Disclosure Getting Up to Date with LASIK...May 01, 2018 · • Refraction is automatically...
13
1 Getting Up to Date with LASIK Gary S. Schwartz, MD, MHA Associated Eye Care Stillwater, MN Adjunct Associate Professor University of Minnesota Gary S. Schwartz, MD, MHA Associated Eye Care Disclosure • I am not a paid consultant to any drug or device company. Gary S. Schwartz, MD, MHA Associated Eye Care LASIK • Use one instrument to make a flap. • Use a second instrument to change the shape of the cornea. Gary S. Schwartz, MD, MHA Associated Eye Care Modern advancements • Better flaps • Better ablations • Better nomogram adjustment • All shoud lead to better visual acuity, better quality of vision, and happier patients. Gary S. Schwartz, MD, MHA Associated Eye Care What we’re “curing” • Myopia • Hyperopia • Regular astigmatism • Irregular astigmatism Gary S. Schwartz, MD, MHA Associated Eye Care Changing the corneal surface • Myopia – flatten it • Hyperopia – steepen it • Regular astigmatism – steepen and flatten accordingly • Irregular astigmatism – smooth out the irregularities
Transcript of Disclosure Getting Up to Date with LASIK...May 01, 2018 · • Refraction is automatically...
1
Getting Up to Date with LASIK
Gary S. Schwartz, MD, MHA
Associated Eye Care
Stillwater, MN
Adjunct Associate Professor
University of Minnesota Gary S. Schwartz, MD, MHA Associated Eye Care
Disclosure
• I am not a paid consultant to any drug or
device company.
Gary S. Schwartz, MD, MHA Associated Eye Care
LASIK
• Use one instrument to make a flap.
• Use a second instrument to change the
shape of the cornea.
Gary S. Schwartz, MD, MHA Associated Eye Care
Modern advancements
• Better flaps
• Better ablations
• Better nomogram adjustment
• All shoud lead to better visual acuity, better
quality of vision, and happier patients.
Gary S. Schwartz, MD, MHA Associated Eye Care
What we’re “curing”
• Myopia
• Hyperopia
• Regular astigmatism
• Irregular astigmatism
Gary S. Schwartz, MD, MHA Associated Eye Care
Changing the corneal surface
• Myopia – flatten it
• Hyperopia – steepen it
• Regular astigmatism – steepen and flatten
accordingly
• Irregular astigmatism – smooth out the
irregularities
2
Gary S. Schwartz, MD, MHA Associated Eye Care
Excimer laser
• Photochemical reaction
• Not photothermal or photodisruptive
• Breaks carbon-carbon bonds without
generating heat.
• Solid tissue turns into vapor in a reaction
that is called “ablation”.
• The tissue is “ablated” away
Gary S. Schwartz, MD, MHA Associated Eye Care
Excimer laser on human hair
Gary S. Schwartz, MD, MHA Associated Eye Care
Excimer Laser Ablation
• Myopia – remove more tissue centrally
Gary S. Schwartz, MD, MHA Associated Eye Care
Myopic Ablation
Gary S. Schwartz, MD, MHA Associated Eye Care
Excimer Laser Ablation
• Hyperopia – remove more tissue
peripherally
Gary S. Schwartz, MD, MHA Associated Eye Care
Hyperopic Ablation
3
Gary S. Schwartz, MD, MHA Associated Eye Care
Excimer Laser Ablation
• Astigmatism
• Torus = sphere + cylinder
• Flatten steep axis
• Steepen flat axis
+ =
Gary S. Schwartz, MD, MHA Associated Eye Care
Astigmatic Ablation
Post-op Pre-op
PRK vs. LASIK
Gary S. Schwartz, MD, MHA Associated Eye Care
Corneal Anatomy
Gary S. Schwartz, MD, MHA Associated Eye Care
Surface Ablation (PRK)
• Advantages over LASIK
• Very safe to perform
• Minimal risk of long term problems
• Ectasia, dry eye
• Disadvantages compared to LASIK
• Discomfort for 2-3 days
• Vision may take weeks to months to stabilize
Gary S. Schwartz, MD, MHA Associated Eye Care
LASIK
• Advantages over PRK
• Fast visual recovery
• Probably better for higher refractive errors
• Lest risk of scarring or haze
• Disadvantages compared to PRK
• Higher risk during and after surgery
• More chronic discomfort, dry eye problems
4
Gary S. Schwartz, MD, MHA Associated Eye Care
Where has the progress come?
• Flaps – safety
• More predictable diameter
• More predictable depth
• Ablations – improved quality of vision
• Less night-time vision problems
• Customization
• Nomogram adjustment – improved results
Flap creation
Gary S. Schwartz, MD, MHA Associated Eye Care
Mechanical Microkeratomes
• Initially, flaps were created by metal blade
instruments called microkeratomes
Gary S. Schwartz, MD, MHA Associated Eye Care
Mechanical Microkeratomes
Gary S. Schwartz, MD, MHA Associated Eye Care
Mechanical Microkeratomes
Gary S. Schwartz, MD, MHA Associated Eye Care
Problems with microkeratomes
• Small risk of operator error that could
result in large problems.
• Not overly precise
• Set the blade for 160 microns, and flaps could
range from 120-200 microns thick.
• Patients with occult ABMD could end up
with sloughing of epithelium
5
Gary S. Schwartz, MD, MHA Associated Eye Care Gary S. Schwartz, MD, MHA Associated Eye Care
A lot of parts…
Femtosecond Laser
Gary S. Schwartz, MD, MHA Associated Eye Care
Femtosecond laser flaps
• Femtosecond laser works by creating a
series of contiguous bubbles a specific
depth below the surface of the cornea.
• Intralase femtosecond laser approved by
FDA in 2001.
• Eventually bought by AMO
• Now 4 lasers approved by FDA 2001-2010
• AMO, Technolas, Ziemer, Alcon
Gary S. Schwartz, MD, MHA Associated Eye Care
Photo of some of the lasers
Gary S. Schwartz, MD, MHA Associated Eye Care
6
Excimer laser ablation
Gary S. Schwartz, MD, MHA Associated Eye Care
Improvements
• Laser delivery
• Trackers
• Autocentration
• Managing torsion
Gary S. Schwartz, MD, MHA Associated Eye Care
Delivering Laser Energy
• Broad beam
• Flying spot
• Scanning slit
Gary S. Schwartz, MD, MHA Associated Eye Care
Gary S. Schwartz, MD, MHA Associated Eye Care
Flying Spot
Gary S. Schwartz, MD, MHA Associated Eye Care
Flying spot technology
• All modern lasers use flying spot
technology.
• Some use combination of spots of different
sizes.
7
Gary S. Schwartz, MD, MHA Associated Eye Care
Trackers
• Tracker will “see” where the eye is over
1000 times per second.
• If the eye moves a little, the laser will move
with it.
• If the eye moves a lot, the laser will shut
off.
Gary S. Schwartz, MD, MHA Associated Eye Care
Gary S. Schwartz, MD, MHA Associated Eye Care
Autocentration and Iris Registration
• Modern lasers will identify the center of the
pupil, and center the treatment on it.
• Surgeon can adjust center of treatment to
account for angle-kappa, etc.
• By identifying iris structures, the laser can
adjust for cyclotorsion.
Gary S. Schwartz, MD, MHA Associated Eye Care
Iris Registration
Gary S. Schwartz, MD, MHA Associated Eye Care
Ready for the next stage
• Flying Spot
• Trackers
• Autocentration
• Iris registration
Customized Ablations
8
Gary S. Schwartz, MD, MHA Associated Eye Care
Customized ablation
• Like buying custom made clothes.
• Off-the-rack clothes fit us all OK, but
having someone make you clothes from
your actual measurements should fit you
better.
• The more data points used, the better the fit.
Gary S. Schwartz, MD, MHA Associated Eye Care
Customized (wavefront) ablation
• Treats concept that not all astigmatism is
regular
Gary S. Schwartz, MD, MHA Associated Eye Care
Conventional LASIK
Gary S. Schwartz, MD, MHA Associated Eye Care
Customized ablation
• Wavefront
• Tries to get entire optical image as regular as
possible.
• Topo-link
• Tries to get the corneal surface as spherical as
possible.
Wavefront
AMO VISX S4
TECHNOLAS 217Z
Gary S. Schwartz, MD, MHA Associated Eye Care
Emmetrope – parallel light going in
9
Gary S. Schwartz, MD, MHA Associated Eye Care
Perfect wavefront
Gary S. Schwartz, MD, MHA Associated Eye Care
Myope
Gary S. Schwartz, MD, MHA Associated Eye Care
Hyperope
Gary S. Schwartz, MD, MHA Associated Eye Care
Most people aren’t exactly “regular”
Gary S. Schwartz, MD, MHA Associated Eye Care
Perfect wavefront
Gary S. Schwartz, MD, MHA Associated Eye Care
Aberrated wavefront
10
Gary S. Schwartz, MD, MHA Associated Eye Care
Treating this with
conventional LASIK
Gary S. Schwartz, MD, MHA Associated Eye Care
under-treat here
over-treat here
under-treat here
Treating this with
conventional LASIK
Gary S. Schwartz, MD, MHA Associated Eye Care
Breaking down “irregular astigmatism”
into “higher order aberrations”
= + +
Gary S. Schwartz, MD, MHA Associated Eye Care
Wavefront aberrations
( 1, -1) ( 1, 1)
( 2, -2) ( 2, 0) ( 2, 2)
( 3, -3) ( 3, -1) ( 3, 1) ( 3, 3)
( 4, -4) ( 4, -2) ( 4, 0) ( 4, 2) ( 4, 4)
1st order
3rd
2nd
4th
Gary S. Schwartz, MD, MHA Associated Eye Care
Wavefront aberrations
2nd
Conventional LASIK only treats second order aberrations
Myopia, hyperopia, astigmatism
Gary S. Schwartz, MD, MHA Associated Eye Care
Wavefront aberrations
( 2, -2) ( 2, 0) ( 2, 2)
( 3, -1) ( 3, 1)
( 4, 0)
3rd
2nd
4th
The biggest aberrations treated by wavefront technology are
myopia, hyperopia, astigmatism, coma, and spherical aberration
11
Gary S. Schwartz, MD, MHA Associated Eye Care
Alcon CustomCornea®
Gary S. Schwartz, MD, MHA Associated Eye Care
Wavefront is within pupil
Gary S. Schwartz, MD, MHA Associated Eye Care
Advantages to Wavefront
• Treats total lower- and higher-order
aberrations without worrying about which
parts of the eye are responsible.
• Holds potential that it can fix corneal
problems from pathology or prior surgery.
• Refraction is automatically incorporated in
the treatment.
Gary S. Schwartz, MD, MHA Associated Eye Care
Disadvantages of Wavefront
• Fails to consider how aberrations from lens
will change over time.
• Only gathers data from inside the pupil.
• Has not proven that it can reduce high
levels of higher-order aberrations
significantly.
Topography-Link
Nidek EC-5000
Alcon Wavelight EX500
Gary S. Schwartz, MD, MHA Associated Eye Care
Topo-link
• Treats based off two separate classes of
data:
• Refraction
• Topography
• The goal is a smooth corneal surface
without small areas of steepness or flatness.
12
Gary S. Schwartz, MD, MHA Associated Eye Care
Topo-link
Gary S. Schwartz, MD, MHA Associated Eye Care
Topo-link
Gary S. Schwartz, MD, MHA Associated Eye Care
Advantages to Topo-Link
• Since most irregularities affecting vision lie
on the corneal surface, it may make sense
to focus on treating these.
• Treats a part of the eye that is stable and
consistent through the lifetime.
• Can treat large diameters.
Gary S. Schwartz, MD, MHA Associated Eye Care
Disadvantages of Topo-link
• No good nomograms to handle cases where
patient’s total astigmatism doesn’t line up
with corneal astigmatism.
• Not yet approved for hyperopia or mixed
astigmatism.
• Not good for enhancements at this time.
Nomogram Adjustment
and Tracking Software
Gary S. Schwartz, MD, MHA Associated Eye Care
Nomogram adjustment
• Lasers come with standard nomograms to
treat refractive errors.
• Changing nomograms is a slow proposition
for the laser companies.
• Many surgeons “tweak” their own
nomograms.
• Some do it based on data, others on
instinct.
13
Gary S. Schwartz, MD, MHA Associated Eye Care
Nomogram adjustment
• Everyone using a particular laser
• Just fine-tune a laser’s nomogram for everyone
• A single surgeon using a particular laser
• Surgeon specific
• Hydration, length of time flap is up
• Site specific
• Temperature, humidity
Gary S. Schwartz, MD, MHA Associated Eye Care
Nomogram adjustment
• Computerized data-collection systems have
been developed to try to standardize
nomograms.
• Most are small, specific for a single laser.
• Most allow surgeons to compare
themselves to others.
Gary S. Schwartz, MD, MHA Associated Eye Care
IBRA
• Created by Swiss company, Zubisoft
• All FDA-approved excimer lasers.
• Also premium IOL’s
• Reference database
• Personal nomogram adjustment
• $1000-$1200 a year depending on package
Gary S. Schwartz, MD, MHA Associated Eye Care
IBRA
• Easy input
• Online interface
• Good output
• Gives immediate nomogram adjustment from
day 1 of use.
• Can get data in table form, chart form
• Statistical analysis.
Gary S. Schwartz, MD, MHA Associated Eye Care
Summary
• Better flaps
• Better ablations
• Better nomogram adjustment
• All lead to better visual acuity, better
quality of vision, and happier patients.
