Transcript Document

A New Technique for Precise,
Predictable SBK Surgery
Using the B&L Zyoptix XP
Microkeratome
David R. Shapiro, MD
Shapiro Laser Eye Center
Ventura, California
No financial interest
Purpose
• Discuss the rationale, technique, and
personal results on Sub-Bowman’s
keratomileusis (SBK) performed with a 90to 110-µm flap created with the Bausch &
Lomb Zyoptix XP microkeratome
Rationale for SBK
• Advantages of LASIK with traditional LASIK
flap
• Quick recovery without the pain, slow recovery
and possible haze associated with PRK
• Advantages of surface ablation procedures
• Avoid biomechanical weakening of the cornea
and possible dry eye following standard LASIK
flaps
• Reduces possibility of ectasia compared with
LASIK
• SBK may combine the best advantages of LASIK
and surface ablation
SBK Flap
• SBK flap defined by 3 characteristics (as
described by Slade and Durrie) 1
• Thickness 90 to 110-µm
• Planar
• Customized diameter
 Minimized to coincide with the edge of
the laser ablation
1
Slade SG, Durrie DS. Six-month visual results of a contralateral prospective
study: Surface ablation versus sub Bowman’s keratomileusis flaps. Presented at
ASCRS Annual Meeting; San Diego; April 2007.
Ideal Flap: Thickness
• SBK with a flap of approximately 100-µm
may combine the best features of PRK and
1,2
LASIK
• Biomechanical stability
• Quick recovery
• Lack of haze
1
Marshall J, Angunawela R, Tengroth J, et al. Wound healing and biomechanics of corneal
flap creation. Keynote address. XXIV Congress of the ESCRS, London; 2006.
2
Marshall J. Sub-Bowman’s keratomileusis (SBK) vs. PRK. Presented at 11th ESCRS Winter
Refractive Meeting; Athens, 2007.
Ideal Flap: Planar
Flap made with Zyoptix XP microkeratome
Flap made with the Intralase FS30
Both flaps exhibit planar flap architecture (uniform thickness center through
the periphery)
Images taken with Visante anterior segment, high resolution, non-contact optical coherence
tomography (Carl Zeiss, Medictec, Inc.) Images courtesy of Barbara Lege, M.D. Munich, Germany.
Ideal Flap: Diameter
• Customized flap diameter, the third characteristic
of SBK (as defined by Slade and Durrie), may not
be significant
• Flap approximately 100 µm thick has no significant
biomechanical weakening effect due to the strength of
the underlying corneal tissue1,2
• Due to crossing angle differences, peripheral collagen
is stronger than central collagen, theoretically further
diminishing any trivial effect of increasing flap
diameter1,2
1
Marshall J, Angunawela R, Tengroth J,et al. Wound healing and biomechanics of corneal flap
creation. Keynote address. XXIV Congress of the ESCRS, London; 2006.
2
Marshall J. Sub-Bowman’s keratomileusis (SBK) vs. PRK. Presented at 11th ESCRS Winter
Refractive Meeting; Athens, 2007.
Sub-Bowman’s Keratomileusis with
the Zyoptix XP Microkeratome
Study Methods
• First eye of patient: 9.5 mm diameter,19 -
mm suction ring, 120-µm microkeratome
head
• Second eye of patient: 9.5 mm diameter,
20 -mm suction ring, 120-µm
microkeratome head
• Surgical technique in all eyes: Neutral to
the z-axis (results in suction inherent to that
from the machine)
• Subtraction pachymetry for flap
measurements
SBK Results
Preop Corneal
Thickness (µm)
Mean ± SD
Min, Max
Postop Corneal
Thickness (µm)
Mean ± SD
Min, Max
Diff. Pre to Post
Min, Max
First eye (N=20)
19 mm ring
9.5 mm diameter
Second eye (N=12)
20 mm ring
9.5 mm diameter
544.7 ± 31.6
514, 653
533.6 ± 16.1
514, 578
439.3 ± 25.4
413, 519
105.4 ± 9.8
93,134
439.1 ±19.9
418, 493
94.5 ± 7.0
84, 107
Zyoptix SBK Flap Results
• Zyoptix XP microkeratome with this new
technique safely and reproducibly produced
an SBK flap
• Buttonholes or free caps were not seen
• The XP flap can be tailored for each
individual eye in diameter, hinge position,
and centration on the cornea
• The Zyoptix XP shows less variation in flap
thickness than the Hansatome and is less
affected by measurable preoperative
variables, such as spherical equivalent
Limitations of Study
• Small Cohort
• Use of subtraction pachymetry
Future Study
• Large cohort
• Flap measurement with Optical Coherence
Tomography
Conclusion
• Our study suggests that the surgeon can
enjoy performing SBK effectively and safely
without the need to procure an entirely
different set of flap making equipment