Quality Control in Refractive Surgery

Transcription

1 Quality Control in Refractive Surgery Stefan Pieger*, M.Sc. Ingenieurbüro Pieger GmbH, Wendelstein, Germany Introduction Personal experience as application specialist for refractive excimer lasers since (Meditec, Schwind, Nidek) PRK & LASIK Nomogram development based on systematic outcomes analysis. Excimer Laser Surgery and refractive surgery in general well suited for a systematic approach on quality control. 1

2 Why Quality Control? Verify current nomogram settings and make adjustments if necessary. Reduce enhancement rate. Use for marketing and advertisement. Discover trends and technical problems in order to react more rapidly. Fulfill requirements of ophthalmic societies. Increase confidence level about refractive procedures offered in your center. How to collect your data? Patients files Excel Spread Sheet Database Software (Access; Filemaker; etc.) Outcomes Analysis Software (; ASSORT; Refr. Consultant; etc.) 2

3 How to analyze refractive data? Standard Refractive Outcomes (JRS) Stability / Safety / Predictability / Efficacy Additional Outcome Parameters Astigmatism Outcomes: SIRC - Surgically Induced Refractive Change (= Vector Analysis ); Double Angle Scatter Plot Defocus Equivalent / Contrast Sensitivity in mesopic conditions / pre OP BSCVA vs. post OP UCVA Wavefront Based Outcomes Defocus + Cyl ( aberrometer refraction ) Higher Order RMS / Spherical Aberration (Z12) / Coma / Trefoil Standard Outcomes 3

4 vol164/war.pdf Standard Refractive Outcomes: Safety 100% 90% 80% 2 or more lines lost 3 % at 1 m post OP 70% 60% 50% 40% 30% 20% 10% 0% 1% 0% 2% 0% 22% 13% 54% 57% 25% 19% 2% 3% 0% 0% lost > 2 lost 2 lost 1 unchanged gained 1 gained 2 gained > 2 month (eyes) 1 (770) 3 (653) Number of eyes per Follow up visit. Follow up time interval 2. SAFETY: Change in BSCVA - Percent 4

5 Standard Refractive Outcomes: Efficacy 100% 90% 80% 72% 20/20 or better 3 month post Op 70% 60% 50% 40% 30% 20% 10% 0% 4% 6% 20/12 or better 18% 26% 46% 40% 14%14% 10%7% 3%4% 5% 3% 20/15 20/20 20/25 20/30 20/40 20/50 or worse month (eyes) 1 m (691) 3 m (562) Number of eyes per Follow up visit. Follow up time interval 4. EFFICACY: UCVA - Percent Standard Refractive Outcomes: Cumulative UCVA vs. preop SCVA 100% 90% 80% 70% 60% 50% 90% 95% 95% 100% 100% 88% 84% 76% 48% Number of eyes at Follow up visit. month (eyes) 40% 30% 20% 10% 8% 32% 12% PreOP SCVA 0% 3 m (25) prescva (39) '20/10' 20/12,5 or better 20/16 or better 20/20 or better 20/25 or better 20/32 or better 20/40 or better preop SCVA vs. postop UCVA - Percentage 20/50 or better 20/63 or worse 5

6 Standard Refractive Outcomes: Stability (SEQ) 1,00-0,15-0,20-0,18-0,22 0,00 pre OP 1 m 3 m 6 m 12 m -1,00 ± 1 StDev -2,00-3,00-4,00-5,00-6,00-4,70 Follow up time interval Mean value of SEQ -7,00-8, STABILITY: Achieved Change in Refr. over Time Number of eyes per Follow up visit. Standard Refractive Outcomes: Predictability (SEQ) Achieved [D] PREDICTABILITY: Attempted vs Achieved (Scatter) 744 eyes overcorrected y = -0.00x x undercorrected Attempted delta SR equiv. [D] Number of eyes at follow up ±1 D happiness Zone Trend line y = -0.00x x Regression Formula: Achieved = 0.94*Attempted (~6% undercorrection) 6

7 Astigmatism Outcomes: must be based on Vector Analysis! SIRC (Surgically Induced Refractive Change) PreOP: -5/-2 x month: Plano/-1 x 130 SIRC: -4.31/-2.39 x 12 'The cylinder was actually overcorrectd and the axis has been misaligned by 12!' Astigmatism Outcomes: SIA (based on Vector Analysis) Achieved [D] Attempted Cyl vs SIA (Scatter) overcorrected 3 month postop 490 eyes 0/-0.5 x 180-2/-1@ D Cyl Undercorrection! 0/-0.5 x 90 (-0.5/+0.5x180 ) 0.5 D Cyl Overcorrection! 3 2 y = -0.00x x undercorrected Attempted Cyl [D] y = 0.90 * x (~10% undercorrection) 7

8 Astigmatism Outcomes: Double Angle Scatter Plot PreOP Cyl & Axis PostOP Cyl & Axis Double Angle Minus Cyl Scatter Plot (160 eyes) Double Angle Minus Cyl Scatter Plot (79 eyes) Mean Cyl 6,9-5 Mean Cyl 162, Additional Outcomes: Defocus Equivalent 100% 90% 80% 86% 88% 99%99% 100%100% 100%100% 100%100% SEQ = SPH + ½ CYL 70% 60% 50% 40% 60% 64% DEQ = SEQ + ½ CYL 30% 20% 10% month (eyes) 1 m (615) 3 m (554) 0% <=0,5D <=1D <=2D <=3D <=4D <=5D DEFOCUS EQUIVALENT - Percent 8

9 Defocus Equivalent vs. Refractive Outcome 100% 90% 80% 70% 76% 72% 92% 92% 99% 99% 100%100% -5.0/+10.0 x 90 SEQ Plano DEQ +5 60% 50% 40% 100% 90% 86% 88% 99% 99% 100%100% 1 m (615) 3 m (554) 30% 80% 20% 10% 70% 60% 60% 64% 0% 50% +- 0,5 +- 1,0 +- 2,0 +- 3,0 40% Refractive outcome - % within Attempted 1 m (744) 3 m (662) 30% 20% DEQ ~ Blur Circle 10% 0% <=0,5D <=1D <=2D <=3D DEFOCUS EQUIVALENT - Percent Additional Outcomes: Mesopic Contrast Sensitivity Contrast Sensitivity Mesopic 2,20 2,00 1,80 1,60 1,68 1,63 1,92 1,88 1,61 1,57 month (eyes) pre op (112) 1 m (72) Normal Population Range (Vector Vision CSV 1000) 1,40 1,20 1,22 1,21 1,00 0,80 0,60 0,40 A (3cpd) B (6cpd) C (12cpd) D (18cpd) Spatial Frequency [cycles/degree] VA in LogMar Scale 9

10 Wavefront based Outcomes Work in progress! Important parameters: HO RMS, spherical Aberration and Coma Report on same (6mm) pupil diameter or convert to diopters Presenting horizontal and vertical Coma individually? Vector calculation to present magnitude and axis in [D]! (0.5 D 230 ) Wavefront based Outcomes Higher Order RMS [µm ±StDev] 0,80 0,70 0,60 0,53 Pupil Diameter: 6.0 mm 0,54 0,54 0,51 0,50 0,40 0,31 0,30 0,20 0,10 0, pre OP 1 m 3 m 6 m 9 m RMS higher order over time 10

11 Wavefront based Outcomes Spherical Aberration [µm] or [D] 2,50 0,10 0,05 Pupil Diameter: 6.0 mm 2,00 0,00-0,03 pre OP 1 m 3 m 1,52 9 m -0,05 1,31 1,36 1,42 1,50-0,10-0,15 1,00-0,20-0,25 0,50-0,30 0,41-0,23-0,25-0,24-0, , ,40 pre OP 1 m 3 m 6 m 9 m Spherical Spherical Aberration Aberration (Z12) (Z12) DEQ over over time time [µm] [D] Coma as Vector- Scatter Plot Coma Scatter Plot (18 eyes) 90-2,5 Coma [D] 202,4-2,0-1,5-1,0-0, ,0-2,5-2,0-1,5-1,0-0,5-0,0-0,5-1,0-1,5-2,0-2,5-0,5 0-1,0-1,5-2,0-2,

12 Making Outcome-based Nomogram Adjustments Comparison of Laser Settings vs. Achieved change in refraction (and not Attempted vs. Achieved). Reduce random errors as far as possible as nomograms can only compensate systematic errors! Must be specific for major laser parameters like OZ, TZ, ablation profile type as well as for refraction types. Nomograms for Individual Patient Groups Data must be filtered on certain parameters: Refraction Type (Myp/MyoAsti/Hyp/HypAsti ) Surgery Type (PRK; LASIK; LASEK; Custom ) Optical Zone Diameter Others (age, laser software version; humidity ) 12

13 Nomogram Improvements Laser Settings vs. Achieved Achieved [D] Laser Settings vs Achieved 1166 eyes overcorrected y = -0,01x 2 + 1,22x - 0, undercorrected Laser setting [D] y = -0,01x 2 + 1,22x - 0,08 reduce attempted SEQ by 22%! Identify and exclude outliers Achieved [D] Laser Settings vs Achieved 1166 eyes overcorrected y = -0,01x 2 + 1,22x - 0, undercorrected Laser setting [D] 13

14 Laser Setting CYL vs. Surgical Induced change in Astigmatism Achieved [D] 7 Laser Setting (cyl) vs SIA 1480 eyes 6 overcorrected y = 0.03x x High Scatter! (further analysis necessary!) % systematic undercorrection 1 undercorrected LaserSetCyl [D] Nomograms: General Comments 1. Reduce Scatter by Standardized Surgery and OR Environment 2. Exclude Outliers from Data Analysis 3. Exclude Enhancements (separate nomogram) 4. Choose appropriate follow up interval ( 3 m) 5. Create Formula ( -10% ) / Lookup Table or use Nomogram Software 14

15 Summary Improving the results of refractive surgery procedures must be based on an individual quality control system. Nomograms can compensate for systematic errors, but not for random errors. Modern outcomes analysis software allows constant monitoring of your results. Conventional Outcomes will be extended by HO-RMS, Spherical Aberration and Coma. Thank You! 15

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