Understanding Presbyopia-correcting IOLs
Understanding Presbyopia-correcting IOLs
Replace the cataract with a lens that increases visual acuity and minimizes the need for eyeglasses and contact lenses.
By Marc Bloomenstein, O.D., F.A.A.O.
Like some advances in new technology, presbyopic IOLs have grown slowly in popularity and haven't yet attained widespread use. I believe we're missing the boat.
We have three presbyopic lenses from which to choose, including one that corrects both presbyopia and spherical aberration. As patient advocates, I believe it's imperative to educate our patients about these lenses. We have an aging population with money to spend on the best available vision correction. By meeting their needs and properly managing their expectations, we can work with patients to maximize both vision and satisfaction after cataract surgery.
To help select the right IOL for cataract patients, I use a questionnaire developed by Steven J. Dell, M.D. The questions help me make a recommendation based on the patient's ocular health and status, lifestyle, personality and expectations. Good candidates for presbyopic IOLs meet these criteria:
■ A desire to avoid or stop wearing eyeglasses
■ A wish to improve near vision activities within reasonable expectations
■ Age and prior refractive history that harmonize with an IOL option
■ Functional and occupational requirements for which presbyopic correction will help
■ Preexisting ocular pathology that suggests likelihood for success
■ Visual demands that are achievable with presbyopic IOLs.
On the other hand, some characteristics should serve as a red flag warning to avoid presbyopic IOLs:
■ More than 1.0D of corneal astigmatism
■ Preexisting ocular pathology
■ Previous refractive surgery
■ Hypercritical attitude
■ Unrealistic expectations
■ A desire to wear eyeglasses
■ Occupational night driving
■ A monofocal lens in the fellow eye.
Finally, because reading is such an important functional limitation of presbyopia, it's important to discuss reading in detail with presbyopic-IOL candidates. Patients need to know that when we say, "You'll be able to read," we don't mean that they'll be able to read anything and everything. Most people do the bulk of their reading in newspapers, on computer screens, on food labels, and on street signs while driving. But these basic examples are very different reading situations. Ask your patient what exactly he wants to read without spectacles and go from there.
Presbyopic IOLs give us an excellent opportunity to help patients' vision function at both distance and near, but there's no perfect solution for anything. Managing expectations is important with these lenses. Will patients be out of eyeglasses forever? No. Will they have zero glare and halos at night? No. Will they be free of eyeglasses most or all of the time in the years immediately following the procedure? In most cases, yes. I help patients understand these facts.
I also want them to grasp that this is bilateral surgery. This lens will cause some glare and halos, but patients who've had just one eye done should know that the procedure works best when the lens is implanted in both eyes.
I also want patients to understand that visual disturbances are likely. For example, about 5% of patients experienced severe halos or glare in clinical trials with the ReSTOR lens. When night driving is very important for a patient, a 1 in 20 chance of severe glare and halos doesn't look appealing. However, 87% of the same ReSTOR patients described night vision problems as "none to mild," and patients with mild-to-moderate disturbances tended to improve over time.1
The key is to manage patients' expectations and address possible issues. These are some of my counseling considerations:
■ In the clinical chart, I document what I tell the patient — and what the patient tells me.
■ I give each patient an information booklet.
■ I counsel the patient about visual disturbances.
■ The patient and I discuss reading distance and preferences in depth.
■ I tell patients that it takes time to fully adapt to the new lenses, so they won't experience optimal results right away. Range tends to increase within a few weeks.
■ I never promise patients they'll never wear eyeglasses again.
All of this expectation-setting occurs with an important piece of shared knowledge: These lenses cost more. When patients pay more out of pocket, they expect more. It's our job to ground their expectations in reality.
Two presbyopic IOLs
Currently, surgeons can choose from two presbyopic IOLs: Crystalens (Eyeonics) and the ReZoom multifocal IOL (Advanced Medical Optics).
Crystalens is an accommodating IOL with a hinged optic to increase movement and lengthened haptics to maximize amplitude. It's suitable for in-bag placement only. The posterior fixation of Crystalens allows the 4.5-mm optic to be equivalent to a 6.0-mm optic, and it helps to minimize glare. Maximal posterior positioning enhances distance vision and gives Crystalens the greatest potential forward movement. Crystalens doesn't give patients the near vision that other IOLs promise. It's more of an intermediate lens.
Made of a hydrophobic acrylic material, the ReZoom has what the manufacturer calls an OptiEdge triple-edge design. The three-piece lens has a 6.0-mm optic and 13-mm overall length, with a power range of 6.00D to 30.00D in half-diopter increments.
The ReZoom is a phenomenal distance lens. It has five different refractive zones, and it spreads out the light. As a result, patients get more of an intermediate effect, rather than tremendous close vision. This "spreading out" of the light is what the ReZoom manufacturer calls balanced view optic technology. Zones are proportioned to provide good visual function across a range of distances in varying light conditions. Five concentric refractive zones create true multifocal vision. Zones 1, 3 and 5 are distance dominant, zones 2 and 4 are near dominant, and aspheric transition between zones provides balanced intermediate vision.
Aspheric presbyopic IOL
The final presbyopic IOL option is the AcrySof ReSTOR Aspheric IOL (Alcon), the only lens approved by the FDA for correction of both presbyopia and spherical aberration. In practical terms, this means that we don't need to choose between improving the reading problems of presbyopia or limiting the glare, blur and poor night vision of spherical aberration.
The AcrySof ReSTOR Aspheric is an apodized lens. Designed to improve image quality while minimizing visual disturbances, apodization is a gradual reduction or blending of the diffractive step heights. It optimally manages light energy delivered to the retina as it distributes the appropriate amount of light to near and distant focal points, regardless of the lighting situation. The step height at the periphery of the diffractive portion of the AcrySof ReSTOR Aspheric is just 0.2 microns.
For near vision, the AcrySof ReSTOR Aspheric has a +4.00D correction at the lenticular plane, which makes it about +3.20D at the spectacle plane. Its aspheric nature reduces spherical aberration for less glare and halos. It's safe and comfortable, and it delivers good reading ability.
When patients receive AcrySof ReSTOR lenses bilaterally after cataract surgery, 80% are spectacle-free.2 They have high-quality, uncorrected near and distance vision, with 85% of patients achieving functional uncorrected intermediate vision of 20/40.3 More than 95% of patients with bilateral implants would choose the lens again.2
In my experience, dry eye is the main reason some patients don't experience excellent vision quality. A healthy corneal surface is important to gaining optimal patient satisfaction. For all of our presbyopic IOLs, we use cyclosporine 0.05% (Restasis, Allergan) as our pre- and postoperative drop.
Our patients' success
Finally, I think that our patients' success in any IOL starts with choosing the right lens for the right patient. A standard questionnaire and a good conversation will help nail down patients' needs and desires.
Of course, all IOL measurements and calculations need to be accurate, and we need to set realistic expectations to help ensure that patients are satisfied with the results.
By interviewing and connecting with an experienced cataract-based refractive surgeon, optometrists can share their understanding that surgery isn't the end of treatment. After the IOL is implanted, patients may still undergo YAG or LASIK procedures. And our involvement in postoperative care completes the picture. OM
- United States Food and Drug Administration. Available at fda.gov/cdrh/pdf4/p040020.html. Last accessed April 20, 2008.
- Based on clinical study results submitted to FDA (models SA60D3 and MA60D3). See package insert or acrysofrestor.com/acrysof-intraocular-lens/acrysof-restor-iol.asp. Last accessed April 20, 2008.
- Kohnen T, Allen D, Boureau C, et al. European multicenter study of the AcrySof ReSTOR apodized diffractive intraocular lens. Ophthalmology. 2006;113:584.
Optometric Management, Issue: June 2008