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Phakic lens implant viable option to correct patients with extreme myopia
In addition, LASIK can be performed after implantation to treat astigmatism and ensure sharp vision.
 Uday Devgan |
LASIK has a strong track record for the correction of a wide range of refractive errors, from hyperopia to myopia and with varying degrees of astigmatism. But what happens when a patient is so myopic that he falls outside of the ideal range for LASIK?
Phakic lens implants may be appropriate options here. And for extremely myopic eyes, combining LASIK with phakic lens implantation provides the necessary range to achieve sharp, high-quality vision for these challenging patients.
Extreme degrees of myopia and the challenge of corneal astigmatism
Many surgeons consider the upper limit for LASIK to be somewhere between –8 D and –10 D because higher degrees of myopic LASIK may be less accurate and may induce visual aberrations that can negatively affect image quality. A better option in extreme cases of myopia may be a phakic IOL because it can correct the myopia while preserving the accommodation.
There are two U.S. Food and Drug Administration-approved phakic IOL implants, the Verisyse (Advanced Medical Optics) and the Visian ICL (STAAR Surgical), and these allow the correction or reduction of myopia of up to –20 D. The Verisyse is an anterior chamber lens that is fixated to the iris with two integral claws. It requires a larger incision that then must be sutured. The Visian ICL is a posterior chamber lens that is securely positioned in the ciliary sulcus, and it uses a much smaller sutureless incision.
In addition to having an extreme degree of myopia, this patient has a significant degree of corneal astigmatism (Figure 1). Because neither of the FDA-approved phakic IOLs has a toric correction, we need a second surgical procedure to correct the astigmatism to ensure sharp vision. For this patient, the Visian ICL will be implanted to correct most of the myopia, and then LASIK will be performed to treat the astigmatism and any residual myopia.
Surgical procedures and technique
LASIK involves placing a suction ring on the eye during flap creation, and for safety, this should be avoided after recent intraocular surgery to prevent incision leakage. For this reason, the corneal flap can be made before the intraocular surgery and then lifted a few weeks after the phakic lens is implanted so that the residual refractive error can be treated with the excimer laser. In this case, I elected to perform a femtosecond laser flap without actually lifting it. Because these laser-made corneal flaps are adherent, there was essentially no risk of flap slippage.
 Corneal topography shows significant corneal astigmatism in both eyes of this highly myopic patient.  (A) The leading corners of the ICL are placed under the nasal iris using just the inserter system. (B) The trailing corners of the ICL are placed under the temporal iris using just the inserter system. (C) The ICL is in perfect position without the need for any further manipulation. (D) Bimanual irrigation and aspiration probes are used to remove the viscoelastic from the eye. Images: Devgan U |
The Visian ICL was selected to address the high degree of myopia, and it was performed bilaterally, with both eyes done the same day but each eye treated as a separate surgery to minimize the risk of infection. It is important to have the corneal incisions barely nick the limbal blood vessels because the tiny amount of blood will allow the incisions to heal faster and stronger as compared with avascular incisions.
My preferred technique of placing the ICL is via the “no-touch” technique, in which all four corner footplates can be properly positioned under the iris using just the lens inserter. There is no need for further manipulation of the ICL, which can lead to complications such as cataract development or excessive inflammation. Once the leading corners are placed securely under the distal iris, the injector can be tilted so that the trailing corners also self-tuck into position. Note that the anterior chamber is carefully filled with a dispersive viscoelastic before ICL placement to protect the ocular structures. Care is also taken to place the ICL without any contact of the human crystalline lens (Figure 2).
Once the ICL is in position, the viscoelastic can be removed through the use of bimanual irrigation and aspiration instruments. To keep the anterior chamber stable, adjust the fluidic settings so that the inflow of fluid is greater than the outflow of fluid. The 25-gauge instruments that I have designed have an out-the-front fluid inlet so that the viscoelastic can be easily washed out of the anterior chamber. The incisions are sealed with stromal hydration with balanced salt solution, and the eye is mediated with antibiotics and anti-inflammatories. The patient starts to recover vision immediately.
After a few weeks of healing, the patient’s residual focusing issues are measured, including the lower-order aberrations of myopia or astigmatism, as well as the higher-order aberrations such as spherical aberration, coma or trefoil. The femtosecond laser corneal flaps are then lifted and LASIK is performed. The patient did beautifully, recovering sharp vision in both eyes.
For more information:
- Uday Devgan, MD, FACS, is in private practice at Devgan Eye Surgery in Los Angeles, Beverly Hills, and Newport Beach, California. Dr. Devgan is Chief of Ophthalmology at Olive View UCLA Medical Center and an Associate Clinical Professor at the Jules Stein Eye Institute at the UCLA School of Medicine. Dr. Devgan can be reached at 11600 Wilshire Blvd., Suite 200, Los Angeles, CA 90025; 800-337-1969; fax: 310-388-3028; e-mail: devgan@gmail.com; Web site: www.DevganEye.com. Dr.Devgan is a consultant to Abbott Medical Optics and Bausch & Lomb, and is a stockholder in Alcon Laboratories and formerly in Advanced Medical Optics.
Reference:
- Zaldivar R, Oscherow S, Piezzi V. Bioptics in phakic and pseudophakic intraocular lens with the Nidek EC-5000 excimer laser. J Refract Surg. 2002;18:S336-339.