1. Hong Kong Eye Hospital Biometry Audit 2012 SN60WF IOL Dr. Rose Chan
Resident, Hong Kong Eye Hospital

2. Acknowledgement Pre-admission and post-discharge (PAPD) nursing staff
Medical Record Office (MRO) staff
Ms Chiu Wai Yee
Dr. Victoria Wong

3. Introduction Importance of auditing cataract surgery outcomes
Most commonly performed surgery
Increased patient expectation
Adopt practices that promote the patient’s best interests and safety in performing cataract surgery

4. Possible complications in cataract surgery

5. Refractive surprise Diminished quality of life Binocular diplopia
Altered depth perception
Lens exchange
Medicolegal implications

6. Purpose of audit
Royal College of Ophthalmologists Cataract Surgery Guidelines 2010
“The accuracy of the biometry should be continuously audited by comparing the expected spherical equivalent with the achieved spherical equivalent.”
Refraction within 1 diopter of target is considered to be satisfactory
A benchmark standard of 85% is suggested

7. Summary of last year result
Mean difference between target and post-op SE: D (range, -3.22D to +3.7D)
Within ± 1 D of target SE
64.6 % (177/274)
Biometry performance significantly better for
PAPD nursing staff
Nidek machine

8. Suggestions from last year
To concentrate biometry service by experienced staff
To aim emmetropia for SN60WF
Choose target refraction between 0D and -0.5D
To repeat audit next year
To refine A-constant if similar outcome

9. Methods
July 2010– Oct 2011
Patients implanted with SN60WF (15-20% of IOL in 2011)
Biometry by PAPD NS, optometrists and orthoptists
SRK/T formula regardless of axial length
Uneventful phacoemulsification + IOL
Major reasons for exclusion
Combined surgeries
No refraction available
Complicated surgery
Which machine is used by who and in what proportion

10. Methods Data Collected Demographics Axial length, keratometry
Biometry machine and staff
Target and outcome refraction

11. Biometry staff and machine
Nursing
Optometrist
Orthoptist
Nidek Echoscan
n= 196/390 (50.3%) ● ○
Quantel Medical Axis
n= 110 (28.2%)
Canon KU-1
n= 40 (10.3%)
Alcon Ocuscan
n= 22 (5.6%)
Zeiss IOL Master

12. Current A-constant
For USG biometry: 118.7
For Optical biometry: 119.1

13. Results 897 SN60WF IOL were implanted
~15% total IOL
390 eyes were included into audit
Female : Male 225:135
Left : Right 189:201
Age 74.4 years (range, years)
Axial length mm (range, 20.0 – 30.28mm)

14. Refractive outcomes Mean post-op spherical equivalent (SE) –
-1.13 D (range, -7.25D to D)
Pearson correlation
r = -0.21
P = 0.735

15. Comparison of outcomes
Mean target SE D (range, -4.66D to +0.44D)
Mean post-op SE D (range, -7.25D to +3.12D)
p< (two-tailed t-test)
Mean difference between target and post-op SE: D (-3.8D to +3.46D)
Calculation based on surgeon’s chosen target refraction
Within ± 1 D of target SE
64.9 % (253/390)

17. Factor analysis SRK/T formula used in all patients
Calculation based on surgeon’s chosen target refraction
Comparing proportion of patients within target refraction range (+/- 1D of target), and those not within target range
Chi-square test
Sex
p=0.45
Age (<60, 60-80, >80 years old)
p=0.83
Laterality of eyes
p=0.733

18. Factor analysis Axial Length (mm) <22 22 – 26 >26 No. of eyes 34
325 31
Mean difference in SE from target (D)
-0.86 (-1.58 to 3.8)
-0.52 (-3.46 to 2.87)
-0.14 (-1.76 to 2.59)
Similar trend (but stat. insignificant) last year
One-way ANOVA: p=0.012

19. Factor analysis 145 (74%) 53 (48%) 24 (60%) 14 (63.6%) 17 (77.3%) 51
Biometry machine performance
Nidek
Axis
Canon
Ocuscan
IOL Master
Wiithin +/- 1D target refraction
145 (74%) 53
(48%) 24
(60%) 14
(63.6%) 17
(77.3%)
Not within target 51 57 16 8 5
Total
196
110 40 22
Chi square test p<0.0001

20. Factor analysis Biometry staff performance by group
Chi-square test p<0.0001
Nursing
Optometrist
Orthoptist
Within +/- 1D of target refraction
103 (77.4%)
86 (51.8%)
64 (64.9%)
Out of target refraction range 30 80 27
Total
133
166 91

21. Factor analysis
Machine performance?
Staff performance?

22. Factor analysis Axis II Chi-square test P<0.001
Used by Optometrist and Orthoptist
Optometrist
Orthoptist
Within target
30 (38%)
23 (74.2%)
Not within target 49 8
Total 79 31
Chi-square test P<0.001

23. Factor analysis Excluding cases of Axis II machine Nursing Optometrist
Orthoptist
Within +/- 1D of target refraction
103 (77.4%)
56 (64.4%)
41 (68.3%)
Out of target refraction range 30 31 19
Total
133 87 60
Chi square test: p=0.091

24. Factor analysis
No significant difference of individual optometrist performance
P=0.658 (Chi-square)
A=C, B=Ch, C=D, D=H, E=J, F=S

25. Discussion Suboptimal biometry outcomes not reaching 80% target
Overall biometry performance significantly better for
PAPD nursing staff
Nidek / IOL master machines
Previous years: most biometry performed by nursing staff
But more biometry service to be taken up by optometrist
Need further enhancement of skills and technique
Orthoptist: previous more difficult case, should improve with IOL master (also done by nursing)

26. Discussion Current biometry service allocation Nursing Optometrist
Orthoptist
No. of sessions per week 6 3 1
Patient share
40 %
20 %

27. Discussion Mean target refraction of our surgeons: SN60WF
Aspheric
Reduced spherical aberration best when emmetropic
Myopic shift significantly more in short AL eyes
Aim emmetropia especially for short eyeball

28. Discussion
Poor results from Axis II machine
No longer in use

29. Recommendations Further streamline biometry service is essential
Too many machines and groups of staff
 high variability
To concentrate biometry service by experienced staff
Machines in current use:
Nursing
Optometrist
Orthoptist
Nidek old model ●
Nidek new model
IOL Master

30. Optometrist service improvement
Audit for individual performance
Establish protocol for double check mechanism
Improve setting for biometry measurement
Head support, fixation target
Use of IOL master
Less technique demanding
To aim emmetropia for SN60WF
Choose target refraction between 0 and -0.5D
Especially for short eyes

31. Recommendations Using Dr Warren Hill Constant Calculation spreadsheet
Re-calculation of optimized A-constant (excluding cases by Axis-II and IOL master)
Using Dr Warren Hill Constant Calculation spreadsheet
Modified optimized A-constant 118.2

32. Recommendations
Current optimization not applicable to IOL master (optical biometry)
To review in coming year
More cases anticipated coming year
2/3 cases of nursing (VA better than 3/24)

33. Thank You