Phacoemulsification some Basic Ideas…

1. Khalid M. Al-Arfaj, MD Phacoemulsification some Basic Ideas… Dammam University

2. 1-Quiz … 2- lecture … 3-Vedio …

3. Basic Phaco Settings

4. Basic Phaco Settings Sculpting • 60 / 80 / 24 • US, Vac, Asp.

5. Quadrant Removal/Burst • 45 / 400 / 37 BW 50 - 120

6. Quadrant Removal/Pulse • 45 / 376 / 35 PR 6

7. Horizontal Choping

8. Vertical Choping Courtesy of David Chang, MD

9. Evolution of IOL Calculation Formulas • Clinical History Formula • Used before 1975 • Simple formula to calculate IOL power • P = 18 + (1.25 x Ref) • Poor accuracy • >50% had >1D error • “9 D surprise”– some huge errors due to the inaccuracy of calculating refractive error prior to cataract formation

10. Formulas and Their Derivations • Regression Formulas • Derived from retrospective computer analysis of postoperative data from a large number of patients • SRK Formula • P = A – 2.5L – 0.9K • Derived by Sanders, Retzlaff and Kraff1 • Required measurements • L – Axial length (mm) • K – Corneal power (D) • A – A Constant 1 Sanders DR, Retzlaff J, Kraff MC. Arch Ophthalmol 1983;101:965-967

11. Formulas and Their Derivations • SRK and early Theoretical formulas fairly accurate for eyes of moderate length • Inaccuracies occurred at extremes of axial length

12. Modern Theoretical Formulas • Most important concept is postop Anterior Chamber Depth is related to IOL placement in the eye, not to preop ACD • All have a personalizable factor to improve accuracy of calculations • Holladay/Holladay 2 • S factor– personalized surgeon factor • SRK/T • A constant– based on multiple variables (IOL manufacturer, implant style, surgeon’s technique, etc.) • Hoffer Q • Personalized ACD value

13. Modern Theoretical Formulas • All based on Thin Lens Optics

14. Modern Theoretical Formulas Modern Theoretical Formulas • Found to be more accurate than older formulas • All basically the same in predicting IOL power in average eyes • Differences occur at extremes of AL and K’s • Personalized factors based on optimal cases (PCIOL, intact capsule) • Must change when surgical plan changes (Sulcus PCIOL or ACIOL)

15. Axial Length Measurement • Current methods • Contact A Scan Biometry • Optical Biometry • Partial Coherence Interferometry

16. A Scan Biometry • Use of A scan ultrasound to measure axial length • Contact

17. Normal Phakic Contact A Scan • C1 – Anterior surface of Cornea • C2 – Posterior surface of Cornea • L1 – Anterior surface of Lens • L2 – Posterior surface of Lens • R – Retina

18. Optical Coherence Biometer • IOL Master • Fine beam of infrared laser used to measure axial length

19. ultrasound vs. optical biometry Ultrasound A-Scan 10MHz sound wave IOLMaster 780nm laser beam ILM RPE averaging across foveal cup reflection at Bruch's membrane • Foveal thickness is about 150µ (±20) from ages 10 to 80 years. • The parafoveal area is between 0.10 mm and 0.16 mm thicker.

20. Ultrasound A-Scan 10MHz sound wave ? ? fixation blob ? ? ? ? ? IOLMaster 780nm laser beam fixation point alignment precision: ultrasound vs. optical A-scan US does not measure to the exact center of the fovea, but samples an area around it due to the broad angle of the U/S beam and fixation light. IOLMaster uses a point fixation light, measures along visual axis to the RPE at foveal center and then adds back the foveal thickness.

21. partial coherence interferometrynon-contact laser devicephakic, pseudophakic, phakic IOLsposterior staphyloma, silicone oilnot limited by wavelengthor retinal thickness variations applanation A-scan falsely short axial length variable corneal compression corneal micro-abrasions highly operator dependent source of IOL power errors myopia myopia hyperopia hyperopia -2.0 -1.00.0 1.0 2.0 -0.50.00.5 Comparison of three methods 90% 80% 70% 60% 50% 40% 30% 20% 10% 90% 80% 70% 60% 50% 40% 30% 20% 10% spherical equivalent prediction error (D) Data courtesy of Warren E. Hill, MD, FACS

22. Pearls and Pitfalls • Measure axial length of both eyes • Take multiple readings of each to assure accuracy • Compare eyes • Shouldn’t be a significant disparity in axial lengths unless a significant difference in refraction • Axial Length • measure too short - myopic surprise • measure too long - hyperopic surprise • Normal Eye: 1.0 mm error  2.5 to 3.0 D surprise • Short Eye: 1.0 mm error  7.5 D surprise • Keratometry • 1D curvature error  1D surprise

23. IOL Power Selection • What is your target postop refraction? • Examine patient data • Discuss with patient • Match other eye? • Monovision? • Binocular distance? • Binocular near?

24. IOL Choices • How do you choose IOL? • Material • Silicone • Acrylic • PMMA • Configuration • One piece • Three piece • Delivery system • Fold vs. Inject

25. Haptic Edge Optic Basic IOL Design Features

26. Haptic 1-piece 3-piece diameter Edge Optic Basic IOL Design Features

27. Haptic Design 1 • 13.0

28. Haptic Edge square rounded Optic Basic IOL Design Features

29. Square reduced PCO dysphotopsias? Rounded anterior reduced PCO reduced internal reflections Edge Design

30. Material Rigid PMMA Foldable acrylic silicone collamer Focality/Sphericity Monofocal spheric toric wavefront aspheric Multifocal accomodative pseudoaccomodative Optic Design • Diameter • 5.0 to 7.0 mm • 6.0

31. Which lens? • Consider matching IOL design features with individual patient needs

32. Lens choice • High myopia • Considerations: IOL size, power • longer haptic span, larger optic diameter • low power

33. Lens choice • High hyperopia • Considerations: IOL size, power • smaller haptic span, smaller optic diameter • high power IOL

34. Lens choice • Presbyopia • Considerations: spectacle independence • multifocal IOL (accomodative, pseudoaccomodative) • monovision using two monofocal IOLs

35. Lens choice • Astigmatism (corneal) • Considerations: correct corneal astigmatism • Toric IOL

36. Lens choice • Improved functional vision • Considerations: maximize contrast sensitivity aspheric

37. Lens choice • Macular degeneration • Considerations: block toxic UV light • blue blocking chromophore

38. Lens choice • Pseudoexfoliation • Considerations: Long term zonular stability • avoid silicone material (capsular phimosis)

39. Crystalens “ Accommodating” Lens –single optic

40. Crystalens

41. Crystalens

43. The Multifocals ReZoom & ReSTOR The good Less capsule issues Known material Good near vision The Bad: Unwanted photopsia Contrast sensitivity

45. ReZoom

46. AcrySof® ReSTOR®Apodized Diffractive IOL

47. Anatomy of the Apodized Diffractive IOL Step heights decrease peripherally from 1.3 – 0.2 microns Central 3.6 mm diffractive structure A +4.0 add at lens plane equaling +3.2 at spectacle plane

48. Patient SelectionPre-operative Exclusion Criteria • Subjective Exclusion • Hypercritical patients • Patients with unrealistic expectations • Occupational night drivers • Medical Exclusion • >1.0 D of corneal astigmatism? • Pre-existing ocular pathology • Previous refractive patients

49. Patient Satisfaction • Crystalens, ReZoom, and ReSTOR all have clinical studies extolling the level of spectacle independence, excellent near, intermediate, and far vision of patients with these lenses.

50. Future Technology The HumanOptics IOL ( 1CU) is a single optic accommodative lens continuing in clinical trials in Europe. (Image courtesy of HumanOptics, Ophthal Clinics of N. Amer. March 2006.)