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Up Front | Oct 2008

Astigmatic Correction With a Toric Phakic IOL

Toric phakic IOLs correct both sphere and cylinder in one procedure.

Phakic IOLs are gaining popularity in large part because they provide accurate, predictable, and stable refractive results, which are also independent of tissue healing. In most instances, implantation of a phakic IOL offers patients increased BCVA because it leaves the natural refractive structures of the eye (eg, cornea and lens) untouched. New toric models are now available to correct cylinder in addition to the spherical correction that standard phakic IOLs offer.

The most important advantage of toric phakic IOLs is that the surgeon is able to perform the correction of sphere and cylinder in one easy-to-manage session. With spherical phakic IOLs, the surgeon had to wait approximately 2 months after IOL implantation to perform LASIK to correct the astigmatism. Now, it is possible to immediately address the issue with IOL implantation.

There are two toric phakic IOLs on the market, the Visian Toric ICL (T-ICL; STAAR Surgical, Monrovia, California), and the Toric Artiflex (Ophthec BV, Groningen, Netherlands), both of which I have experience implanting. The biggest difference I have noticed between the T-ICL and the Toric Artiflex is that the T-ICL, being size dependent, may rotate within the eye, reducing the astigmatic correction. Because the Toric Artiflex is fixated to the iris with PMMA haptics and is a one-size-fits-all lens, rotation, and therefore change in astigmatism does not occur.

The Toric Artiflex is available in two versions, one with the cylinder correction parallel to the haptics and a second with the cylinder correction perpendicular to the haptics (Figure 1). The surgeon may select the appropriate model, depending on the axis of error in the patient, to avoid too much manipulation of the lens inside the eye. Each version is available for the correction of myopia between -1.00 and -13.50 D and cylinder between -1.00 and -7.50 D.

I am currently one of seven clinical investigators studying the Toric Artiflex. As a whole, we have implanted 120 Toric Artiflex IOLs with excellent results. All patients had myopia between -2.00 and -14.00 D and cylinder between -2.00 and -5.00 D. I have implanted 13 Toric Artiflex IOLs since April, 2008, and results are similar to what I experienced with the spherical Artiflex. The big difference here is the correction of cylinder (Figure 2). In most cases, my patients' refraction was plano at postoperative day 1 (Figure 3). With 5 months of follow-up, they have all remained stable and satisfied with their outcomes (Figure 4).

IMPLANTATION TECHNIQUE
I prefer implantation of a toric phakic IOL to LASIK if patients' spherical equivalent is more than -7.00 D, and even in lower powers if their cornea is too thin or if they have an abnormal topography. In patients with low astigmatism (ie, -2.00 to -3.00 D) or low myopia, I typically perform LASIK.

I have noticed that most patients who are good candidates for phakic IOLs have some level of astigmatism. Therefore, I consider the toric model in many cases; however, toric phakic IOLs are currently used only in patients with high astigmatism. In the future when the means to manufacture toric phakic IOLs is more efficient, I think more toric models will be available to treat any level of astigmatism.

CONTRAINDICATIONS
There are no specific contraindications for the implantation of a toric phakic IOL; however, the same contraindications that apply to phakic IOLs apply to their toric counterparts. The surgeon must first consider the anatomy of the anterior chamber. The minimum depth for safe implantation, measuring from the endothelium to the anterior surface of the lens, is 3 mm. Devices that can measure anterior chamber depth include the Orbscan (Bausch & Lomb, Rochester, New York), Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany), and the Visante OCT (Carl Zeiss Meditec AG, Jena, Germany). Common ultrasound biometry should be avoided because it reduces corneal thickness in the anterior chamber depth measurement. The surgeon may miss diagnosis of a shallow anterior chamber if the patient's cornea is thick.

Iris shape is also important, and surgeons should make sure the patient's iris is flat. A convex iris may lead to serious complications, such as posterior synechia or pigmentary glaucoma. Other considerations include pupil size (mesopic pupil diameter should be smaller than the optic diameter of the IOL), a healthy corneal endothelium, and good hexagonality of the cells. Eyes with high rates of polymegathism and pleomorphism are also contraindicated for a phakic or toric phakic IOL.

PEARLS
I am currently implanting the Toric Artiflex through a 3.2-mm incision. Other surgeons create incisions as small as 3 mm; however, I feel that the incision stretches too easily during implantation at this size. Because of the PMMA haptics, the Toric Artiflex would be hard to implant through a sub–3-mm incision. The optic of the lens is made of silicone.

One of the most important things to remember when implanting the Toric Artiflex is to mark the axis of astigmatism before surgery begins. This is different from the spherical phakic IOL models, which do not require a specific orientation for astigmatism.

My routine for marking the axis of astigmatism is as follows: first, at the slit lamp, mark the patient's axis of astigmatism at 0° and 90°. We prefer using a plastic surgery marking pencil. This is important because when the patient is lying down, the eye may rotate. Afterward, using a standard corneal degree marker—just as we used to use for radial keratotomy, arcuate incisions, and corneal rings—we mark the correct axis of astigmatism to fix the toric phakic IOL in that direction. This is the most important step in implanting a toric phakic IOL. The rest of the surgery is performed just as if it was a spherical phakic IOL.

The foldable Toric Artiflex phakic IOL is a wonderful addition to my practice. My patients are typically plano at 1 day after surgery and continue to show stability at 5 months postoperatively. This is a promising lens, and I would suspect its use will grow in the near future.

António A.P. Marinho, MD, PhD, is the Chairman of the Department of Ophthalmology, Hospital Arrábida, Porto, Portugal. Dr. Marinho states that he has no financial interest in the products or companies mentioned. He may be reached at tel: +35 1936093345; e-mail: marin@mail.telepac.pt.

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