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Phakic IOLs useful tool to correct refractive error in cases not amenable to excimer laser surgery
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LASIK is the most common refractive surgery performed worldwide. Some patients, however, are not suitable candidates for excimer laser refractive surgery due to high refractive error, issues with pupil diameter, corneal thickness or questionable corneal biomechanics. There are also some concerns regarding quality of vision and contrast sensitivity when very high refractive errors are corrected using excimer laser.
Phakic IOLs, which entered the market in the 1980s, did not incite significant interest due to the complications associated with the initial versions of the lenses and the success of the excimer laser. It was only in the late 1990s and early 2000s that there was a resurgence of interest in phakic IOLs, with the Verisyse/Artisan (Abbott Medical Optics/Ophtec) and the ICL (STAAR Surgical) being the two most commonly used designs. Angle-supported phakic IOLs are no longer used, with the latest design, the Alcon Cachet, withdrawn from the market over concerns regarding endothelial damage.
Over the last decade, with improvements in design, the ICL has become the preferred phakic IOL for clinical use. Preoperative screening is of paramount importance in having a good refractive outcome and long-term safety. Patients with anterior chamber depth of less than 2.8 mm (from the endothelium) in the case of the ICL and 3.2 mm in the case of the Verisyse (Artisan/Artiflex) are not suitable candidates. Sizing of the ICL still is not an exact science because we use white-to-white as a guide to decide the size of the ICL. The anatomical variation between the white-to-white and sulcus diameter can result in few cases having suboptimal vaults (either low or high). Lower vault can predispose to increased incidence of cataract and cause rotation of ICL. Higher vault can predispose to glaucoma.
The simplicity of the surgical procedure, the refractive predictability, the extended range of corrections possible, and the excellent quality of vision that the procedure offers have resulted in an increased use of phakic IOLs for high myopia greater than 8 D. In case of moderate myopes between 3 D and 8 D, head-to-head comparisons between phakic IOLs and excimer laser correction have shown equal efficacy, safety and predictability.
The long-term risks with phakic IOL are concerns regarding corneal endothelial damage, uveitis, secondary glaucoma and cataract formation. The ICL has been found to be fairly safe with respect to the corneal endothelium and uveitis. The main concern with the ICL is the incidence of cataract. The reported incidence of visually significant cataract requiring surgery varies between 0% and 18%, and this is a concern that should be discussed with the patient preoperatively. The recent change in design to the V4C with the central Aquaport should further reduce the risk of cataract by improving the nourishment to the anterior lens capsule, and recent short-term results show no cataract in eyes implanted with V4C model lenses. The port can also be used to remove the residual viscoelastic material below the ICL. The risks with the Verisyse include endothelial changes, uveitis, displacement due to loss of enclavation and cataract.
Recently, a presbyopia-correcting optic design has been incorporated in the IPCL (Care Group); however, results are awaited. Another interesting use of the ICL has been in cases of stable keratoconus with high myopic astigmatism that is reasonably regular, in which the ICL has been used to reduce dependency on glasses.
To conclude, the mid-term and long-term results of phakic IOLs are encouraging with respect to refractive outcome, stability and safety profile. The ICL is the preferred phakic IOL at present. Phakic IOLs are a useful tool to correct refractive error not amenable to excimer laser surgery. They may also become an option for cases amenable to excimer laser surgery, but more data would be needed to confirm safety and efficacy.
References:
Alfonso JF, et al. J Cataract Refract Surg. 2015;doi:10.1016/j.jcrs.2014.07.039.
Barsam A, et al. Cochrane Database Syst Rev. 2010;doi:10.1002/14651858.CD007679.pub4.
Guber I, et al. JAMA Ophthalmol. 2016;doi:10.1001/jamaophthalmol.2016.0078.
Sanders DR. J Refract Surg. 2007;doi:10.3928/1081-597X-20070601-02.
Shimizu K, et al. Medicine (Baltimore). 2016;doi:10.1097/MD.0000000000003270.
Stulting RD, et al. Ophthalmology. 2008;doi:10.1016/j.ophtha.2007.08.039.
For more information:
Dennis S.C. Lam, MD, FRCOphth, can be reached at State Key Laboratory in Ophthalmology, Sun Yat-Yen University, 54 South Xianlie Road, Guangzhou 510060, People’s Republic of China; email: dennislam.gm@gmail.com.
Disclosure: The authors report no relevant financial disclosures.