flacs ie femtosecond laser assisted cataract surgery - unbiased review

87
FEMTOSECOND LASER CATARACT SURGERY Revolution, Evolution, or No Solution? Making Sense of the Literature Ken Lipstock, M.D. Richmond, Virginia

Upload: rajesh-fogla

Post on 23-Dec-2014

2.812 views

Category:

Health & Medicine


2 download

DESCRIPTION

laser cataract surgery

TRANSCRIPT

  • 1. Revolution, Evolution, or No Solution? Making Sense of the Literature Ken Lipstock, M.D. Richmond, Virginia

2. emtosecond laser provides an ultrafast burst of energy. Argon, excimer, and Nd: YAG lasers: nanosecond (10 ) pulses Femtosecond: 10 second Excimer: photoablates Argon: photocoagulates Nd: YAG and Femtosecond: photodisrupt. Their light energy can be absorbed by optically clear tissue and create microcavitation bubbles that cause an acoustic shock wave that incises the target tissue. -9 -15 3. Femtosecond lasers ultrafast pulse allows smaller amounts of energy to provide similar power output to the NdYag. This results in much smaller cavitation bubbles therefore reduced collateral damage to adjacent tissues. 4. Femtosecond laser first FDA approved for LASIK flaps in 2001 and then approved for cataract surgery in 2010. With guidance systems (OCT or Scheimpflug-like technology) it is used to make: Cataract clear corneal incisions and limbal relaxing incisions Capsulorhexis Lens fragmentation/softening; a pretreatment prior to phacoemulcification and/or irrigation/aspiration. 5. Mistrust but Verify We are witnessing one of the most intense marketing campaigns ever in Ophthalmology. And this is a sentence from a scientific study in a respected peer reviewed journal! Is Femtolaser Cataract Surgery the most important evolution since the transition to phacoemulsification? Much has been claimed but how much is substantiated? In the following presentation I will review the literature to try to shed some light on the subject. Since the vast majority of journal articles are written by those with financial ties to the femtosecond companies, the authors of the journal articles will be color coded red for financial ties and green if not. (The lead author will be in red if at least one of the authors has financial ties.) It has automated, computer-guided laser precision with minimal collateral tissue damage......with emerging evidence of ......greater precision and accuracy of the anterior capsulotomy, and more stable and predictable positioning of the intraocular lens. 6. Company Mode of docking Imaging LensSx Alcon, Ca. Curved glass at first, now uses soft contact interface OCT LensAR Privately Held Orlando, Fl. 2 piece non contact interface Scheimpflug-like Catalys AMO, Ca. Liquid-optics interface OCT Victus B & L Curved glass interface OCT 7. Capsulorhexis Hypothesis: a capsulorhexis (rhexis) should overlap the IOL optic approximately .5 mm symmetrically 360 degrees and be larger than 4 mm . This will give a better and more consistent effective lens position (ELP) because of less asymmetric contractile force from the fibrosing anterior capsule on the IOL. The IOL should then not position more anteriorly or posteriorly than anticipated or with decentration or tilt. A better ELP leads to: 1. Closer to targeted spherical equivalent and less cylinder a. Better uncorrected distance vision (UCDVA) 2. Less higher order aberrations like spherical aberration and tilt a. Better corrected distance vision (CDVA) b. Better quality of vision with less glare, halos, and better contrast sensitivity. 1,2,3 8. Claim of the Femtolaser Companies: The femto anterior capsulotomy is more precise (consistent) and more accurate than a manual curvilinear capsulorhexis (CCC). Better size, more circular, better centered thus better overlap of the IOL. And better overlap yields less IOL decentration and tilt and better anterior-posterior position. 4,5 4 5 Assymetric Overlap Decentered IOLCCC vs. Femto Buttons Friedman; JCRS; 2011 Kranitz; JRS; 2011 9. Continuous curvilinear capsulorhexis (CCC) technique was developed simultaneously by Neuhann in Germany and Gimbel in Canada around 1987. 6,7 Prior rhexis techniques (eg. can opener) led to 100% anterior capsular tears during cataract surgery and CCC tear rate approached 0%. 8 Prior to CCC capsular tears led to IOLs with haptics commonly with one in the bag and one in the sulcus or with both in the sulcus. 10. Continuous Curvilinear Capsulotomy: A Revolutionary Change for IOL Positioning 9 Assia, Apple (Oph 1993) showed: Bag-Sulcus Fixation mean Decentration= .64 .39mm (range up to 1.76mm) Note: 1 SD =66.6% thus: 1.0mm decentration was common Bag-bag Fixation mean Decentration= .18 .09 11. IOL Mean dec. Mean tilt Akkin (1994) 0.15 1.1 Hayashi (1997) MZ60BD 0.27 .15 2.62 1.33 SI30NB .30 .16 2.53 1.36 MA60BM .30 .15 2.71 1.84 Mutlu (1998) 0.28 .14 2.83 .89 Kim (2001) MZ60BD 0.31 .15 2.67 .84 SI-30NB 0.32 .18 2.61 .83 AcrySof MA60BM 0.33 .19 2.69 .87 Taketani (2004) AcrySof MA30BA 0.30 .17 3.43 1.55 Baumeister (2005) CeeOn 911A 0.24 .13 3.03 1.79 PhacoFlex SI-40 0.23 .13 3.26 1.69 CeeOn 911A 0.29 .21 2.34 1.81 AcrySof MA60BM 0.24 .10 2.32 1.41 Mutlu (2005) AcrySof SA30AL 0.34 .08 2.70 .55 AcrySof MA30BA 0.39 .13 2.72 .84 Rosales (2006) UNKNOWN 0.25 .28 .87 2.16 de Castro UNKNOWN 0.34 .19 2.34 .97 Baumeister (2009) AR40C 0.19 .12 2.89 1.46 Z9000 0.27 .16 2.85 1.36 Hayashi (2014) H60M 0.25 .17 4.88 1.45 MA60BM 0.28 .16 4.85 1.52 10 Mean IOL decentration 0.28 .16 mm and tilt 2.61 1.2 Mean follow-up= 12.2 months Range= 3 to 48 months Clinical Studies in the CCC Era Measuring IOL Decentration and Tilt 12. How Much Does 0.28 .16mm Decentration and 2.6 1.2 Tilt Effect Vision? Let`s look at the Non-Femto Literature first. Would even less decentration and tilt provide better UCVA and CDVA? Would even less decentration and tilt provide better contrast sensitivity and less glare and halos? Would even less decentration and tilt have more or less effect depending on whether the IOL is spherical, negative aspheric, neutral aspheric, accommodating, multifocal? 13. Remember: Femto Companies Claim Better Rhexis Better ELP Better Vision Better Vision can mean both smaller refractive error and better quality of CDVA. Okada has shown that a better rhexis does NOT lead to a Smaller Refractive Error (spherical equivalent or cylinder.) Okada (Oph 2014) : Does the Rhexis Circularity or Centration effect Post-op Refractive Error? 93 eyes Phaco mostly by residents Pre-op spherical equivalent -7.75 to +4.50 Alcon Spherical IOL (SN60AT) Results for One Month and 1 year Measurements: Rhexis Circularity (comparison to perfect circle; ratio 1.0=perfect) Rhexis (not IOL) Decentration from pupil center Complete Overlap of Rhexis (360 over the IOL Optic) yes or no 11 14. 1 Month mean 1 Year mean from 1 month 1 year Circularity .83 .01 .87 .03 p < .001 Decentration (mm) .30 .14 .23 .13 p < .001 360 overlap (% of eyes) 88% 90% p = .02 Okada Results (Contd): (Stabilization Change from 1 Month to 1 Year) Over time the rhexis became more circular, less decentered and with more overlap. 15. Circularity of Rhexis NO significant correlation of circularity with post-op target spherical equivalent at 1 month or 1 year NO significant correlation of circularity with post-op cylinder at 1 month or 1 year Okada Results (Contd) 16. Decentration of Rhexis NO correlation with change in cylinder from 1 month to 1 year. It did correlate with the change in spherical equivalent between 1 month and 1 year (p=.03). But Bottom Line: NO significant correlation of Decentration with post-op target spherical equivalent at 1 month or 1 year. NO significant correlation of Decentration with post-op cylinder at 1 month or 1 year. Okada Results (Contd) 17. 360 Overlap vs. Incomplete Overlap NO correlation with change in spherical equivalent between 1 month and 1 year. It did correlate with change in cylinder between 1 month and 1 year. But Bottom Line: NO significant correlation of Overlap with post-op target spherical equivalent at 1 month and 1 year NO significant correlation of Overlap with post-op cylinder at 1 month and 1 year Okada Results (Contd) 18. Rhexis Centration and Circularity and Overlap do not correlate with Post-op Refractive error. Rhexis Centration and Overlap do play some role in stability of refraction but not enough to effect the average post-op refractive error at one year. Conclusion: 19. Effect of IOL Position on Quality of Vision Remember, Femto companies hypothesize: Better Overlap Better IOL Position Better Vision Okadas Study Showed: Better Overlap Does Not Better Refractive Error Question: Could Better Overlap Better Quality of Vision Lower order Aberrations: myopia, hyperopia, astigmatism Higher Order Aberrations (HOAs): coma, spherical aberration, trefoil, etc. can effect the quality of vision. These are measured with a wavefront analyzer. Decentration and Tilt may effect Aspheric IOLs more than spherical IOLs so we will spend some time reviewing this subject now. 20. Remember this: The larger the pupil the more HOAs there are. The pupil size increases in dim light and decreases with age. 55 years old (cataract age) pupil diameter: Bright mesopic= 3.2mm Mesopic= 4.0mm Low Mesopic= 5.0mm 12 Effect of IOL Position on Quality of Vision (Contd) 21. The First Negative Aspheric IOL was Tecnis (Pharmacia now AMO). Holladay and Piers did the early theoretical research for Pharmacia. Basic Idea: A. The amount of total eye spherical aberration could be manipulated with an IOL because spherical aberration unlike other HOA`s like coma and trefoil is not very sensitive to the position of the IOL (rotation, decentration and tilt). However decentration and tilt could still possibly effect the results. B. The cornea has positive asphericity and this is stable despite aging. It is approximately +.27. The lens has negative asphericity to balance the cornea so the total eye spherical aberration is minimized. The lens becomes more positively aspheric after age 40 causing more total eye positive asphericity. 41 y.o. 6.0mm pupil mean s.a.=.10 65 y.o. 6.0 pupil mean s.a=.19 13 Effect of IOL Position on Quality of Vision (Contd) Aspheric IOLs 22. A spherical IOL has positive asphericity which increases the spherical aberration of the eye. Pharmacia developed a -.27 negative aspheric IOL (Tecnis) to eliminate total eye spherical aberration and thereby improve the quality of vision eg., contrast sensitivity. Tilt and decentration can induce HOA`s but much more in a negative aspheric IOL than a spherical IOL. Question: Would tilt and decentration be a problem with negative aspheric IOL`s? 23. Holladay and Piers (JRS 2002) They calculated the Modular Transfer Function (MTF) at different amounts of tilt and decentration. MTF is a mathematical/theoretical calculation of contrast (the contrast of an image relative to the contrast of the object traveling through an optical medium). This relates to quality of vision. Amount of tilt and decentration of Tecnis where the MTF (quality of vision) becomes worse than a spherical IOL: Decentration= 4mm Tilt= 7 Holladay used monochromatic light for his calculations. In 2007 Piers corrected the calculations based on the more physiologic polychromatic light we experience: 14 Decentration= .8mm Compare to 0.28 .16mm actual mean decentration of IOLs with a CCC Tilt= 10 Compare to 2.6 1.2 actual mean tilt of IOLs with a CCC 15 24. 16 Ignore top dotted line (theoretical IOL with all HOAs corrected) Solid line= Tecnis Dashed line= Spherical IOL l a w l e s s l a w l e s s Decentration Tilt PolychromaticMTF PolychromaticMTF .28 .44 2.6 3.8 Decentration .28 .16 .44mm Note: Minimal effect on MTF for most patients. 0.8 Tilt 2.6 1.2 3.8 Note: Tilt effects MTF even less than decentration. 10 Piers Graph 25. 1. Spherical aberration was less with Tecnis at all pupil sizes (the bigger the pupil the larger the difference). 2. Total HOA`s were lower with Tecnis only if pupil 6.0 mm (most cataract patients pupils are smaller) and coma and trefoil were no different at all pupil sizes. 3. Even though spherical aberration was less, Tecnis gave no improvement in CDVA photopic with high contrast charts or mesopic low contrast charts. 4. Tecnis gave no improvement in Contrast Sensitivity photopic or mesopic. Kohnen`s team in Germany 17,18,19 A series of intraindividual studies (same patient with one eye spherical IOL and other eye Tecnis). Aspheric IOL Clinical Studies 26. 5. Were these less than expected results with Tecnis due to tilt and decentration? a) The Kohnen group measured it: Tecnis: decentration= 0.27 .16mm (as expected from other studies) tilt= 2.9 1.5 (as expected from other studies) (Decentration and Tilt of Spherical IOLs studied were almost exactly the same.) b) Multiple Regression Analysis showed no statistically significant correlation between decentration or tilt with the HOAs. ie, Decentration and Tilt were not the reason why Tecnis performed worse than expected. c) This is consistent with the Piers graphs: Decentration and Tilt with a CCC are too small to significantly effect HOAs even with negative aspheric IOLs. Kohnen (Contd) 27. So why didnt Tecnis eyes see better? They had significantly less spherical aberration and we know decentration and tilt were too small to effect that impact. Puzzling. Possible explanations: a) Pupil size: average pupil in the study in mesopic conditions was 3.8mm. Negative spherical correcting IOLs have a much larger effect in pupils 6.0mm. b) Interactions with other HOAs. It is not just spherical aberration we are dealing with. Some HOAs may interact with others in a negative or positive way. Take home message: Factors effecting quality of vision are complex. (Marketing companies may use that to their advantage.) Negative aspheric IOLs are not significantly effected by decentration and tilt for most patients. 20 28. Neutral Aspheric IOL Studies Developed Several Years Later Concept 1. Do not add or subtract from the total eye spherical aberration. 2. Neutral aspheric IOLs may not actually decrease the total eye spherical aberration but they are less effected by decentration and tilt than negative spherical IOLs. 29. Model Eye Study calculation of MTF with Decentration; comparing Aspheric, Neutral Aspheric, & Spherical IOLs. Two pupil sizes and three types of IOLs. Verticle lines = .3 and .4mm decentration from the literature. (Mean and with one standard deviation.) Monochromatic light (Holladay) was used. Slope should be less narrow as per Piers/ Polychromatic light. Decentration has no effect on neutral aspheric and spherical IOL.. Tecnis is more beneficial in larger pupil. 21 Modulation Tecnis Negative Aspheric Modulation Soft Port Neutral Apheric Modulation Spheric .4.4.4 .4 Eppig (JCRS 2009) 21 ModulationModulationModulation 30. Tilt has minimal effect on Tecnis even with monochromatic MTF calculations. 22 31. Swedish Multicenter Double masked study of 80 patients with Tecnis in one eye and Neutral aspheric Akreos in the other. Results (3 months post-op): Total HOA`s less for Tecnis for 4, 5 and 6mm pupils (p