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

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

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

Possible complications in cataract surgery

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

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

Summary of last year result Mean difference between target and post-op SE: -0.58 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

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

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

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

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

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

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, 38-93 years) Axial length 23.64 mm (range, 20.0 – 30.28mm)

Refractive outcomes Mean post-op spherical equivalent (SE) – -1.13 D (range, -7.25D to +3.125D) Pearson correlation r = -0.21 P = 0.735

Comparison of outcomes Mean target SE -0.61D (range, -4.66D to +0.44D) Mean post-op SE -1.13 D (range, -7.25D to +3.12D) p<0.0001 (two-tailed t-test) Mean difference between target and post-op SE: -0.52 D (-3.8D to +3.46D) Calculation based on surgeon’s chosen target refraction Within ± 1 D of target SE 64.9 % (253/390)

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

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

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

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

Factor analysis Machine performance? Staff performance?

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

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

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

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)

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

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

Discussion Poor results from Axis II machine No longer in use

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

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

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

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)

Thank You