Two-step LASIK after penetrating keratoplasty.

Abstract

The point of interest of this retrospective case review is to study refractive changes caused by the hinged lamellar keratotomy and the refractive outcome after laser ablation in a second step within the scope of laser in situ keratomileusis (LASIK) in patients with penetrating keratoplasty.
Data from eight patients obtained before lamellar keratotomy, before laser ablation, and three months later were evaluated. Keratotomies were performed with the Moria((R)) LSK one and the Amadeus((R)) 2 microkeratome, laser ablation was performed with the Schwind((R)) Keratome I and the Wavelight((R)) Allegretto WaveEyeQ.
Uncorrected visual acuity (UCVA) improved significantly from 1 [logMar] to 0.4 [logMar] at the last visit. Median gain of UCVA was 7.38 +/- 2.96 Snellen lines. Best spectacle-corrected visual acuity did not change significantly. Preoperative manifest refraction spherical equivalent decreased from -4.02 +/- 4.77 diopters (D) to -1.11 +/- 2.45 D after laser ablation. Mean preoperative manifest astigmatism was -7.27 +/- 3.65 D, after lamellar keratotomy -6.72 +/- 3.68 D, and after laser ablation -2.08 +/- 1.80 D. Manifest astigmatism did not change significantly after the keratotomy.
Lamellar keratotomy causes biomechanical changes to the cornea. We favor a two-step LASIK in penetrating keratoplasty patients in order to improve precision and predictability of the refractive outcome.

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Two-step LAsiK after penetrating keratoplasty
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O R i g i n A L R e s e A R C h
Aris n Kollias
Markus M schaumberger
Thomas C Kreutzer
Michael W Ulbig
Carlo A Lackerbauer
University eye hospital,
Ludwig-Maximilians University,
Munich, germany
Correspondence: Aris Kollias
University eye hospital, Ludwig-
Maximilians University, Mathildenstr. 8,
80336 Munich, germany
Tel +49 89 5160 3811
Fax +49 89 5160 5160
email akollias@med.uni-muenchen.de
Purpose: The point of interest of this retrospective case review is to study refractive changes
caused by the hinged lamellar keratotomy and the refractive outcome after laser ablation in a
second step within the scope of laser in situ keratomileusis (LASIK) in patients with penetrating
keratoplasty.
Methods: Data from eight patients obtained before lamellar keratotomy, before laser ablation,
and three months later were evaluated. Keratotomies were performed with the Moria® LSK one
and the Amadeus® 2 microkeratome, laser ablation was performed with the Schwind® Keratome
I and the Wavelight® Allegretto WaveEyeQ.
Results: Uncorrected visual acuity (UCVA) improved significantly from 1 [logMar] to
0.4 [logMar] at the last visit. Median gain of UCVA was 7.38 ± 2.96 Snellen lines. Best
spectacle-corrected visual acuity did not change significantly. Preoperative manifest refraction
spherical equivalent decreased from -4.02 ± 4.77 diopters (D) to -1.11 ± 2.45 D after laser
ablation. Mean preoperative manifest astigmatism was -7.27 ± 3.65 D, after lamellar keratotomy
-6.72 ± 3.68 D, and after laser ablation -2.08 ± 1.80 D. Manifest astigmatism did not change
significantly after the keratotomy.
Conclusions: Lamellar keratotomy causes biomechanical changes to the cornea. We favor a
two-step LASIK in penetrating keratoplasty patients in order to improve precision and predict-
ability of the refractive outcome.
Keywords: two-step, cornea, LASIK, keratoplasty, astigmatism
Introduction
Microsurgical techniques have improved the functional outcome of penetrating keratoplasty
(PK), but high spherocylindrical refractive errors are quite common after PK.1 They often
cannot be corrected by spectacles due to aniseikonia, therefore surgical approaches are of
interest. Laser in situ keratomileusis (LASIK) is a widely accepted method for treating a
great range of refractive errors and has been successfully used in treating patients requiring
refractive surgery after PK as well.2–7 The purpose of this retrospective chart review was to
examine the refractive changes induced by the hinged lamellar keratotomy alone and the
refractive outcome after laser ablation in a second step in patients with corneal grafts.
Patients and methods
Data from eight consecutive patients who had two-step LASIK after PK in
our department was evaluated. The study included five female and three male
patients. The mean age was 54 years (range 8 to 90 years). Four patients suffered
from Fuchs endothelial dystrophy, two patients from keratoconus, one from
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posttraumatic scares, and in one case the cause for PK
was unknown. Three patients were pseudophacic, the other
five participating patients had a clear crystalline lens. All
participating patients had an average intraocular pressure
of 14.7 mm of mercury (range 8 to 18 mmHg) and besides
the corneal transplant no other abnormal ocular findings.
Data collected included uncorrected visual acuity
(UCVA), best spectacle-corrected visual acuity (BSCVA),
manifest refraction (Table 1), corneal refractive power,
and corneal thickness, and were obtained before lamellar
keratotomy, before laser ablation, and three months later. The
average interval between date of PK and lamellar keratotomy
was 6.1 years (range 1.8 to 10.5 years). The time between
PK and suture removal was in all cases over six months
and the average period between lamellar keratotomy and
laser ablation was 51.9 ± 31.6 days (range 21 to 100 days).
Keratotomies were performed in one case with the Moria®
LSK One microkeratome (Moria, Antony, France), in the
other seven cases with the Amadeus® II microkeratome
(Ziemer Ophthalmic Systems, Port, Switzerland) and the
hinges were placed nasally. The size of the corneal flap
ranged from 8.5 to 9.0 mm and cut depth from 140 to 160 µm.
In all cases the complete corneal transplant was included in
the lamellar flap. Laser ablation was performed in one case
with the Schwind® Keratome I excimer system (Schwind,
Kleinostheim, Germany) and in the other cases with the
Wavelight® Allegretto WaveEyeQ excimer laser (WaveLight
AG, Erlangen, Germany). The treatment goal was primarily to
reduce the refractive error to a great extent and not necessarily
emmetropia since the preoperative refractive disorders were
quite high (Table 1). Postoperatively, patients were treated
with levofloxacin (Floxal®) and prednisolone (Inflanefran
forte®) eye drops four times a day for one week and unpre-
served artificial tears for three months. All surgeries as well
as the postoperative period were uneventful.
Statistical analysis was performed with SPSS 16.0® for
Windows® (SPSS Inc., Chicago, IL, USA). Statistically
significant differences between data were determined by
the Wilcoxon signed rank test. A P value less than 0.05 was
considered statistically significant.
Results
Visual acuity
Median preoperative UCVA (Figure 1) was 1 [logMar]
(range 0.50 to 0.70 [logMar]), after lamellar keratotomy
1.15 [logMar] (range 0.50 to 0.70 [logMar]), and after
laser ablation it improved to 0.4 [logMar] (range 0.70 to
0.20 [logMar]). Median gain of UCVA by the overall treatment
was 7.38 ± 2.96 lines (range 2 to 12 lines) and was statistically
highly significant (P = 0.008). Median change in UCVA by
the keratotomy was -0.5 ± 1.41 lines (range -4 to 0 lines)
and was not statistically significant (P = 1). Median gain in
lines of UCVA by the laser ablation was 7.88 ± 3.03 lines
(range 2 to 12 lines) and statistically was highly significant
(P = 0.008). Median preoperative BSCVA (Figure 2) was
0.2 [logMar] (range 1 to 0 [logMar]), after lamellar keratot-
omy 0.25 [logMar] (range 0.50 to 0 [logMar]), and after laser
ablation 0.04 [logMar] (range 0.50 to 0 [logMar]). Median
gain of BSCVA by the overall treatment was 1.63 ± 3.07
lines (range -1 to 8 lines) and not statistically significant
(P = 0.25). Median change in BSCVA by the keratotomy was
0.75 ± 1.83 lines (range -1 to 5 lines) and not statistically
significant (P  0.4). Median gain in lines of BSCVA by the
laser ablation was 0.87 ± 1.64 lines (range -1 to 3 lines) and
statistically not significant (P  0.2).
Refraction
Mean preoperative manifest refractive spherical equivalent
(MRSE) (Figure 3) was -4.02 ± 4.77 diopters (D) (range
-11.00 to +1.00 D), after lamellar keratotomy -4.11 ± 4.64 D
Table 1 Refraction before surgery, after lamellar keratotomy, intended refraction after laser ablation, and achieved refraction after laser
ablation
CasePreoperative refraction Refraction after keratotomy Intended refractionRefraction after laser ablation
1
+1.0 -8.0 × 55°
+6.50 -11.0 × 160°
+1.25 -6.50 × 7°
-6.25 -6.0 × 93°
-7.75 -0.75 × 28°
+2.50 -6.50 × 96°
-4.50 -13.0 × 144°
+4.25 -6.50 × 105°
+0.50 -7.25 × 60°
+6.50 -11.0 × 165°
-0.50 -4.50 × 11°
-5.75 -6.0 × 89°
-8.75 -0.25 × 32°
+2.50 -7.25 × 96°
-4.50 -12.0 × 144°
+4.0 -5.50 × 100°
-0.50 -0.25 × 60°
+6.50 -6.0 × 165°
-0.50
-3.75 -3.0 × 89°
-2.25 -0.25 × 32°
+0.50 -1.0 × 96°
0 -1.0 × 144°
-0.25
+2.0 -1.0 × 40°
+4.50 -5.0 × 155°
0 -0.75 × 67°
-3.25 -2.25 × 85°
-1.75 -0.50 × 139°
-0.50 -0.75 × 175°
-2.25 -4.75 × 155°
+0.75 -1.75 × 122°
2
3
4
5
6
7
8

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1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
Preoperative
logMAR Snellen sc
After keratotomy
After laser ablation
Figure 1 Median preoperative uncorrected visual acuity improved from preoperative
1 [logMar] to 0.4 [logMar] after laser ablation.
1.0
0.8
0.6
0.4
0.2
0.0
Preoperative
logMAR Snellen cc
After keratotomy
After laser ablation
Figure 2 Median preoperative best spectacle-corrected visual acuity did not change
significantly from 0.2 [logMar] preoperatively to 0.04 [logMar] after laser ablation.
Preoperative
–12
–10
–8
–6
–4
–2
+2
0
Spherical equivalent [D]
After keratotomy
After laser ablation
Figure 3 Mean preoperative manifest refractive spherical equivalent was reduced
from preoperatively -4.02 D ± 4.77 to -1.11 D ± 2.45 after laser ablation.
(range -10.50 to +1.25 D), and after laser ablation -1.11 ±
2.45 D (range -4.62 to +2.00 D). Changes in MRSE by
overall treatment and by keratotomy were not statistically
significant. Change in MRSE by the laser ablation was
statistically significant (P = 0.039). Mean preoperative sphere
was -0.38 ± 5.16 D (range -7.75 to +6.50 D), after lamellar
keratotomy -0.75 ± 5.22 D (range -8.75 to +6.50 D) and
after laser ablation -0.06 ± 2.50 D (range -3.25 to +4.50 D).
Change of the manifest sphere by the overall treatment and
by each individual step was statistically not significant.
Mean preoperative manifest astigmatism (Figure 4)
was -7.27 ± 3.65 D (range -13.0 to -0.75 D), after lamel-
lar keratotomy -6.72 ± 3.68 D (range -12.0 to -0.25 D),
after laser ablation -2.08 ± 1.80 D (range -5.0 to –0.50 D).
Change of the manifest astigmatism by the keratotomy alone
was statistically not significant (P = 0.12). The change of
manifest astigmatism by the overall treatment was statistically
highly significant (P = 0.008) as well as the change by the laser
ablation alone (P = 0.016). Comparing the intended refraction
with the achieved refraction after laser ablation there is a
mean deviation of 1.16 D (range -1.0 to + 4.0 D) in spherical
equivalent (Table 1).
Corneal topography
Mean preoperative corneal refractive power was 44.24
± 3.82 D (range 37.50 to 49.85 D), after lamellar kera-
totomy 44.90 ± 3.86 D (range 39.14 to 51.10 D), and after
laser ablation 42.38 ± 3.24 D (range 35.55 to 47.10 D).
Changes of mean corneal refractive power by the overall
treatment and by each individual step were not statisti-
cally significant (P  0.05). Axis of the flattest merid-
ian preoperatively was 72.75° ± 59.52 (range 7.50° to
159.60°), after lamellar keratotomy 95.10° ± 59.11 (range
9.90° to 162.80°), and after laser ablation 93.8° ± 64.91
Preoperative
–12
–10
–14
–2
–4
–6
–8
0
Manifest astigmatism [D]
After keratotomy
After laser ablation
Figure 4 Manifest astigmatism was not affected significantly by the keratotomy. It was
reduced from preoperatively -7.27 D ± 3.65 to -2.08 D ± 1.80 after laser ablation.

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(range 8.70° to 175°). Axis of the steepest meridian
preoperatively was 117.75° ± 45.14 (range 60.20° to
179.30°), after lamellar keratotomy 95.10° ± 56.37 (range
22.10° to 177.10°), and after laser ablation 93.8° ± 39.62
(range 33.70° to 139.3°). Changes of the axis of the flattest
meridian by each individual step of the procedure and by the
overall treatment were not statistically significant. Changes
of the axis of the steepest meridian by the overall treatment
were statistically significant (P = 0.039), changes by the
keratotomy (P  0.3) and by the laser ablation (P  0.7)
alone were statistically not significant.
Corneal pachymetry
Mean preoperative corneal pachymetry was 557.81 ± 51.77 µm
(range 454.2 to 633.0 µm), after lamellar keratotomy
563.67 ± 61.50 µm (range 460.1 to 660.5 µm), and after laser
ablation 473.06 ± 60.39 µm (range 383.5 to 574.9 µm).
Discussion
High refractive errors are a frequent finding after PK8–10
and reduce the patient’s perception of success following
corneal transplantation. High anisometropia impairs visual
rehabilitation and compromises the patient’s ability to return
to normal binocular functions. Correcting these refractive
disorders with spectacles is not possible in most of the cases
when anisometropia exceeds 3 D. Contact lenses provide a
high quality of vision, although they are associated with
problems like intolerance, corneal vascularization, and risk
of corneal infections.10–12 Some patients may face difficul-
ties wearing contact lenses due to poor manual dexterity,
tremor, or reduced visual acuity in the fellow eye. Surgical
approaches such as relaxing incisions,13,14 wedge resec-
tion,15,16 and selective suture removal17 have been used to
address these refractive errors, but provide less predictable
and stable results and are associated with risk of wound
dehiscence, induction of a graft rejection, and a long healing
process with fluctuations of corneal topography and refrac-
tion. Lens surgery with the implantation of toric lenses18,19
or the implantation of additional intraocular lenses20 have
shown good results, but it increases the risk of serious
complications like endophthalmitis, elevation of intraocular
pressure, retinal detachment, and loss of endothelial cells.
Surface ablation such as photorefractive keratectomy21–24
and laser-assisted sub-epithelial keratomileusis25 have shown
moderate results because of haze formation and regression
of the refractive effect.
LASIK has been widely used since its inclusion in the
clinical routine in the early 90s to treat a great range of
refractive disorders. By performing laser ablation in the
corneal stroma, postoperative wound healing reaction is
very mild and the risk of scarring and haze formation is very
low.26,27 It combines a high patient convenience due to the
lack of postoperative complaints and fast visual recovery with
predictable, precise, and stable results. In addition the rate
of serious complications is very low28,29 due to the evolution
of the hardware used and the standardized procedure, which
makes LASIK the most frequently used mode of treatment
in corneal refractive surgery.
In our study, UCVA improved significantly after overall
treatment. None of the patients lost a line of visual acuity
and all improved by at least 2 and up to 12 lines on the
Snellen chart. BSCVA did not change significantly; only
one patient lost a line of BSCVA while the rest improved by
up to 8 Snellen lines. These findings are accordant to other
studies,2–7,30–36 which have shown LASIK as an effective mode
of treatment for refractive errors following PK.
An open issue in performing LASIK after PK is
whether the lamellar keratotomy alone causes alterations
of the corneal shape and should therefore be performed in
two steps, in order to obtain more predictable and precise
results by collecting the necessary data for laser ablation
after the corneal flap has stabilized and the refraction is
stable. The analysis of the refraction showed no statistically
significant changes in sphere and astigmatism by the lamellar
keratotomy alone. Similarly, corneal refractive power showed
no statistically significant changes concerning the amount of
the refractive power, nor the axis of the steepest or flattest
meridian. Comparing the preoperative refraction with the
post-keratotomy refraction in detail, there was a decrease in
myopic spherical equivalent of 0.25 to 1.5 D in half of the
patients, whereas an increase was seen only in one patient
(Table 1). Comparing the preoperative cylinder with the
post-keratotomy cylinder (Table 1) there was a reduction of
the preoperative cylinder in five out of eight patients of 0.5 D
up to 2.0 D. These changes were statistically not significant,
probably due to the small size of our patient cohort. However,
these changes would definitely have an impact when planning
a refractive surgery. Our results match only in part those of
the studies conducted by Lee and colleagues37 and Bussin and
colleagues38 who found a significant reduction of preoperative
sphere and cylinder after keratotomy.
The goal of our treatment was not the same as for
correcting refractive disorders in other refractive patients due
to the height of the preoperative refraction with the exception
of patient number 5 (Table 1). It was primarily the reduction
of refractive errors to an extent that correction of the residual

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refractive error by other means like spectacle or contact lenses
is possible. In addition, assessing data from refraction means
and corneal topography is often difficult. Based on preopera-
tive data of limited certainty, it is not necessarily desirable to
try to reach the maximal feasible ablation depth in order to
reach emmetropia, which endangers the outcome of the entire
procedure. The precision of laser ablation was satisfactory
when preoperative data showing high refractive errors was
considered. Regarding the spherical equivalent, three patients
were overcorrected, four patients were undercorrected, and
one patient was on target. All surgeries were uneventful. We
did not face any complications while creating the corneal flap
or relifting it before laser ablation. Wound healing reaction
was mild and no incidence of graft rejection occurred during
the period of review.
Many factors such as the size, curvature, and thickness
of the corneal transplant, the underlying disease for the PK,
preoperative refraction, the trephination technique, the type
of suture, size and alignment of the corneal flap, whether
the complete transplant is included in the lamellar flap or
not, location of the hinge, the kind of mikrokeratome, and
the used settings (advance rate, vacuum), the excimer laser
and the chosen ablation profile as well as healing processes
which vary among patients affect the refractive outcome
of LASIK after PK. The interactions between these fac-
tors are to a great extent still unknown. Keratotomy causes
biomechanical changes in the cornea after PK and these are
unpredictable. Despite the small patient sample of this study
and its limited validity we share the opinion of Alió and
colleagues30 and Kwitko and colleagues33 and favor a two-step
approach. Further clinical studies are necessary to investigate
the biomechanical effects of keratotomy in corneal grafts in
order to clarify whether a one-step or two-step LASIK is the
most eligible method to improve precision and predictability
of LASIK after corneal transplantation.
Disclosures
The authors report no conflicts of interest in this work.
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