Wavefront-guided Photorefractive Keratectomy to Correct

Report
Wavefront-guided Photorefractive
Keratectomy to Correct Ametopia
following ReSTOR Implantation
Irene C. Kuo, MD
Associate Professor of Ophthalmology
Wilmer Eye Institute
I have no financial interests; research supported by an unrestricted
grant from Research to Prevent Blindness, NY, NY
ASCRS 2009, San Francisco, P-191A
Co-authors
• Elliott Myrowitz, OD
• Oliver Schein, MD, MPH, MBA
• Roy S. Chuck, MD, PhD (consultant for
Advanced Medical Optics, Inc., and Alcon
Laboratories, Inc.)
Introduction
• expectations of refractive outcomes after
cataract surgery are increasing.
• ametropia can still occur with multifocal lens
implantation despite advanced surgical
techniques and sophisticated methods to
predict intraocular lens power.
Kuo , ASCRS 2009
Introduction
• few reports of excimer laser surgery to
correct residual refractive error in
patients implanted with multifocal lenses
– questions about accuracy of wavefront
acquisition in multifocal lenses, both
diffractive and refractive types
Kuo , ASCRS 2009
ReSTOR lens: apodized diffractive, refractive IOL
Two primary focal points--distance and near (approx 3.2 D add power in spectacle plane). 12 diffractive
discontinuities (steps) in the anterior surface of the cast-molded acrylic optic provide the diffractive add
power. The steps cover the central 3.6 mm diameter of the IOL. The optic from 3.6 mm to the 6.0 mm
edge is comprised of a refractive surface dedicated to distance vision. ≤2 mm pupil, 41% distance, 41%
near, 18% to higher diffractive orders (with permission from Davison JA, Simpson MJ. History and
development of the apodized diffractive intraocular lens. J Cataract Refract Surg 2006;32:849-585).
Methods
• IRB-approved protocol for refractive patients
• thorough preoperative evaluation
–
–
–
–
–
detailed medical, ocular, social history
uncorrected and best corrected visual acuity
manifest refraction , cycloplegic refraction
corneal topography, pachymetry
slit-lamp examination, pupillary exam, Schirmer
testing, dilated exam
Kuo, ASCRS 2009
Methods
• Orbscan (Bausch and Lomb)
• CustomVue Wavescan (Advanced Medical Optics)
– three or more measurements are obtained with
undilated pupil; 5 mm pupil or larger needed for
wavescan capture
– measurement where wavefront sphere best
matches manifest sphere is chosen for treatment
– physician adjustments to sphere are performed
where needed to improve match between manifest
and wavefront sphere
Kuo, ASCRS 2009
Methods
• VISX STAR S4 (Advanced Medical Optics)
was used in all cases
– eye tracker and iris registration were engaged in all
eyes
– off-label use of VISX laser in setting of
pseudophakia was discussed with each patient
Kuo, ASCRS 2009
Case
• 78-year-old man with bilateral cataracts
– Preoperative Ks 40.27 x 42.99 D in OS at 169 degrees by
IOL Master
• November 2006: uncomplicated cataract extraction OS, with
19.5 D ReSTOR SN6AD3 (+4 diopter add in IOL plane) and
limbal relaxing incisions
• YAG laser capsulotomy in June 2007
• August 2007: UCVA was 20/40 and BCVA was 20/30 with
manifest refraction of -1.25 + 2.00 x 175—wavefront PRK
Kuo, ASCRS 2009
Case
• corneal pachymetry was 580 microns. Keratometry
was 41.25 x 42.75 D at 175 by Orbscan
• CustomVue Wavescan showed an RMS of 0.43 µm
• patient underwent wavefront-guided PRK in OS with
goal of postoperative emmetropia
• wavefront data from a 5.25 mm pupil was used.
Physician adjustment of -0.75 diopters was
incorporated in treatment
Kuo, ASCRS 2009
Kuo, ASCRS 2009
Kuo, ASCRS 2009
Results
Post-CE-IOL and pre-PRK
UCVA
Case 1
20/50
OS
Case 2
OS
OD
20/40
20/40
MR, BCVA
plano+1.25x020
20/20
-1.25+2.00x175
20/30
-0.25+1.50x035,
20/30
near
Post-PRK
1-2 months
3-6 months
7-10 months
UCVA
MR, BCVA
UCVA
MR, BCVA,
Near
UCVA
MR, BCVA, Near
J6
20/25
-0.50+0.75x145,
20/25
20/25
-0.25, 20/25,
J3
20/20
Plano, 20/20, J1+
J4
20/40
J5
20/40
-0.25+0.25x040,
20/40
-0.75+0.50x100
20/30
20/25
20/30
-0.25, 20/25,
J3
20/25
Plano, 20/25, J3
-0.25+0.50x110
20/30 J2+
20/25
16 months
20/25 -0.25
J2
0.25+0.50x090
20/25, J2
Visual acuity of eyes with ReSTOR lens before and after PRK. CEIOL=cataract extraction with ReSTOR implantation, UCVA=uncorrected
Snellen visual acuity, BCVA=best-corrected Snellen visual acuity,
MR=manifest refraction, J=Jaeger. All manifest refractions are in diopters.
Kuo, ASCRS 2009
Hartmann-Shack Aberrometer
CCD-Image
CCD-Camera
Outcoming Wave
Lens Array
With permission from AMO, Inc.
Hartmann-Shack Aberrometer
Each Spot or lenslet
lets in light
Each spot is analyzed
as to how the light is
traveling in that part
of the eye
WaveScan® software
calculates the wavefront
map and generates a
wavefront treatment for
the laser to follow
240 points in a 7 mm pupil
With permission from AMO, Inc.
Why wavefront-guided treatment?
• seems appropriate to correct refractive error
after implantation of an aspheric multifocal
lens
• offers iris registration
– compensates for cyclotorsion and pupil centroid
shift, thus correcting astigmatism more precisely
than conventional treatment
Kuo, ASCRS 2009
Role of excimer laser after
multifocal lens implantation
• unavailability of toric multifocal lenses
• “refractive surprises”
• range of lens powers for the ReSTOR lenses is
smaller than range for monofocal lenses
• any residual refractive error after multifocal
lens implantation will affect vision (and
contrast sensitivity) at all distances
Kuo, ASCRS 2009
Drawbacks of H-S sensor with
multifocal IOL
• diffractive discontinuities in lens may result in
locally distorted wavefronts
– spatial distribution of stray centroids (just inside or
outside pixel subarray of charge-coupled device)
may be hard to predict
– scattering incurred by discrete junctions between
diffractive zones
– may lead to overestimation of the optical quality of
eyes with diffractive multifocal IOLS
Kuo, ASCRS 2009
Drawbacks of H-S sensor with
multifocal IOL
• concentric zones in ReSTOR vs. square
microlens array may lead to inaccurate
reconstruction of wavefront
Kuo, ASCRS 2009
Drawbacks of H-S sensor
• Perhaps the findings from our three cases will
not be true with larger refractive errors and/or
with lens tilt/decentration
– tilt/decentration may be more deleterious in
aspheric than in spheric lenses
– size of capsulorhexis and clarity of posterior
capsule may also interfere with good wavefront
capture
Kuo, ASCRS 2009
Why H-S data may still be acceptable
• At the wavelength used, the aberrometer may
be unaffected by the diffractive effect of the
ReSTOR lens
– the higher the wavelength used in the wavefront
sensor, the lower the diffractive efficiency, and the
higher the add power
Kuo, ASCRS 2009
Why H-S data may still be acceptable
• the H-S aberrometers seem more likely to
produce wavefront results corresponding to the
wavefront produced by the distance power of a
diffractive IOL
• Hence, the relative lack of “doubling” of spots
in H-S images in eyes with the ReSTOR
Kuo, ASCRS 2009
Conclusions
• It is possible to obtain good quality wavefront
data in patients with ReSTOR lens and to use
such data to design wavefront-guided
treatment to maximize uncorrected distance
and near visual acuities after ReSTOR
– reproducible, well-focused, properly aligned image
– wavefront and manifest refractions correlate
– Ortiz et al confirmed using another H-S system
Kuo, ASCRS 2009
Conclusions
• It is possible to “mix and match” platforms—
one company’s IOL and another company’s
wavefont-guided laser
Kuo, ASCRS 2009
Conclusions
• in our cases, PRK was chosen over laser in-situ
keratomileusis (LASIK) because of low refractive
error and possibility that LASIK flap might induce
more aberrations
• However, perhaps not all patients with multifocal
IOLs will qualify for wavefront-guided excimer laser
treatment
• type of IOL, amount of refractive error , corneal
topography, pachymetry
Conclusions
• The three eyes in our series had good quality
wavescans which were used for wavefrontguided PRK, with subsequent improvement of
UCVA and in one case, BCVA
– delay in achieving best UCVA and BCVA
– results of (older) patients undergoing conventional
laser surgery to correct post-cataract surgery
ametropia vs. patients who have not had CE-IOL
References
• Charman WN, Montés-Micó R, Radhakrishnan H. Problems in the
measurement of wavefront aberration for eyes implanted with diffractive
bifocal and multifocal intraocular lenses. J Refract Surg. 2008; 24(3):280286.
• Davison JA, Simpson MJ. History and development of the apodized
diffractive intraocular lens. J Cataract Refract Surg 2006;32:849-585.
• Gatinel D. Limited accuracy of Hartmann-Shack wavefront sensing in eyes
with diffractive multifocal IOLs [letter]. J Cataract Refract Surg
2008;34:528
• Jendritza BB, Knorz MC, Morton S. Wavefront-guided excimer laser
vision correction after multifocal IOL implantation. J Refract Surg
2008;24:274-279.
References
• Ortiz D, Alio J, Bernabeu G, Pongo V. Optical performance of monofocal
and multifocal intraocular lenses in the human eye. J Cataract Refract Surg
2008;34:755-762.
• Altmann GE, Wavefront-customized intraocular lenses. Curr Opin
Ophthalmol 2004;15:358-364.
• Holladay JT, Piers PA, Koranyi G, van der Mooren M, Norrby NE. A new
intraocular lens design to reduce spherical aberration of pseudophakic eyes.
J Refract Surg 2002;18:683-691.
• Atchison DA. Design of aspheric intraocular lenses. Ophthalmol Physiol
Opt 1991;11:137-146.
• Altmann GE, Nichamin LD, Lane SS, Pepose JS. Optical performance of 3
intraocular lens designs in the presence of decentration. J Cataract Refract
Surg 2005;31:575-585.

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