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Three accommodative IOLs show high-quality surface on SEM
High quality standards in design and construction are particularly important for the delicate mechanism of action of these lenses.
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ROME — Scanning electron microscopy shows that three types of accommodative IOLs currently available have high-quality surfaces on the optics, haptics and junctions, and meet the gold standard for intraocular implants.
“These lenses have a very particular type of action, which requires high quality standards in design and construction. From our analysis, we can say they appear to be perfect in all details, and therefore there is no contraindication to their implantation from this point of view,” said Rita Mencucci, MD, of Firenze, Italy, here at the Rome 2002 meeting.
The three lenses analyzed were the CrystaLens AT-45 (C&C Vision), the Akkommodative 1CU (HumanOptics) and the BioComFold Type 43E (Morcher). Three IOLs of each type with refractive power of 20 D were analyzed by SEM.
These lenses are available in Europe but not currently in the United States.
CrystaLens AT-45
The CrystaLens currently has the longest follow-up and has completed a Food and Drug Administration phase 3 trial. The optic is made of Biosil, a third-generation silicon, and the plate haptics have specially shaped polyamide loops. (See related article, "More than 2,000 CrystaLens IOLs implanted worldwide").
“The overview examination showed a very smooth optic surface and no irregularities in the haptics. Also, the optic-haptic junction is clean and well cut,” Dr. Mencucci said (figure 1).
Two points in the design of this lens are particularly important for its proper functioning. One is the loops (figure 2), patented by C&C. Their shape and material allow a firm hold of the lens in the capsular bag, which is further stabilized by the natural fibrotic growth over them. The second point is the hinge zone, which allows for the elastic movements of the lens following contraction and relaxation of the ciliary muscle.
“The loops appear extremely solid and well finished, and the hinge zone is smooth and well designed. We also measured the thickness of the hinge in our three specimens and saw that it was exactly the same in all of them. A regular configuration guarantees a durable functioning of the mechanism of these lenses over time,” Dr. Mencucci said.
Also, the posterior surface of the optic was examined, with equally good results.
“The overall impression we had through scanning electron microscopy is that the CrystaLens has been skillfully designed and manufactured from every point of view,” she concluded.
Akkommodative 1CU
The HumanOptics accommodative IOL has the same purpose, but different characteristics compared to the CrystaLens. It is a one-piece, foldable implant made of hydrophilic acrylic, with four haptics that are elements both for fixation and dynamic transmission.
In this case, the overview also showed a very smooth, regular surface and an excellent finish, Dr. Mencucci said (figure 3). The junction between the dynamic transition elements and the optics showed no irregularities.
In the 1CU, the haptic edges are square, to prevent posterior capsulearopacification.
“The edges are shaped with a special lathe-cut procedure that makes a perfect, regular sharp angle, which is clearly visible on SEM. If square edges prevent PCO, this lens certainly does,” Dr. Mencucci said.
In one specimen, small deposits were visible on the optic surface (figure 4). At a higher magnification, they turned out to be crystals, and were identified as small deposits of sodium chloride using X-ray microanalysis. They were probably a residual from the solution in which the lenses, which are hydrophilic, were immersed, Dr. Mencucci said.
“Nothing to worry about, then,” she said.
BioComFold Type 43E
The third type of IOL is yet another design. It is a disc-haptic lens with a negative angle of 12°. The material is a copolymer of PMMA and 2-HEMA.
The overview of the surface revealed a perfect finish, Dr. Mencucci said. The haptic edge is also squared to prevent PCO (figure 5). Both the bulging peripheral ring and the intermediate ring showed no irregularities. The holes in the intermediate ring are also well produced, she said (figure 6).
“I have no clinical experience with this lens, but the quality is certainly as high as in the others,” Dr. Mencucci said.
In conclusion, all three lenses, though design and materials are different, show excellent quality in all aspects of their manufacture and have regular surfaces with no molding defects.
“This is particularly important because surface irregularities will be accompanied by deposition of inflammatory cells, and can lead to the formation of synechiae, which would hinder the delicate mechanism of the accommodative IOLs,” she said.
The larger recess and the holes in the intermediate ring show very well-finished edges, she said.
For Your Information:
- Rita Mencucci, MD, can be reached at Università degli Studi di Firenze, Clinica Oculistica II, Viale Morgagni 85, 50134 Firenze, Italy; (39) 055-411-765; (39) 055-437-7749; e-mail: rita.mencucci@unifi.it.
- Dr. Mencucci has no direct financial interest in the products mentioned in this article, nor is she a paid consultant for any companies mentioned.
- C&C Vision can be reached at 6 Journey, Suite 270, Aliso Viejo, CA 92656; (949) 916-9352; fax: (949) 716-8362.
- HumanOptics can be reached at Spardorfer Strasse 150, 90154 Erlangen, Germany; (49) 9131-506-6586; fax: (49) 9131-506-6590; e-mail: hahn@HumanOptics.com.
- Morcher GmbH can be reached at Kapuzinerweg 12, 70374 Stuttgart, Germany; (49) 711-95320-0; fax: (49) 711-95320-80; e-mail: info@morcher.com.
- Rome 2002, the Seventh Annual Rome Symposium on Cataract, Refractive and Glaucoma Surgery, was sponsored jointly by Ocular Surgery News, the International Society of Refractive Surgery and the Italian Association of Cataract and Refractive Surgery.