Five years ago, we began to implant new-generation multifocal IOLs such as the Tecnis Multifocal (Abbott Medical Optics Inc., Santa Ana, California), the ReZoom (Abbott Medical Optics, Inc.), and the AcrySof Restor multifocal IOL (Alcon Laboratories, Inc., Fort Worth, Texas). The manufacturers of these IOLs warned that patients might experience adaptation problems if the same lens was not implanted in both eyes. Later, colleagues came up with the mix-and-match method, wherein two models of presbyopia-correcting IOL are implanted in a patient's eyes to balance out the drawbacks of one IOL technology with the advantages of another

As multifocal IOLs gained popularity, patients who had previously been implanted with a monofocal IOL in one eye began to ask for a multifocal IOL for their fellow eye. Although IOL manufacturers do not recommend this, I wanted to see if implanting a multifocal IOL in the nondominant eye could improve vision for my patients, particularly plano presbyopes.

Surprisingly, the result in the initial case was satisfactory, and I then began implanting multifocal IOLs in the nondominant eyes of plano presbyope patients. I named this the mono-multi treatment method. Mono stands for single-eye treatment and multi for multifocal IOL implantaion. This is similar to monovision; however, the outcome should be better than monovision because the multifocal-implanted eye can see both near and distance while the monovision eye can see only near.

WHY RLE?
Presbyopes want a near-vision solution. If we treat a plano presbyope with a corneal procedure such as conductive keratoplasty, presby-LASIK, corneal inlays, or monovision, these patients typically will need a second vision-correction procedure a few years later. We also must consider the development of further cataract in phakic presbyopes. Corneal procedures always interfere with distance vision. Therefore, refractive lens exchange (RLE) with a multifocal IOL seems to be a better solution in terms of providing distance and near visual acuity and refractive stability.

RLE is gaining popularity among refractive surgeons. The latest developments in phacoemulsification, IOLs, and axial length measurement technologies, as well as the prophylactic use of intracameral antibiotics, have increased the safety and predictability of RLE.

The benefits of RLE with multifocal IOLs include the correction of near, intermediate, and distance vision; the possibility to fine-tune outcomes with laser touchup procedures; the stability of refraction during the patient's entire lifespan; the elimination of future possibility of cataract development; and preservation of negative spherical aberration with aspheric IOL designs.

MONO-MULTI PEARLS
When performing the mono-multi treatment method, I prefer unilateral surgery; RLE is performed in the nondominant eye only. I implant a diffractive IOL to provide good near visual acuity. Conversely, the dominant eye is not operated on to maintain good distance vision function and to avoid halo and glare problems.

Counseling. Patients are counseled about the known side effects of multifocal IOLs (halo and glare) as well as the possible side effects associated with the monomulti treatment, including dyscoordination between eyes. In the case of patient dissatisfaction, we operate on the fellow eye regardless of the reason.

Corneal topography. Astigmatism can occur in any patient. If the astigmatism is lenticular, the refractive result after RLE will be favorable. However, if the astigmatism is corneal, there are two corrective options: corneal laser surgery can be performed 2 to 3 months after RLE, or a multifocal toric IOL can be implanted.

Biometry. To achieve accurate biometry, we use both immersion biometry and the IOLMaster (Carl Zeiss Meditec, Jena, Germany). Surgeons who want to implant a multifocal IOL must perform at least one of these two techniques. We do not recommend contact biometry.

IOL power calculation formulas are also important. We use the Holladay II for all eyes. If the Holladay II is unavailable, we prefer to use the Holladay I in long eyes, the Hoffer Q in short eyes, and SRK-T and Holladay I in average eyes. The optimized Haigis formula also works well in all eye types. Optimizing one's IOL constants is recommended, especially if the surgeon is not satisfied with patients' refractive outcomes.

Technique. Phacoemulsification is done under topical anesthesia in all cases. First, flip the nucleus into the iris plane with hydrodissection. Next, emulsify the nucleus. My phaco technique for RLE is different from that for cataract operations. I polish the anterior and posterior capsule to avoid capsular fibrosis. I also inject intracameral cefuroxime at the end of the surgery.

IOL selection. The choice of IOL depends on several factors, including pupil size. I prefer diffractive IOLs such as the AcrySof IQ Restor +3.0 D or the AT LISA (previously Acri.LISA; Carl Zeiss Meditec) because they are not pupil-dependent. According to the mono-multi treatment method protocol, plano presbyopes receive a diffractive IOL in the nondominant eye only; the dominant eye is untouched.

RESULTS
In a prospective study, 10 plano presbyopic patients (age range, 45 to 55 years) underwent RLE with implantation of a diffractive multifocal (AT LISA) in the nondominant eye. Patients were evaluated preoperatively and at 6 months after surgery for near, intermediate, and distance visual acuity, contrast sensitivity, spectacle independence, and satisfaction. Other preoperative assessments included refraction, visual acuity, dry eye tests, corneal topography, anterior and posterior segment examination, biometry, and an eye dominance test to determine the surgical course of action.

The Infiniti Vision System (Alcon Laboratories, Inc.) was used with 2.4-mm clear corneal temporal incisions. Continuous curvilinear capsulorrhexis (CCC) was performed with 23-gauge MST Duet Capsulorrhexis (MicroSurgical Technology, Redmond, Washington) forceps, and CCC diameter was approximately 5 mm.

The mean preoperative UCVA was 0.81 ±0.22, and the mean postoperative UCVA was 0.97 ±0.17. The mean preoperative BCVA was 0.9 2±0.19, and the mean postoperative BCVA was 1.04 ±0.08 (Figure 1). In all eyes, near visual acuity and distance corrected near visual acuity (DCNVA) was J2 or better. In 40% of eyes, intermediate visual acuity was J5 or better. All 10 patients' binocular near visual acuity and binocular DCNVA was J2 or better. Eighty percent of the patients had binocular intermediate visual acuity of J5.

Contrast sensitivity levels were typically lower in operated eyes compared with unoperated. No surgical complications occurred. Three eyes developed mild posterior capsular opacification and underwent Nd:YAG laser capsulotomy. One eye developed cystoid macular edema, which was resolved with topical antiinflammatory treatment (Figure 2).

According to results of a questionnaire, none of the patients experienced problems with glare. One patient reported mild halos, but this did not cause night vision problems. Overall, patients were satisfied with their vision. One patient—a technician in the automotive industry—was dissatisfied with his intermediate vision. I implanted the AcrySof IQ Restor +3.0 D in his fellow eye, which resulted in good intermediate vision.

CONCLUSION
In our study, all patients achieved spectacle independence. Although contrast sensitivity levels were lower than in unoperated eyes, none of the patients reported night-vision problems. Because RLE is performed in the nondominant eye only, the dominant eye maintains good distance vision function, reducing the risks of halo and glare. Single-eye surgery also decreases the risk and cost of the procedure. The mono-multi treatment method works well for young presbyopes between the ages of 45 and 55 years. Patients accept this operation as an antiaging procedure.

Baha Toygar, MD, practices at the Dunya Eye Hospitals Group, Istanbul, Turkey. Dr. Toygar did not provide financial disclosure information. He may be reached at tel: +90 5493838080; e-mail: btoygar@gmail.com; baha.toygar@dunyagoz. com.