will reveal the secret behind communicating to your patients and their surgeons about this vision correction option.
BY LOUIS J. CATANIA, O.D., F.A.A.O.;
JENNIFER HENSON, O.D.;
AND PATRICIA LAMELL, C.O.M.T.
For the past five years, with the use of the Array Multifocal intraocular lens
(IOL), we've been able to teach ophthalmic surgeons something uniquely optometric. When referring our cataract patients to these individuals, we've had the opportunity to teach them about the patient selection, optics and adaptation issues of multifocal
Mastering the basics
Although multifocal IOLs are similar in construction to multifocal contact lenses, they're optically quite different for patient's vision because of the following four factors:
1. near perfect centration
2. no movement
3. positioning the optic as close to the nodal point as possible
4. no flexure of the lens optics.
Lack of these criteria has produced the marginal patient acceptance we've experienced over the years with multiple bifocal contact lens designs. These criteria, however, are achievable with multifocal IOLs if a surgeon understands them and surgically strives toward critically accurate biometry, "in-the-bag" haptics and absolute perfect
Introducing these optical criteria to the surgeon becomes optometry's opportunity to help their cataract surgeons -- and their patients.
The inherent design of a zonal, multifocal optic incorporates two distinct phenomena simultaneous focusing and optical halos that O.D.s must discuss with and educate each multifocal IOL candidate and cataract surgeon.
Simultaneous focusing. With this process, the eye experiences concurrent or coincidental focusing of visual stimuli at both distance and near. In normal static or dynamic vision, only one visual stimulus (either distance or near) is in focus at any given moment in time.
The change to simultaneous focus with a multifocal correcting lens demands a process of neuroadaptation by the brain to learn to "select" a distance or near focus. This could take as long as two to three months for patients to achieve acceptance.
The multifocal lens has optical transition zones between its distance and near rings. These zones don't focus transmitted light, but rather create a mild diffraction of the light, which produces an optical halo effect, particularly in high contrast conditions (e.g., dark illumination) around the points of focus. These optical halos are present at all foci of the lens and are constant in size irrespective of near or distance focus.
Because the size of these halos are constant, patients will interpret their size as small or non-existent relative to a larger point foci at near, and larger relative to a smaller point focus at distance (e.g., car headlights on a dark road). Thus, variable size, which people normally use as a clue for depth perception or distance discrimination, is altered with a multifocal correction. Once again, neuroadaptation is required to adapt to the "new visual system" multifocal correction creates through "size constancy."
The patient and the surgeon must understand that optical halos don't go away but that the brain will suppress them so that their presence goes unnoticed.
Multifocal IOL candidates must demonstrate adaptable personalities and must be emotionally stable. They shouldn't be seeking or demanding "perfect vision" nor have extensive night driving responsibilities. Also, they'll need to understand the two- to three- month neuroadaptation period associated with multifocal
Patient selection is best assessed by the optometrist, who serves as the patient's preoperative counselor and educator. The following straightforward set of three brief questions can quickly identify a patient's potential candidacy and need for additional information (reading material, videos,
FAQs, etc.) about the multifocal IOL lens:
1. "Would you like to be less dependent on glasses for near vision after your surgery or would you be happier continuing to wear bifocals or reading glasses?
If the patient says he'd be happy to continue wearing bifocals or reading glasses then end the discussion and recommend monofocal IOL correction. If he says he'd prefer reducing or eliminating his need for glasses, then go to question two.
2. "Would you accept the use of reading glasses for certain limited occasions?"
If the patient says he wouldn't accept reading glasses for limited occasions, then recommend monofocal IOL correction. If he says he could accept reading glasses for limited use, then go to question three.
3. "The multifocal IOL does produce some halos around lights at night that the brain must adapt to over several months. Would that bother you?"
If the patient says he wouldn't be able to tolerate halos at night, recommend monofocal IOL correction. If he says he might be able to tolerate halos at night then this patient warrants additional discussion and education on multifocal IOL correction.
Numerous surgeons have reported success with monocular Array patients, but generally bilateral implantation has the greatest likelihood for maximal effect and benefits.
Moderate amounts (<1.00D) of astigmatism left uncorrected with multifocal IOLs usually produce increased difficulties in visual adaptation, especially for near. The goal is to eliminate post-op residual cylinder or to leave minimal amounts, which may not affect uncorrected vision or could be reduced post-op with additional limbal relaxing incision
Explain to the patient and to the surgeon that the patient's pupil size should be no less than 3 mm in scotopic conditions and should be mobile. Also point out that lower contrast reading materials with normal or reduced illumination to facilitate a normally dilated pupil will provide the optimal reading condition with multifocal correction.
All's well that ends well
With the proper candidate, post-op multifocal correction proves to be a joy for the patient. Their distance vision is optimal from day one, colors are brighter and, over the two- to three-month adaptation period that "we promised them," their near vision improves dramatically and they learn to accept the halos.
O.D.s know how to effectively refract a multifocal corrected eye with a fogging technique and to maximum plus prescription for distance and near. You can usually write a final prescription at about one month post-op, once the patient decides on bifocals or a part-time, single vision near correction.
The success of Array patients and indeed, this IOL as a future refractive technology (for cataract patients or with clear lens extraction for hyperopes and hyperopic
presbyopes), is a product of accurate and often exhaustive patient education and counseling. O.D.s are uniquely trained and positioned for this role. Thus, our participation in the evolution of this unique refractive technology will be its principal determinate for future success.
Dr. Catania is a clinical consultant for Nicolitz Eye Consultants, a multidisciplinary group practice in Jacksonville, Fla. Dr. Henson is chief optometrist with Nicolitz Eye Consultants. Ms. Lamell is head technician and orthoptist at Nicolitz Eye Consultants.
About the Array
The Array Multifocal intraocular lens
(IOL) is designed for pseudophakic correction of cataract patients older than 60 years. It is a 6.0 mm, foldable, silicone, UV-blocking lens with extruded PMMA
haptics. It's Nd:YAG tolerant, has an index of refraction of 1.46 and a power range of +6.0D to +30.0D in 0.5D steps with a +3.50 add at the IOL plane, producing an effective add power at the spectacle plane of approximately +2.60.
The Array is a distant-dominant, zonal construction design with a central disk portion of a 2.1 mm diameter surrounded by a first near zone of a 3.4 mm diameter. There are five zones: One, three and five are distant dominant and two and four are near dominant.
Optometric Management, Issue: June 2003