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Z-LASIK and Trans-PRK for correction of high-grade myopia: safety, efficacy, predictability and clinical outcomes

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Purpose: The aim of the study was to examine the outcomes of transepithelial photorefractive keratectomy (Trans-PRK) and Femtosecond Laser-assisted in situ keratomileusis (Z-LASIK) for the correction of high myopia. Methods: A retrospective cohort study design was used. The study group included 792 eyes with high-grade myopia (- 6.0 diopters or higher) or high-grade myopia with astigmatism that were treated with Z-LASIK or Trans-PRK in 2013 through 2014 in an optical outpatient clinic of a large private medical service. The Trans-PRK group comprised of 674 eyes with a spherical equivalent (SE) of - 7.87 ± 1.46 and the Z-LASIK group comprised of 118 eyes with a SE of - 7.19 ± 0.81 (P < 0.001). Results: The mean postoperative SE in the Trans-PRK group was - 0.06 and - 0.02 in the Z-LASIK group (P = 0.545). Efficacy index values were 0.92 in the Trans-PRK group and 0.95 in the Z-LASIK group (P = 0.083), and corresponding safety index values were 0.95 and 0.97 (P = 0.056). An UCVA of 20/40 or better was achieved in 94.20% of eyes in the Trans-PRK group, and 98.31% in the Z-LASIK group (P = 0.063). The majority of eyes in both the Trans-PRK and Z-LASIK groups were within ± 0.5D of attempted correction: 59.35 and 64.71%, respectively (P = 0.271). Conclusions: Both Trans-PRK and Z-LASIK demonstrated excellent efficacy, safety and predictability profiles, with results comparable and in some cases superior to the current literature. Results of Z-LASIK were slightly better than those of Trans-PRK, though the preoperative SE of the latter was higher.
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ORIGINAL PAPER
Z-LASIK and Trans-PRK for correction of high-grade
myopia: safety, efficacy, predictability and clinical outcomes
Assaf Gershoni .Michael Mimouni .Eitan Livny .Irit Bahar
Received: 12 June 2017 / Accepted: 15 February 2018
ÓSpringer Science+Business Media B.V., part of Springer Nature 2018
Abstract
Purpose The aim of the study was to examine the
outcomes of transepithelial photorefractive keratec-
tomy (Trans-PRK) and Femtosecond Laser-assisted
in situ keratomileusis (Z-LASIK) for the correction of
high myopia.
Methods A retrospective cohort study design was
used. The study group included 792 eyes with high-
grade myopia (-6.0 diopters or higher) or high-grade
myopia with astigmatism that were treated with
Z-LASIK or Trans-PRK in 2013 through 2014 in an
optical outpatient clinic of a large private medical
service. The Trans-PRK group comprised of 674 eyes
with a spherical equivalent (SE) of -7.87 ±1.46 and
the Z-LASIK group comprised of 118 eyes with a SE
of -7.19 ±0.81 (P\0.001).
Results The mean postoperative SE in the Trans-
PRK group was -0.06 and -0.02 in the Z-LASIK
group (P=0.545). Efficacy index values were 0.92 in
the Trans-PRK group and 0.95 in the Z-LASIK group
(P=0.083), and corresponding safety index values
were 0.95 and 0.97 (P=0.056). An UCVA of 20/40
or better was achieved in 94.20% of eyes in the Trans-
PRK group, and 98.31% in the Z-LASIK group
(P=0.063). The majority of eyes in both the Trans-
PRK and Z-LASIK groups were within ±0.5D of
attempted correction: 59.35 and 64.71%, respectively
(P=0.271).
Conclusions Both Trans-PRK and Z-LASIK demon-
strated excellent efficacy, safety and predictability
profiles, with results comparable and in some cases
superior to the current literature. Results of Z-LASIK
were slightly better than those of Trans-PRK, though
the preoperative SE of the latter was higher.
Keywords High myopia FS-LASIK Trans-PRK
Refractive surgery Efficacy Safety Predictability
Introduction
Myopia, which is the most common refractive error of
the eye, has become more prevalent in recent years.
Traditionally, it is divided according to the level of
myopia to mild, moderate and high, the latter of which
is used by the American Academy of Ophthalmology
A. Gershoni E. Livny I. Bahar (&)
Assuta Optic, Assuta Medical Center, Tel Aviv, Israel
e-mail: iritbahar@gmail.com
A. Gershoni E. Livny I. Bahar
Division of Ophthalmology, Beilinson Hospital, Rabin
Medical Center, Petach Tikva, Israel
A. Gershoni E. Livny I. Bahar
Sackler Faculty of Medicine, Tel Aviv University,
Tel Aviv, Israel
M. Mimouni
Department of Ophthalmology, Rambam Health Care
Campus, Haifa, Israel
123
Int Ophthalmol
https://doi.org/10.1007/s10792-018-0868-4
to describe myopia which is above 6.0 diopters (D).
The presence of high-grade myopia is one of the
leading reasons for not performing refractive surgery
[1,2].
In the 1990s, photorefractive keratectomy (PRK)
was the most performed surgical procedure to correct
low to moderate myopia. Even though it is considered
safe and effective, the side effects include postoper-
ative pain, slow visual rehabilitation, glare or halos
and the risk of iatrogenic corneal haze and poor
predictability, especially in high myopia [3,4].
Transepithelial PRK (Trans-PRK) refers to the
Schwind Amaris platform (Schwind eye-tech-solu-
tions GmbH, Kleinostheim, Germany) which uses an
excimer laser to ablate the epithelium and then reshape
the cornea in order to correct the refractive error. This
platform can obviate the need of alcohol epithelial
debridement or mechanical removal of the epithelium
during PRK but has the potential to interfere with the
final refractive outcomes of the procedure. Trans-PRK
has been shown to be faster to perform, less painful
and stressful, inducing less postoperative haze and
faster healing time than alcohol-based PRK [57].
The other procedure which evolved over the years
alongside PRK is the Laser In Situ Keratomileusis
(LASIK) which nowadays is the most popular proce-
dure for the surgical correction of refractive error. It
provides faster visual recovery, minimal postoperative
pain, less regression and the ability to correct high
degrees of myopia with little postoperative corneal
haze [8]. Shortt et al. [9] compared LASIK with PRK
and concluded that the former had superior efficacy
and safety than the latter.
Nevertheless, one should be aware of LASIKs’
complications profile: flap- and interface-related com-
plications, flap-related corneal biomechanical insta-
bility, and iatrogenic keratectasia, which is more of a
concern in high myopia [1018]. The technological
evolution of flap creation enabled the creation of a
more precise and reproducible flap with the femtosec-
ond laser in general, and with the Ziemer-Laser In Situ
Keratomileusis (Z-LASIK) procedure in particular
[1925]. In their research from 2011, Alio et al. [26]
concluded that LASIK for high myopia with the
Amaris Excimer laser and a femtosecond platform for
flap creation is safe, effective and predictable. A recent
publication which compared FS-LASIK with alcohol-
assisted PRK for the treatment of a wide range of
refractive errors found superior visual outcomes in the
FS-LASIK group [27].
The purpose of the current study was to examine the
safety, efficacy, predictability and clinical outcomes
of Trans-PRK and Z-LASIK for the correction of high-
grade myopia.
Materials and methods
A retrospective cohort study design was used. The
study followed the tenets of the Declaration of
Helsinki and was approved by the Institutional Review
Board of Assuta Medical Center.
Study cohort
The study group consisted of 792 eyes with high-grade
myopia (-6.0D or higher) or high-grade myopia with
astigmatism that were treated with Z-LASIK or Trans-
PRK at the optical outpatient clinic of the largest
private medical service in Israel from January 2013
through December 2014. All procedures were per-
formed by one of 7 experienced staff surgeons.
Patients were included in the study if they were
18 years or older, had a myopic spherical equivalent
(SE) of -6.0D or higher, underwent Z-LASIK or
Trans-PRK and had a complete medical record.
Exclusion criteria were age lower than 18 years,
change of more than 0.5D in refraction during the year
prior to the initial consultation, abnormal or kerato-
conus topography, coexisting ocular pathology or
previous surgery, inflammatory or infectious corneal
disease, relevant systemic dermatologic or connective
tissue disorders, myopic spherical equivalent (SE)
lower than -6.0D, hyperopia, intended monovision,
pregnancy and incomplete medical records.
Preoperative evaluation
The preoperative evaluation included manifest and
cycloplegic refraction, autorefraction, slit lamp biomi-
croscopy, dilated fundoscopy, Goldmann tonometry
and mesopic pupil diameter measurement. Slit-scan
corneal Scheimpflug tomography (Sirius, Schwind
eye-tech-solutions GmbH, Kleinostheim, Germany)
and total ocular wavefront measurement (Hartmann-
Shack Aberrometer/ORK-Wavefront Analyzer; Sch-
wind eye-tech-solutions) were carried out as well.
Int Ophthalmol
123
Surgical technique
Decision to perform Z-LASIK or Trans-PRK was left
to the discretion of the operating physician.
In the Trans-PRK group, all treatments were
aspheric aberration-neutral non-wavefront-guided
profiles and excimer laser application was preceded
by standardized wet sponge application. Single-step
laser delivery with the Schwind Amaris 500E excimer
laser (Schwind eye-tech-solutions GmbH, Kleinos-
theim, Germany) was carried out immediately after-
ward with a 5.7–7.0 mm optical zone. Mitomycin C
(MMC 0.02%) was immediately applied for 50 s using
a damp Merocel sponge, then copiously irrigated with
BSS (balanced normal saline solution), and dried. One
drop of ofloxacin (0.3%) was subsequently instilled,
and a bandage contact lens (purevision, Baus-
ch&Lomb) was inserted. After surgery, all eyes
received topical ofloxacin (0.3%) qid until removal
of the contact lens, dexamethasone (0.1%) drops qid
with a slow tapering down over 12 weeks, and
artificial teardrops qid for 3 months.
In the Z-LASIK group, a minimum residual stromal
bed of 300 microns was mandatory for the procedure.
The corneal flaps were created under topical anesthe-
sia using the Ziemer LDV Z6 Femtosecond laser
(Ziemer Ophthalmic Systems, Allmendstrasse,
Switzerland). Nominal flap thickness was set at
110 lm and flap diameter, to 9.5 mm, with a 0.4-
mm hinge placed superiorly. After the flap was lifted,
ablations were performed using the Schwind Amaris
500E excimer laser with a 5.7–7.5 mm optical zone
and 0.5 mm transition zone. The corneal flap and
stromal surface were irrigated with balanced salt
solution, and the flap was repositioned. After surgery,
patients were instructed to instill topical ofloxacin
(0.3%) qid for 1 week, dexamethasone (0.1%) drops
qid for 2 weeks, and artificial tears qid for 3 months.
Patients were examined immediately after surgery
and invited for follow-up visits at 1 day, 1 week, 1, 3,
6 months and 1 year after surgery.
Study procedure
Patients who met the study criteria were divided into
those who underwent Z-LASIK surgery and those who
underwent Trans-PRK.
The medical files of the patients were reviewed for
demographics, operative data, length of follow-up,
manifest refraction, uncorrected and best-corrected
visual acuity (UCVA and BCVA), corneal thickness,
and postoperative complications. Efficacy was calcu-
lated as the ratio of mean postoperative UCVA to
mean preoperative BCVA (efficacy index). Safety was
calculated as the ratio of mean postoperative BCVA to
mean preoperative BCVA (safety index). Findings
were compared between the Z-LASIK and Trans-PRK
groups.
Postoperative haze was defined as clinically appar-
ent haze and was noted even if it was visible in only
one follow-up appointment and did not affect the
patients’ vision considerably.
Statistical analysis
Data were analyzed with the Minitab Software,
version 16 (Minitab Inc, State College, PA). Normal-
ity of the data was assessed by the Kolmogorov–
Smirnov test. Student’s t test was used for variable
comparisons between both groups when normal
distribution could be assumed, whereas the Kruskal–
Wallis test was used for non-normally distributed data.
For the analysis of categorical variables, Chi-square or
Fisher exact test was used. A Pvalue of less than 0.05
was considered statistically significant.
Results
Subject demographics
After an exclusion of patients who were lost to follow-
up (24.60% in the Trans-PRK group and 29.88% in the
Z-LASIK group), the Trans-PRK group comprised
674 eyes and the Z-LASIK group of 118 eyes. While in
the former group there was a male predominance of
54.01%, in the latter there was a female one of 68.64%.
Mean age was higher in the Z-LASIK group. As
Z-LASIK was not performed on corneas thinner than
500 microns, the mean corneal thickness of the Trans-
PRK group was lower than that of the Z-LASIK group.
The preoperative spherical equivalent (SE) was higher
in the Trans-PRK group (Table 1).
Efficacy
The efficacy index was 0.92 in the Trans-PRK group
and 0.95 in the Z-LASIK group (P=0.08) (Table 2).
Int Ophthalmol
123
An UCVA of 20/40 or better was achieved in 94.20%
of eyes in the Trans-PRK group and 98.31% in the
Z-LASIK group (P=0.06). Rates for UCVA 20/25 or
better were 62.20 and 69.49%, respectively
(P=0.13) (Fig. 1).
Predictability
Both Z-LASIK and Trans-PRK proved efficient at
achieving the attempted correction, and the postoper-
ative SE was comparable between the two groups
(Table 2, Fig. 2). The mean postoperative SE in the
Trans-PRK group was -0.06 and -0.02 in the
Z-LASIK group (P=0.55) (Table 2). The distance
from target was marginally but significantly more
accurate with the Z-LASIK group. The majority of
eyes in both the Trans-PRK and Z-LASIK groups were
within ±0.5D of attempted correction: 59.35 and
64.71%, respectively (P=0.271) (Table 2). Figure 3
shows the SE refractive accuracy in the two groups,
and Figs. 4and 5show the preoperative and postop-
erative differences in refractive astigmatism between
the groups.
Safety
The safety index was marginally, but not significantly,
higher in the Z-LASIK group (Table 2). Two lines or
more of BCVA were lost in 47 out 674 (7%) in the
Trans-PRK group, while only 1 eye out of 118 (0.8%)
lost 2 lines or more in the Z-LASIK group (Fig. 6).
Complications
The types and rates of postoperative complications are
shown in Table 3. Haze was identified in 55 out of 674
eyes (8.16%) that underwent Trans-PRK and was
associated with a BCVA loss of 1 line or more in 25
patients (3.71%). A grading of the postoperative
corneal haze alongside its respective mean
Table 1 Patient’s
demographics and
preoperative data
Values are mean ±SD
unless otherwise indicated
Parameter Trans-PRK (n=674) Z-LASIK (n=118) P
Male 54.01% 31.36% \0.001
Age (year) 26.08 ±7.52 28.39 ±6.52 0.001
Corneal thickness (lm) 533.4 ±31.1 549.0 ±26.0 \0.001
Spherical equivalence (D) -7.87 ±1.46 -7.19 ±0.81 \0.001
Sphere (D) -7.45 ±1.50 -6.73 ±1.01 \0.001
Cylinder (D) -0.83 ±0.79 -0.92 ±0.98 0.38
Table 2 Postoperative
outcomes
Values are mean ±SD or
percent of eyes
UCVA uncorrected visual
acuity, BCVA best-corrected
visual acuity
Parameter Trans-PRK (n=674) Z-LASIK (n=118) P
Follow-up time (months) 4.57 ±3.39 3.55 ±3.33 0.003
Spherical equivalence (D) -0.06 ±0.91 -0.02 ±0.65 0.55
Sphere (D) 0.24 ±0.89 0.28 ±0.67 0.51
Cylinder (D) -0.59 ±0.44 -0.60 ±0.41 0.81
Efficacy index 0.92 ±0.22 0.95 ±0.16 0.08
UCVA 0.84 ±0.19 0.88 ±0.14 0.001
Safety index 0.95 ±0.20 0.97 ±0.14 0.06
20/20 or better 29.46% 29.66% 0.97
20/25 or better 62.20% 69.49% 0.13
20/30 or better 85.27% 94.07% 0.01
20/40 or better 94.20% 98.31% 0.06
20/50 or worse 5.36% 1.69% 0.09
BCVA 0.86 ±0.17 0.90 ±0.12 0.002
Distance from target (D) 0.64 ±0.66 0.50 ±0.42 0.004
% Within ±0.50 D 59.35% 64.71% 0.27
Int Ophthalmol
123
preoperative SE is described in Table 4and Fig. 7.
A Pearson’s correlation was conducted as well and
exhibited a statistically significant negative linear
correlation between the patient’s preoperative SE and
the postoperative grade of corneal haze (r=-0.20,
P\0.001). Elevated intraocular pressure (IOP) was
measured in only 6 eyes out 792 eyes in the study
(0.76%) with no statistical difference between the 2
groups. Diffuse Lamellar Keratitis (DLK) was not
diagnosed in any patient. Flap-related complications,
Fig. 1 Uncorrected
distance visual acuity
achieved
Fig. 2 Spherical equivalent
attempted versus achieved
Int Ophthalmol
123
including nonvisual compromising microstria,
occurred in 5 eyes out of 118 in the Z-LASIK group
(4.24%).
Discussion
The adequate treatment for patients with high myopia
has been a topic of controversy for many years in the
field of refractive surgery. Two emerging technolo-
gies, the Z-LASIK and the Trans-PRK presume to give
a safe and effective solution for these patients. The
current study compared these two bladeless
approaches in the correction of eyes with high myopia,
and found that both Z-LASIK and Trans-PRK showed
excellent safety, efficacy and predictability. To the
best of our knowledge, this is the first report compar-
ing Z-LASIK with Trans-PRK for the treatment of
high myopia.
When discussing elective refractive procedures,
one should be aware that the most critical factor to our
patients is eliminating their dependency on spectacles.
This factor can be assessed most accurately with the
efficacy index and with the percentage of eyes
achieving an UCVA of 20/40 or better, which is the
mandatory minimum requirement for driving without
spectacles in the USA. In the contemporary literature,
Trans-PRK for the treatment of high myopia achieved
rates of UCVA of 20/40 or better between 95.4 and
100% [28,29]. Efficacy index values for the treatment
Fig. 3 Postoperative spherical equivalent refractive accuracy
Fig. 4 Refractive astigmatism in Trans-PRK group
Int Ophthalmol
123
Fig. 5 Refractive astigmatism in Z-LASIK group
Table 3 Complications
Values represent percent of
eyes
IOP intraocular pressure,
DLK diffuse lamellar
keratitis
Parameter Trans-PRK (n=674) Z-LASIK (n=118) P
Haze 8.16% N/A N/A
Elevated IOP 0.59% 1.69% 0.221
DLK N/A 0.00% N/A
Flap-related complications N/A 4.24% N/A
Regression 1.93% 0.00% 0.235
Overcorrection 0.00% 1.69% 0.022
Fig. 6 Change in corrected distance visual acuity
Int Ophthalmol
123
of high myopia with FS-LASIK range between 0.91
and 0.97 [2123,26], and rates of UCVA 20/40 or
better, between 88.2 and 99% [21,2326].
In our study, the efficacy of both procedures was
comparable and in some cases even superior to
previous studies describing treatment for high myopia.
With an efficacy index of 0.95 and with 98.31% of
eyes achieving an UCVA of 20/40 or better, the results
of the Z-LASIK group were marginally better than
those of the Trans-PRK group which had an efficacy
index of 0.92 and 94.20% of eyes achieving an UCVA
of 20/40 or better, though the advantage was not
statistically significant. As a rule, due to the fact that
we did not exclude patients with an impaired BCVA
preoperative (numerous studies included only eyes
with a BCVA of 20/25 or better preoperatively and
some even of 20/20 or better), our percentage of eyes
achieving an UCVA of 20/20 or better was lower than
reported in some studies. This does not mean that the
reported operations were not successful, as can be seen
in our very high efficacy index which takes into
account the preoperative BCVA.
In terms of predictability, the literature suggests
that the percentage of eyes treated for high myopia that
were within ±0.5D of intended correction ranged
between 17 and 71.6% for LASIK [28,30,31], 91.4
and 95.4% for Trans-PRK [28,29], and 56 and 100%
for FS-LASIK [20,21,2326].
All of the patients in both our groups were targeted
for emmetropia. In the Trans-PRK group 59.35% of
the patients and 64.71% in the Z-LASIK group were
within ?/0.50D of the intended correction, a margin
which was not statistically significant. For predictabil-
ity, our Trans-PRK results were lower than those
reported in the previous studies [28,29], but one study
excluded patients with myopia higher than -10.0D
and above -4.0D astigmatism, and one study was
conducted on only 35 eyes and patients with over
-3.5D astigmatism were excluded as well.
Until recently, a relatively high percentage of the
patients undergoing refractive surgery for the correc-
tion of high myopia would lose 2 lines or more of
BCVA postoperatively. In the book ‘‘refractive
surgery outcomes and complications’’ from 2008
[32], the authors advised that an acceptable percentage
of loss of 2 or more lines of BCVA at 6 months of
follow-up must be between 1 and 5%.
Fig. 7 Interval plot of
preoperative spherical
equivalent and
postoperative corneal haze
grading
Table 4 Postoperative corneal haze grading and its respective
preoperative SE
Postoperative haze grade Preoperative SE (D)
Grade 0 (619 eyes) -7.79 ±1.40
Grade 1 (43 eyes) -8.42 ±1.47
Grade 2 or more (12 eyes) -10.03 ±2.35
Values are mean ±SD
ANOVA: P\0.001
Pearson’s correlation: r=-0.20 (P\0.001)
Int Ophthalmol
123
The percentage of eyes with high myopia that lost 2
of more lines of BCVA postoperatively in similar
studies ranged between 0.6 and 27% for LASIK
[24,28,30,33,34], 0% for Trans-PRK [28,29], and 0
to 2.3% for FS-LASIK [20,22,23]. In our study, 47
out 674 (7%) in the Trans-PRK group lost 2 or more
lines—a higher percentage than advised in the afore-
cited book, though we have a negative bias in our
group as will be explained further on. This rather high
percentage might also be explained by the large rate of
clinically apparent postoperative haze in our Trans-
PRK group (8.16%), which indeed needs to be further
evaluated. Only 1 eye out of 118 (0.8%) lost 2 lines or
more in the Z-LASIK group (Fig. 6) which is
extremely low, especially when considering the large
amount of eyes examined.
In our study, the safety index in the Trans-PRK
group and in the Z-LASIK group was 0.95 and 0.97,
respectively, which is acceptable with regard to the
safety index reported in the literature for high myopia
[2123,30].
The complications of Trans-PRK and FS-LASIK
are not vastly reported in the literature with regards to
high myopia. The total incidence of all intraoperative
LASIK flap complications that have been published in
studies of C1000 eyes ranges from 0.3 to 5.7% [11].
Kulkamthorn et al. [23] reported on 5 eyes out of 43
that had stria postoperatively. Kojima et al. [24] found
one DLK case, one flap-related complication and one
epithelial ingrowth out of 320 eyes. There were other
publications which did not mention having any
complications [20,22,25,26]. In our study, flap-
related complications occurred in 5 eyes out of 118
(4.24%), 3 of which were nonvisual compromising
microstria, and there was no DLK present in any eye.
Aslanides et al. [29] reported on up to 37% of eyes
with clinically apparent haze 3 months postopera-
tively which reduced to about 2% 12 months postop-
eratively, while in our study the incidence of haze was
8.16%. This relatively high incidence of haze can be
attributed to differences in the diagnosis and grading
of haze, which can be variable among different
observers. Another possible explanation is that the
higher the preoperative SE is, so is the increased
cumulative ablation energy which is employed in
order to correct it, a reasoning which also explains the
correlation we discovered between the preoperative
SE and the grade of postoperative haze, which was
further validated by a Pearson’s correlation. Further
studies are needed to investigate whether the Trans-
PRK platform causes more haze than the PRK one, or
is it merely a coincidence.
There are several limitations to this study. First,
although the sample was large, we used a retrospective
study design with a limited follow-up time of
12 months. Second, because we do not practice
alcohol deepithelization in our clinic, and we rarely
practice mechanical deepithelization, we were unable
to perform a comparison between the above-men-
tioned and Trans-PRK—a comparison which would
have added valuable knowledge regarding complica-
tions, haze level and reepithelization timing. Third,
patients undergoing surgery at our clinic are not
obliged to attend follow-up appointments. Therefore,
those with a very good UCVA in the early postoper-
ative examinations tended not to adhere to the full
12-month follow-up, whereas those with worse early
outcomes were motivated to appear for reexamination.
The consequent high attrition rate probably caused a
negative bias in terms of efficacy in both groups.
Fourth, there was also a potential negative bias in
terms of the safety index/loss of BCVA because we do
not routinely examine BCVA in patients with a good
postoperative UCVA; instead, we use the postopera-
tive UCVA value for both parameters. This may have
lowered the expected safety index and increased the
number of eyes that lost lines of BCVA postopera-
tively, in both groups. Another bias between both
procedures consists of the fact that eyes with a degree
of myopia higher than 10D were rarely operated with
the Z-LASIK approach—thus creating a bias against
the Trans-PRK group. In addition, when a patient
underwent another operation to correct the remaining
myopic error we only related to the results of the first
operation in the analysis, thus lowering our cumulative
results. The last negative bias acting against our results
is that we did not exclude patients with a very high
myopia which were excluded in some other studies,
thus, again, lowering the eyes achieving an UCVA of
20/20 or better.
In conclusion, in this single-center retrospective
study, we found both procedures to have excellent
efficacy, safety and predictability profiles, with results
comparable and in some cases superior to the current
literature. The results of the Z-LASIK operation were
slightly better than those of the Trans-PRK one,
though the preoperative SE of the latter was signifi-
cantly higher than that of the former. The findings
Int Ophthalmol
123
should be confirmed in prospective trials with longer
follow-up.
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... Seven recent studies have shown that TransPRK is also similarly or more effective than conventional PRK and LASIK in high myopia [24][25][26][27][28][29][30]. For example, the recent randomized trial of Mounir et al. showed that SCHWIND TransTRK and LASIK associated with similar efficacy (80.0% and 80.3%) and safety (95.0% ...
... Our case series resembled the other TransPRK cohorts in terms of preoperative myopia and postoperative UCVA and efficacy and safety indices. Our predictability index (96%) tended to be higher than those of the other TransPRK cohorts (59-87%), possibly because refraction stabilizes at 6-12 months; our study duration was 6 months whereas the studies that reported predictability had durations of 12 months [25,26,[28][29][30]34]. Our low rate of clinically significant haze was also observed by six of the studies (0-1% of patients had Fantes grade �2 at the end of follow-up). ...
... Transepithelial refractive surgery has been criticized for not accounting for potential individual variations in epithelial thickness, which could theoretically affect refractive results [20,30]. The good outcomes of our cohort, and the other studies in myopia in general, do not support this notion [1,[16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. ...
Article
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Background: Studies suggest that transepithelial photorefractive keratectomy (TransPRK) with the all-surface laser ablation (ASLA)-SCHWIND platform is effective and safe for both low-moderate myopia and high myopia. In most studies, mitomycin-C is administered immediately after surgery to prevent corneal opacification (haze), which is a significant complication of photorefractive keratectomy in general. However, there is evidence that adjuvant mitomycin-C induces endothelial cytotoxicity. Moreover, a recent study showed that omitting adjuvant mitomycin-C did not increase haze in low-moderate myopia. The present case-series study examined the efficacy, safety, and haze rates of eyes with high myopia that underwent ASLA-SCHWIND TransPRK without adjuvant mitomycin-C. Methods: All consecutive eyes with high myopia (≤-6 D) that were treated in 2018-2020 with the SCHWIND Amaris 500E® TransPRK excimer laser without adjuvant mitomycin-C in a tertiary-care hospital (France) and were followed up for 6 months were identified. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and spherical equivalent (SE) were recorded before and after surgery. Postoperative haze was graded using the 4-grade Fantes scale. Efficacy rate (frequency of eyes with 6-month UCVA ≤0.1 logMAR), safety rate (frequency of eyes that lost <2 BSCVA lines), predictability (frequency of eyes with 6-month SE equal to target SE±0.5 D), efficacy index (mean UCVA at 6 months/preoperative BSCVA), and safety index (BSCVA at 6 months/preoperative BSCVA) were computed. Results: Sixty-nine eyes (38 patients) were included. Mean preoperative and 6-month SE were -7.44 and -0.05 D, respectively. Mean 6-month UCVA and BSCVA were 0.00 and -0.02 logMAR, respectively. Efficacy rate and index were 95.7% and 1.08, respectively. Safety rate and index were 95.7% and 1.13, respectively. Predictability was 85.5%. Grade 3-4 haze never arose. At 6 months, the haze rate was zero. Conclusions: ASLA-SCHWIND TransPRK without mitomycin-C appears to be safe as well as effective and accurate for high myopia.
... In our study, the efficacy and safety of both procedures was comparable, and no eyes showed 2 or more lines worse CDVA postoperatively, compared to preoperative CDVA. The postoperative UDVA and CDVA in both groups were acceptable, but when compared with other studies, percentage of UDVA achieving 20/40 or better was 95.4 to 100% in TPRK group [14][15][16] and the percentage was 88.2 to 99% in other FS-LASIK groups [17][18][19][20]. Comparisons of visual outcomes between TPRK and FS-LASIK group in our studies were similar to two others that described treatment for high myopia. ...
... Aslanides [15] found that TPRK for correction of high myopia demonstrated comparable refractive outcomes to LASIK and PRK, with relatively favorable visual acuity outcomes. Contrary to those studies and ours, Gershoni [20] reported that clinical outcomes of FS-LASIK were slightly better than those of TPRK. Another study compared the results of FS-LASIK and PRK for the correction of high myopia and found that FS-LASIK improved UDVA better than PRK [21]. ...
... Our efficacy and safety indices in both groups (all more than 1.00) were superior to those of previous studies that corrected myopia. Gershoni [20] reported that efficacy index values were 0.92 in their TPRK group and 0.95 in their FS-LASIK group. Corresponding safety index values were 0.95 and 0.97. ...
Article
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Background: To compare the clinical outcomes of transepithelial photorefractive keratectomy (TPRK) with femtosecond laser-assisted in situ keratomileusis (FS-LASIK) for correction of high myopia. Methods: In this prospective, non-randomised, cohort study, 85 eyes of 46 patients treated with TPRK and 80 eyes of 42 patients treated with FS-LASIK were included. All eyes were highly myopic (spherical equivalent refraction <- 6.00 diopters). Both TPRK and FS-LASIK were performed by Schwind Amaris 750S excimer laser. Visual acuity, refraction, corneal high order aberration (HOA) and other variables were analyzed before and at 1, 3, 6, 12 months after surgery. Results: At 12 months after surgery, uncorrected logMAR distance visual acuity (UDVA) in the TPRK and FS-LASIK groups was - 0.04 ± 0.04 and - 0.01 ± 0.08, respectively (P = 0.039). Corrected logMAR distance visual acuity (CDVA) was - 0.06 ± 0.05 and - 0.04 ± 0.05 in both groups (P = 0.621). For UDVA, 86% of eyes in the TPRK group and 80% in the FS-LASIK group remained unchanged or improved one or more logMAR lines (P = 0.314), compared to preoperative CDVA. For CDVA, 97% of eyes in the TPRK group and 90% in the FS-LASIK group remained unchanged or improved one or more lines (P = 0.096), compared to preoperative CDVA. Spherical equivalent refraction was - 0.05 ± 0.39 and - 0.26 ± 0.47 in both groups (P = 0.030). 87% of eyes in the TPRK group and 73% in the FS-LASIK group achieved ±0.50 D target refraction (P = 0.019). All 85 eyes (100%) in the TPRK group and 75 eyes (92%) in the FS-LASIK group were within ±1.00 D of target (P = 0.003). Root mean square (RMS) of corneal total HOA and vertical coma in the TPRK group were lower compared with the FS-LASIK group (P < 0.001 for both variables). Conclusions: TPRK and FS-LASIK showed good safety, efficacy and predictability for correction of high myopia. Clinical outcomes of TPRK were slightly better than FS-LASIK.
... The results were comparable. 17 One year post operative follow up of T-PRK was reported by Luger et al. They showed that postoperative results of T-PRK were equivalent to those of femtosecond-assisted LASIK. ...
Article
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Purpose: To compare the results of LASIK versus Trans Epithelial Photorefractive Keratectomy (T-PRK) in correcting astigmatic refractive error. Methods: One hundred and twenty-six eyes of 63 patients, age 18 to 35 years, of either gender, presenting with astigmatism were enrolled in this study. Myopes with spherical equivalent (SE) ≤-13.0 diopter sphere (DS), hyperopes with SE ≤ +5.0 DS and astigmatism ≥ 1.5 D with visual acuity better or equal to 0.3 LogMAR were included. Astigmatic eyes with < 1.5D and with any other ocular pathology were excluded. Refractive status was assessed by Canon Autorefractor and Heine Retinoscope. The average reading of both methods was taken. Patients were divided into two groups (31: LASIK; 32: trans-PRK) by the spin of a coin method. Refractive surgery was done in both groups. Results: Mean age of the patients was 25.83 ± 3.09 years. The difference in the residual sphere, amount of cylinder, the axis of the cylinder, and CCT (central corneal thickness) after surgery in the two groups was insignificant. P values were as follows; for sphere p = 0.85, amount of cylinder p = 0.22, axis of cylinder P = 0.46 and CCT p = 0.07. Conclusion: Both techniques are equally good in correcting astigmatism (p = 0.22). LASIK or T-PRK can be done alternatively in patients with astigmatism.
... LASIK had a slightly better efficacy, predictability, and lower enhancement rate, 28 while haze was still a problem in PRK for myopia > 10 D. 21 Recent PRK outcomes have been excellent for high myopic (>6 D) correction compared to femtosecond laser-assisted LASIK (F-LASIK). 29,30 Moreover, PRK induced less HOA than F-LASIK. 30,31 Compared to our previous study on F-LASIK outcomes with the same excimer laser machine and treatment profile (WFO), the efficacy of PRK in this present study for both treatment groups are slightly better than those of F-LASIK. ...
Article
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Purpose: To evaluate the 12-months outcomes of photorefractive keratectomy (PRK) in patients with high myopia (≥ 6.0 diopters, D) compared with low-to-moderate myopia (< 6.0 D). Patients and methods: Records of 46 patients (69 eyes) who underwent PRK for myopic and astigmatic correction between October 2015 and December 2018 were reviewed. High myopic eyes (29 eyes) were compared with low-to-moderate myopic eyes (40 eyes). All surgeries were adjunct with 0.02% mitomycin C intraoperatively. Measured outcomes included postoperative uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction spherical equivalent, corneal haze rate, and any complications. Results: At 12 months post-PRK, 26 eyes (89.7%) in the high myopia and 39 eyes (97.5%) in the low-to-moderate myopia group had UDVA ≥ 20/20, (p=0.30). Average postoperative logMAR UDVA at 12 months was -0.04 (20/18) and -0.11 (20/15) for the high myopia and low-to-moderate myopia groups, respectively. No eyes in either group had residual refractive errors >1 D. No eyes in both groups developed significant corneal haze at month 12. No eyes had a loss of greater than two Snellen lines of CDVA at 12 months post-surgery. The efficacy and safety indices at 12 months post-surgery were not significantly different between groups (1.06±0.26 vs.1.14±0.27, p =0.25 and 1.14±0.27 vs 1.17±0.26, p=0.60 for low-to-moderate myopia vs high myopia groups, respectively). Conclusion: PRK with high myopic correction provides excellent refractive outcomes and is safe, compared to those of low-to-moderate myopic correction.
... Previous studies of PRK postoperative symptoms, for the most part, reported less pain and better healing with the tPRK technique (19)(20)(21)(22)(23)(24)(25)(26)(27)(28) . These studies, however, used laser systems different from that used in the present study. ...
Article
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Purpose: To compare postoperative pain and discomfort between mechanical and transepithelial photorefractive keratectomies. Methods: This prospective comparative study included 190 eyes of 95 patients with hyperopia (up to +4.00 D), astigmatism (up to -5.00 D), and myopia (up to -8.00 D) who underwent mechanical photorefractive keratectomy in one eye and transepithelial photorefractive keratectomy in the contralateral eye using Wavelight Allegretto EX500 excimer laser. The patients were unaware of the side treated with each technique. The interval between operations in the same patient was 15-30 days. Both eyes had similar refraction before surgery, with a maximum of 15-µm difference in ablation. Postoperative questionnaires were administered on days 1 and 7 to assess the patients' level of discomfort (0=no discomfort to 5=extreme discomfort) with the following symptoms: pain, burning sensation, itchiness, tearing, photophobia, eye redness, foreign body sensation, and eyelid swelling. Patients were also asked about which method they preferred. Results: The sample consisted of 61 women (64.21%) and 34 men (35.79%). The mean (SD) patient age was 31.66 (6.69) years (range, 22-54 years). On postoperative day 1, the patients reported significantly less discomfort in terms of pain (1.9 ± 1.74 vs 2.5 ± 1.83; p=0.017), burning sensation (1.8 ± 1.56 vs 2.5 ± 1.68; p=0.004), tearing (2.3 ± 1.71 vs 3.1 ± 1.69; p=0.001), and foreign body sensation (1.9 ± 1.77 vs 2.5 ± 1.86; p=0.024) in the eye that received mechanical photorefractive keratectomy than in the eye that received transepithelial photorefractive keratectomy. No significant differences were found between the mechanical and transepithelial photorefractive keratectomies on postoperative day 7. Fifty-nine patients (62.10%) preferred mechanical photorefractive keratectomy, while 32 (33.68%) preferred transepithelial photorefractive keratectomy. Four patients (4.22%) expressed no preference. Conclusions: Our results showed that pain scores were significantly lower in the mechanical photorefractive keratectomy-treated eyes than in the transepithelial photorefractive keratectomy-treated eyes on postoperative day 1, which may have provided greater patient comfort after surgery and led patients to prefer the mechanical photorefractive keratectomy technique.
... Additional factors like nutritional deficiency, change of geographic location or inflammation during the healing phase may lead to the development of late-onset haze. [11] Other risk factors associated with corneal haze include exposure to UV-B rays, atopy, small ablation zone, autoimmune diseases, keloid and age. [28,[35][36][37] ...
Article
Over the past two decades, excimer laser-based refractive surgery procedures have been successfully established for their safety and satisfactory visual outcomes. Surface ablation procedures or photorefractive keratectomy (PRK) are practised commonly for the correction of refractive errors including myopia, astigmatism and hyperopia. Satisfactory visual outcomes are achieved in majority of cases, although a very small percentage have issues related to corneal haze, regression, and its associated visual disturbances. To ensure optimal outcomes and to minimize complications, certain keys to success have been designed on the basis of the current review of literature on surface ablation procedures.
Article
Purpose: To assess the number of recruits for military service in the Israeli Defense Force (IDF) who underwent refractive surgery prior to enlistment and examine whether the procedure affected their ability to accomplish combat training. Setting: Medical records of IDF recruits. Design: Retrospective analysis of medical records of recruits with ametropia who underwent or did not undergo refractive surgery prior to enlistment. Methods: Recruits were categorized into ametropes and recruits who underwent refractive surgery. Fitness and assignment to combat units and completion status of combat training were compared between the two groups. Results: The study included 334,688 (182,969 males, 151,719 females) ametropes of which 5231 (4753 males, 478 females) underwent refractive surgery prior to recruitment. Refractive surgery prevalence increased from 9/1000 ametropes in 2005 to 18.5/1000 ametropes in 2018 (r = 0.912, p < 0.001); 2643 of the operated recruits (50.5%) had their surgery at the age of 17-18. Dropout rates from combat training were significantly lower in the refractive surgery group during the study period (1.68% vs. 6.14%, respectively, p < 0.001). Soldiers in the operated group were more frequently referred to ophthalmologists than those in the ametropes group and less frequently referred to optometrists. Conclusions: The prevalence of refractive surgery in IDF recruits has increased substantially during the last decade with more of them applying to combat units. Refractive surgery opened new possibilities for recruits who were unfit for combat duty prior to surgery and did not appear to impair the chances of successfully completing combat training.
Article
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Purpose: To describe and compare the cost-effectiveness of small incision lenticule extraction (SMILE), femtosecond laser-assisted in situ keratomileusis (FS-LASIK), and photorefractive keratectomy (PRK) for treating myopia and myopic astigmatism in a private eye center. Methods: The perspectives for this cost-effectiveness analysis were for the payer and the health care sector. For the payer's perspective, a decision tree model was made, with a time period of 30 years, and the average weighted utility values and quality-adjusted life years (QALY) were computed for each procedure. The average weighted costs were derived for each procedure and divided by the QALY to obtain the incremental cost-effectiveness ratios (ICER). For the health care sector's perspective, the direct and indirect costs of acquiring the equipment and maintaining the facilities-including consumables and personnel salaries-were obtained to compute the minimum number of patients treated per year. Results: The weighted utility values were 0.8 for SMILE and PRK and 0.77 for FS-LASIK. The weighted QALYs were 24 for SMILE and PRK, and 23.1 for FS-LASIK. The average weighted costs were 335.45, 443, and 346.96€, respectively. The resulting incremental cost-effectiveness ratios were 13.98 €/QALY for SMILE, 18.46 €/QALY for PRK, and 15.02 €/QALY for FS-LASIK. There was a negative correlation between the ICER and the time (in years) after the surgery. To achieve a profit, the minimum number of patients treated per year is 155 for SMILE, 136 for PRK, and 155 for FS-LASIK. Conclusions: Laser corneal refractive surgery is cost-effective for a person desirous of refractive correction for myopia. SMILE had the lowest ICER, followed by FS-LASIK and PRK. This trend was noted at all time periods. The cost of investing in laser refractive surgery facilities is outweighed by the potential income in high-volume eye centers. [J Refract Surg. 2022;38(1):21-26.].
Article
Purpose: The aim of this study was to evaluate the efficacy, safety and predictability of transepithelial photorefractive keratectomy (TransPRK) for correcting myopia, astigmatism and hyperopia. Setting: Department of Ophthalmology, Saarland University Medical Center, Homburg/Saar, Germany DESIGN:: Meta-analysis of retrospective or prospective studies METHODS:: Relevant studies were collected from Medline and included when meeting the following predefined criteria: randomized controlled trials, at least one of main outcome measures efficacy, safety or predictability and one common TRPK laser ("Schwind Amaris"). The parameters estimates and 95% confidence intervals (CI) were derived from random-effects meta-analysis to account for possible heterogeneity. Results: Since hyperopia studies did not meet the inclusion criteria, the results are centered around myopia and astigmatism. Sixteen studies with a total of 1,924 treated eyes were included in the meta-analysis. The mean efficacy, safety and predictability had a probability of 94% CI=0.86-0.97, 0% CI= 0.00-0.03 and 89% CI=0.82-0.93, respectively. The mean correction index, difference vector and index of success had a value of 1.01 CI=1.01-1.02, 0.2 CI=0.06-0.34 and 0.12 CI=0.07-0.18, respectively. Conclusion: This summary estimate shows that the TransPRK is highly effective, safe and predictable in correcting myopia and/or astigmatism.
Article
Introduction The purpose of this study was to compare the outcomes of transepithelial photorefractive keratectomy (Trans-PRK) with femtosecond laser assisted in situ keratomileusis (FS-LASIK) for the correction of low to moderate myopia. Methods A retrospective cohort study design was used. The study group included patients with myopia less than −6.0 D, with or without concomitant astigmatism under 2.0 D, who were treated with FS-LASIK or Trans-PRK in 2013 through 2014. Background, clinical and outcome data were collected from the patient files. A comparison between eyes treated with FS-LASIK or Trans-PRK was performed. Results The Trans-PRK group was comprised of 1793 eyes and the FS-LASIK group of 666 eyes. Mean ± SD spherical equivalent (SE) refraction prior to surgery was −3.43 ± 1.27 D in the Trans-PRK group and −3.18 ± 1.34 D in the FS-LASIK group ( p < 0.001). Efficacy index values were 0.95 ± 0.14 in the Trans-PRK group and 0.98 ± 0.12 in the FS-LASIK group ( p < 0.001), and corresponding safety index values were 0.96 ± 0.13 and 0.99 ± 0.12 ( p < 0.001). Distance from target refraction was 0.45 ± 0.42 D in Trans-PRK group and 0.43 ± 0.38 D in the FS-LASIK group ( p = 0.537); 71.6% and 74.2% of eyes were within ±0.5 D of attempted correction, respectively ( p = 0.193) Conclusions Both Trans-PRK and FS-LASIK demonstrated excellent results, mostly comparable with the current literature. FS-LASIK achieved better results than Trans-PRK surgery in the efficacy and safety parameters.
Article
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Purpose To compare visual outcomes and satisfaction among patients of photorefractive keratectomy (PRK; Wavelight EX 500, Alcon, Ft Worth, TX, USA) and femtosecond laser-assisted in situ keratomileusis (FAL; Wavelight FS 200 laser and Wavelight EX 500, Alcon, Ft Worth, TX, USA). Methods We performed a retrospective study of 409 eyes in 207 patients that underwent either PRK (n=90) or FAL (n=117) at the two centers of Hashmanis Hospital, Karachi, Pakistan. The included refractive outcomes were sphere diopters (D), cylinder D, and spherical equivalent D. Additionally, visual acuities were included. All of these were assessed preoperatively and at the one-month postoperative check-up. Patient satisfaction was gauged at the time of chart review by contacting the patient. Results When looking at the postoperative outcomes, we found all values to be statistically significant (p<0.001) with superior outcomes in the FAL cohort. Additionally, 90% and 15% of eyes achieved a postoperative uncorrected visual acuity (UCVA) of 20/20 in FAL and PRK, respectively. Furthermore, the efficacy indexes of the FAL and PRK arms were 1.00 and 0.82, respectively. The predictability of the procedures were 92.1% and 64.9%, respectively. Lastly, 93.3% of patients were satisfied with FAL and 95.7% with PRK. Conclusion Our study shows superior visual outcomes in patients undergoing FAL. However, we found a higher satisfaction rate in those that underwent PRK, perhaps due to the higher cost of FAL.
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Background. To investigate the correlation between corneal biomechanics and the surgically induced corneal high-order aberrations (HOAs) after small incision lenticule extraction (SMILE) and femtosecond laser in situ keratomileusis (FS-LASIK). Methods. A total of 150 right myopic eyes that underwent SMILE or FS-LASIK surgery were included in this retrospective study, 75 eyes in each group. The corneal hysteresis (CH) and the corneal resistance factor (CRF) with the corneal HOAs of the anterior, posterior, and total cornea were assessed preoperatively and three months postoperatively. Multivariate linear regression was applied to determine the correlations. Results. The preoperative CRF was significantly correlated with the induced 3rd-6th-order HOAs and spherical aberration of the anterior surface and the total cornea after SMILE and FS-LASIK surgeries (P < 0.05), postoperatively. The CRF was significantly correlated with the induced vertical coma of the anterior and posterior surfaces and the total cornea after SMILE surgery (P < 0.05). There was a significant correlation between the CRF and the induced posterior corneal horizontal coma after FS-LASIK surgery (P = 0.013). Conclusions. The corneal biomechanics affect the surgically induced corneal HOAs after SMILE and FS-LASIK surgery, which may be meaningful for screening the patients preoperatively and optimizing the visual qualities postoperatively.
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We wanted to compare the outcomes of single-step modified transepithelial photorefractive keratectomy (tPRK) termed a SCHWIND all surface laser ablation (ASLA) versus conventional alcohol-assisted photorefractive keratectomy (PRK) and laser-assisted in situ keratomileusis (LASIK) for the correction of higher myopia of 6.00 diopters (D) or more, in an area with high risk of haze due to high intensity of sunlight. We used a prospective interventional cohort with matched retrospective control groups. Patients with >6 D myopia and <3.5 D of astigmatism were included. All treatments were performed with the SCHWIND Amaris system using aspheric ablation profiles. Mitomycin C was used in all PRK and ASLA cases. Outcomes were postoperative refraction, visual acuity, stability, and complications. The follow-up period was up to 12 months. In total, 101 eyes were included after exclusions. Mean preoperative spherical equivalent refraction was -7.9 D, -8.2 D, and -7.4 D in the ASLA (n=41), PRK (n=29), and LASIK (n=31) groups. Mean postoperative spherical equivalent at 12 months postoperatively was -0.1 (standard deviation [SD]: 0.34), -0.2 (SD: 0.59), and -0.08 (SD: 0.36) in the ASLA, PRK, and LASIK groups, with 91.4%, 85.7%, and 83.9% within 0.5 D of target, respectively. Refractive outcomes and regression at 12 months did not vary among groups (P>0.05). Mean logMAR (logarithm of the minimum angle of resolution) uncorrected distance visual acuity at 12 months was 0.00 (SD: 0.05), 0.06 (SD: 0.1), and 0.05 (SD: 0.09) in the ASLA, PRK, and LASIK groups, with significantly better vision in the tPRK group versus LASIK (P=0.01) and PRK (P=0.01) groups. ASLA (SCHWIND) tPRK with mitomycin C for high myopia demonstrates comparable refractive outcomes to LASIK and PRK, with relatively favorable visual acuity outcomes. There was no increased incidence of haze in the ASLA group.
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Purpose. To evaluate the risk factors for post-laser in situ keratomileusis (LASIK) ectasia. Materials and Methods. Medical records of 42 eyes of 28 (10 women, 18 men) patients who developed corneal ectasia after LASIK were retrospectively reviewed. Topographical features and surgical parameters of those patients were evaluated. Results. The mean age of patients was 34.73 ± 6.50 (23-48) years and the mean interval from LASIK to the diagnosis of post-LASIK ectasia was 36.0 ± 16.92 (12-60) months. The following factors were determined as a risk factors: deep ablation (>75 μ m) in 10 eyes, FFK (forme fruste keratoconus) in 6 eyes, steep cornea (>47 D) in 3 eyes, pellucid marginal degeneration (PMD) in 2 eyes, thin cornea (<500 μ m) in 2 eyes, thin and steep cornea in 2 eyes, thin cornea and deep ablation in 5 eyes, FFK and steep cornea in 2 eyes, and FFK, steep cornea, and deep ablation in 1 eye. However no risk factor has been determined in 9 eyes (21.4%). Conclusion. The findings of our study showed that most of the patients who developed post-LASIK ectasia have a risk factor for post-LASIK ectasia. However, the most common risk factor was deep ablation.
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To compare the efficacy, predictability, and safety outcomes of 2 femtosecond laser platforms for flap creation during laser in situ keratomileusis (LASIK) for myopia and myopic astigmatism. Singapore National Eye Centre, Singapore. Retrospective case review. In this single-center multisurgeon study, patients had LASIK with flaps created using a Visumax 500 kHz or Intralase 60 kHz femtosecond laser system. Ablation was performed with the Wavelight Allegretto Eye-Q 400 Hz excimer laser in all patients. Preoperative and 3-month postoperative manifest refraction, attempted treatment spherical equivalent (SE), visual acuity, and complications were compared. The 500 kHz femtosecond laser group comprised 381 patients (381 eyes) and the 60 kHz femtosecond laser group, 362 patients (362 eyes). Three months postoperatively, the uncorrected distance visual acuity was 20/40 or better in 99.1% of eyes in the 60 kHz laser group and 99.4% of eyes in the 500 kHz laser group (P=.678). Regarding predictability, 98.6% of eyes and 97.4% of eyes, respectively, were within ±1.0 diopter of the attempted SE correction postoperatively (P=.228). The safety index was similar in the 60 kHz laser group and the 500 kHz laser group (mean 1.06 ± 0.16 [SD] versus 1.05 ± 0.14) (P=.321). The safety, predictability, and efficacy profiles of the 500 kHz femtosecond platform for LASIK were excellent and comparable to those of the 60 kHz platform. No author has a financial or proprietary interest in any material or method mentioned.
Chapter
There is no risk-free surgical procedure. There are enough data in literature to determine the risk for the majority of the refractive surgery procedures. Refractive surgery risks and benefits should be evaluated individually in order to choose the surgical approach properly. Not only incidence, but also morbidity of each possible complication should be considered in this choice. Decision making in refractive procedure is an individualized process that should be based on scientific knowledge, patient’s characteristics, and surgeon experience.
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To evaluate the clinical outcomes of laser in situ keratomileusis (LASIK) to correct myopia or myopic astigmatism using the Amaris 750S 750 Hz excimer laser. Private LASIK center, Tokyo, Japan. Case series. Patients with myopia or myopic astigmatism (spherical equivalent -0.50 to -11.63 diopters [D]), a corrected distance visual acuity (CDVA) of 20/20 or better, and an estimated residual bed thickness of 300 μm or more had LASIK using the aspheric aberration-free ablation profile of the 750 Hz scanning-spot laser and the Femto LDV Crystal Line femtosecond laser for flap creation. Study parameters included uncorrected distance visual acuity (UDVA), CDVA, manifest refraction, astigmatism, and higher-order aberrations (HOAs). The study included 1280 eyes (685 patients). At 3 months, 96.6% of eyes had a UDVA of 20/20 or better and 99.1% had 20/32 or better; 94.1% of eyes were within ±0.50 D of the intended correction and 98.9% were within ±1.00 D; 89.7% of eyes had no residual cylinder and 96.0% had a postoperative astigmatism of less than 0.50 D. All eyes had a postoperative CDVA of 20/20 or better. The HOAs increased postoperatively (P<.001), with mean total postoperative corneal and ocular HOAs of 0.66 μm ± 0.20 (SD) and 0.56 ± 0.23 μm, respectively. The efficacy index and safety index were 1.02 and 1.06, respectively. Laser in situ keratomileusis with the 750 Hz scanning-spot laser was safe, effective, and predictable. No specific clinical side effects that might be associated with a high repetition rate occurred. Mr. Magnago is an employee of Schwind eye-tech-solutions GmbH. No other author has a financial or proprietary interest in any material or method mentioned.
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Laser in situ keratomileusis (LASIK) is a safe and effective treatment for refractive error. A combination of technological advances and increasing surgeon experience has served to further refine refractive outcomes and reduce complication rates. In this article, we review LASIK as it stands in late 2012: the procedure, indications, technology, complications and refractive outcomes.
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To compare the postoperative efficacy, safety, and higher-order-aberrations (HOAs) between transepithelial photorefractive keratectomy (PRK) and alcohol-assisted PRK in contralateral eyes. Private clinic, Utrecht, The Netherlands. Comparative case series. Consecutive patients were randomized to have transepithelial PRK in 1 eye and alcohol-assisted PRK in the contralateral eye. In both eyes, aspheric treatments were planned with Custom Ablation Manager software and ablations performed with the Schwind Amaris system. Clinical outcomes were predictability, refraction, visual acuity, wavefront aberrations, and contrast and glare sensitivity. Paired t tests were applied for statistics. The study evaluated 66 eyes (33 patients). All patients completed the 1-year follow-up. At 1-year, 97% of eyes in both groups achieved an uncorrected distance visual acuity (UDVA) of 0.1 logMAR or better. No eye lost 2 or more lines of corrected distance visual acuity (CDVA); 97% of transepithelial PRK eyes and 91% of alcohol-assisted PRK eyes were within ±0.50 diopter (D) of the targeted refraction. The postoperative mean spherical equivalent was +0.07 D ± 0.23 (SD) and +0.01 ± 0.27 D, respectively. The CDVA, UDVA, and safety outcomes between transepithelial PRK and alcohol-assisted PRK were comparable. Profiles for both techniques applied to regular corneas preserved the eye's natural HOAs. Transepithelial PRK is faster to perform and it is an all-laser procedure, which might be less stressful for the patient. Mr. Ewering and Mr. Arba-Mosquera are employees of Schwind eye-tech-solutions. Dr. Luger has no financial or proprietary interest in any material or method mentioned.