Transcript Long-Term Excimer Laser Enhancements: Myopic PRK Following

Long-Term Excimer Laser
Enhancements: Myopic PRK
Following Myopic LASIK
Jonathan M. Davidorf, M.D.
Davidorf Eye Group
Los Angeles, CA
ASCRS Annual Symposium
San Diego, CA
March, 2011
Financial Interest Disclosure
The author has no financial interest in any of the
devices or techniques used in this study
Purpose
• To study the predictability and safety of myopic
PRK in eyes previously treated with myopic
LASIK.
Background
Three main options for performing laser vision
enhancements following myopic lasik
1. Flap re-lift
2. flap re-cut
3. PRK
Options for LASIK Enhancements
Benefits
Concerns
Flap Re-Cut
Quick recovery; accurate
Flap complications;
difficult with intralase
Flap Re-Lift
Quick recovery; accurate
Flap depth/dimensions
(particularly if initial
treatment performed
elsewhere); epithelial
ingrowth (reports that
incidence higher if initial
treatment 3+ years
prior1)
PRK
Size/depth of initial flap
irrelevant
predictability; haze;
recovery
Concerns About Epithelial Ingrowth
The reported incidence of epithelial ingrowth ranges significantly in
the literature1-5. Some authors have reported that there is a lower
incidence of epithelial ingrowth in femtosecond laser created flaps
compared to microkeratome created flaps3. At a minimum, patients
with epithelial ingrowth need to be followed more closely (to
identify progression) than non-epithelial ingrowth patients. The
extra visits alone can become an inconvenience and source of
concern for patients (even in the cases in which the epithelial
ingrowth does not require intervention). If the epithelial ingrowth
becomes significant (progression, visually significant, foreign body
sensation), it must be treated, constituting additional, from the
patient’s perspective, unanticipated inconvenience: office visits,
procedures, risks.
Concerns About Epithelial Ingrowth
On the other hand, PRK is almost always inconvenient. Whether discussing
the visual recovery or postoperative pain, there is little debate that
uncomplicated LASIK (initial treatment or enhancement) provides, from
the patient’s perspective, an easier postoperative process than
uncomplicated PRK. However, the recovery with PRK is fairly predictable
and easy to counsel. The surgeon and patient must decide between one
procedure that carries with it the known downside of a slow recovery (PRK)
and another that carries with it the somewhat difficult to predict
complication of epithelial ingrowth.
The incidence of epithelial ingrowth has been shown to rise when the initial
LASIK procedure had been performed three or more years prior.2,5 After
reading recent such reports, we began using the three year mark as a
guideline for recommending PRK to patients requesting enhancement of
their initial LASIK procedure.
Concerns about PRK following LASIK
Apart from the visual recovery and postoperative pain, anticipated concerns
of predictability arise when contemplating PRK following LASIK. For
example, can epithelial hyperplasia impact the refractive outcome when the
thickened area of epithelium is removed? In the case of prior myopic lasik,
a hyperplastic central epithelial disk, if removed, could induce a hyperopic
shift on its own, without any laser treatment being applied.
Additionally, the risk of corneal haze always exists with PRK and has been
reported to be an increased problem with post-LASIK eyes.6 However,
intraoperative application of Mitomycin C may offset that risk somewhat.
Methods
• Ongoing prospective study
Inclusion criteria:
• eyes with a history of myopic LASIK performed
more than three years prior
• Eyes with myopia, with or without astigmatism
Methods
• PRK with EtOH epithelial debridement
• B&L Technolas Excimer Laser (PlanoScan
software)
• Post-laser 12 second application of 0.02%
mitomycin C
Demographics
• 16 eyes of 15 patients
• Mean follow-up 4.6 months (1 to 12 months)
• Mean preoperative manifest refraction spherical
equivalent:
-1.37 + 0.69 D (-0.63 to -2.88 D)
• Mean preoperative refractive cylinder:
-0.78 + 0.55 D (-0.50 to -1.75 D)
Results
MRSE
Cylinder
Pre-op
-1.37 + 0.69 D
-0.78 + 0.55 D
(-0.63 to -2.88 D) (-0.50 to -1.75 D)
1M
0.27 + 0.33 D
-0.47 + 0.36 D
(-0.13 to +0.75 D) (0 to -1.25 D)
3M
-0.17 + 0.25 D
-0.39 + 0.32 D
(-0.50 to +0.13 D) (0 to -0.75 D)
Uncorrected Visual Acuity at 1 Month
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
92%
92%
69%
46%
8%
Pre-op
1M Postop
8%
0
20/20+
20/25+
20/40+
< 20/200
Best Spectacle Corrected Vision
• All eyes 20/20 or better pre- and postoperatively
• No eyes lost or gained lines of BSCVA.
Haze
• No eyes developed visually significant corneal
haze
Predictability
M-PRK over M-LASIK Entered vs. Achieved MRSE
-3.50
-3.00
-2.50
-2.00
-1.50
-1.00
-0.50
0.00
0.00
Entered MRSE (D)
-0.50
-1.00
-1.50
-2.00
y = 0.8139x - 0.1852
R² = 0.7025
-2.50
-3.00
-3.50
Achieved MRSE (D)
Predictability
• 100% within 0.75D of target
• 69% within 0.50D of target
Discussion
While firm conclusions cannot be drawn from this small series of
treated eyes, the data suggests that PRK for low myopia and
astigmatism is a predictable and safe means for treating eyes with a
remote history of myopic LASIK. The refractive outcomes parallel
the published data on myopic LASIK enhancements performed with
flap re-lifting.1,4 Concerns of poor predictability owing to variable
epithelial thicknesses, and safety concerns, including the possibility
of corneal haze or disruption of the prior LASIK flap did not
manifest as problems in this current series of eyes.
Discussion
Only one patient in this series had a bilateral treatment. Since this
cohort comprised primarily patients with relatively low levels of
refractive error, desiring treatment in only one eye, the patients
would be expected to function reasonably well with the untreated
eye while waiting for the treated eye to achieve good functional
vision. With only one eye being treated, the recovery inconveniences
of PRK are lessened compared to a bilateral simultaneous or
bilateral sequential treatment. It is noteworthy that all of the treated
eyes attained a good visual outcome by the one month visit.
Conclusions
In light of the published data on the incidence of
epithelial ingrowth, combined with our
encouraging preliminary data, we are continuing
to recommend PRK for prior LASIK patients
considering enhancement if their initial last
LASIK procedure was performed over three
years previously. Ultimately, longer term followup on a larger series of eyes is needed before
firm guidelines and conclusions can be drawn.
References
1. Brahma A, McGhee CNJ, Craig JP, Brown AD, Weed KH, McGhee J, Brown R. Safety and
predictability of laser in situ keratomileusis enhancement by flap reelevation in high myopia.
Journal of Cataract & Refractive Surgery . April 2001 (Vol. 27, Issue 4, Pages 593-603)
2. Caster A, Friess DW, Schwendeman FJ. Incidence of epithelial ingrowth in primary and
retreatment laser in situ keratomileusis. Journal of Cataract & Refractive Surgery. January 2010
(Vol. 36, Issue 1, Pages 97-101)
3. Hyunseok Ahn H, Jin-Kook Kim, Chang Kook Kim, Gyu Heon Han, Kyoung Yul Seo, Eung Kweon
Kim, Tae-im Kim. Comparison of laser in situ keratomileusis flaps created by 3 femtosecond
lasers and a microkeratome. Journal of Cataract & Refractive Surgery. February 2011 (Vol. 37,
Issue 2, Pages 349-357)
4. Rubinfeld RS , Hardten DR, Donnenfeld EO, SteinRM, Koch DD, Speaker MG, Frucht-Pery,
Kameen JA, Negvesky GJ. To lift or recut: Changing trends in LASIK enhancement . Journal of
Cataract & Refractive Surgery . December 2003 (Vol. 29, Issue 12, Pages 2306-2317)
5. Waring , GO.; Durrie, DS.; Stahl, JE.; Schwendeman, FJ. Natural History of Epithelial Ingrowth
After Lift Flap Enhancement Procedures for LASIK: Prospective Single-Center Evaluation.
Abstract number 413055 presented at the American Society of Cataract and Refractive Surgery
Annual Symposium, 2008.
6. Liu A, Manche EE. Visually significant haze after retreatment with photorefractive keratectomy
with mitomycin-C following laser in situ keratomileusis . Journal of Cataract & Refractive
Surgery . September 2010 (Vol. 36, Issue 9, Pages 1599-1601)