DualFlex IOL system helps improve distance, near visual acuity
A new accommodative system has shown good early results. A larger study is in the planning stages.

by Raymond M. Stein, MD, FRCS(C)
Special to OCULAR SURGERY NEWS

A new dual lens IOL system that facilitates accommodation following clear lensectomy and cataract extraction has the potential to revolutionize refractive surgery and implant protocols. I began performing double implants with the DualFlex IOL System to treat high degrees of hyperopia because of limits with laser vision correction. Not only did we correct hyperopia with the double implants, but the patients reported an accommodative effect. I coined the term DualFlex to describe a double implant technique using two standard STAAR Surgical IOLs.

Initial study
The initial study included 24 eyes in 13 patients who received double implants using STAAR Surgical's standard silicone plate lens in the capsular bag and the company's standard three-piece IOL in the sulcus. All patients were hyperopic (+5 D to +16 D) and underwent clear lens extraction. Fifteen of the 24 eyes were 20/40 or better uncorrected for distance, and 20 eyes could see J4 or better uncorrected for near. Moreover, 20 eyes could see J4 or better - and 17, J3 or better - with only distance correction in place. Thirteen eyes were 20/40 or better for distance and J4 or better for near vision.

DualFlex System
The DualFlex system was initially developed to treat hyperopic patients who required more power than was available in a single lens. For example, one patient in the study group was +16 D in both eyes and implant power called for a +59 D lens. After placing a +30 D plate lens and a +29 D three-piece lens in the bag, not only did the patient have an excellent level of uncorrected distance vision, he was able to read J2 at an extremely close range. Results from the DualFlex study show that the higher the degree of preop hyperopia, the better the near acuity. Also, near vision correction has remained stable in all patients who received dual lens implants with an average of 13 months follow-up. All of the clear lens extraction cases were hyperopes, but the system also can be used to improve accommodation for myopes. Currently, about two-thirds of the power is in the bag, with the balance in the sulcus. But changing the power distribution could possibly benefit patients with longer eyes. The accommodative effect of the DualFlex system appears to be the result of ciliary muscle contraction and increased vitreous pressure pushing the lens in the sulcus forward, with nothing holding the lens back other than the iris. But one question yet to be answered is whether putting both lenses in the bag and doing a large capsulorrhexis will yield similar results.

Technique
The surgical technique I use, following a clear lensectomy, is to make a 3-mm clear corneal incision, a standard capsulorrhexis and standard phaco before inserting the plate lens through the shooter into the capsular bag. The best results have come from using the STAAR Elastic lens in the bag in combination with the Elastimide lens in the sulcus. The viscoelastic is removed and pupil constricted before inserting the three-piece lens into the sulcus. Additional viscoelastic is then placed on top of the first lens to expand the pupil before placing the three-piece lens in the sulcus. The viscoelastic is then removed, the wound is hydrated, and 1 mg of vancomycin is placed into the posterior chamber. With higher hyperopes, it is important not to let the anterior chamber collapse. When removing the phaco tip from the eye, it is worthwhile to come in with the side port incision and use viscoelastic to prevent the anterior chamber from collapsing, minimizing the risk of choroidal effusion. Another approach is to use an anterior chamber maintainer to maintain the depth of the anterior chamber. Patients with small eyes have a greater risk of iris prolapse, so it is important to make the corneal lip incision slightly longer than in a routine case. Only one complication occurred among the patients in the initial study group, and it was literally caused by the patient standing on her head. We had one lens that came forward and was captured by the pupil. This was a very interesting patient who practices power yoga 6 or 7 days a week, and stands on her head for an hour a day. She was standing on her head within a week postop. She was completely asymptomatic, but came in about 6 weeks out with pupillary capture. The lens was repositioned and she has done well since then.

Further study planned
Since discovering the accommodative effect from dual lenses, I have been trying different power and lens combinations to achieve the best outcomes for accommodation. We are currently planning a study of DualFlex patients using wavefront analysis to assess the shift of the lenses and the changes in power that takes place in the eye. A new physician-sponsored study, which also includes John Vukich, MD, Richard Lindstrom, MD and Stephen Bylsma, MD, will also help to further refine the DualFlex approach. The study group, which includes three sites in the United States, will conduct a randomized controlled study. The independent multicenter study will randomize the DualFlex system with a control group using a one-piece IOL.

Toric IOL designed to reduce pre-existing astigmatism in cataract patients.
Approximately 20 percent of patients who need cataract surgery have 1.5 diopters or more of preexisting astigmatism. Until recently, patients with clinically significant preexisting astigmatism were either left uncorrected or required corneal curvature-altering procedures to correct this condition. Now, the STAAR TORIC™ Intraocular Lens (IOL) delivers unsurpassed vision in a single refractive procedure. This innovative lens incorporates a toric optic into an injectable, UV-absorbing, plate-haptic lens that enables correction or reduction of astigmatism at the time of cataract surgery.

The anterior surface of the STAAR TORIC™ IOL is a sphero-cylindrical refracting element and the posterior surface is a spherical lens which creates a biconvex, toric optic 6mm in diameter. The STAAR TORIC™ IOL is highly flexible to facilitate folding and implantation through a clear corneal incision of 3mm or less and has two large fenestrations at opposite ends of the plate haptic to secure fixation in the capsular bag. The IOL also has an increased length of 10.8mm for added stability and centration.

The ideal STAAR TORIC™ IOL patient has a corneal astigmatism between 1.5 and 3.5 diopters of regular preexisting astigmatism. Once a patient has been selected, careful astigmatic measurements are taken with keratometry, corneal topography and refraction to verify the steep corneal meridian.

On the day of surgery, the steep meridian of the astigmatism is marked with the patient erect at the slit lamp or under the operating microscope so that the IOL is accurately aligned. The STAAR TORIC™ IOL is loaded under the surgical microscope with the toric side up and is injected into the capsular bag where the axis markings are aligned with the steep corneal meridian. Three aspects which must be considered in optimizing the effect of the STAAR TORIC™ IOL postoperatively, include using "astigmatically neutral cataract surgery" so as not to alter the curvature of the cornea, orientating the IOL axis at the desired meridian and minimizing rotation of the IOL postoperatively.

The STAAR TORIC™ IOL offers the most accurate correction of astigmatism at the time of surgery and eliminates the need for astigmatic keratotomy which can potentially compromise the integrity of the cornea. Although some patients may have some residual cylinder, it will be significantly reduced as compared to using a non-toric conventional IOL.

Toric IOL Calculation Program now available at no charge.
STAAR Surgical has developed the SRK/T Toric IOL calculation software on CD rom for easy calculation of IOL powers for toric lenses. To receive a free copy of the SRK/T toric calculation software, please contact STAAR Surgical at 626-303-7902 x2330 or e-mail salessupport@staar.com.