Transcript Table 1

Osama M. Al Nahrawy (1), Ehab M. Ghoneim (2),
Amr I. Sharawy (3) and Yasser M. Khalifa (4)
(1): Assistant Professor of Ophthalmology, Faculty of Medicine, Suez Canal University,
Ismailia. Egypt.
Mobile: +20123154002 Email: [email protected].
(2): Assistant Professor of Ophthalmology, Faculty of Medicine, Suez Canal University,
Ismailia. Egypt.
Mobile: + 20123639848 Email: [email protected]
(3): Professor of Ophthalmology department, Faculty of medicine, Benha University.
Egypt.
Mobile: +20122465786 Email: [email protected]
(4): Lecturer of Ophthalmology, Faculty of Medicine, Suez Canal University, Ismailia.
Egypt.
Mobile: +20114039301 Email: [email protected]
Authors have no financial interest in the machines and equipment
mentioned in this presentation
ASCRS ASOA Boston April, 9-14, 2010.
Osama M. Al Nahrawy, MD
ABSTRACT
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Purpose : To evaluate the safety, efficacy, and clinical outcomes of wavefrontguided laser in situ keratomelieusis (LASIK) surgery for the treatment of myopia
and compound myopic astigmatism.
Methods: This retrospective study included thirty four eyes of 17 patients with
myopia and myopic astigmatism. Setting: Cortoba Eye and lasik Center, Ismailia,
Egypt.Timing: during 2007-2008. A flap was created with a Moria M2
microkeratome, 90 or 130 micron blades were used. A superior hinge was used in all
cases. They were treated with wavefront-guided LASIK using the WaveScan linked
to the CustomVue system (AMO USA, Inc.). Preoperative mean manifest refraction
spherical equivalent, Wavescan data of total high order aberrations Root Mean
square (RMS), spherical aberration and coma, all were compared to data obtained
6 months postoperatively. Safety and efficacy indices are defined and their means
are calculated for all patients
Results :The mean patient age was 27 ± 7.14 years (SD). Thirty four eyes of 17
patients were evaluated over a period of 6 months. The mean manifest refraction
spherical equivalent was -1.899 ± 2.53 D (range from -0.2 to -10.68 D) preoperatively
and -0.1± 0.67D (range from +1.71 to -1.92 D) 6 months postoperatively. Ninety one
percent of the eyes were within ± 1.00 D of the intended correction. The mean
preoperative total HOA RMS error in all eyes was 0.108± 0.14 . The error was
increased by a factor of 1.37 after 6 months. A significant increase in coma and to a
less extent spherical aberration was observed at 6 months , while Trefoil decreased
at 6 months. For all eyes, the safety index was 1.00 and the efficacy index was 1.18.
Conclusion : The data support the safety and efficacy of correcting myopia and
compound myopic astigmatism using wavefront-guided LASIK. Coma and spherical
aberration increased after wavefront- guided lasik, while trefoil decreased.
Purpose
The purpose of this study was to evaluate the predictability, safety, efficacy,
complications, and change in ocular aberrations after wavefront-guided
LASIK in patients with myopia and compound myopic astigmatism.
Methods
Study Design This retrospective study included 34 eyes of 17
healthy patients. Setting: Cortoba Eye and lasik Center, Ismailia,
Egypt. Timing: during 2007-2008. Patients were treated with
wavefront-guided LASIK surgery using the Visx Star S4 excimer
laser with software version 5.18 and the Visx WaveScan
aberrometer with software version 3.6 (AMO USA, Inc.).
Enrollment Criteria A group of patients with myopia and myopic
astigmatism was retrospectively selected from a large group of
myopic eyes consecutively treated with the wavefront-guided
platform.
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Clinical Outcome Measures: In addition to general medical and ophthalmic
histories, preoperative measures included uncorrected visual acuity (UCVA),
best corrected visual acuity (BCVA), manifest spherical refraction, cycloplegic
refraction, ultrasonic pachymetry (Nidek. Japan), anterior and posterior corneal
surface topography (Orbscan, Bausch & Lomb), slitlamp examination of the
anterior segment, and fundoscopy. Analysis of HOAs was performed using the
Visx WaveScan aberrometer. The safety index was defined as the mean
postoperative BCVA divided by the mean preoperative BCVA and the efficacy
index, as the mean postoperative UCVA divided by the mean preoperative
BCVA 1.
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Statistical Analysis
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Patient data were compiled in Microsoft Excel. Statistical significance was
calculated using the Student t test (P<.05). Data are expressed as means ±
standard deviation and ranges (minimum to maximum). For safety and efficacy,
visual acuity was calculated using the logMAR scale for each individual eye and
subsequently reconverted to the respective Snellen fraction.
Results
Demographics and Refractive Errors:
 The myopic population was composed of 34 eyes of 17 patients. The
mean age of patients was 27.0 ±7 years (range 26 to 50 years). Table 1
shows the preoperative and post-operative refractive data for all 34 eyes.
The preoperative refractive error by sphere and cylinder, the mean
spherical correction in all 34 eyes was -3.59 ± 2.84 D (range -0.52 to -9.91
D), the mean cylinder was -1.42 ±1.66 D (range +0.25 to –4.94D), and the
mean manifest refraction spherical equivalent (MRSE) was -1.89 ± 2.53 D
(range -0.2 to -10.68 D) preoperatively.
 Stability: table 1 shows the stability outcomes. After 6 months post-lasik,
the change in MRSE from emmetropia was within 1.0 D of the intended
correction in 31 (91.2%) of the 34 eyes in myopic eyes.
 Safety : Six months after surgery, 10 (29.4%) of 34 eyes of myopia had
improved BCVA and 24 (70.6%) had BCVA similar to the preoperative
BCVA. No eye lost 1 or more lines of visual acuity (Table 2). The safety
index (ratio of postoperative and preoperative BCVA) in all eyes at 6
months was 1.00.
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Table: (1): Pre and Post-operative refractive data
Spherical correction
(D)
Mean ± SD
Range
Cylinder (D)
Mean ± SD
Range
MRSE (D)
Mean ± SD
Range
Pre-operative
refractive data
Post-operative
refractive data
-3.59 ± 2.84
-0.52 to -9.91
-0.1± 0.67
+1.71 to -1.92
-1.42 ±1.66
+0.25 to –4.94
-0.3 ±0.83
+2.11 to -2.25
-1.899 ± 2.53
-0.2 to -10.68
0.27± 0.34
+1.4 to -1.09
MRSE = mean refractive spherical equivalent
Back
Table 2.
Change in postoperative BCVA in myopic eyes at 6 months.
Myopic eyes (n = 34)
Change
Lost >0 to <1 line
None
Gained >0 to <1 line
No
0
24
10
Percentage
0
(70.6)
(29.4)
Efficacy
Regarding the comparison of the UCVA preoperatively and 6 months
postoperatively. At 6 months, 24 (70.6%) of 34 eyes in the myopia
eyes had a UCVA better than or equal to 20/20, and 34 eyes (100%)
had a UCVA better than or equal to 20/40. Furthermore, 20 of the
total 34 eyes (58.8%) had a postoperative UCVA that was equal to or
better than the preoperative BCVA. The efficacy index (ratio of
postoperative UCVA and preoperative BCVA) in all eyes at 6 months
was 1.18.
Back
Higher-Order Wavefront Aberrations
 Table 3 shows the HOA parameters, including total HOA root mean square
(RMS), coma, trefoil, spherical aberration, in myopic eyes preoperatively
and 6 months postoperatively. Measurements were taken at the 6.0 mm
optical zone without dilation. The mean preoperative total HOA RMS error
in all eyes was 0.108± 0.14 . The error was increased by a factor of 1.37
after 6 months. A significant increase in coma and to a less extent spherical
aberration was observed at 6‫ آ‬months , while Trefoil decreased at 6
months. These data is shown in Fig. (1).

Table 3: Root mean square parameters before and after 6 months of surgery in
myopic patients.
Mean ‫آ‬± SD (Range)
Parameter
Preoperative
Postoperative 6
months
Increase Factor
P Value
Total HOA
RMS
Coma
0.108± 0.14
0.148 ± 0.14
1.37
<.001
0.083 ±0.105
0.19 ± 0.28
2.29
<.001
Trefoil
0.10 ± 0.134
0.08 ± 0.104
0.8
.77
Spherical
aberrations
0.60 ±0.07
0.117± 0.147
1.2
<.001
HOA = higher-order aberration; RMS = root mean square
Complications: No flap complications (epithelial defects, microstriae, or
macrostriae) were observed. No eye developed epithelial ingrowths. There was
no topographic evidence of ectasia.
 Discussion and Conclusions: Our retrospective review of patients supports
that the commercially available wavefront-guided LASIK procedure is
predictable, safe, and effective. At 6 months, more than 91% of eyes with
myopia were within ± 1.0 D of the intended correction at 6 months.
 Our postoperative results are consistent with the U.S. Food and Drug
Administration's (FDA) summary of safety and effectiveness data for the Visx
ophthalmic excimer laser system (Accessed October 3, 2007) 2. In that report,
184 eyes had a preoperative MRSE ranging between - 5.0 D and - 12.0 D. Six
months postoperatively, 95.3% of eyes (102 of 107) in the FDA report were
within ± 1.0 D of the intended spherical correction compared with 91.2% (45 of
50) in our study. These comparisons show that the wavefront-guided LASIK
procedure is predictable and effective in cases of moderate to high myopia.
 Changes in HOAs, notably spherical aberrations, are observed postoperatively
with conventional LASIK and photorefractive keratectomy (PRK) 3,
4. Customized ablation such as wavefront-guided LASIK was designed to help
minimize postoperative HOAs. Despite limited evidence that wavefront-guided
laser ablation has notably better outcomes than conventional treatment 5 , it is
evident that wavefront-guided laser procedures induce fewer aberrations than
conventional treatments, suggesting improved vision quality 6.

Recent studies show that wavefront-guided LASIK induces increases in HOAs,
especially spherical aberration, although the increases are minimal 7. It is also
important to note that creating a LASIK flap has been shown to increase HOAs in
previous studies 8, 9, but it is still unclear whether this translates into a good
measure of visual performance 7. Our study is consistent with the literature in that
we reveal an increase in total HOA RMS, coma, and spherical aberration at
6 months postoperatively in myopic patients. Although the postoperative trefoil
value decreased in myopic patients, the overall total HOA RMS increased.
 A limitation to our HOA analysis is that we did not control for pupil size in
preoperative and postoperative measurements. Spherical-like aberrations have
been shown to increase significantly with increasing pupil size in unoperated
corneas10. In our study, all eyes had pupils of at least 6.0 mm in diameter
preoperatively and postoperatively, and the lighting conditions for aberrometry
images were identical for all preoperative and postoperative measurements (3 lux).
Based on the minimum pupil size and standardized lighting conditions, we believe
our data are worth reporting in this study.
 The CustomVue system showed excellent efficacy, predictability, and safety.
Further comparison studies with larger sample sizes and longer follow-up are
needed to confirm a true advantage over conventional LASIK.

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