A range of options for presbyopia correction is available for our patients today, including corneal refractive surgical and lenticular approaches. For all practical purposes, a lens-based solution will be the most appropriate the majority of our patients.
Lenticular options for presbyopia correction include (1) blended reading vision with monofocal IOLs, (2) accommodating IOLs, and (3) pseudoaccommodating or multifocal IOLs.
In blended reading vision, sometimes called monovision, the dominant eye is corrected for distance, and the nondominant eye is corrected to provide some reading vision. For example, the surgeon might choose a +23.50 D monofocal IOL to provide an uncorrected postoperative refraction of -0.50 D in the patient's right eye and a +26.00 D IOL for a postop refraction of -2.00 D in the left. Choice of the range of near or intermediate correction in the nondominant eye depends on the patient's lifestyle and vision needs, which must be determined preoperatively. This approach works for some patients, but it compromises stereoscopic vision.
Accommodating IOLs available in Europe include the Eyeonics Crystalens (Bausch & Lomb, Rochester, New York), the Synchrony IOL (Visiogen, Irvine, California), and the 1CU (HumanOptics AG, Erlangen, Germany). These IOLs, whether designed with a dual optic like the Synchrony or with a single optic as in the other two models, use the residual power of the ciliary muscle to change the vitreous bulk and move the IOL backward and forward, changing the focus on the retina.
Pseudoaccommodating IOLs, also called multifocal IOLs, use optical features built into the IOL optic surface to produce more than one focal point, providing near and distance, and in some cases intermediate, foci on the retina. This is accomplished through diffractive or zonal refractive optic designs. Available multifocal IOLs include the ReZoom (Advanced Medical Optics, Inc., Santa Ana, California), Tecnis Multifocal (Advanced Medical Optics, Inc.), AcrySof Restor (Alcon Laboratories, Inc., Fort Worth, Texas), and the M-Flex (Rayner Intraocular Lenses, Hove, England).
KEY PATIENT CHARACTERISTICS
Presbyopia correction has the potential to make many of our patients happier with their vision than they have been in years. However, in the wrong eye or in a patient with certain characteristics or personality traits, some technologies may not be appropriate and may lead to dissatisfaction.
Proper patient selection begins with a number of preoperative considerations:
- The surgeon should choose patients who express a desire to no longer wear glasses. Cataract surgery patients who have worn glasses all their lives and are happy doing so may not have the motivation to adapt to lenticular presbyopia correction;
- In addition to knowing the patient's history regarding ocular pathology, it is also desirable to know his refractive surgical history, if any. IOL power calculation is more complicated in eyes that have undergone previous refractive corneal surgery;
- It is also important to understand the patient's visual demands, including hobbies or occupational activities that involve specific visual tasks. For instance, a musician may want an intermediate focus at a certain distance to read sheet music; and
- As with any medical procedure, it is important to assess the patient's overall state of alertness and ability to understand and give informed consent.
THE IDEAL PATIENT
For the refractive surgeon who wishes to add presbyopia correction to his surgical repertoire, it is important to choose appropriate candidates for one's early cases.
The ideal patient to start with will have these characteristics: (1) low hyperopia of 1.00 to 3.00 D, (2) no macular disease, (3) no ocular surface disease, (4) less than 0.75 D of cylinder, and (5) a target refraction that is within the range of correction of the chosen IOL.
It is also important to choose a patient who will be able to understand how his vision will change. With almost any lenticular approach to presbyopia correction, there will be a period of neural or visual adaptation, and the patient must comprehend what this period will involve. Negative surprises result in unhappy patients.
PATIENTS TO AVOID
At all costs, avoid patients who believe that your presbyopia surgery can miraculously transform them into a 25-year-old with film-star looks and perfect vision. This is good advice whether it is your first case or your 1,000th.
For the first several cases, however, there are some other types of patients it would be wise to avoid. Exclude patients with more than 0.75 D of astigmatism, unless you are confident managing astigmatism surgically. Avoid low myopes who are used to reading without glasses. Avoid patients with previous refractive surgery and those with a monofocal IOL already implanted in the contralateral eye. People who drive at night occupationally may also be inappropriate candidates.
Additionally, there are some ocular conditions that should be considered contraindications. Exclude patients with (1) macular disease, (2) corneal disease, or (3) tear-film deficiency. These characteristics will compromise the image produced by the presbyopia-correcting IOL and prevent it from working properly.
If complications are encountered during surgery, it may be advisable to abandon the plan to implant a presbyopia-correcting IOL and go with a backup monofocal IOL. Potential surgical exclusions include (1) significant vitreous loss, (2) trauma to the pupil, (3) zonular damage, (4) a tear or rupture to the capsulorrhexis, (5) a capsular rupture, and (6) any other factor that may affect long-term performance of the IOL.
EDUCATING THE PATIENT
Given the indications and contraindications I have outlined, how do we lead the patient through the consent process for a lenticular presbyopia correction?
First, we must be sure the patient wants the procedure. He may express a desire to be rid of glasses or the surgeon may suggest this possibility based on the patient's refraction. Once one of these things occurs, a thorough discussion should take place between the patient and surgeon, including the options available, the effects on vision of each option, and the potential risks and benefits of each procedure.
We use a patient questionnaire to elicit information about the patient's visual needs, personality, and lifestyle. The checklist includes questions about what zones of vision are most important to the patient, which will help to determine what type of correction is most appropriate for this individual's needs and desires.
There should be a full ocular examination and full investigation of BCVA and UCVA, corneal topography, and biometry with the IOLMaster (Carl Zeiss Meditec AG, Jena, Germany).
Once a treatment plan is decided upon, this is further discussed with the patient to make sure every aspect is understood.
Following these guidelines in my own practice, patients have achieved excellent unaided near and distance vision after refractive lens exchange. Figure 1 shows distance UCVA results with bilateral refractive lens exchange using the AcrySof Restor apodized diffractive multifocal IOL.
More than 90% of patients achieved 6/6 or better bilateral UCVA for distance. All patients are N5 or better for near bilaterally.
The bottom line is that we, as refractive surgeons, must manage expectations in our patients who want presbyopia correction. If we under-promise and over-deliver, we have the best chance of making these patients happy by restoring a measure of the spectacle independence that presbyopia has taken from them.
Richard B. Packard, MD, FRCS, FRCOphth, is in practice at The Prince Charles Eye Unit, King Edward VII Hospital ,Windsor, UK. He states that he is a consultant to Alcon Laboratories, Inc., Advanced Medical Optics, Inc., and Bausch & Lomb. He is a member of the CRST Europe Editorial Board. Dr. Packard may be reached at tel: +44 1753 860441; e-mail: firstname.lastname@example.org.