Comparison of Elasticity and Fracture Strength of Manual, Femtosecond laser and Selective Laser Capsulotomies SHERAZ M. DAYA MD FACP FACS FRCSE FRCOphth SOON-PHAIK CHEE FRCOphth FRCS(Ed), FRCS(G), MMed(S’pore) SENG EI TI FRCS(Ed), MMed(S’pore) RICHARD PACKARD MD, FRCS, FRCOphth CENTRE FOR SIGHT
Financial Disclosure Company Code 1. Abbott Medical Optics Inc. S C = Consultant / Advisor 2. Bausch + Lomb C,L E = Employee 3. Carl Zeiss Meditec C L = Lecture Fees O = Equity Owner 4. Clarvista C P = Patents / Royalty 5. Ellex L S = Grant Support 6. Excellens C, O 7. LinCor Biosciences C 8. Lumenis C 9. Medicem C 10. Nidek, Inc. C,L 11. Omeros C 12. Physiol L 13. PRN O 14. STAAR Surgical C,O 15. Strathspey Crown C 16. Scope Pharmaceuticals C 17. Rayner C CENTRE FOR SIGHT
Anterior Capsulotomy • Increased interest – Circular, central and consistent sizing • Rapid, reproducible and affordable – Automated devices • Femtosecond laser • Radiofrequency cautery (Zepto, Mynosys) • Selective Laser Capsulotomy (CAPSULaser, EXCEL-lens) CENTRE FOR SIGHT
Non-pulsatile Laser Capsulotomy CAPSULaser CENTRE FOR SIGHT
Capsule strength • Anterior capsule tears – hazardous – Posterior capsule involvement – up to 50%* – Lens tilt, decentration * Marques, F. F., et al. (2006). "Fate of anterior capsule tears during cataract surgery." J Cataract CENTRE FOR Refract Surg 32 (10): 1638-1642. SIGHT
STUDY- Purpose Compare capsule strength – Femtosecond Laser capsulotomy (FLACS) – Continuous curvilinear capsulorrhexis (CCC) – Selective Laser Capsulotomy (SLC) CENTRE FOR SIGHT
Materials and Methods • Human cadaver paired eye study – 3 GROUPS of 10 paired eyes each – Study group 1: SLC to CCC – Study group 2. CCC to FLACS – Study group 3 FLACS to SLC • Scanning electron microscopy of capsule edge CENTRE FOR SIGHT
Parameters that affect Capsule strength • Laboratory study – influence of: – Capsule size 4.7-5.0 vs 5.2-5.7mm- Bigger is better – Capsule continuity – discontinuous is weaker CENTRE FOR SIGHT
Materials and Methods All eyes, Cornea and iris removed for visibility Exclusion Criteria: • Circularity – minor axis was less than 90% of the major axis – 4π area of the best-fit-circle / perimeter distance from point to point being less than 90%. • Size – outside diameter of 5.0 mm of +/- 0.2 mm. CENTRE FOR SIGHT
Materials & Methods Lens nucleus hydroexpressed • I/A of remaining cortex • • Waxed probe inserted into bag Zonules cut and bag removed • Instron device used to measure load • and extension to tear STATISTICAL ANALYSIS Wilcoxon Signed Ranks Tests • CENTRE FOR SIGHT
RESULTS: Comparative Extension and Perimeter Extension (mm) Perimeter (mm) Load (mN) Study 1 SLC 7 ± 1 29 ± 2 277 ± 38 CCC 5 ± 1 25 ± 2 190 ± 37 Study 2 CCC 5 ± 1 24 ± 2 186 ± 37 FLACS 5 ± 1 23 ± 2 145 ± 35 Study 3 FLACS 5 ± 1 23 ± 2 148 ± 31 SLC 7 ± 1 28 ± 2 269 ± 38 CENTRE FOR SIGHT
RESULTS Group 1 SLC to CCC PERIMETER: SLC vs CCC LOAD: SLC vs CCC SLC CCC SLC CCC p= <0.01 p= <0.01 35.0 350 Threshold Perimeter (mm) 30.0 300 Threshold Load (mN) 25.0 250 20.0 200 15.0 150 10.0 100 5.0 50 0.0 0 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10 p= <0.01 p= <0.01 Pair # Pair # CENTRE FOR SIGHT
RESULTS Group 2 CCC to FLACS PERIMETER: CCC vs FLACS LOAD: CCC vs FLACS p= <0.01 p= <0.2 CCC FLACS CCC FLACS 35.0 350 Threshold Perimeter (mm) 30.0 300 25.0 Threshold Load (mN) 250 20.0 200 15.0 150 10.0 100 5.0 50 0.0 0 11 12 13 14 15 16 17 18 19 20 11 12 13 14 15 16 17 18 19 20 Pair # Pair # CENTRE FOR SIGHT
RESULTS Group 3 SLC vs FLACS PERIMETER: SLC vs FLACS PERIMETER: SLC vs FLACS p= <0.01 p= <0.01 SLC FLACS SLC FLACS 35.0 350 30.0 300 Threshold Perimeter (mm) Threshold Load (mN) 25.0 250 20.0 200 15.0 150 10.0 100 5.0 50 0.0 0 21 22 23 24 25 26 27 28 29 30 21 22 23 24 25 26 27 28 29 30 p= <0.01 p= <0.01 Pair # Pair # CENTRE FOR SIGHT
RESULTS SLC CCC FLACS PERIMETER (mm) 28 ± 2 24 ± 2 23 ± 2 Relative to CCC 120 ± 10% 100% 95 ± 10% (mN) LOAD 273 ± 37 186 ± 40 146 ± 32 Relative to CCC 146 ± 20% 100% 78 ± 20% CENTRE FOR SIGHT
SEM CCC 10 µ m 10 µ m CENTRE FOR SIGHT
SEM - FLACS Figure 4C: Femtosecond Laser Assisted Cataract Surgery (FLACS) REGIONS OF ABERRANT HOLES 10 µ m 20 µ m CENTRE FOR SIGHT
SEM SLC EDGE EDGE EDGE EDGE ANTERIOR CAPSULE AMORPHOUS COLLAGEN 250 µ m 10 µ m CENTRE FOR SIGHT
SLC Strength 1. doubling of the capsular edge thickness 2. the rolled-over folded edge which itself increases mechanical strength 3. smooth edge devoid of irregularity and defect 4. thermal change of the anterior capsule = regular ordered Collagen Type IV to amorphous collagen with AMORPHOUS COLLAGEN increased elasticity CENTRE FOR SIGHT
Study Strengths 1. Pairwise HUMAN cadaver eyes 2. Standardised variables: size and circularity 3. Consistent load and perimeter findings between groups (SLC vs CCC vs FLACS) CENTRE FOR SIGHT
CONCLUSIONS 1. SLC significantly stronger than both CCC and FLACS 2. CCC significantly stronger than FLACS (not previously evaluated in human eyes) 3. SLC strength may be accounted for by SEM findings CENTRE FOR SIGHT
Thank you… Courtesy of Burkhard Dick CENTRE FOR SIGHT
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