Phakic IOLs: Good benefit-to-risk ratio

June 15, 2014

The benefit-to-risk ratio of phakic IOLs is well balanced, according to one surgeon, who explained why phakic IOLs may be a good additional option for refractive surgery.

 

Take-Home Message

The benefit-to-risk ratio of phakic IOLs is well balanced, according to one surgeon, who explained why phakic IOLs may be a good additional option for refractive surgery.

 

Dr. Kohnen

By Lynda Charters; Reviewed by Thomas Kohnen, MD, PhD

Frankfurt, Germany-The benefit-to-risk ratio of phakic IOLs is well balanced, according to Thomas Kohnen, MD, PhD.

Though there is a risk of decreased endothelial cells counts and cataract formation in some eyes with certain phakic IOLs, the optical quality achieved with the IOLs is very good and the procedure is reversible, said Dr. Kohnen, professor and chairman, Department of Ophthalmology, Goethe-University, Frankfurt, Germany.

The German standards for phakic IOLs are myopia over –6 D and hyperopia over +3 D, he noted. Borderline implications depend on the surgical goals and include myopia over –3 D and hyperopia of +2 D.

“The most important factor for phakic IOLs are implant-specific regulations for the anatomy, including the anterior chamber, the endothelium, and patient age,” he said.

Dr. Kohnen discussed the pros and cons of three phakic IOL designs:

  • The angle-supported AcrySof Cachet IOL (Alcon Laboratories).

  • The iris-fixated Artisan/Verisyse IOL (Ophtec/Abbott Medical Optics).

  • The sulcus-supported Visian ICL (STAAR Surgical).

He has to date implanted a total of 1,300 phakic IOLs that include all three types.

 

Hydrophobic acrylate IOL

The 3-year results with the hydrophobic acrylate IOL (AcrySof Cachet) (optic, 6 mm; overall diameter, 12.5, 13, and 13.5 mm; range, –6 to –16.5 D), indicated for moderate to high myopia, showed that the lens was placed well, did not change position, and remained stable. The accommodative effect remained the same from preoperatively to postoperatively, and the postoperative visual acuity was superior to the preoperative level. The defocus curve of the lens did not affect accommodation; patients had the same accommodative effect postoperatively as they did preoperatively.

In the FDA study, 106 eyes completed the 5-year evaluation and of those only 1% had a two-line decrease in visual acuity. The visual acuity was maintained over a long period and the spherical equivalent was very stable. The endothelial cell loss was 1.1% annually, which is slightly more than the natural rate of endothelial cell loss; the cells maintained their shape and size.

The refractive effect for the lens is well proven, Dr. Kohnen noted. There is minimal change in the endothelial cell count annually, but it is important to re-examine these patients on a yearly basis, he emphasized. An important factor with this lens is maintenance of the anterior chamber depth (ACD), the minimal depth with this IOL is 2.8 mm from the endothelium for implantation.

 

Iris-fixated IOL

With the iris-fixated IOL (Artisan/Verisyse), indicated for myopia, hyperopia, and astigmatism, the minimal ACD must be 3 mm from the epithelium. Some researchers even pointed out that the crystalline lens rise must be part of the new safety criteria to be taken into consideration when inserting the implant.

The lens, made of polymethylmethacrylate covers a wide range of refractive errors, i.e., for myopia, –1 to –23.5 D and for hyperopia +1 to +12 D. The toric IOL can be used for cylinder ranging from 1 to 7.5 D and sphere ranging from +6.5 to –23 D.

The 10-year follow-up data showed good outcomes, but with long-term endothelial cell loss. Occasional precipitates are seen on the eye with the foldable version of the IOL (Artiflex) possibly related to the silicone material, but the outcomes are good.

“This IOL can be associated with occasional inflammation,” Dr. Kohnen noted.

 

Posterior chamber sulcus-supported lens

The new posterior chamber sulcus-supported lens (Visian ICL), indicated for myopia and hyperopia, has a central hole that promotes more aqueous circulation through the pupil. The IOL is indicated for patients 21 to 50 years of age and maybe even older, and for refractive errors ranging up to +10 D of hyperopia and to –20 D of myopia and up to 6 D of astigmatism, if the ACD is 2.8 mm from the endothelium. The IOL provides stable refraction over the long term.

Study results showed 95% of patients within ±0.5 D and 100% within ±1 D of the intended correction and the loss of best-corrected visual acuity is very low. Indications for implantation are thin corneas with no LASIK indication, contact lens intolerance, and dry eye. One drawback is cataract formation in young patients when the IOL without the central hole was implanted (1% to 33% of patients); in the model with the central hole, that incidence has decreased to below 1%.

 

Weighing risks, benefits

When considering implantation of phakic IOLs the anatomic factors are crucial-i.e., the corneal thickness, ametropia, pupillary diameter, and optical quality. Each phakic IOL has advantages and disadvantages, but all three lenses provide optical quality and fast visual rehabilitation, Dr. Kohnen noted.

“The risks and benefits of each phakic IOL must be considered, such as cataract formation and the percentage of endothelial loss,” said Dr. Kohnen, noting that close follow-up of patients is necessary.

“The benefits are definitely optical quality, rapid visual rehabilitation, and reversibility,” he said. “The risks are small. Therefore, phakic IOLs are a good additional option for refractive surgery.”

 

Thomas Kohnen, MD, PhD

E: kohnen@em.uni-frankfurt.de

Dr. Kohnen is a consultant to Abbott Medical Optics and Alcon Laboratories and has received research funding and honoraria.