Today, indications for refractive lens exchange (RLE) are slightly different than in the past because of recent developments in IOL technology and power calculations. Before, we seldom performed RLE, for which we used monofocal IOLs to correct high myopia and hyperopia. Now, we perform RLE with a wide range of lenses, including multifocal, accommodating, toric, and multifocal toric IOLs.
Most appropriate candidates for RLE initially come in for laser vision correction. Corneal refractive surgery is always our first choice for the correction of any refractive error, especially if the patient is under the age of 45 years. Corneal surgery is easier and cheaper for the patient. Additionally, the public is more aware of cornea-based than IOL-based refractive surgeries. If the refractive error cannot be corrected with laser surgery, I then consider implanting a phakic IOL or performing RLE with a multifocal IOL. If a patient is 45 years old and has myopia (with or without astigmatism), I prefer laser vision correction; however, if they are hyperopic, then the best method of correction is RLE with a multifocal IOL.
Plano presbyopes are challenging patients who want a solution for their near vision problems. Recently, we have seen these patients with more frequency. If we treat a plano presbyope with a corneal procedure, such as conductive keratoplasty, presby-LASIK, corneal inlays, or monovision, they typically might need a second vision correction procedure a couple of years later. Corneal procedures always interfere with distance vision. Therefore, RLE with a multifocal IOL seems a better solution in terms of providing better distance and near visual acuity and stability.
WHO IS A GOOD CANDIDATE FOR RLE?
Following is a list of patients for whom I would consider performing a RLE.
Myopia. High myopic patients who are not suitable for laser vision correction or a phakic IOL procedure may benefit from a RLE. Patients over 45 years old who want be rid of their reading spectacles are also good candidates for RLE; however, low myopic patients should not undergo RLE.
Hyperopia. Usually, most hyperopic patients are not good candidates for phakic IOL implantation due to low anterior chamber depth values. However, high hyperopic patients under the age of 45 years who cannot undergo laser vision correction or phakic IOL surgery and those with a refraction greater than 6.00 D are great candidates for RLE. For those high hyperopic patients who are older than 45 years, as well as low and moderate hyperopic patients in this age group, RLE is also appropriate.
Plano presbyopes. I prefer to offer single eye surgery in these patients. RLE is performed on the nondominant eye only; I implant a diffractive IOL to provide good near visual acuity and avoid halo and glare problems. The dominant eye remains unoperated, allowing good distance vision function. Single eye surgery also decreases the risk and cost of the procedure. I call this method a mono/multi treatment, which works well for young presbyopes between the ages of 45 and 55 years.
PREOPERATIVE ASSESSMENTS
Always perform preoperative assessments, including refraction, visual acuity, dry eye tests, corneal topography, anterior and posterior segment examination, biometry, pachymetry, and eye dominance test, to determine the surgical course of action.
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, we have two options: (1) we can correct astigmatism with corneal laser surgery 2 to 3 months after RLE or (2) we can implant a multifocal toric IOL.
Biometry. To achieve accurate biometry, we use both immersion biometry and the IOLMaster (Carl Zeiss Meditec AG, 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 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 (Figure 1). The optimized Haigis formula also works well in all eye types. Optimizing the IOL constants is recommended, especially if the surgeon is not satisfied with the patient's refractive outcomes.
Understanding an individual's needs is critical. Have a conversation preoperatively with the patient to understand his psychology and expectations. Find out what the patient's profession and hobbies are. Ask if he more frequently performs near vision tasks, or does he need good intermediate vision? Night drivers and patients who have unrealistic expectations are not good candidates.
The preoperative evaluation is also the time for the surgeon to provide detailed information about the procedure. Explain the risk of complications, such as endophthalmitis and retinal detachment, and the possibility of needing secondary or additional refractive procedures.
Inform patients about the risk of halo and glare problems after multifocal IOL implantation. Explain that there is a 6- to 12-month adaptation period, and if problems persist for more than 12 months, they may need an IOL exchange. We recommend exchanging the IOL in the dominant eye first, as the problem usually resolves and unaided near vision is maintained with the nondominant eye.
IOL SELECTION
IOL selection depends on several factors, including visual acuity and pupil size. If the patient's visual acuity is too low (0.3 or lower), we prefer a monofocal IOL because it provides better contrast sensitivity postoperatively. I prefer diffractive IOLs, such as the AcrySof Restor (Alcon Laboratories, Inc., Fort Worth, Texas), Tecnis Multifocal (Advanced Medical Optics, Inc., Santa Ana, California), or the Acri.LISA (Carl Zeiss Meditec AG, Jena, Germany), for both eyes if the photopic pupil is less then 3 mm because they are not pupil dependent. If the pupil is larger then 3 mm, I choose the IOL according to patient needs, usually implanting a refractive IOL (ReZoom; Advanced Medical Optics, Inc.) in the dominant eye and a diffractive IOL (Restor, Tecnis, or Acri.LISA) in the nondominant eye. Plano presbyopes receive a diffractive IOL in the nondominant eye according to our mono/multi treatment protocol. The dominant eye is untouched.
The surgeon must be confident in his ability to perform RLE because he is performing surgery on a healthy eye. RLE patients can judge the surgeon more aggressively than they would with a standard cataract surgery, even though the procedure is almost the same as standard phaco surgery.
RLE may be done under topical anesthesia, performing a well-centered, 5 mm capsulorrhexis. I prefer the 23-gauge Duet microincision capsulorrhexis forceps (MicroSurgical Technology, Redmond, Washington). I always take my time to polish the anterior and posterior capsule to avoid capsular fibrosis. I also inject intracameral cefuroxime at the end of the surgery.
RLE is gaining popularity among refractive surgeons. The latest developments in phacoemulsification and IOL and axial length measurement technologies and the prophylactic use of intracameral antibiotics have increased the safety and predictability of RLE. Public awareness is very important. Surgeons can start by explaining the many advantages of RLE with multifocal IOLs: (1) we can correct far vision, (2) we can correct near and intermediate vision, (3) laser touch-up procedures can be performed for fine-tuning outcomes, (4) refraction will be stable during the patient's entire lifespan, (5) patients will not develop cataract, and (6) negative spherical aberration can be preserved with aspheric IOL designs.
Presbyopia is a disease of crystalline lens, and the crystalline lens is the best place to correct presbyopia. RLE represents the future of refractive surgery, especially for our presbyopic patients. Excimer laser can be performed after RLE as a fine-tuning procedure.
Baha Toygar, MD, practices at the Dunya Eye Hospitals Group, Istanbul, Turkey. Dr. Toygar states that he has no financial interest in the products or companies mentioned. He may be reached at +90 21233623200; btoygar@superonline.com or baha.toygar@dunyagoz.com.
