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  • Advances in Angle-supported Phakic Lens Implants

    Refractive Mgmt/Intervention
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    Phakic lens implants (pIOLs) are increasingly being used to correct high refractive errors. Improved pIOL designs and outcomes may soon lead to their wider acceptance and use. These newer designs allow insertion through smaller incisions. Other advantages include minimal astigmatic effects, unchanged corneal aberrations, reversibility and lack of an effect on accommodation. However, all phakic lens implants can potentially increase the risk of endophthalmitis, endothelial damage, pupil ovalization and cataracts.

    Evolution of pIOLs

    The initial lens designs dating back to the 1950s were PMMA (polymethylmethacrylate) anterior chamber pIOLs with rigid haptics. Sizing issues in some patients led to iris chaffing, pupil ovalization, glaucoma and uveitis, which was known as UGH (uveitis glaucoma hyphema) syndrome. Georges Baikoff, MD, introduced the Baikoff ZB (Domilens, Lyons, France) in 1986, followed by modifications in 1990. Twelve-year follow-up studies showed well-maintained best spectacle-corrected visual acuity (BSCVA). However, a 10.6 percent reduction in endothelial cell density (ECD) occurred during the first year, with a subsequent annualized drop of 1.77 percent.1

    Iris-fixated pIOLs using various modifications of the iris claw were later introduced and evolved into the Verisyse IOL (Advanced Medical Optics, Inc., Santa Ana Calif.), also known as the Artisan pIOL in Europe.

    Posterior chamber pIOLs were pioneered by Fyodorov in 1986. Most use a one-piece silicone design, sulcus-supported and positioned between the posterior leaflets of the iris and the native lens. Presently in the United States, AMO's iris-fixated Verisyse and the posterior chamber Visian ICL 4 Implantable Collamer Lens, (STAAR Surgical Co., Monrovia, Calif.) are the only posterior chamber pIOLs approved by the FDA.

    Anterior chamber pIOL development saw Alcon's phakic AC-IOL (Fort Worth, Texas) obtain regulatory approval in Europe in September 2008. The product is nearing regulatory approval in Canada and the U.S.

    Iris-fixated pIOLs

    Verisyse is a PMMA iris-fixated lens available as a 5.0 mm or 6.0 mm optic approved for the correction of -5.00 D to -20.00 D of myopia. Outcomes have been excellent, with uncorrected vision better than 20/40 in 83 percent of eyes and better than 20/25 in 50 percent.2 Potential problems include pigment dispersion, corneal ECD loss, induced astigmatism from the 6.2 mm incision and potential difficulties with fixation or enclavation to the iris. Late subluxation of the lens may also occur. Endothelial cell loss of 3.3 percent after one year and a mean of nine percent after five years has been reported.3

    The Artiflex (Ophtec)/Veriflex (AMO) has a polysiloxane foldable optic that can be inserted through a small incision, but the product is not yet available in the U.S.

    Posterior Chamber pIOLs

    The good visual outcomes and minimal side effects of posterior chamber pIOLs have led to an increasing use of pIOLS. Posterior chamber pIOL implantation has grown by an estimated 30 percent over the past five years.

    STAAR's Visian Implantable Collamer Lens was approved by the FDA in December 2005. Its sulcus placement offers the advantages of avoiding angle contact and potentially reducing ECD loss.5 Issues remain regarding lens sizing, as an oversized lens can lead to excessive vaulting anteriorly and iris contact. An undersized lens is more likely to come into contact with the natural lens and induce cataract development. However, it is more common to see anterior cortical opacities that do not progress than visually significant cataract formation.4 Visual outcomes after one year are also excellent, with 60.1 percent of eyes achieving UCVA of at least 20/20 and 84.7 percent within 1.0 D of predicted refraction.4

    The Visian and Verisyse posterior chamber pIOLs are available outside of the U.S. in both hyperopic and toric models. Correction of astigmatism is important as high myopes often have some astigmatism.

    Angle-supported Anterior Chamber pIOLs

    There has been increased interest in AC pIOLs (Figures 1A and 1B) following the introduction of the Alcon AcrySof AC pIOL in Europe in 2008 and results presented at the ASCRS meeting in Berlin in September and the World Congress of Ophthalmology 2008 in Hong Kong.

    Image courtesy of Simon P. Holland, MD
    Figure 1A. Centration of a phakic AC lens implant with flexible haptics with a normal pupil.

    Image courtesy of Simon P. Holland, MD
    Figure 1B. Centration of phakic AC lens implant with flexible haptics with a dilated pupil.

    The Alcon AC pIOL uses the same acrylic material as the Alcon pseudophakic one-piece lens and can be folded and inserted through a 3.2 mm incision. The lens has four flexible haptics for angle fixation and a 6.0 mm optic.

    Outcomes were evaluated in 360 subjects in the U.S., Europe and Canada who received the Alcon AcrySof acrylic AC pIOL, which has not yet been approved by the FDA. Trial entry criteria were stable high myopia of -6.00 D to -16.5 D. Exclusions were astigmatism greater than 2.0 D, pupil size greater than 7 mm and anterior chamber depth less than 2.3 mm. Follow-up is scheduled to last five years. Three-year results were reported at ESCRS, including visual acuity, predictability, safety, ECD and adverse events.

    UCVA of 20/20 was obtained in 46 percent of eyes and 20/40 or better in 97.1 percent. BSCVA of 20/20 or better was reported in 81 percent of eyes and 20/40 or better in 100 percent. A high degree of predictability was obtained, and refraction stabilized after six months to three years.

    A review of adverse events for the 360 subjects over the three-year period showed no pupil ovalization or features of UGH syndrome. The rate of adverse events was low: cataract formation occurred in 1.9 percent of eyes, synechiae in 1.7 percent, secondary surgical intervention in 1.7 percent and temporarily-raised IOP requiring treatment in 1.4 percent. Five lenses (1.1 percent) were explanted for incorrect power or cataract, three at the patients' request.

    Concerns over chronic endothelial cell loss led to market withdrawal of earlier AC pIOLs, such as the GBR Vivarte/Newlife (IOL Tech/Carle Zeiss Meditec, La Rochelle, France) and the I-CARE (Corneal, Pringy, France), as several patients developed excessive ECD loss requiring lens explantation.1 Thus all angle-supported pIOLs need to demonstrate that they do not significantly affect ECD before gaining wider acceptance. Three-year follow-up results from the Acrysof AC pIOL trials showed annualized ECD loss of 0.4 percent centrally and 1.1 percent peripherally.

    Other AC pIOL lens designs have not been demonstrated to have an increased ECD loss rate until after three years.1 Potential advantages of a flexible AC pIOL, such as the AcrySof, include ease of insertion compared to other pIOLs. Potential disadvantages include possible rotation of the lens due to its flexible loops, which at present precludes consideration of a toric model.

    ECD examination requires evaluation of both the peripheral and central zones, as migration from the periphery will occur if there is any central loss. The expected annualized central ECD loss in normal subjects has been estimated at between 0.5 percent and 1.0 percent. After the initial loss in the first six months attributed to surgery, subsequent ECD loss is expected to be similar to that of the normal population.

    Conclusion

    The introduction of flexible-loop angle-supported phakic lens implants, such as the AcrySof, which has not yet been FDA-approved, has added a further option in refractive surgery. Phakic IOLs may well show long-term improved quality of vision and visual acuity for higher corrections compared with outcomes with PRK or LASIK, which would increase phakic IOL acceptance. There is likely to be considerable debate and shifting of opinions over the next five years regarding the use of angle-supported pIOLs both compared with other pIOLs and in combination with laser refractive surgery. Long-term ECD studies are critical to ensure the long-term safety of pIOL use, especially of angle-supported models.

    The newer angle-supported pIOLs, such as the AcrySof, promise to add another excellent option for refractive surgeons considering iris- or sulcus-supported pIOLs or laser refractive surgery for patients with high myopia or corneal contraindications to laser refractive surgery.

    References 

    1. Knorz M, Zaldavir R. Special focus on bioptics and angle-supported pIOLs and visual outcomes of these techniques in European studies. Eurotimes. 2007; 2:4-10.
    2. Espandar L, Meyer JJ, Moshirfar M. Phakic intraocular lenses. Curr Opin Ophthalmol. 2008;19:349-356.
    3. Benedetti S, Casamenti V, Benedetti M. Long-term endothelial changes in Phakic eyes after Artisan intraocular lens implantation to correct myopia: five-year study. J Cataract Refract Surg. 2007;33:784-790.
    4. Solomon R, Donnenfeld ED. Refractive intraocular lenses: multifocal and phakic IOLs. Int Ophthalmol Clin. 2006; 46:123-143.
    5. Dejaco-Ruhswurm I, Scholz U, Pieh S, et al. Long-term endothelial changes in Phakic eyes with posterior chamber intraocular lenses. J Cataract Refract Surg. 2002; 28:1589-1593.

    Author Disclosure

    Dr. Holland served as an investigator for the Alcon, Inc., trial of the phakic AC IOL and for WaveLight's Allegretto.