refractive
iols
LASIK Versus Refractive Lens Implants
How to incorporate new refractive lens technology
in a co-management relationship.
GREGORY
PAMEL, M.D., & JORDAN KASSALOW, O.D.,
New York, N.Y.
Co-management
of vision correction procedures has fostered mutually beneficial relationships between
optometrists and ophthalmologists. The advent of phakic, multifocal and accommodating
intraocular lens implants broadens co-management opportunities. We can now work
together to provide patients, impaired by the highest levels of refractive error,
sight restorative surgery.
There are several critical stages in the co-management relationship.
First, determine which procedure is optimal for each patient. After counseling the
patient extensively, you and the surgeon must decide which procedure is optimal.
Second, complete a thorough preoperative work-up. The operative procedure is then
performed, and lastly, you must provide postoperative care. Being knowledgeable
about new lens technologies and understanding the respective roles of the optometrist
and ophthalmologist throughout this process can help patients achieve the best possible
outcome.
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Medicare
and Refractive Surgery |
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The Centers for Medicare
and Medicaid approved a patient-share billing rule for IOL implants in May.
Under the new rule, Medicare patients undergoing cataract surgery have the option
of paying out-of-pocket for the difference between a Medicare-covered cataract procedure
and the total cost of IOL implantation. For now, the ruling applies to the crystalens,
ReSTOR and ReZoom intraocular lenses. When a surgeon and patient chooses one of
these lenses, Medicare will reimburse for standard cataract surgery with a monofocal
lens insertion and the patient pays for additional charges. |
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Lens implants vs. LASIK
Not all patients are candidates for lens implantation, just as
not all patients are candidates for LASIK. Parameters like refractive error, age,
presence of cataract, corneal thickness and shape all impact whether one procedure
or the other is appropriate for a particular patient. There are also patients who
may be candidates for either LASIK or IOL implantation. Patients fall into four
categories when making the determination about which refractive procedure is optimal
for each patient.
• LASIK candidates. Pre-presbyopic patients with refractive
errors of less than -8.00D of myopia or less than +4.00D of hyperopia, are generally
good candidates for LASIK surgery. These patients must have healthy corneas with
appropriate thickness in relation to the refractive error, normal corneal topography,
normal tear film and the absence of significant medical conditions like diabetes,
collagen vascular diseases and pregnancy. Wavefront-optimized and wavefront-guided
treatments provide excellent visual results in this group of patients.
• Phakic lens candidates. We prefer phakic lens implants
in myopic patients with errors of -10.00D or more. The ablation profile in LASIK
can lead to an increase in higher-order aberrations with subsequent glare and night
vision problems for this group.
These lenses are also a good option for patients with refractive
errors as low as -5.00D in whom LASIK is contraindicated due to insufficient corneal
thickness, irregular astigmatism or profound dry eyes.
• Multifocal/accommodating lens candidates. Presbyopic patients,
including patients with early cataracts, may prefer the multifocal or accommodating
lens implants because they can achieve good distance and near vision. Although monovision
LASIK is an option, it is often unacceptable because depth perception is compromised.
These implants are ideal for high hyperopes (+4D or greater) who
are most interested in eliminating their dependency on distance and reading glasses.
However, patients with myopia above -6.00D are at a higher risk for retinal detachment
after cataract or refractive lens exchange. Counsel patients about the additional
risk appropriately.
• Candidates for both procedures. Myopic patients who fall
between -5.00D and -10.00D with sufficient corneal thickness and normal topography
may be candidates for either procedure.
For this group, it is imperative to discuss options with the patient
to determine which is the best procedure. Considerations include age, range of myopia,
amount of astigmatism, endothelial cell count and anterior chamber depth.
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Ease
Patient Apprehension |
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Despite the changes
to the CMS reimbursement policy, many patients are concerned about the high-cost
of refractive surgery procedures. Consider allowing them financing options and set
a low monthly-fee arrangement.
Some insurance flex plans will allow
patients to pay for some of the procedure with pretax dollars. The cost of refractive
surgery procedures may also be tax deductible. Check with your accountant to find
out if the procedure may be considered a deductible health expense. |
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Pre-op work-up
Co-managing doctors must agree on the division of labor when performing
the pre-operative tests. Unlike LASIK, which is typically performed bilaterally,
IOLs are implanted one eye at a time. Depending on surgeon and patient preference,
there may be a one to four week interval between procedures for the first and second
eyes. During this interval, patients may need to wear a contact lens in the untreated
eye to minimize anisometropia or aniseikonia. In our case, Dr. Kasslaow performs
all pre-operative tests with the exception of the anterior chamber depth, endothelial
cell count, A-scan and IOL calculation.
No matter what the choice for correction, a thorough and precise
preoperative work-up must be performed. Critical tests include: a careful dry and
wet refraction; pupil size measurement; keratometry; IOP measurement and dilated
fundus exam. The refraction is the most important part of the preoperative work
in these patients. Young, highly myopic patients can easily accommodate more minus
in their prescription. Take care to measure the refraction both with contact lenses
in (over-refraction) and after lenses have been kept out for the appropriate time
(one week for soft lenses, two weeks for gas permeable). In addition, for highly
myopic refractions, keep the vertex distance constant to ensure accuracy. A full
cycloplegic refraction should be performed as well.
Calculating the lens implant parameters is a critical step in
achieving optimal results with lens implants. To calculate phakic lens implant power,
refraction is the critical value. Since this procedure is additive — nothing
is removed from the eye — the axial length does not have to be measured. Keratometry
measurements and anterior chamber depth measurements are necessary to calculate
the implant using the Van Der Heijde formula. However, these values are significantly
less important than the measured refractions. Use immersion A-scan to eliminate
the effect of corneal compression seen when using a contact probe to measure anterior
chamber depth.
When calculating IOL values for younger patients, target slight
hyperopia in anticipation of continued myopic progression with age. For presbyopic
patients over age 40, target slight myopia to reduce reading spectacle dependence.
Pre-op cylinder should be less than or equal to 0.50D for implantation.
For either multifocal or accommodating implants, it's important
to get a very accurate A-scan using either immersion A-scan technique or non-contact
biometry. Pupil size should be a minimum of 2.5mm in those patients receiving a
multifocal lens, because smaller pupils will marginalize the multifocality of the
implant. Uncorrected astigmatism should be no greater than 0.5D postoperatively.
Counsel patients on the importance of implanting both eyes to achieve the near-vision
benefit.
Address astigmatism with patients preoperatively, since residual
postoperative astigmatism will interfere with the effect of phakic, accommodating
or multifocal implants and reduce visual acuity. Phakic IOLs do not correct astigmatism,
but can reduce it if the incision is well-placed on the axis of astigma- tism. Most
patients have with-the-rule astigmatism, which makes it convenient for the surgeon
to operate at 12 o'clock location. Astigmatism can also be managed at the time of
surgery or postoperatively with limbal or corneal relaxing incisions.
Post-op care
After the implant procedure is complete, close post-op management
is key. We see our patients at: day one, one week, three weeks, one month, three
months, six months, one year and then on an annual basis. In our office, Dr. Pamel
sees the patient on day one. He checks the incision, the suture where indicated,
the IOL placement and checks for infections or abnormal intraocular inflammation.
He then tests the patient's visual acuity and performs a refraction. He also reviews
the proper dosage of medications. Typically, patients will benefit from a fourth
generation fluoroquinolone, an NSAID and a steroid q.i.d. for one week. After one
week, discontinue the antibiotic and NSAID and taper steroid by one drop per week
for three weeks.
The optometrist, Dr. Kassalow, sees patients for the one-week
visit. He measures visual acuity, performs a refraction, checks the IOP, examines
the anterior chamber reaction, checks sutures and the incision, ensures the IOL
placement is optimal and prescribes medication based on the clinical findings.
At the two-week point, it's back to the M.D. to schedule the procedure
for the second eye. If all is normal, the patient will undergo the second procedure
at the one-month point. The post-op management schedule for the second eye repeats
that of the first.
After the sutures are removed from the second eye, the patient
will see the O.D. at three and six months. At 12 months, the phakic IOL patient
will return to the surgeon for an endothelial cell count.
Some patients may require additional procedures to attain optimal
vision. The most common reason for enhancement is residual ammetropia or progression
of myopia following surgery. High myopes are likely to become more myopic. LASIK
or LASEK can successfully treat small myopic refractive errors in these patients.
We wait a minimum of three to six months before performing enhancements in these
patients.
Throughout the last ten years, the limitations of LASIK as a refractive
procedure have become more apparent. The availability of new lens implants offers
eye care providers new technologies to support the co-management relationship in
surgical cases. These implants may prove a better modality to treat patients who
are outside the treatment range or have contraindications for LASIK.
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Intraocular
Lens Implants |
 Phakic
Lens Implant. The Verisyse lens
implant (Advanced Medical Optics, (AMO)) is a phakic lens implant designed to treat
myopia ranging from -5.00D to -20.00D. Approximately three million people in the
United States have myopia above -6.00D. The Verisyse is a rigid PMMA lens available
in a 6mm optic, in powers from -5.00D to -15.00D, and in a 5mm optic in powers over
-15.00D to -20.00D. Because it is a rigid lens implant, it requires placement through
either a 5.2mm- or 6.2mm-incision, which requires closure with one suture. A critical
distance of at least 1.5mm from the corneal endothelium after implantation is necessary
to avoid excessive endothelial cell loss. Endothelial cell counts must be taken
preoperatively and age adjusted to determine if enough cells are present. Anterior
chamber depth must be greater than 3.2mm preoperatively, which is common in highly
myopic patients.
Accommodating
Lens Implants. The crystalens
(Eyeonics Inc.) is the first pseudoaccommodating implant (below) approved by the
FDA. It is designed to correct distance, intermediate and near vision through movement
of the optic via a hinged design. The implant requires the removal of the natural
crystalline lens (through a 3.5mm-scleral tunnel incision) as in cataract surgery.
The lens is designed with two hinges attached to the optic, which allows the lens
to move from a posterior vaulted position to correct distance vision, to an anterior
vaulted position to correct near vision.
Multifocal Lens
Implants. Two new multifocal
lens implants, the AcrySof ReSTOR (Alcon Laboratories) and ReZoom (AMO) were recently
approved in March 2005. These implants are designed using a series of concentric
rings to provide distance, intermediate and near vision. The ReSTOR (above) lens
employs apodized diffractive technology, which uses apodization, diffraction and
refraction. The refractive optics are in the outer half of the lens, which provides
for good night vision when the pupil enlarges. The diffractive optics, located in
the central 3.6mm of the lens, consist of ring elements that are equally divided
between distance and near vision. ReSTOR's apodized diffractive optic reduces the
incidence of glare and halos after implantation. The near vision add measures 4.00D
in the spectacle plane.
 The
ReZoom (left) is a three-piece acrylic implant with Balanced View Optics technology.
This involves a refractive, distance-dominant, multifocal optic with five optical
zones designed to optimize light distribution on the retina in varying lighting
conditions and pupil sizes. The near-vision add measures 2.80D in the spectacle
plane. Zones 1, 3 and 5 are distant-dominant; zones 2 and 4 are near-dominant. Aspheric
transitions between zones provide good intermediate vision.
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Dr.
Pamel is board certified in ophthalmology,
specializing in corneal, LASIK and cataract surgery. He also serves as an attending
surgeon at Manhattan Eye, Ear and Throat Hospital. Dr. Pamel was a principal investigator
for the Verisyse phakic IOL clinical trials.
Dr. Kassalow specialized in contact lenses,
and has a strong interest in primary care and public health. He is director of the
River Blindness programs at Helen Keller International. He is also a consultant
to the World Health Organization and is a member of the Council on Foreign Relations.
Optometric Management, Issue: September 2005