Transcript [Poster title] - ASCRS/ASOA 2008

Refractive Accuracy of LASIK
Using the IntraLase and Zyoptix
Jonathan M. Davidorf, MD (Davidorf Eye Group; Los Angeles, CA)
Entered vs. Achieved Spherical Equivalent
METHODS
Wavefront guided customized lasik procedures are designed to correct both lower
order (sphere and cylinder) and higher order optical aberrations (HOAs). Zyoptix is
the customized, wavefront guided platform for the Bausch & Lomb Technolas 217-Z
excimer laser. The system incorporates a Hartmann-Shack aberometer (Zywave) and
topography data (Orbscan II-z). The Hartmann-Shack aberrometry data from the
Zywave is combined with the Orbscan data to generate the custom treatment plans.
The IntraLase femtosecond laser (AMO) uses pulsed infrared light to photodisrupt
corneal tissue at a preset depth in order to construct the lamellar flap for LASIK.
LASIK with the IntraLase has been demonstrated to improve refractive outcomes
compared to LASIK with mechanical microkeratomes1.
While there are factors extraneous to the excimer laser ablation profile (such as flap
creation, wound healing, laser centration, and ocular surface abnormalities) in LASIK
that influence postoperative HOAs and refractive accuracy, wavefront guided custom
treatments attempt to minimize the induction of laser induced HOAs.2 Perhaps more
important, is the accuracy of the wavefront guided treatments in correcting the lower
order aberrations. The purpose of this study is evaluate the refractive efficacy and
predictability in myopic eyes undergoing Lasik with Zyoptix software version 2.38
using the IntraLase femtosecond laser for flap creation.
OBJECTIVE
As part of an ongoing nonrandomized, unmasked, prospective study of
myopic eyes were treated with Lasik using Zyoptix. The most recent
one hundred treated eyes with one month follow-up are presented.
Preoperatively, patients had complete ophthalmologic examinations,
including manifest and cycloplegic refractions, undilated and dilated
wavefront measurements (Zywave), corneal topography/pachymetry
(Orbscan II-Z), and mesopic pupil size measurement. Patients with a
history of prior ocular surgery or with poorly controlled medical problems
were excluded from the study.
Treatment plans were calculated preoperatively using the Zylink software
version 2.38. A customized nomogram developed from previously
treated eyes was used. The nomogram is based on a regression
equation with the mean of the manifest and cycloplegic spherical
equivalent refractions as the independent variable, and the inputted
spherical equivalent as the dependent variable. All eyes were targeted
for best possible uncorrected distance vision. The information from the
Zyoptix workstation was brought to the excimer laser on a floppy disk
and the data then transferred to the laser. Lamellar flaps were created
using the Intralase with an intended flap thickness between 90 and 120
microns (depending on preoperative corneal thickness and calculated
maximum ablation depth). When appropriate, bilateral simultaneous
Lasik was performed. The spot scanning excimer laser, the Bausch &
Lomb Technolas 217-Z, was used in all cases. Optical zone sizes from
5.50 to 6.70 mm were used depending on the amount of correction,
mesopic pupil size, and corneal thickness.
Ent v. Ach Avg MRCR M-Zx Last 100 3/31/08
-12.00
Higher Order Aberrations (RMS - m)
0.47
0.36
-6.00
-4.00
-2.00
-4.00
-6.00
0.31
0.23
-8.00
Pre-op
Post-op
-10.00
ach Avg MRCRSE
5 mm
Graph of the spherical equivalent entered into the Zyoptix treatment versus
the postoperatively achieved spherical equivalent (mean of preoperative
manifest and cyloplegic spherical equivalent refraction minus postoperative
spherical equivalent refraction)
6 mm
Pre-op (m)
Post-op (m)
5 mm
0.23 + 0.09
0.31 + 0.15 D
6 mm
0.36 + 0.14
0.47 + 0.23
Discussion
Wavefront guided custom lasik with Zyoptix and Intralase
demonstrated excellent efficacy and predictability regarding
lower order aberrations as manifest by 74% of eyes realizing
20/20 or better uncorrected visual acuity and over 1/3 of eyes
attaining 20/15 or better uncorrected visual acuity. All eyes had
best spectacle corrected visual acuity of 20/20 or better
preoperatively and postoperatively. The Entered vs. Achieved
graph of spherical equivalent shows a tight data series with an
R2 of 0.97. Continued nomogram refinements may further
improve subsequent data.
Intraoperative Flap Complications
No visually significant flap complications occurred in this series of
treated eyes. Of note, two eyes demonstrated a faint horizontal
ridge in the stromal bed upon flap elevation. Both cases occurred
inferiorly (superior hinged flaps), outside the visual axis, and did
not affect the excimer laser treatments nor the visual outcomes.
One patient with a small horizontal corneal diameter (“white-towhite”) had three small air bubbles identified in the anterior
chamber following flap creation. The bubbles were within the pupil
margin and did inhibit eye tracker acquisition, and there were no
visual sequelae. The bubbles were gone by the first postoperative
day.
The Bausch & Lomb
Technolas 217-Z
Excimer Laser
-8.00
y = 0.9362x - 0.4877
2
R = 0.9653
Mean optical zone diameter: 6.06 + 0.34 mm (5.50 to 6.70 mm)
Postoperatively, patients underwent additional Zywave testing at the one
month interval. Only undilated Zywave measurements were performed
postoperatively. Uncorrected distance visual acuity, manifest refraction,
and loss of best spectacle corrected visual acuity were evaluated. Data
was entered into an Excel spreadsheet for evaluation.
-10.00
0.00
-2.00
0.00
Ent SE
BACKGROUND
RESULTS
The main limitation of this study is the lack of comparison of the
effects (using similar nomogram adjustments) of Zyoptix Lasik
treatments with Intralase compared to either conventional
treatments or to Zyoptix treatments using a standard
microkeratome.
CONCLUSIONS
To study the refractive predictability in myopic eyes
undergoing wavefront guided LASIK with the
Intralase and Bausch & Lomb’s 217-Z excimer
laser using software version 2.38 (Zyoptix).
Postoperative Uncorrected Visual Acuity
Sample preoperative Zywave maps
74%
Demographics
# eyes (pts)
The Zyoptix Dual Workstation (Zywave
and Orbscan II-Z)
Lasik with Zyoptix and IntraLase demonstrated:
100 eyes (55 pts)
Gender
63 F, 37 M
Mean age
34 yrs (17 – 56)
Mean Pre-op SE
-4.27 + 2.08 D (-0.50 to -9.63D)
Mean Pre-op Cyl
-0.68 + 0.54 D (0 to -2.75 D)
Mean Pupil Size
6.1 + 0.9 mm (4.0 to 8.3 mm)
• Excellent efficacy and safety
99%
87%
• Excellent predictability
References
34%
20/15+
20/20+
20/25+
20/40+
1.
Dezirian GM, Stonecipher KG. Comparison of the IntraLase femtosecond laser and
mechanical keratomes for laser in situ keratomileusis. J Cataract Refract Surg.
2004;30:804-811.
2.
Bühren J, Kohnen T. Factors affecting the change in lower-order and higher-order
aberrations after wavefront-guided laser in situ keratomileusis for myopia with the Zyoptix
3.1 system. J Cataract Refract Surg. 2006;32:1166-1174.
For additional information please contact:
Jonathan M. Davidorf, MD
Davidorf Eye Group
www.davidorf.com