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Version No: 3.4 Healthcare Performance Measurement &
Report for LASIK surgery
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Ver.Date: 19 May 2011 Protocol No.:HR2010-02
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Report Title: Healthcare Performance Measurement & Reporting for LASIK surgery
services provided by OPTIMAX Malaysia
Protocol number: HR2010-02
Document type: Healthcare Performance Report
Document status: FINAL
Release Date: 19 May 2011
Number of pages: 22
Client Optimax Eye Specialist Centre
Investigators Stephen Chung SH MS.Ophth
Chuah KL FRCOphth
NorAzlina BN MS.Ophth
Yen SS MS.Ophth
Site Coordinator Lim Yee Yin
Daniel Jones
Consultant Lim T.O. FRCP, M.Stat
Statisticians Hoo LP PhD, Lena Yeap MSc
Data management & audit Teo JS MSc
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Contents More analysis
Summary .................................................................................................................................... 3 1.0 Introduction .......................................................................................................................... 5
2.0 Analysis set .......................................................................................................................... 6 4.0 Outcomes of LASIK surgery ............................................................................................... 9 5.0 Performance measurement for LASIK surgery & Risk adjustment model ....................... 11
5.1 Performance measures for LASIK surgery .................................................................... 11 5.2 Risk adjustment .............................................................................................................. 11 5.3 Risk adjusted Performance results ................................................................................. 13
6.0 Conclusion ......................................................................................................................... 16 Appendix .................................................................................................................................. 17
Glossary ............................................................................................................................... 17 List of Abbreviations ........................................................................................................... 18
Tables and Figures
Table 1: Reason for ineligibility ............................................................................................ 6 Table 2a: Reason for exclusion from efficacy analysis set .................................................... 7
Table 2b: Reason for exclusion from safety analysis set ....................................................... 7 Table 3: Baseline characteristics of patients undergoing LASIK surgery ............................. 7 Table 4A: Visual Outcomes of LASIK surgery at 6-month post-op ..................................... 9
Table 4B: Refractive Outcomes of LASIK surgery at 6-month post-op ............................... 9 Table 4C: Safety Outcomes of LASIK surgery ................................................................... 10
Table 5: Outcomes of LASIK surgery by individual surgeons............................................ 10 Figure 1a: Comparative performance of Risk adjusted Visual acuity outcome of LASIK
surgery among 4 surgeons ................................................................................................... 13 Figure 1b: Comparative performance of Risk adjusted Visual acuity outcome of LASIK
surgery among 4 surgeons ................................................................................................... 13
Table 6a: Comparative quarterly performance of Risk adjusted Visual acuity outcome of
LASIK surgery among 4 surgeons. ...................................................................................... 14 Figure 6a: Comparative quarterly performance of Risk adjusted Visual acuity outcome of
LASIK surgery (Uncorrected visual acuity (UCVA) >=6/7.5 at 6 months post-op ) .......... 14 Table 6b: Comparative quarterly performance of Risk adjusted Visual acuity outcome of
LASIK surgery among 4 surgeons. ...................................................................................... 15
Figure 6b: Comparative quarterly performance of Risk adjusted Visual acuity outcome of
LASIK surgery (Uncorrected visual acuity (UCVA) >=6/12 at 6 months post-op ) ........... 15 Table 7: Performance measures for LASIK surgery............................................................ 20 Table 8a: Relationship between Visual outcome of LASIK surgery (Uncorrected visual
acuity (UCVA) >=6/7.5 at 6 months post-op) and various putative prognostic factors ...... 21
Table 8b: Relationship between Visual outcome of LASIK surgery (Uncorrected visual
acuity (UCVA) >=6/12 at 6 months post-op) and various putative prognostic factors ....... 22
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Summary
Introduction
We measure the performance of LASIK surgery services provided by Optimax Eye Specialist
Centre. The surgical service was provided by 4 surgeons at its TTDI branch.
Three performance measures were selected:
1. Post-operative Uncorrected visual acuity. This is the acuteness or clearness of vision as
measured using standard vision chart that is achieved after surgery. This is a measure of
visual outcome, a standard measure of treatment effectiveness.
2. Post-operative refraction within +0.5 Diopters of target refraction. This measures the
precision of the refractive correction, a standard measure of refractive outcome of LASIK
surgery
3. Worsening of visual acuity. While the intended effect of LASIK surgery is to improve the
patient’s visual acuity by correcting the refractive error, complications or other
unintended effects of surgery could result in worsening of visual acuity. This is therefore
an important measure of patient safety
Data & Model
For purpose of performance measurement, data were available from 932 patients who have
had 1620 LASIK surgical procedures among them (most patients have had surgery for both
eyes) for correction of myopia between January and December 2010.
For efficacy analysis, data from 287 procedures on 167 patients were excluded from analysis
for the following reasons:
Without post-op visual acuity data at all (57 procedures)
Without post-op visual acuity data at 1 week post op for INTRALASIK, LASIK and
LASIK-XP surgeries (33 procedures)
Without post-op visual acuity data at 3-month post op for LASEK and Epi-LASIK
surgeries (195 procedures)
Too few procedures performed by single doctor (2 procedures)
For safety analysis, data from a further 7 procedures were excluded for lack of BCVA data.
Performance results were risk adjusted using a statistical model that included 4 patients’
factors that affect the visual outcome of surgery. These are age, sex, degree of myopia and
astigmatism.
Results
All surgeons achieved excellent results in 2010:
The mean success rate (defined as UCVA at 6-month post-op 6/7.5 or better) among the 4
surgeons was 95%, and 99% for UCVA 6/12 or better.
Their risk adjusted success rate varies from 93% to 97% ; all 95% confidence intervals
overlap 100% success rate. For UCVA 6/12 or better, all surgeons uniformly achieved
99% risk adjusted success rate.
Their success rates were also consistent, without significant variation in outcomes from
quarter to quarter throughout the year 2010.
The overall on-target refractive error correction rate (defined as MRSE at 6 months
within + 0.5D of Target=0) was 91%; for correction of spherical error alone, the on-target
rate was higher at 95%.
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The result of patient safety outcome was also reassuring.
No patient has suffered serious loss of visual acuity as a result of LASIK surgery at 6
months post-op.
All patients had best spectacle corrected visual acuity (BCVA) better than 6/12 at 6
months post-op.
Caution is however warranted in interpreting the performance results reported here.
The analysis was based entirely on retrospective data collected for administrative purpose
rather than specifically for performance measurement. Not surprisingly, there was
substantial data error and extensive data cleaning efforts were required prior to analysis.
Several known prognostic factors (corneal curvature, corneal thickness, pupil size etc)
could be included in the statistical model for risk adjustment. The risk model will require
further development and validation, pending improvement in data quality and availability
of data on known prognostic factors
Both the above issues are being addressed at the prospective phase of this initiative (started
since January 2011) where data required will be defined clearly and data will be collected
prospectively using systematic data reporting mechanisms and subject to ongoing data QC to
assure data quality.
Conclusion
The performance of LASIK surgery services as provided by the Optimax eye care group is
reassuring.
These results also established a sound scientific basis and operational experience for the
Optimax eye healthcare group to embark on routine prospective measurement of the
performance LASIK surgery services. This has been initiated since January 2011.
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1.0 Introduction
Laser-Assisted In-Situ Keratomileusis or LASIK in short, is a surgical technique for the
correction of myopia, hyperopia and astigmatism. It involves the use of excimer laser to
ablate corneal tissue thus reshaping in order to correct the refractive error. LASIK [1,2] has
evolved from a variety of techniques including lamellar keratoplasty, photorefractive
keratectomy, and since the 1990s has been widely used. The technology associated with the
LASIK procedure has also advanced rapidly since then. Recent innovations include new
femtolaser microkeratome, newer laser technology (Faster laser speed, finer laser spots, eye-
tracking system etc), wavefront and topographic custom ablation. Numerous prospective
randomized controlled trials and meta-analyses of these trials have demonstrated the safety
and efficacy of LASIK for the correction of refractive errors [3-11].
Refractive surgery was first introduced into Malaysia by Optimax in 1995. Since then its use
has increased rapidly with the vast majority of the procedures still being performed by
Optimax. Optimax has also grown from a single centre with a lone surgeon to become the
leading provider of LASIK and other specialist eye care services in Malaysia with a network
of 12 centers and 9 ophthalmologists.
Worldwide there is an increasing interest in measuring the performance of healthcare
providers [12,13,14]. The publication of the highly influential report, Performance
Measurement: Accelerating Improvement, by the Institute of Medicine in 2006 [15], has
added greater impetus for performance measurement as a central tenet of health care reform.
Our government has also recently introduced KPI to measure the performance of government
services as part of the Government Transformation Programme [16]. However, this has yet to
impact on the public health services where performance measurement and reporting activity
remains undeveloped. Similarly in the private healthcare sector, while financial performance
measures are well established and routinely reported, robust healthcare performance
measures that reflect the core business of the healthcare industry are practically non-existent.
As a testament to Optimax’s leadership position in the field of LASIK surgery services in
Malaysia, Optimax has agreed to subject its LASIK services to performance measurement
and reporting by an independent third party. This is intended not just to support quality
improvements initiatives within Optimax, but also as a reflection of Optimax’s commitment
to a high standard of accountability in healthcare. To this end, measuring and reporting the
performance of Optimax’s LASIK surgery services is intended to assure healthcare payers
(insurance companies, employers) that they are getting value for their money, to respond to
the requirements of quality certification/ accreditation organizations (ISO9000, JCI) and
regulators (CKAP MOH), and most importantly to aid customers, both patients as well as
health professionals who refer patients, in making informed choices.
This is the first in a series of reports on the performance LASIK surgery by Optimax.
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2.0 Analysis set
Between Jan and December 2010 inclusive, data were available from 953 patients who have
had 1760 LASIK surgical procedures (most patients have had surgery for both eyes) for
correction of myopia performed by 5 surgeons at Optimax’s TTDI centre.
Of these, only 932 patients who have had 1620 procedures were eligible for inclusion in this
analysis for the purpose of performance measurement.
Efficacy analysis set
For efficacy analysis (visual and refractive outcomes), a further 167 patients who have had
287 procedures were excluded from analysis for missing efficacy measure data as follows:
Without post-op visual acuity data at all (57 procedures)
Without post-op visual acuity data at 1 week post op for INTRALASIK, LASIK and
LASIK-XP surgeries (33 procedures)
Without post-op visual acuity data at 3-month post op for LASEK and Epi-LASIK
surgeries (195 procedures)
Safety analysis set
For safety analysis (BCVA outcome), data from 7 procedures were excluded because of
missing BCVA data (These 7 procedures were from 5 patients, but only 2 patients completely
excluded as data for procedures on both eyes were missing)
LASIK surgery on 1760 eyes for
953 patients
Eligible for analysis
1620 eyes from 932 patients
Ineligible
140 eyes, 21 patients
Refer table below for details
Efficacy analysis set
1333 eyes from 765 patients
Excluded from Efficacy analysis set
287 eyes, 167 patients
Refer table below for details
Safety analysis set
1326 eyes from 763 patients
Excluded from Safety analysis set
7 eyes, 2 patients
Refer table below for details
Table 1: Reason for ineligibility
Reason Procedure % Patient %
Both eyes were treated for hypermetropia 26 1 13 1
Sole eye treated for monovision 3 0 3 0
Sole eye treated for hypermetropia 5 0 5 1
One of two eyes treated for hypermetropia or
monovision
106 6 0 0
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Table 2a: Reason for exclusion from efficacy analysis set
Reason Procedure % Patient %
No post-op UCVA 285 18 166 18
All 57 4 32 3
1 week post op for INTRALASIK,
LASIK and LASIK-XP
33 2 15 2
3-month post op for LASEK and Epi-
LASIK
195 12 119 13
Too few procedures by a doctor 2 0 1 0
Table 2b: Reason for exclusion from safety analysis set
Reason Procedure % Patient %
No post-op BCVA at all 7 1 2 0
3.0 Baseline descriptive analysis
The table below summarizes the patients’ characteristics and LASIK surgery for the 765
patients included in this analysis.
Table 3: Baseline characteristics of patients undergoing LASIK surgery
Patient characteristics Statistics
Number of patients=765
Mean (SD) Age, years 31.46 (7.12)
Sex, No. (%)
Male 263 (34.38)
Female 502 (65.62)
Number of procedures=1333
Prior Refractive surgery, No. (%) No data
Type of LASIK, No. (%)
INTRALASIK 1183 (88.75)
LASIK 44 (3.3)
LASIK XP 35 (2.63)
EPILASIK 65 (4.88)
LASEK 6 (0.45)
Pre-Op Visual Acuity(VA)
No. (%) with manifest Best spectacle Corrected VA (BCVA) >=
6/6 1302 (97.67)
No. (%) with manifest BCVA >= 6/12 1333 (100)
Mean (SD) manifest BC VA (decimal scale) 0.997 (0.0405)
Mean (SD) manifest BCVA (LogMAR scale) 0.0017 (0.0183)
No. (%) with cycloplegic BCVA >= 6/6 1279 (95.95)
No. (%) with cycloplegic BCVA >= 6/12 1333 (100)
Mean (SD) cyclo BCVA (decimal scale) 0.993 (0.0489)
Mean (SD) cyclo BCVA (LogMAR scale) 0.0036 (0.0231)
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Pre-Op Refractive measurements
Spherical Error (SER), Dioptre (D)
Mean (SD) Manifest Spherical Error -4.87 (2.2)
Range(max, min) Manifest Spherical Error (-0.25, -12.5)
Mean (SD) Cycloplegic Spherical Error -4.68 (2.21)
Range(max, min) Cycloplegic Spherical Error (-0.25, -12)
No. (%) with Manifest Spherical Error >=(neg) -6.0 D (Low to
moderate Myopia) 954 (71.57)
No. (%) with Manifest Spherical Error < -6.0 D (Moderate to
High Myopia) 379 (28.43)
No. (%) with Cycloplegic Spherical Error >=(neg) -6.0 D 982 (73.67)
No. (%) with Cycloplegic Spherical Error < (neg)-6.0 D 351 (26.33)
Cylindrical Error (CER), Dioptre (D)
Mean (SD) Manifest Cylindrical Error -0.92 (0.81)
Range (max, min) Manifest Cylindrical Error (0, -5.5)
Mean (SD) Cycloplegic Cylindrical Error -0.92 (0.82)
Range (max, min) Cycloplegic Cylindrical Error (0.25, -5.75)
No. (%) with Manifest Cylindrical Error >= (neg)-2.0 D (Low to
moderate Astigmatism) 1220 (91.52)
No. (%) with Manifest Cylindrical Error < (neg)-2.0 D (Moderate
to High Astigmatism) 113 (8.48)
No. (%) with Cycloplegic Cylindrical Error >= (neg)-2.0 D 1220 (91.52)
No. (%) with Cycloplegic Cylindrical Error < (neg)- 2.0D 113 (8.48)
Spherical Equivalent (SEQ) [SEQ=SER + 0.5 CER], Dioptre (D)
Mean (SD) Manifest Spherical Equivalent -5.33 (2.26)
Range(max, min) Manifest Spherical Equivalent (-0.62, -12.75)
Mean (SD) Cycloplegic Spherical Equivalent -5.14 (2.26)
Range(max, min) Cycloplegic Spherical Equivalent (-0.5, -12.37)
Other Pre-Op/ Intra-op Ophthalmic measurements
Mean (SD) Corneal Curvature (Keratometry) Flat K 43.17
(1.34)
Mean (SD) Corneal Curvature (Keratometry) Steep K 44.48
(1.46)
Mean (SD) Corneal Curvature (Keratometry) Average k
Average k = (Flat K+Steep K)/2
43.83 (1.35)
Flap thickness (Pachymetry), mm No data
Pupil size, mm No data
Refer Appendix for results on Baseline characteristics of patients who had required enhanced
LASIK surgical procedures
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4.0 Outcomes of LASIK surgery
The table below summarizes the outcomes (visual acuity, refractive and safety) of LASIK
treatment for all procedures included in this analysis.
Table 4A: Visual Outcomes of LASIK surgery at 6-month post-op
Visual Outcome Statistics 6-month post-op, N= 1333
UCVA (Fractional scale) Median 6/6
IQR (6/6, 6/6)
Min, Max (6/45, 6/4.5)
UCVA (Decimal scale) Mean 0.96
SD 0.12
UCVA (LogMAR scale) Mean 0.02
SD 0.07
UCVA 6/7.5 or better No. 1262
(%) (94.67)
UCVA 6/12 or better No. 1319
(%) (98.95)
Table 4B: Refractive Outcomes of LASIK surgery at 6-month post-op
Refractive Outcome Statistics 6-month post-op
N= 1333
Manifest Refractive Spherical Equivalent
(MRSE)
Mean (SD) -0.14 (0.3)
Min, Max (-1.5, 1.75)
MRSE within + 0.5D of Target=0 No. (%) 1213 (91)
MRSE < - 0.5D of Target=0 No. (%) 102 (8)
MRSE > + 0.5D of Target=0 No. (%) 18 (1)
Change in Post-op MRSE from Baseline MRSE Mean (SD) 5.19 (2.3)
Min, Max (0.5, 12.75)
Manifest Spherical Error (MSPH) Mean (SD) -0.04 (0.33)
Min, Max (-1.5, 2)
MSPH within + 0.5D of Target=0 No. (%) 1260 (95)
MSPH < - 0.5D of Target=0 No. (%) 36 (3)
MSPH > + 0.5D of Target =0 ie Over-Correction No. (%) 37 (3)
Change in Post-op MSPH from Baseline MSPH Mean (SD) 4.83 (2.27)
Min, Max (0, 13)
Manifest Cylindrical Error (MCYL) Mean (SD) -0.29 (0.25)
Min, Max (-2.5, 0)
MCYL within + 0.5D of Target=0 No. (%) 1233 (93)
MCYL < - 0.5D of Target=0 No. (%) 100 (8)
MCYL > + 0.5D of Target =0 No. (%) 0 (0)
Change in Post-op MCYL from Baseline MCYL Mean (SD) 0.64 (0.78)
Min, Max (-0.75, 4.75)
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Table 4C: Safety Outcomes of LASIK surgery
Safety Outcome Statistics 6-month post-op,
N= 1326
Loss of >= 2 lines of BCVA No. 0 (%) (0)
Final BCVA equal or worst than 6/12 No. 0
(%) (0)
Table 5: Outcomes of LASIK surgery by individual surgeons
Surgeons A B C D
N 381 98 783 71
Outcome measures
Visual outcome
No (%) with UCVA 6/7.5 or better at 3
months 370(97.11) 95(96.94) 727(92.85) 67(94.37)
No (%) with UCVA 6/12 or better at 3
months 379(99.48) 96(97.96) 775(98.98) 70(98.59)
No (%) with UCVA 6/7.5 or better at 6
months 371(97.38) 95(96.94) 730(93.23) 66(92.96)
No (%) with UCVA 6/12 or better at 6
months 377(98.95) 97(98.98) 775(98.98) 70(98.59)
Refractive outcome
No (%) with MRSE at 3 months within +
0.5D of Target=0
355(93.18) 86(87.76) 697(89.02) 64(90.14)
No (%) with MRSE at 6 months within +
0.5D of Targe=0
356(93.44) 87(88.78) 704(89.91) 66(92.96)
Safety outcome
No (%) with Loss of >= 2 lines BSCVA at 3
months
0 (0) 0 (0) 0 (0) 0 (0)
No (%) with Final BSCVA at 3 months
worse than 6/12
0 (0) 0 (0) 0 (0) 0 (0)
No (%) with Loss of >= 2 lines BSCVA at 6
months
0 (0) 0 (0) 0 (0) 0 (0)
No (%) with Final BSCVA at 6 months
worse than 6/12
0 (0) 0 (0) 0 (0) 0 (0)
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5.0 Performance measurement for LASIK surgery & Risk adjustment model
5.1 Performance measures for LASIK surgery
In healthcare, performance measures are those process, structure, efficiency, or outcome
measures that have been developed using rigorous methodology. These measures are
intended not only for clinical quality improvement but they have attributes rendering them
suitable for public reporting, explicit comparisons of care between healthcare providers,
accreditation, pay for performance programs, or other forms of accountability.
For LASIK surgery, we selected three performance measures:
1. Post-operative Uncorrected visual acuity. This is the acuteness or clearness of vision as
measured using standard vision chart that is achieved after surgery. This is a measure of
visual outcome, a standard measure of treatment effectiveness.
2. Post-operative refraction within +0.5 Diopters of target refraction. This measures the
precision of the refractive correction, a standard measure of refractive outcome of LASIK
surgery
3. Worsening of visual acuity. While the intended effect of LASIK surgery is to improve the
patient’s visual acuity by correcting the refractive error, complications or other
unintended effects of surgery could result in worsening of visual acuity. This is therefore
an important measure of patient safety
Details on the selected performance measures are described in the Appendix
5.2 Risk adjustment
Valid measurement of performance also requires statistical methods that account for
differences in patient characteristics (between providers and over time) as well as random
variation arising from small sample size or infrequent outcome event of interest. In other
words, performance results need to be so called risk-adjusted to eliminate the influence of
those elements of the patient population that affect results but are out of the control of the
healthcare providers whose performance are being assessed.
We were unable to identify an established statistical model for the purpose of risk adjustment.
Based on a literature review, we consider the following known prognostic factors for
inclusion in the model development. However, not all factors could be included for reasons
given below too:
# Risk factors Inclusion in risk model.
If not, reason for exclusion
1. Age Included
2. Sex Included
3. Prior refractive surgery No data
4. Pupil size No data
5. Spherical errors or degree of myopia Included
6. Cylindrical errors or degree of astigmatism Included
7. Corneal thickness No data
8. Corneal topography (Steep and Flat K) Included
9. Intra-ocular pressure No data
10. Laser transition zone No data
11. Types of LASIK surgery Some types of surgery have too few records,
hence excluded
For the purpose of risk modeling, we define successful visual outcome is defined as LASIK
surgery that results in a patient attaining uncorrected visual acuity (UCVA) of 6/7.5 or better
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at 6 months post-op. This is justified by the marked variability in the relationship between
measure of refractive error (eg spherical error) and UCVA which can be subjective. The
scatter plot from the data below illustrates this:
0.5
.81
1.5
UC
VA
6 m
ths p
ost-
op
: de
cim
al sca
le
-2 -1 0 1 2MRSE 6 mths post-op
bandwidth = .8
Lowess smoother
Our model building results were as follows:
Age appears to have an effect with the youngest and oldest age groups less likely to have
successful visual outcomes but these did not reach statistical significance.
Female patients have poorer UCVA results. Subsequent investigation showed that this ws
entirely due to systematic bias in measuring females’ UCVA. For a given refractive error,
female reported worst UCVA than male.
The degree of myopia and astigmatism were clearly highly influential, the more severe
the myopia or astigmatism, the worst the outcome, as is well reported in the literature too.
Corneal curvature is expected to be influential. However, patients with high or low
corneal curvature were systematically excluded from treatment by the treating physicians
according to current practice standard. Hence, the range of values found among the
treated patients were too restricted (mean k 43.8, SD 1.35, min. 38.9 and max. 47.9) to
elicit an effect on outcome.
Based on the above findings, the final model to be used for risk adjustment includes only age,
sex, degree of myopia and astigmatism. This will require refinement as more data on more
prognostic factors as well as for more patients become available in future.
Details on the risk modelling are shown in the Appendix
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5.3 Risk adjusted Performance results
We use the risk model developed above to adjust the visual acuity outcome results for the 4
surgeons (anonymized as A, B, C and D) included in this analysis. Results are shown in the
figures below
Figure 1a: Comparative performance of Risk adjusted Visual acuity outcome of LASIK surgery among 4 surgeons
Values are Percent of patients with UCVA >=6/7.5 at 6 months post-op (95% confidence
interval)
Surg-
eons
Risk adjusted
Visual Acuity
outcome (%)
95% CI
A 97.42 (87.51, 100)
AB
CD
Su
rge
on
70 75 80 85 90 94.67 100Adjusted success rate
(lower 95% CI, Upper 95% CI)
B 96.68 (77.24, 100)
C 93.27 (86.50, 100)
D 92.62 (70.27, 100)
All 94.67
Figure 1b: Comparative performance of Risk adjusted Visual acuity outcome of LASIK surgery among 4 surgeons
Values are Percent of patients with UCVA >=6/12 at 6 months post-op (95% confidence
interval)
Sur-
geons
Risk adjusted
Visual Acuity
outcome (%)
95% CI
A 99.00 (79.30, 100)
AB
CD
Su
rge
on
75 80 85 90 95 98.95Adjusted success rate
(lower 95% CI, Upper 95% CI)
B 98.97 (92.00, 100)
C 98.95 (88.96, 100)
D 98.68 (75.57, 100)
All 98.95
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Table 6a: Comparative quarterly performance of Risk adjusted Visual acuity outcome of LASIK surgery among 4 surgeons.
Values are Percent of patients with Uncorrected visual acuity (UCVA) >=6/7.5 at 6 months
post-op (95% confidence interval)
Surgeon Q1 Q2 Q3 Q4 Overall
A 100% 100% 97.12% 98.84% 97.42%
(82.04, 100) (82.44, 100) (72.74, 100) (79.75, 100) (87.51, 100)
B 99.96% 93.62% 97.79% 100% 96.68%
(72.25, 100) (42.73, 100) (54.93, 100) (44.9, 100) (77.24, 100)
C 91.25% 92.29% 92.75% 90.79% 93.27%
(76.74, 100) (78.99, 100) (80.49, 100) (77.26, 100) (86.5, 100)
D 93.51% 89.71% 90.22% 88.98% 92.62%
(54.43, 100) (52.22, 100) (41.18, 100) (30.84, 100) (70.27, 100)
Figure 6a: Comparative quarterly performance of Risk adjusted Visual acuity outcome of LASIK surgery (Uncorrected visual acuity (UCVA) >=6/7.5 at 6 months post-op )
70
80
90
97
Adju
ste
d s
uccess r
ate
Q1 Q2 Q3 Q4Period
(lower 95% CI, Upper 95% CI)
Quaterly Performance of Doctor A
40
50
60
70
80
97
Adju
ste
d s
uccess r
ate
Q1 Q2 Q3 Q4Period
(lower 95% CI, Upper 95% CI)
Quaterly Performance of Doctor B
70
80
93
100
Adju
ste
d s
uccess r
ate
Q1 Q2 Q3 Q4Period
(lower 95% CI, Upper 95% CI)
Quaterly Performance of Doctor C
30
40
50
60
70
80
93
Adju
ste
d s
uccess r
ate
Q1 Q2 Q3 Q4Period
(lower 95% CI, Upper 95% CI)
Quaterly Performance of Doctor D
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Table 6b: Comparative quarterly performance of Risk adjusted Visual acuity outcome of LASIK surgery among 4 surgeons.
Values are Percent of patients with Uncorrected visual acuity (UCVA) >=6/12 at 6 months
post-op (95% confidence interval)
Surgeon Q1 Q2 Q3 Q4 Overall
A 99.95% 99.92% 95.43% 100% 99%
(72.52, 100) (47.58, 100) (53.6, 100) (43.59, 100) (79.3, 100)
B 99.48% 98.57% 99.51% 98.38% 98.97%
(84.26, 100) (84.73, 100) (86.7, 100) (84.16, 100) (92, 100)
C 99% 99.06% 97.10% 99.93% 98.95%
(79.88, 100) (80.02, 100) (73.12, 100) (81, 100) (88.96, 100)
D 99.81% 99.70% 99.49% 89.98% 98.68%
(59.02, 100) (59.81, 100) (47.37, 100) (31.19, 100) (75.57, 100)
Figure 6b: Comparative quarterly performance of Risk adjusted Visual acuity outcome of LASIK surgery (Uncorrected visual acuity (UCVA) >=6/12 at 6 months post-op )
40
50
60
70
80
90
99
Adju
ste
d s
uccess r
ate
Q1 Q2 Q3 Q4Period
(lower 95% CI, Upper 95% CI)
Quaterly Performance of Doctor A
80
85
90
95
99
Adju
ste
d s
uccess r
ate
Q1 Q2 Q3 Q4Period
(lower 95% CI, Upper 95% CI)
Quaterly Performance of Doctor B
70
75
80
85
90
95
99
Adju
ste
d s
uccess r
ate
Q1 Q2 Q3 Q4Period
(lower 95% CI, Upper 95% CI)
Quaterly Performance of Doctor C
30
40
50
60
70
80
90
99
Adju
ste
d s
uccess r
ate
Q1 Q2 Q3 Q4Period
(lower 95% CI, Upper 95% CI)
Quaterly Performance of Doctor D
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6.0 Conclusion
We measure the performance of LASIK surgery services provided by Optimax Eye Specialist
Centre. The surgical service was provided by 4 surgeons at its TTDI branch.
Three performance measures were selected, (1) Post-operative Uncorrected visual acuity. (2)
Post-operative refraction within +0.5 D of target refraction and (3) Worsening of visual
acuity post-op, a measure of patient safety.
The performance results achieved by Optimax in 2010 were excellent.
The mean success rate (defined as UCVA at 6-month post-op 6/7.5 or better) among the 4
surgeons was 95%, and 99% for UCVA 6/12 or better.
Their risk adjusted success rate varies from 93% to 97% ; all 95% confidence intervals
overlap 100% success rate. For UCVA 6/12 or better, all surgeons uniformly achieved
99% risk adjusted success rate.
The on-target refractive error correction rate (defined as MRSE at 6 months within +
0.5D of Target=0) was 91%; for correction of spherical error alone, the on-target rate was
higher at 95%.
The safety record of LASIK surgery as provided by Optimax was excellent. No patient
has suffered any significant loss of visual acuity as a result of LASIK surgery at 6 months
post-op. All patients had a final BCVA better than 6/12 at 6 months post-op.
Caution is however warranted in interpreting and using the performance results reported here.
The results were based on data collected retrospectively and the risk model used requires
further refinement.
These results however have established a sound scientific basis and operational experience
for the Optimax eye healthcare group to embark on routine prospective measurement of the
performance LASIK surgery services. This has been initiated since January 2011.
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Appendix
Glossary
This section defines the various technical terms found in this protocol/ report in simple non-
technical language for the benefits of readers unfamiliar with the subject matter under
investigation.
Accountability The requirement that healthcare providers who have voluntarily
taken on the responsibility to provide healthcare services and are so
accredited or licensed, and to whom the necessary authority and
resources are provided in order for them to discharge their
responsibility, be held answerable for results
Astigmatism One form of refractive error where the focusing power of the eye is
only affected in one meridian than it is in another.
Epi-LASIK The Epi-LASIK procedure employs a unique microkeratome, called
the “Epikeratome”, to mechanically “separate” the epithelium from
the stroma, creating a flap of epithelial cells only (Epi-flap). Unlike
LASIK, no sharp blades or knives are required and unlike LASEK,
no alcohol is required. The Epi-flap is moved aside so that the laser
can reshape the exposed cornea. After laser application, the Epiflap
is replaced over the corneal bed and a bandage soft contact lens is
placed on top at the end of procedure.
Healthcare
providers
Refers to both institutional providers of health care services (e.g.,
clinics, hospitals, nursing homes) and clinicians (e.g., physicians,
nurse practitioners, nurses, physician assistants).
Hyperopia One form of refractive error where the optical power of the eye is
too weak to focus light on the retina. This can arise from a cornea
with too little curvature or an eyeball that is too short
INTRALASIK IntraLASIK is a procedure that similar to LASIK where corneal flap
is created for laser ablation. However in this procedure, flap is
created using femtosecond laser instead of mechanical blade
(microkeratome)
The procedure uses a software to direct the Femtosecond laser to
optically focus its beam into a tiny, 1 micron (.001mm) spot of
energy that passes harmlessly through the outer layers of the cornea
until reaching its exact depth within the stroma (central deeper layer
of the cornea). The laser beam creates a separation plane by forming
an interconnecting series of bubbles made of carbon dioxide and
water vapor.
The laser beam stacks a pattern of bubbles along the periphery of
the treatment plane, leaving a separated section of tissue to act as a
hinge. As with a traditional LASIK approach, the surgeon then folds
the tissue back to expose the underlying corneal layer to prepare for
the excimer laser treatment that will re-shape the cornea. With All-
Laser-Lasik, surgeons can avoid the complications related to
surgical blade problems. The Femtosecond laser precisely delivers
the laser energy directly to the outer surface of the eye, which
suffers no trauma.
LASEK Laser epithelial keratomileusis or LASEK is a modified form of
photorefractive keratectomy (PRK). This procedure requires the
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outer layer of the cornea- epithelium to be loosened with the diluted
alcohol solution for around 30 seconds. Then the loosened
epithelium (Epi-flap) is moved aside so that the laser can reshape
the exposed cornea. After laser application, the Epi-flap is replaced
over the corneal bed and a bandage soft contact lens is placed on top
at the end of procedure.
LASIK Laser-assisted in situ keratomileusis
A surgical procedure for the correction of refractive error.
A circular superficial cornea flap is made initially with a
mircokeratome (a special steel blade). The flap is then folded back
to allow a type of laser (excimer laser) to ablate and reshape the
deeper layers (stroma) of the cornea according to the patient’s
spectacles prescription. Following laser ablation, the flap is
repositioned and will adhere itself naturally without the need for
stitches.
Myopia One form of refractive error in which the focusing power
(refraction) of the eye is too strong such that when viewing distant
object, the image of the viewed object is brought into focus in front
of the retina rather than on it. Myopia can arise from a cornea with
too much curvature or an eyeball that is too long
Performance The activity of a healthcare provider intended to accomplish the
goals of healthcare. These goals are healthcare should be safe,
effective, patient-centered, timely, efficient, and equitable.
Performance
measure
Performance Measures are those measures of process, structure,
efficiency, or outcome that have been developed using rigorous
methodology , and are intended not only for clinical quality
improvement but they have attributes rendering them suitable for
public reporting, explicit comparisons of care between healthcare
providers, accreditation, pay for performance programs, or other
forms of accountability.
Refractive error An error in the focusing of light on the retina (this is back portion of
the eye) and a frequent reason for reduced visual acuity.
Refractive surgery Changing a patient’s optical measurements for the purpose of
correction of refractive error by means of an operation
Risk adjustment A process that modifies the analysis of performance measurement
results by those elements of the patient population that affect
results, are out of the control of providers, and are likely to be
common and
not randomly distributed
Visual acuity Acuteness or clearness of vision. It is often measured according to
the size of letters viewed on a Snellen chart
List of Abbreviations
AvSR Average Success rate
BCVA Best Spectacle Corrected Visual acuity
CDM Clinical Data Management
CER Cylindrical Error
CI Confidence interval
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CKAPS Cawangan Kawalan Amalan Perubatan Swasta MOH
CRA Clinical Research Associate
CRF Case Report Form
CRM Clinical Research Manager
D Dioptre
DBMS Database Management System
EC Ethics Committee
eCRF Electronic CRF
EDC Electronic Data Capture
ESR Expected Success rate
HPG Healthcare provider group
HPMRS Healthcare Performance Measurement & Reporting System
IC Malaysian National Registration Card or otherwise called the Identity Card
ICT Information and Communication Technology
ID Identity
IEC Independent Ethics Committee
IQR Interquartile Range
IRB Institutional Review Board
IT/IS Information Technology and Information System
JCI Joint Commission International
KPI Key Performance Indicator
LASIK Laser-assisted in situ keratomileusis
Max Maximum
Min Minimum
MOH Ministry of Health, Malaysia
MRSE Manifest Refractive Spherical Equivalent
N Number
N/A Not Applicable
N/K Not known
No. Number
OSR Observed Success rate
QA Quality Assurance
QC Quality control
RASR Risk adjusted Success rate
SAP Statistical Analysis Plan
SC Site Coordinator
SD Standard Deviation
SDV Source Document Verification
SE Standard Error
SEQ Spherical Equivalent
SER Spherical Error
TTDI Taman Tun Dr Ismail
UCVA Uncorrected Visual acuity
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Table 7: Performance measures for LASIK surgery
1. Performance measure Post-operative Uncorrected visual acuity
Description & Rationale Acuteness or clearness of vision as measured using a vision
chart. This is the most commonly used measure to evaluate
visual acuity outcome of LASIK surgery services; just as it is
the most well accepted efficacy measure in clinical trial of
LASIK surgery.
Period of care At the time of LASIK surgery and continued throughout the
period of care being assessed
Denominator All patients undergoing LASIK surgery for correction of
myopia at an Optimax centre
Numerator Number of patients with uncorrected visual acuity (UCVA)
6/12 or better at 6 months post-op
Data sources Patient medical record
Operating room record
2. Performance measure Post-operative Refraction within +0.5 Diopters of target
Refraction
Description & Rationale Measure of the precision of the refractive correction
This is the most commonly used measure to evaluate refractive
outcome of LASIK surgery services; just as it is a well accepted
efficacy measure in clinical trial of LASIK surgery.
Period of care At the time of LASIK surgery and continued throughout the
period of care being assessed
Denominator All patients undergoing LASIK surgery for correction of
myopia at an Optimax centre
Numerator Number of patients with mean spherical equivalent within +0.5
Diopers of target refraction at 6 months post-op
Data sources Patient medical record
Operating room record
3. Performance
measure
Loss of visual acuity
Description & Rationale Visual acuity as measured using a vision chart.
Loss of 2 or more lines post-op is commonly used to evaluate
loss of visual acuity as a measure of patient safety, just as it is
the most well accepted safety measure in clinical trial of
LASIK surgery.
Period of care At the time of LASIK surgery and continued throughout the
period of care being assessed
Denominator All patients undergoing LASIK surgery for correction of
myopia at an Optimax centre
Numerator Number of patients with loss of 2 or more lines of Best
spectacle Corrected Visual Acuity (BCVA) at 6 months post-op
Data sources Patient medical record
Operating room record
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Table 8a: Relationship between Visual outcome of LASIK surgery (Uncorrected visual acuity (UCVA) >=6/7.5 at 6 months post-op) and various putative prognostic factors
Uni-
variable
analysis
Multi-
variable
Logistic
regression
analysis
(k included)
Multi-
variable
Logistic
regression
analysis
(k excluded)
Factors N Odds Ratio P value Odds Ratio P value Odds Ratio P value
Age in years
< 25 Ref
254 1 - 1 - 1 -
25-29 374 0.68 0.40 0.72 0.49 0.72 0.48
29-34 351 0.56 0.20 0.55 0.21 0.55 0.20
35-39 354 0.29 0.003 0.25 0.002 0.25 0.002
Sex
Male Ref
462 1 - 1 - 1 -
Female 871 0.68 0.15 0.69 0.21 0.68 0.17
Myopia, manifest
Low-
Moderate (<=
6 D) Ref
954 1 - 1 - 1 -
Moderate to
High ( > 6.0
D)
379 0.52 0.01 0.52 0.01 0.52 0.01
Astigmatism,
manifest
Low-
Moderate (<=
2 D) Ref
1220 1 - 1 - 1 -
Moderate to
High ( > 2.0
D)
113 0.48 0.03 0.35 0.004 0.35 0.004
Corneal curvature
Mean K 1333 0.89 0.05 0.96 0.68
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Table 8b: Relationship between Visual outcome of LASIK surgery (Uncorrected visual acuity (UCVA) >=6/12 at 6 months post-op) and various putative prognostic factors
Uni-
variable
analysis
Multi-
variable
Logistic
regression
analysis
(k included)
Multi-
variable
Logistic
regression
analysis
(k excluded)
Factors N Odds Ratio P value Odds Ratio P value Odds Ratio P value
Age in years
< 25 Ref
254 1 - 1 - 1 -
25-29 374 0.98 0.98 1.04 0.96 1.09 0.92
29-34 351 1.38 0.75 1.49 0.69 1.61 0.64
35-39 354 0.39 0.25 0.38 0.24 0.42 0.29
Sex
Male Ref
462 1 - 1 - 1 -
Female 871 0.51 0.31 0.41 0.18 0.47 0.25
Myopia, manifest
Low-
Moderate (<=
6 D) Ref
954 1 - 1 - 1 -
Moderate to
High ( > 6.0
D)
379 0.99 0.99 0.97 0.96 1.03 0.96
Astigmatism,
manifest
Low-
Moderate (<=
2 D) Ref
1220 1 - 1 - 1 -
Moderate to
High ( > 2.0
D)
113 1.21 0.86 0.88 0.91 0.95 0.96
Corneal curvature
Mean K 1333 1.16 0.46 1.25 0.27