Version No: 3.4 Healthcare Performance Measurement & Report for LASIK surgery Page 1 of 22 Ver.Date: 19 May 2011 Protocol No.:HR2010-02 1 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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Version No: 3.4 Healthcare Performance Measurement &
Report for LASIK surgery
Page 1 of 22
Ver.Date: 19 May 2011 Protocol No.:HR2010-02
1
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
Version No: 3.4 Healthcare Performance Measurement &
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
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
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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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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Report for LASIK surgery
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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
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