Add-on refractive correction safe and effective with new lenses

The design of two new lenses specifically made for placement in the sulcus overcomes the drawbacks of the older piggybacking technique.

Issue: April 2012

Michael Amon

Supplementary IOLs are effective for enhancement of surgical results in pseudophakic eyes or in primary duet implantation, according to a surgeon.

Piggybacking, with two standard biconvex lenses implanted in the capsular bag, often resulted in interlenticular opacification and hyperopic defocus. First introduced in 1993, the technique was eventually abandoned due to the high rate of IOL explantation.

“Lens epithelial cells were growing in the interface, and there was no way to treat this opacification with laser because it was right in the interface of the lenses,” Michael Amon, MD, said. “Also, because of the biconvex design, there was a central zone of contact between the two optics that produced flattening and hyperopic defocus. Optic results were not at all good with standard IOLs.”

Sulcus implantation of lenses that were not primarily designed for this purpose also caused pigment dispersion and pigmentary glaucoma in some cases.

“We want to avoid this complication and find a safe lens design that is made to be placed in the sulcus,” Dr. Amon said.

Two lenses

Two lenses specifically designed for duet implantation are now available on the market. According to Dr. Amon, these lenses are a safe and effective option for patients who are not entirely satisfied with their refraction after cataract surgery. The Rayner Sulcoflex 653 is a hydrophilic acrylic lens, whereas the HumanOptics MS 714PB is made of silicone.

“Both lenses have shown to have a high uveal compatibility, which is essential because they are in direct contact with the uveal tissue. Both lenses have a large optic diameter of 6.5 mm to 6.7 mm and a round optic edge to prevent glare and halos. No square edge is needed because stopping [posterior capsule opacification] is the job of the first lens. They have a concave posterior surface to avoid central contact of the two optics. The haptics are large in both lenses, and you have an angulation that creates iris clearance to avoid pigment dispersion,” Dr. Amon said at the meeting of the European Society of Cataract and Refractive Surgeons in Vienna.

“Both IOLs are also available in toric and multifocal models,” he said.

Power calculation is essential but not difficult.

“You don’t need anything like the IOLMaster (Carl Zeiss Meditec), but just the patient refraction. You can use the [refractive] vergence formula or, even easier, if you have a hyperopic eye within +7 D, you can just calculate the spherical equivalent [times] 1.5, and if the eye is myopic you multiply by 1.2. You can almost guarantee your patients that they’ll end up with the wanted value,” he said.

Implantation is straightforward, much easier and safer than lens exchange. Iridotomy is optional, and Dr. Amon performs it only in small children and in short or unusual eyes.

Avoiding complications

“We have used these lenses in over 90 eyes, and preliminary results are encouraging. Surgery was atraumatic in all cases, with no pigment dispersion or iris trauma. There was always a nice distance between iris and lens and between the two lenses. We had no case of interlenticular opacification or pupil ovalization,” Dr. Amon said.

There was a rotation of more than 10· observed postoperatively in 3% of the cases. Such a rotation is, according to Dr. Amon, not negligible and has an impact on visual performance.

“The problem is that you can’t guarantee rotational stability with sulcus-placed lenses, because they are not fixed by something like capsule contraction,” he said.

Suturing the lens is the only way this complication can be prevented. Although suturing might appear tricky, it works well if an appropriate technique is used, he said.

The potential risk of pupillary block can be avoided by doing iridotomy in small eyes. Pupil ovalization will not occur if the haptics are positioned correctly in the ciliary sulcus.

“As well as addressing postoperative ametropia, supplementary lens implantation can be used for primary duet implantation to correct all types of refractive error, to convert monofocal to multifocal vision or monovision to emmetropia in cases of difficult adaptation. Dysphotopsia is another indication because, thanks to the large optic, you can get rid of negative dysphotopsia,” Dr. Amon said.

Specific indications are related to the concept of dynamic refraction, as in pediatric cataract, with changes in the refraction over time. Other situations that might require dynamic adjustment are corneal alterations and silicone oil or buckling procedures.

“Explanting this lens when you need to change it is very easy. You perform a 2.5-mm incision, grasp the lens by the optic and pull it out. We can consider it as an almost reversible procedure,” Dr. Amon said.

Other options to correct postoperative ametropia hold several disadvantages. Corneal refractive surgery is an irreversible procedure and also depends on the availability of the surgeon. Hospitals normally do not offer this kind of surgery, so patients have to be referred to private specialists.

IOL exchange, on the other hand, is not an easy surgery and involves risks such as capsular tears and vitreous loss. In addition, there are lens materials that generate a strong fibrotic reaction and make the lens difficult to remove.

Safest option

Add-on IOLs might be the best and safest option, Dr. Amon said.

“Of course, a drawback is that they are still intraocular surgery. We use cefuroxime to minimize the risk of endophthalmitis, but nevertheless we open the eye,” he said.

Follow-up with add-on IOLs now spans several years, and more than 20,000 of these implants have been performed worldwide. However, there is a lack of peer-reviewed publications, and further studies are needed, he said. – by Michela Cimberle

For more information:

Michael Amon, MD, professor and head of the ophthalmology at Academic Teaching Hospital of St. John, Vienna, Austria, can be reached at +43-1-211 21-1140; email: amon@augenchirurg.com.

Disclosure: Dr. Amon is a consultant for Rayner.

PERSPECTIVE

Detlef Holland

The spectrum of refractive IOL implantation has been greatly broadened by modern add-on technology. These IOLs offer the possibility of primary implantation during RLE or secondary implantation in cataract surgery. Both sphere and cylinder can be treated safely with very high predictability. Also, multifocal add-on IOLs show excellent results for both near and distance acuity and are easy to explant should adaptation problems arise after surgery. The only problems that may occur with add-on implants are rotation with toric models and the onset of pigment dispersion glaucoma.

This new technology is likely to affect to a great extent our clinical practice. The rate of IOL explantation and excimer laser touch-up due to miscalculation or residual astigmatism will be reduced. A large number of pseudophakic patients with near emmetropic refraction will benefit from the possibility of secondary multifocal add-on implantation to achieve spectacle independence.

Primary multifocal add-on implantation will give a chance to difficult patients to try the multifocal option.

Further studies are necessary to prove the long-term safety of these implants and to compare the add-on multifocal option with standard multifocal IOLs.

— Detlef Holland, MD
Augenklink Bellevue, Kiel, Germany
Disclosure: Dr. Holland has no relevant financial disclosures.