers over the pupil, which is advantageous in some cases. The IOL can be refixated in cases of subluxation, without the dangers associated with subluxation when it occurs in the anterior chamber. Finally, the implantation of the IOL is easy."

A noteworthy point about the procedure is that the IOL is not fixated on the pigment layer, but rather on the iris stroma.

"This is a highly atraumatic fixation," he emphasized.

A more sophisticated implantation can be performed with a new forceps (Artifix implantation forceps, Humanvision). He demonstrated using the forceps to take the lens through the iridectomy behind the iris and into the posterior chamber.

"This forceps is very helpful in this situation. When the lens is in the posterior chamber, the pupil is not affected by the forceps. This procedure facilitates the ability to see the lens margins and the IOL is centered beautifully over the pupil. The enclavation process is much easier in an aphakic patient using this technique than in the anterior chamber," he explained.

The average age of the 35 patients with this IOL implanted was 62 years (range, 21 to 89 years). Two patients (5.8%) had to undergo a second surgery because of severe ovalization of the pupil, and in one patient (2.9%) fixation of one claw was lost. Dr. Neuhann reported that less than 1 D of astigmatism was induced following implantation of the IOL, and the endothelial cell loss was 10% or less 1 year after implantation. At 12 months after implantation, all IOLs appeared to have stable fixation.