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Today's Practice | Jan 2014

Implantology: The Evolution From Large Rigid to Small Foldable IOLs

An exploration of incision size and lens design over 35 years.

After nearly 3.5 years as a resident at Moorfields Eye Hospital High Holborn, I moved at the end of 1978 to join Eric J. Arnott, MBBSBAO, FRCS, at Charing Cross Hospital. During my time at Moorfields, I had seen only one IOL implanted, a Choyce Mark VIII anterior chamber lens (Rayner Intraocular Lenses, Ltd.), while visiting a colleague in Santa Monica, California. Imagine my surprise when, on the day I started at Charing Cross, I saw Robert J. Azar, MD, who was visiting from the United States, implanting an anterior chamber lens of his own design following phacoemulsification.

FIRST LENS IMPLANT

That same month, Eric stood over me while I implanted my first IOL, a Fyodorov Mark I iris clip lens (Rayner Intraocular Lenses, Ltd.; Figure 1) that was a modification of the Binkhorst four-loop lens (Morcher GmbH). The anterior haptics of the Fyodorov lens were shifted 90º to give it better balance. The lens was inserted under air, as no ophthalmic viscosurgical device (OVD) was yet available.

The following month, after I had done my first phacoemulsification procedure under Eric’s tutelage, I implanted his new lens, the Little-Arnott Mark IV (Rayner Intraocular Lenses, Ltd.; Figure 2), a posterior chamber lens with anterior haptics that held the lens in the pupil to allow capsular fixation to take place. The patient was placed on pilocarpine drops for 6 weeks postoperatively.

Soon after I arrived at Charing Cross, I started a study in rabbits with poly-HEMA, a soft hydrogel lens material that had initially been used by Edward Epstein, MD, an early pioneer of implantology and a founding member of the Intra-Ocular Implant Club. The object of the study was to test the idea of folding a lens and passing it through an unenlarged incision after phacoemulsification. Some lenses were deliberately placed in the anterior chamber, adjacent to the corneal endothelium, to see what damage might occur (Figure 3). The editors at the American Intra-Ocular Implant Society journal originally rejected the paper because they believed the reported pathology in the rabbit eyes was not satisfactory; it was eventually published, unchanged, in another journal in August 1981.1 The delay in publication meant that, when Thomas R. Mazzocco, MD, filed his patent in early 1982 for a foldable silicone lens material, it was not rendered invalid by our prior article.

POSTERIOR CHAMBER AND SILICONE IOLs

In 1980, posterior chamber IOLs became available in the United Kingdom. The first one I implanted—under the watchful eye of Henry M. Clayman, MD, designer of the Clayman lens implantation forceps, during a live surgery phaco course at Charing Cross Hospital—was a Kratz lens (Precision Cosmet Co.; Figure 4) with four dialing holes and modified J loops.

For phacoemulsification to have mass appeal, and for surgeons to switch to this new modality from their familiar extra- or intracapsular surgery techniques, it was important to have a lens that would go through the much smaller phaco incision. Although I had been involved with foldable technologies at an early stage, the rabbit study did not lead to a commercial product. The Mazzocco plate-haptic lens (STAAR Surgical; Figure 5) was the first foldable IOL developed for human use. I first used this silicone lens at the beginning of 1986, having smuggled it into the United Kingdom in my carry-on luggage.

About the same time, surgeons started using the first three-piece silicone lenses. In 1988, I presented the accumulated world data on the PhacoFlex SI-18 and SI-20 lenses (American Medical Optics Inc.; now Abbott Medical Optics Inc.; Figure 6) at the European Intra-Ocular Implant Council (EIIC) meeting in Copenhagen, Denmark. Around the same time, Charles D. Kelman, MD, developed a PMMA lens, the Phacofit PC-28LB (American Medical Optics Inc.; now Abbott Medical Optics Inc.), with a hinge in the optic that allowed it to be implanted through a 4.0-mm incision (Figure 7). I implanted a fair number of these IOLs, as they were more stable in the eye than silicone plate-haptic lenses. However, due to the space under the optic, the rate of capsular opacity was high.

HYDROPHOBIC ACRYLIC LENS MATERIAL

In 1990, as a result of an extensive search for a new class of lens material, the AcrySof lens (Alcon) was first used. This lens, made of a hydrophobic acrylic, had a tacky surface in its original iteration (Figure 8). We were advised by the company to press the two halves of the lens together before pushing it through a 3.2-mm incision. Unfortunately, this could result in a prolonged wait of more than 2 minutes while the two halves separated in situ.

I was fortunate to be the first surgeon to implant the original AcrySof lens model on December 14, 1990. I have followed the implanted patient for more than 20 years, and I have serial photographs of her still-clear posterior capsule. To this day, she has 6/6 unaided distance vision and unaided N8 near vision (Figure 9).

In its various iterations, the hydrophobic acrylic material has become the world’s most-often implanted lens material, with nearly 70 million to date (personal communication with Alcon). One of the surprises with the design of this lens was the effect of its sharp edge, which was originally created for manufacturing reasons. It took 8 years before Okihiro Nishi, MD, recognized the importance of this feature in the prevention of posterior capsular opacification (Figure 10).

MODERN DESIGNS

We are now able to do more things with IOLs than ever before, mainly due to new lens designs, reduced incision sizes, and improved phaco technologies.

The first multifocal lenses were made of PMMA with a diffraction grating on the lens surface, but due to the large incisions required for implantation they failed to control astigmatism and therefore were never successful. The idea of placing a diffraction grating on the surface of an IOL, however, persisted, and today this design element is still used. A zonal refractive lens on a silicone optic was the first multifocal implant designed to fit through an incision small enough to limit surgically induced astigmatism.

Now that phacoemulsification technology offers modulated power delivery and increased anterior chamber stability, and surgeons can use smaller incisions to implant IOLs, the range of lens options continues to increase. I use an incision of 2.0 mm or smaller, most of the time implanting lenses that will correct presbyopia and astigmatism; I have implanted just under 800 patients with presbyopia-correcting lenses since 2001. These lenses have improved asphericity characteristics, different options for reading and intermediate vision, and enhanced ability to correct astigmatism.

For surgeons who find wound-assisted implantation through reduced-size incisions challenging, a new handpiece with an electronically driven lens inserter is now available (Intrepid AutoSert IOL Injector; Alcon). Driven by the Centurion Vision System (Alcon), this handpiece provides a highly controlled method of implantation; countertraction is provided by a second instrument placed in the sideport incision, and there seems to be less immediate wound stretch compared with a manual approach. Any stretch has generally disappeared within 2 hours of surgery. There are also new IOL designs on the horizon that will make microincision implantation even easier.

Although presbyopia-correcting IOLs cannot yet emulate the vision of a 20-year-old emmetrope, they offer a good compromise for most patients who have been properly consented and counseled prior to surgery. Results with two trifocal lens designs, the FineVision IOL (PhysIOL) and the AT LISA trifocal IOL (Carl Zeiss Meditec), are promising, and patient acceptance seems satisfactory. Although most would consider a fully accommodating IOL that could pass through a microincision to be the holy grail, no design has yet come close to achieving this without some sort of compromise on incision size or accommodative amplitude.

In order to make these new lenses work, the means by which we calculate lens power must evolve. Although the use of optical devices with partial coherence laser interferometry, combined with optimized A-constants, helps to improve refractive outcomes, new devices are also coming. Intraoperative aberrometry looks interesting, but adoption of this technology will require surgical facilities to carry even larger lens inventories for both spherical and cylindrical powers. As we get more accurate measurements of required IOL power, manufacturers will need to put the measurement of the actual lens power on the box as part of their quality control processes.

CONCLUSION

It has been a fascinating journey for me over the past 35 years since implanting my first lens. Our patients today are lucky to have a range of options for correcting almost all refractive errors. It is intriguing to speculate what the next 35 years will bring in IOL implantology.

Richard Packard, MD, DO, FRCS, FRCOphth, practices at the Prince Charles Eye Unit, King Edward VII Hospital, Windsor, and is Director of Arnott Eye Associates, London, England. Mr. Packard states that he is a consultant to and receives lecture fees from Alcon. He may be reached at e-mail: mail@eyequack.vossnet.co.uk.

  1. Packard RB, Garner A, Arnott EJ. Poly-HEMA as a material for intraocular lens implantation: a preliminary report. Br J Ophthalmol. 1981;65(8):585-587.

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