New multifocal IOLs offer excellent results

The best patients for these lenses are hyperopes and those who wish to achieve freedom from spectacle use.

Uday Devgan

Newer lens implants allow us to address presbyopia after cataract surgery, with new designs recently achieving U.S. Food and Drug Administration approval.

Every generation of presbyopia-addressing lens implant gets better and better, but the only perfect lens is the human one in a 22-year-old. Accommodating IOL designs have the challenge of a variable amount of unaided near vision, depending on the patient and the individual eye. Multifocal IOLs can deliver a more consistent level of near vision but may limit contrast sensitivity. For these reasons, I have found that by offering the full spectrum of IOL choices, including multifocal and accommodating lenses, I am better able to match patients’ needs and ocular status to a lens that will meet or exceed their expectations.

The Tecnis multifocal (Abbott Medical Optics) and the ReSTOR +3 D add (Alcon) provide aspheric optics and a diffractive design to produce good vision at near and far. The ReSTOR has diffractive rings in the center of the lens so that the lens is more distance dominant as the pupil expands. The Tecnis multifocal features diffractive rings from the center of the lens, all the way to the periphery, and as such, it can provide near vision for all pupil sizes and lighting conditions, such as in dim lighting when the pupil is large.

The ReSTOR has a +3 D add, compared with its predecessor’s +4 D add, to provide better intermediate vision. It also features a blue-blocking chromophore and a correction for some of the spherical aberration of the cornea. The Tecnis multifocal provides a wide range of vision, including intermediate and near, via the correction of spherical aberration and chromatic aberration and a larger central zone. It also has the highest aspheric correction and features the diffractive rings on the posterior surface, which may create a sharper focus of light by reducing internal reflections.

Preop assessment

The best patients for presbyopia-addressing IOLs, particularly multifocal IOLs, are those patients who wish to achieve freedom from spectacle use.

This may sound obvious, but when a patient is motivated to see well without glasses, he is more inclined to work with the surgeon to achieve that goal, even if it means an added expense or an additional refractive procedure.

I also find that hyperopic patients tend to be among the most appreciative candidates for multifocal IOLs because they have not had unaided near vision for decades. In doing IOL calculations for multifocal IOLs, I tend to choose the IOL power that is predicted to make the patient just slightly hyperopic, between plano and +0.25 D. This tends to give the best distance vision and most comfortable near vision.

Macular function is critical, and any significant central retinal pathology, such as macular degeneration, epiretinal membrane or vitreoretinal traction, is a contraindication to multifocal IOL implantation. If there is any doubt as to macular function, optical coherence tomography can be done, and a potential acuity meter can be used for further testing.

A detailed examination of the ocular surface and cornea should also be performed, with particular attention to any tear film deficiencies. Remember that cataract surgery and any other corneal incisions can worsen dry eye syndrome and lead to compromised vision. A proactive approach of treating tear film deficiencies before and after cataract surgery can help stabilize the ocular surface, which leads to better quality vision.

Intraoperative techniques

Success with presbyopia-addressing IOLs requires refractive accuracy for the sphere and the cylinder, with the goal of having 0.5 D or less of defocus and astigmatism. Accuracy in the sphere calculation comes from honing the A-constant of the lens to your particular technique and achieving a consistent surgical outcome, such as a capsulorrhexis that overlaps the optic edge.

This maintains the IOL in the correct effective lens position as the patient heals and leads to refractive stability. The astigmatic effect of your cataract incision must be known to calculate the anticipated residual corneal astigmatism to determine if a limbal relaxing incision is required. Programs such as the online www.LRIcalculator.com will do the vector analysis for you and make suggestions for performing the limbal relaxing incision.

Figure 1. The Tecnis multifocal IOL is well-centered in the patient’s pupil and visual axis and is held securely by an overlapping capsulorrhexis at the lens edge. Note that the diffractive rings extend all the way to the lens periphery to aid in providing near vision, even in large pupil, dim light situations.

Figure 2. The Tecnis multifocal lens is oriented vertically at the 90° meridian during removal of the viscoelastic. This will allow the IOL to be nudged nasally to achieve centration within the pupil and visual axis. The purple marks on the conjunctiva indicate the 90° meridian and will serve as a reference during IOL insertion, as well as astigmatic correction with limbal relaxing incisions. Images: Devgan U

Multifocal IOLs perform best with good centration in the pupil and visual axis, both of which tend to be a little nasal from the center of the cornea. For this reason, I prefer to orient the IOL in the vertical (12 o’clock to 6 o’clock) meridian so that I can nudge the lens nasally until I am happy with centration. For surgery under topical anesthesia, the microscope light can be dimmed, and the patient can be asked to fixate on the center of the light to give a visualization of the lens centration.

Postop management

Some patients, particularly those with extreme preoperative refractive errors or more than 2 D of pre-existing corneal astigmatism, will require a second procedure to fine-tune the refractive result.

I find the most accurate technique to be an excimer laser procedure on the cornea. For most senior patients, PRK offers the same level of accuracy as LASIK and may induce less neurotrophic dry eye issues. PRK is also a simple technique that can be performed by any cataract surgeon. If the patient has more than 0.5 D of defocus or astigmatism, testing with trial frames can help determine if an enhancement procedure would be helpful.

Postop medications should include an NSAID, which helps resolve inflammation and pain and may help to maximize macular function. The ocular surface is monitored for tear film function, and the patient is encouraged to proceed with surgery of the other eye after the first eye has achieved stability.

Particularly with the new lens designs, I have found that multifocal IOL patients tend to be among my happiest and most appreciative. They can reliably achieve correction of their cataract, as well as freedom from glasses for nearly all of their activities. As one patient put it to me, “I’m amazed that after wearing glasses full-time for 30 years, I can now see everything clearly without them.” Although we did not quite achieve the incredible vision she had when she was 22 years old, we certainly exceeded her expectations.

• Uday Devgan, MD, FACS, is in private practice at Devgan Eye Surgery in Los Angeles, Beverly Hills, and Newport Beach, California. Dr. Devgan is Chief of Ophthalmology at Olive View UCLA Medical Center and an Associate Clinical Professor at the Jules Stein Eye Institute at the UCLA School of Medicine. Dr. Devgan can be reached at 11600 Wilshire Blvd., Suite 200, Los Angeles, CA 90025; 800-337-1969; fax: 310-388-3028; e-mail: devgan@gmail.com; Web site: www.DevganEye.com. Dr.Devgan is a consultant to Abbott Medical Optics and Bausch & Lomb, and is a stockholder in Alcon Laboratories and formerly in Advanced Medical Optics.