Phakic intraocular lenses continue to serve as an excellent option for vision correction in patients who are not ideal candidates for laser vision correction. Within minutes of a minimally invasive procedure, large amounts of myopia can be corrected. This article will review the two currently available phakic IOLs available in the US as well as a look on the horizon of what’s to come.
Verisyse Phakic IOL (Abbott Medical Optics)
The Verisyse lens is indicated for the elimination of myopia in adults ranging from -5 to -20D (1 diopter increments) with less than or equal to 2.5D of astigmatism with anterior chamber depth of at least 3.2mm. A one piece PMMA lens with 5 mm optic, it is designed to be placed within the anterior chamber. A loop on either side of the lens is designed to incorporate iris tissue to hold the IOL in place (enclavation). Serious risks of the procedure can include infection, glaucoma, cataract, corneal decompensation. In the clinical trials of the verisyse lens the rate of post-operative surgical intervention was 13.6%. In speaking with physicians who perform the procedure the consensus is that it is easy to implant but care must be taken to ensure good centration and not incorporate too much iris tissue or risk a cat-eye phenomenon.
Visian ICL (Staar Surgical)
Similar to the Verisyse IOL, this lens is also indicated for the treatment of myopia from -3D to -20D in patients with minimal astigmatism. However, this lens is designed to be placed in the ciliary sulcus rather than the anterior chamber. Made from collamer, a proprietary collagen copolymer, the lens is foldable and can be injected similar to a traditional posterior chamber intraocular lens. Once delivered into the anterior chamber of the eye, four corners of the lens are tucked under the iris into the sulcus. Per Dr. James Goldman, a cataract/refractive surgeon at Arizona Eye Specialists in Scottsdale, AZ, “the procedure is very easy to learn for a skilled cataract surgeon. These patients have much less night vision issues than lasik patients. You should also consider that down the road these are the patients who will be seeking technology such as multifocal IOLs, and by performing phakic IOLs we are preserving their corneas to maximize their results now as well as down the road when they desire that next generation technology. If a patient seeking vision correction has less than 1.25D of astigmatism and greater than 6D of myopia, I will definitely offer them phakic IOLs.” Prior to surgery it is important to create two peripheral iridotomies to prevent pupillary block. While not yet available in the US, a toric version of the lens will likely become available soon.
Which lens is superior?
It depends on the surgeon. Proponents of the Verisyse IOL will cite a greater risk of cataractogenesis, while Visian loyalists will voice their concerns over endothelial cell loss with anterior chamber lenses. Ease of surgery is also debatable – while implantation is easier with the Visian lens, there is a greater probability of having to exchange the lens due to incorrect size (current opinion is that the best way to measure for lens size is with anterior segment ultrasound, something not available to every surgeon leaving them to use the less accurate white-to-white measurement). Centration appears to favor the visian, although this can be correlated with surgeon skill. In essence, the choice of phakic IOL will be up to the surgeon’s preference.
On the horizon
Currently undergoing trials in the US is the Alcon Cachet phakic intraocular lens. Similar to the Verisyse lens, this IOL is designed to sit within the anterior chamber. Made of the traditional acrysof acrylic material, it is foldable and can be injected via Monarch system. While likely easier to implant than the Verisyse counterpart, what remains to be determined is if the phakic eye will tolerate an angle supported phakic IOL. As more data from the clinical trials are released, we should have more information.
The best Phakic IOL?
Whichever lens is chosen, the results are excellent. In addition, there is minimal risk of refractive change over time, which can be seen with both lasik and surface ablation in hyperopes and myopes. Corneal shape is unchanged, preventing significant corneal flattening associated with high myopic treatments that may degrade contrast sensitivity. Furthermore, visual results are immediate, as compared to the delayed fluctuating visual acuity which follows PRK. Again, while some surgeons may prefer PRK for borderline corneal thickness cases, other may choose phakic intraocular lenses.