Figure 8-4 A, After placement with an IOL inserter, the posterior chamber PIOL unfolds in the anterior chamber. B, A posterior chamber PIOL shown unfolded and in position anterior to the crystalline lens in the posterior chamber. (Courtesy of

STAAR Surgical Company.)

Sizing the posterior chamber PIOL The correct IOL length is selected by using the white-to-white measurement between the 3 and 9 o’clock meridians or by direct sulcus measurements made by a variety of techniques, including high-frequency ultrasound, anterior segment OCT, slit-beam or Scheimpflug imaging, and laser interferometry. Although the FDA-approved technique for measurement remains white-to-white measurement, there is growing evidence that direct sulcus measurement using any of these methods is superior and minimizes the risk of incorrect PIOL sizing.

For more information on PIOLs, please see the FDA website at www.fda.gov/MedicalDevices/Pro ductsandMedicalProcedures/ImplantsandProsthetics/PhakicIntraocularLenses/default.htm.

Angle-supported phakic intraocular lens

No angle-supported PIOLs are currently approved by the FDA. Outside the United States, several commercial angle-supported PIOLs are available. The most widely used lens is made of flexible acrylic material and can be inserted through a small incision without the need for pupil dilation.

Outcomes

With better methods for determining PIOL power, outcomes have steadily improved. The significant postoperative gains in lines of corrected distance visual acuity (CDVA; historically referred to as best-corrected visual acuity, BCVA) over preoperative values are likely the result of a reduction in the image minification present with spectacle correction of high myopia. Loss of CDVA is rare. Moreover, the loss of contrast sensitivity noted after LASIK for high myopia does not occur after PIOL surgery. In fact, in all spatial frequencies, contrast sensitivity increases from preoperative levels with best spectacle correction.

Barsam A, Allan BD. Excimer laser refractive surgery versus phakic intraocular lenses for the correction of moderate to high myopia. Cochrane Database Syst Rev. 2012;1:CD007679. Epub 2012 Jan 18.

Boxer Wachler BS, Scruggs RT, Yuen LH, Jalali S. Comparison of the Visian ICL and Verisyse phakic intraocular lenses for myopia from 6.00 to 20.00 diopters. J Refract Surg. 2009;25(9): 765–770. Epub 2009 Sep 11.

Dick HB, Budo C, Malecaze F, et al. Foldable Artiflex phakic intraocular lens for the correction of myopia: two-year follow-up results of a prospective European multicenter study. Ophthalmology. 2009;116(4):671–677.

Hassaballa MA, Macky TA. Phakic intraocular lenses outcomes and complications: Artisan vs. Visian ICL. Eye (Lond). 2011;25(10):1365–1370. Epub 2011 Aug 5.

Kamiya K, Shimizu K, Igarashi A, Hikita F, Komatsu M. Four-year follow-up of posterior chamber phakic intraocular lens implantation for moderate to high myopia. Arch Ophthalmol. 2009;127(7):845–850.

Kohnen T, Kook D, Morral M, Güell JL. Phakic intraocular lenses: part 2: results and complications. J Cataract Refract Surg. 2010;36(12):2168–2194. Lovisolo CF, Reinstein DZ. Phakic intraocular lenses. Surv Ophthalmol. 2005;50(6):549–587.

Parkhurst GD, Psolka M, Kezirian GM. Phakic intraocular lens implantation in United States military warfighters: a retrospective analysis of early clinical outcomes of the Visian ICL. J Refract Surg. 2011;27(7):473–481. Epub 2011 Jan 17.

Pérez-Cambrodí RJ, Piñero DP, Ferrer-Blasco T, Cerviño A, Brautaset R. The posterior chamber phakic refractive lens (PRL): a review. Eye (Lond). 2013;27:14–21. Epub 2012 Dec 7.

US Food and Drug Administration. Summary of Safety and Effectiveness Data. Artisan phakic lens. PMA No. P030028. www.accessdata.fda.gov/cdrh_docs /pdf3/P030028b.pdf. Approval September 10, 2004. Accessed July 3, 2013.

US Food and Drug Administration. Summary of Safety and Effectiveness Data. STAAR Visian ICL (Implantable Collamer Lens). PMA No. P030016. www.ac cessdata.fda.gov/cdrh_docs/pdf3/P030016b.pdf. Approval December 22, 2005. Accessed July 3, 2013.

Complications

PIOL surgery shares the same possible risks and complications as other forms of IOL surgery. However, the most relevant potential complications include raised IOP, persistent anterior chamber inflammation, traumatic PIOL dislocation, cataract formation, and endothelial cell loss. Some of these complications do not manifest for years, thus necessitating long-term follow-up.

Iris-fixated phakic intraocular lens

At 1-year follow-up in FDA clinical trials of 662 patients who had an iris-fixated PIOL implanted for myopia, 1 patient had a hyphema, 5 had IOL dislocations, and 3 had iritis. Preoperative to postoperative change, as assessed by questionnaire, in glare, starbursts, and halos was 13.5%, 11.8%, and 18.2%, respectively. However, improvement in these symptoms from preoperative to postoperative status occurred in 12.9%, 9.7%, and 9.8%, respectively. In general, nighttime symptoms were worse in patients with larger pupil diameters.

Stulting and colleagues reported a 3-year follow-up study on 232 eyes of the 662 eyes enrolled in the FDA study. A total of 5 lenses dislocated and required reattachment, and an additional 20 lenses required surgery for insufficient lens fixation. No eyes required IOP-lowering medications after the first month. The mean decrease in endothelial cell density from baseline to 3 years was 4.8%. Six eyes required retinal detachment repair (rate, 0.3% per year), and 3 eyes underwent cataract surgery.

Pop M, Payette Y. Initial results of endothelial cell counts after Artisan lens for phakic eyes: an evaluation of the United States Food and Drug Administration Ophtec Study. Ophthalmology. 2004;111(2):309–311.

Stulting RD, John ME, Maloney RK, Assil KK, Arrowsmith PN, Thompson VM; U.S. Verisyse Study Group. Three-year results of Artisan/Verisyse phakic intraocular lens implantation. Results of the United States Food and Drug Administration clinical trial. Ophthalmology. 2008;115(3):464–472. Epub 2007 Nov 26.

Posterior chamber phakic intraocular lens

In addition to the potential risks associated with implantation of other types of PIOLs, implantation of posterior chamber PIOLs increases the risk of cataract formation and pigmentary dispersion. If the posterior chamber PIOL is too large, vaulting increases, and iris chafing with pigmentary dispersion could result. If the PIOL is too small, the vaulting is reduced, decreasing the chance of chafing but increasing the risk of cataract. Incorrect PIOL vault can necessitate exchange of the implanted lens for one with a better fit.

In an FDA clinical trial for one posterior chamber PIOL model, the incidence of nighttime visual symptoms was approximately 10%, but a similar percentage showed improvement in these symptoms after surgery. The incidence of visually significant cataract in the FDA clinical trial as reported by Sanders and colleagues was 0.4% for anterior subcapsular cataracts and 1% for nuclear sclerotic cataracts.

Kamiya and colleagues reported 4-year follow-up results on 56 eyes of 34 patients with implanted posterior chamber PIOLs. No eyes developed pupillary block or a significant increase in IOP. The mean central endothelial cell loss from baseline to 4 years was 3.7%. Two eyes developed