Anterior and posterior chamber phakic IOLs have different advantages

Better refractive predictability is balanced against small-incision implantation.

Issue: November 1, 2001

ByMichela Cimberle

MILAN, Italy — Anterior chamber phakic IOL models may offer more predictable refractive results, but posterior chamber models can be inserted through a small incision, said surgeons here in a discussion of the lenses’ pros and cons.

Phakic IOLs are widely recognized as an effective method to correct high myopia, especially in cases where corneal pachymetry and corneal power are contraindications for laser correction.

Simonetta Morselli, MD, and Pietro Giardini, MD, discussed this topic at the Videorefrattiva meeting, organized by Lucio Buratto, MD, during which anterior and posterior chamber lenses and their implantation techniques were compared.

Learning curve

“The implantation of the iris-fixation Artisan lens is not a simple procedure, and it requires experience in anterior segment surgery,” Dr. Giardini said. He also said that anterior chamber angle fixation lenses such as the Bausch & Lomb NuVita (now discontinued) “are perhaps easier to implant.”

Artisan lenses (Ophtec) are made of PMMA. A 5.5- to 6.5-mm scleral tunnel incision is required to insert them without stressing the tissue and to lower the rate of postoperative astigmatism.

Artisan lenses are made of PMMA. A 5.5- to 6.5-mm, scleral tunnel incision is required to insert them without stressing the tissue and to lower the rate of postoperative astigmatism.

When using the foldable ICL (STAAR) posterior chamber lens, a corneal tunnel of about 3.2 mm is sufficient for implantation with an injector, he said.

“The smaller incision allows a better control of postoperative astigmatism,” Dr. Morselli said. “However, the learning curve of ICL implantation is as long as for anterior chamber lens implantation. It is also a more delicate technique, with a higher risk of potential complications.”

Iridectomy and viscoelastics

With ICLs, it is necessary to perform iridectomies preoperatively.

“I prefer to perform two or three preoperative YAG laser iridotomies at a distance of 90° from one another before implanting the lens,” Dr. Giardini said. “It is, in fact, easier to perform surgical iridectomy if surgery requires miosis as in the case of anterior chamber lens implantation.”

“An adhesive viscoelastic protects the endothelium and the crystalline lens during ICL implantation, and it is easy to remove at the end of the procedure,” Dr. Morselli said. “On the other hand, a cohesive, high molecular weight substance is more suitable for anterior chamber lens implantation. It is more effective in maintaining the space in the anterior chamber during the enclavation of the Artisan lens, and it is easy and quick to remove.”

Anesthesia and endothelial cell loss

Topical, peribulbar or general anesthesia can be used for phakic IOL implantation. The choice, the surgeons said, depends on two main factors: the patient’s collaboration and the surgeon’s experience with this type of surgery.

Literature on the subject of phakic IOL implantation reports an average 2% to 4.5% endothelial cell loss caused by surgical maneuvers and by the presence of the lens in the eye.

“With anterior chamber lenses, the higher percentage of endothelial cell loss occurs during surgery and then remains stable around 1% to 2% per year. Also with posterior chamber lens implantation (ICL), 2% of endothelial cell loss is surgery-related and remains stable after a time,” Dr. Morselli said.

Refractive results and complications

Refractive results are more predictable with anterior chamber lenses, according to both surgeons.

“NuVita and Artisan achieve a mean ±0.50 D to ±1 D from expected postoperative refraction in 60% to 70% of the patients. With ICLs, results are on average between ±1 D and ± 2D from expected correction in 50%, and +1D in 10% of the postoperative cases,” Dr. Giardini said.

The ICL postop refractive results, he pointed out, are less predictable than the results of anterior chamber lenses, as a higher number of preop parameters are required.

When using the ICL posterior chamber lens, a corneal tunnel of about 3.2 mm is sufficient for implantation with an injector.

It is necessary to perform iridectomy preoperatively with ICLs.

Cases of cataract, pupillary block, slight mydriasis and decentration of the lens were observed with the ICL. Pupil ovalization, moderate endothelial cell loss and glare were reported with the anterior chamber phakic lenses.

In the case of LASIK enhancement after implantation of posterior chamber lenses, the suction of microkeratome will not interfere with the lens’s position, according to Dr. Giardini. However, some caution will be required with the implantation of angle-supported anterior chamber lenses.

“Perhaps it is better to perform the LASIK flap before implantation of the lens,” he said.

New options

The Vivarte and the PRL are two new types of phakic IOLs marketed by CIBA Vision. Vivarte is an anterior chamber angle-supported lens with rigid haptics, foldable optic and soft footplates (the lens has not yet been CE-marked). PRL is a posterior chamber phakic IOL that floats on the natural lens. They are soft, foldable lenses — similar in design to the ICL — that are introduced with special forceps through a 3- to 3.2-mm corneal tunnel. These lenses are CE-Mark approved.

Vivarte is an anterior chamber angle-supported lens.

The PRL is a posterior chamber phakic IOL.

For Your Information:

Pietro Giardini, MD, can be reached at Reparto Oculistico, Casa di Cura Poliambulanza, Brescia, Italy; (39) 030-242-0935; fax: (39) 030-247-8518; e-mail: pgiard@inwind.it.

Simonetta Morselli, MD, can be reached at Clinica Oculistica, Università di Verona, Italy; (39) 348-412-1324; e-mail: morsell@tiscalinet.it.