سبحانك ال علم لنا إال ما علمتنا إنك أنت العليم الحكيم

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1 سبحانك ال علم لنا إال ما علمتنا إنك أنت العليم الحكيم Corneal Collagen Cross linking ( CCXL) Myth, Realty and Future Refractive Applications ESOIRS 2015 Rifaii Lecture Osama Ibrahim M.D. Professor of Ophthalmology Alexandria University Egypt Avedro Ambassador 1

2 UV-X TM illumination Koehler s beam path E. Spoerl, TU Dresden Radiant exposure at the cornea after 30 min: E ~ 5.4 J/cm 2 Experimental setup for measuring radiant exposure to UV light at the retina. N N' Radiant exposure at the retina after 30 min.: F ~ J/cm 2 Mrochen, 2005 Origins of the 400um Limit Spoerl et al calculated a minimum thickness of 400um ( 2x endothelial safety limit) through the application of the Lambert-Beer Law to the following protocol for CXL: Epithelial removal over central 9mm 30 minutes soaking with 0.1% riboflavin in 20% Dextran 3mW/cm 2 continuous irradiance for 30 minutes Reapplication of riboflavin at 5 minute intervals during irradiation This calculation relies upon: Spoerl, E., Mrochen, M., Sliney, D., Trokel, S., & Seiler, T. (2007). Safety of UVA-riboflavin cross-linking of the cornea. Cornea, 26(4), The applicability of the Lambert-Beer Law 2. The measured absorption coefficient of riboflavin 3. The measured damage threshold at the endothelium 4. The exact details of the cross-linking protocol 4 2

3 Riboflavin shielding Thickness of normal human cornea Prof. Dr. Michael Mrochen, The CXL-effect is deepest in the center and reduced in the periphery (UV-X1000) Corneal cross linking depth ~ 300 microns Leave a safety margin from the endothelium um 50 microns Consider an epithelium thickness of 50 microns = 400 microns for a minimum corneal thickness 3

4 Basic Science: Endothelial Cells Cytotoxicity Study New Work o Tests to be performed under GLP conditions o Cell viability via MTT assay measured 48 hours post treatment. o Cells used are both from an immortal line and primarily cultured cells: o COMSOL Model Assumptions: HCEC-B4G12 Human corneal endothelial cell line (DSMZ, Germany) 20 min pre soak with fast diffusion (6.5 x 10-7 cm 2 /s) 450 µm cornea, 400 µm stroma, 3 mm aqueous humor Rinse before UVA Boettner values for corneal UVA absorption 5% off at surface for Fresnel reflections 12 min UVA at 10 mw/cm 2 ( 7.2J/cm 2 ) Riboflavin Concentration to be used in study: 0.01% 0.02% 0.04% O2 Concentration 10% 21% UVA Irradiance to be used: 3 mw/cm 2 30 mw/cm 2 ( x 10) Results from model at 400 um (stroma) CONC [%, w/v] UVA [mw/cm 2 ] 0.125% % % /27/2014 Oxygen Availability During Cross-linking Role of oxygen in photochemical kinetics of corneal crosslinking, it is important to consider the maximum concentration of oxygen at the endothelium In previous CXL cytotoxicity studies, testing was performed in room air (20% oxygen), while the physiological concentration of oxygen at the endothelium (concentration in the aqueous) is 10%. Actual availabilty of oxygen during CXL may be even less, due to depletion of oxygen by the kinetics of the CXL reaction. Depletion and gradual replenishment of dissolved oxygen below a 100 µm thick corneal flap, saturated with 0.1% RF during 3 mw/cm2 UVA irradiation at 25 C, demonstrating the distribution of predominant reaction types during light exposure. Kamaev P, Friedman MD, 8 Sherr E, Muller D. Photochemical Kinetics of Corneal Cross-Linking with Riboflavin. Investigative Ophthalmology & Visual Science. 2012;53(4):

5 Conclusions There is a 3X factor of endothelial cytotoxic dose between low and high irradiance (10X) Riboflavin concentration is not a factor Endothelial cell cytotoxicity is mediated by rate of available oxygen at endothelium to generate a sufficient concentration of reactive oxygen species (ROS). Therefore in oxygen - limited endothelial environment, higher irradiances will require higher doses to achieve the same concentrations of ROS. Dec 7th 2013 Conclusions Higher doses at higher irradiances and treatment of thinner corneas may be safely optimized by understanding the rate of oxygen consumption and replenishment as a function of depth. Future studies to include different combinations of parameters: irradiance, oxygen concentration, riboflavin concentration, etc. Dec 7th

6 Uniformity is Key to Consistent Cross-linking 3 mw/cm 2 typical UVA light in current use 30 mw/cm 2 KXL System 9 mm Aperture Bowman s Cool edges provide no cross-linking Endothelium Center to edge beam uniformity insures consistent results The VibeX / KXL System is not approved for sale in the United States MA-00057, Rev. A The CXL-effect is deepest in the center and reduced in the periphery (UV-X1000) Only because of the light profile.? 6

7 The CXL-effect is deepest in the center and reduced in the periphery also observed after (KXL I treatments) Cornea November 2014 Optical l. Coherence Tomography and Confocal Microscopy Following Three Different Protocols of Corneal Collagen-Crosslinking in Keratoconus optimized profile UV-X2000 I 0 UV-X1000 8mm 4mm 0 4mm 8mm 7

8 Very similar demarcation lines due to eye motion Mean eyes motions are compensated due to the donut beam profile June 22, Avedro. Contents are proprietary & confidential. 15 New requirements for CXL Allow device to compensate for the eye motion by eye-tracking Allow individulized light profiles to controll the cross linking depth Allow higher energy dose for increase cross linking Integrate corneal tomography for treatment planning June 22, Avedro. Contents are proprietary & confidential. 16 8

9 Pig eyes: deswell the cornea with dextrane Pre-clinical Rabbit eye Do not change formulation Isotonic Ribo HPMC LASIK Xtra Initial clinical Do not change formulation Trans-EPI Avedro s Family of Riboflavin Formulations Name Formulation Procedure Application 0.1% Riboflavin 20% Dextran Cross-Linking for Keratoconus & Post-Lasik Ectasia Epi-Off 0.1% Riboflavin HPMC Cross-Linking for Keratoconus & Post-Lasik Ectasia Epi-Off 0.22% Riboflavin HPMC, BAC EDTA, TRIS Cross-Linking for Keratoconus & Post-Lasik Ectasia Epi-On 0.22% Riboflavin Saline Lasik Xtra for Corneal Strengthening During Lasik Stromal Bed 9

10 Goal Solution 6/22/2015 Cross-linking in Refractive Correction Stabilize the Cornea Restore baseline Strength Prevent Refractive Regression Protect against Ectasia Reshape the Cornea Maintain or improve baseline strength Reduce refractive error Improve corneal shape Lasik Xtra Evenly cross-link the central 9mm of the cornea to stabilize without inducing additional shape change PiXL Differentially cross-link specific zones of the cornea to redistribute stress and alter corneal shape Application of Cross-Linking for Specific Goals: Lasik Xtra Primary Goal: Stabilize the cornea to reduce the risk of refractive drift and ectasia Requirements: 1. Restore corneal strength to its pre- LASIK state 2. Maintain the accuracy and predictability of LASIK 3. Do not disrupt LASIK surgical flow 10

11 Lasik Xtra Lasik Xtra: Restoring corneal strength Creation of the LASIK flap weakens the cornea by as much as 30%. Lasik Xtra treatment protocols are designed to apply sufficient stiffening to restore the cornea to its pre-lasik level of stiffness, without excessive change 11

12 Lasik Xtra: Maintaining Predictability Pan-corneal treatment KXL system with homogenous beam profile and large depth of focus is used to cross-link the entire central 9mm of the cornea Uniform treatment across the large treatment zone restores stability without redistributing corneal stresses (no shape change) This differs from treatment of keratoconus, where the cornea has a focal region of weakness Center to edge beam uniformity insures consistent results Lasik Xtra: Maintaining Clinical Flow Accelerated technique Direct application of dextran-free riboflavin to stromal bed to reduce soak time Riboflavin applied immediately after ablation to avoid extra flap handling Avoiding excessive riboflavin in the flap reduces shielding to maintain lower total UVA dose requirement High irradiance accelerated protocol to reduce UVA treatment time 12

13 Modifying Cross-Linking for Specific Goals: PiXL Primary Goal: Correct refractive error using crosslinking alone to reduce or eliminate risks associated with conventional refractive surgery Requirements: 1. Induce predictable refractive change of clinically significant magnitude 2. Have the ability to be customized for specific patient characteristics or treatment goals 3. Achieve outcomes that are stable for a sufficent duration Requirements for true refractive correction with PiXL Sharply defined edges Eye Tracking Complex patterning Digitial Micromirror Device (DMD) More stiffening than standard technology Pulsed Illumination Higher Energy Doses 13

14 Mosaic/KXL II System A.Main Console with USB flash drive and treatment activation slot B.System Keyboard C.System Body with lift system D.Articulating Arm E.Heads Up Display F.Optical Head G.Wheels A B C D G F E 14

15 768 Rows Relative Irradiance 6/22/2015 Mosaic Software Controlled UV Projection using DMD 1024 Mirrors Customizable UVA pattern 1024 x 768 DMD Array Individually controlled mirrors 1.2 Individually controlled mirrors (8 bit modulation possible) System maintains 60 Hz update frequency to DMD Three-axis motion control +/- 10 mm in each axis Treatment range: 15.5 mm + 20 mm of motor motion Beam Uniformity: < 2% Distance [mm] Beam Profile and Treatment Range (D ~= 15.5mm) 2015 Avedro. 15

16 Frequency 6/22/2015 Mosaic Eye Tracking Positioning Frame rate pupil tracking Average eye tracking response time: 7.4 ms Focus assessment Automated assessment of focus Intensity gradients at pupil boundary Average time between DMD updates: 16.6 ms Time between DMD Updates [ms] Used during fully automated Z alignment Standard deviation ~200 um Avedro. Mosaic Precise application of UVA Best focus following automated Z alignment 20%-80% transition width: 100 um Step edge projection+ following Z alignment 3D profile fit across edge After simulated eye motion* 20%-80% transition width: 210 um Simulated eye motion blur* + UV projection measured with beam gauge 3D profile fit across edge * Assumes standard deviation of 100 um eye motion in a worst case instruction lag of 100 ms Avedro. 16

17 Difference between Rotation Angle Results 6/22/2015 Mosaic Iris Registration Pupil and Limbus segmentations: Pentacam (left) Mosaic (right) Iris texture matched in polar unwrapped reference frame Inter - observer Algorithm vs GT Mean Inter Observer Cyclotorsional image alignment using Iris Registration technique Average difference (Algorithm Mean of observers): 0.23 degrees (95% CI 0.9 to 1.2 degrees) 2015 Avedro Mean Rotation Angle Bland/Altman Analysis Upper Bound Inter Observer Lower Bound Inter Observer Mean Algorithm /GT Upper Bound Algorithi m/gt Iris Rotational Alignment Iris image is unwrapped for polar coordinate representation Pupil and Limbus segmentation on Mosaic display, represented by the red and green circles. Binary texture representation of the polar coordinate image 17

18 Customized Treatment Design Corneal Tomography Biomechanical Properties Customized Treatment Plan PIXL: Photorefractive Intrastromal Cross-linking Riboflavin is applied to the corneal surface The patient is positioned under the Mosaic KXL II device, and an iris tracker precisely aligns the device with the patient s eye A customized UVA treatment pattern is applied 18

19 Customization of treatment PiXL for Keratoconus 15 J/cm 2 10 J/cm J/cm 2 3 Month Post-OP Pre-OP Difference Professor Anders Behndig 19

20 Redistribution of Corneal Stress UVA applied Center (myopia), the Midperiphery (hyperopia),or Bowtie (astigmatism) Riboflavin-soaked cornea Focal stiffening cross-linked regions Bulging untreated regions (response to normal intraocular pressure) MYOPIA: CENTRAL SPOT HYPEROPIA: ANNULUS Images Adapted From: Professor John Marshall, MBE, PhD Clinical Measurement Of Corneal Biomechanics Goal: Develop a technique to directly map corneal stiffness properties in a clinical setting Potential Applications: Measure Effect of Cross Linking Early Diagnosis of Ectasia Pre-Op Screening of Refractive Patients Assessment of other tissues PiXL treatment planning using individual biomechanical properties What is the elastic modulus of this area? 20

21 Current clinical techniques for measuring biomechanics Air puff tonometry Optical coherence elastography Dynamic ultra high speed Scheimpflug imaging Dynamic OCT imaging Quantitative ultrasound spectroscopy Disadvantage: All require applying a mechanical force to achieve measurement 41 Brillouin Scattering Spectroscopy Brillouin scattering is created by the interaction between photons and acoustic phonons in a material Phonons: quantum of the vibration of the crystalline lattice of the material The photon may lose energy (Stokes process) or gain energy (anti-stokes process) from this interaction 21

22 Brillouin Scattering Spectroscopy The change in energy of the photon from the interaction with the crystalline lattice of the material corresponds to a shift in frequency in the Brillouin spectrum. M = ρλ 2 Ω 2 /4n 2 This shift is related to the elastic modulus (M ) of the material where, ρ = mass density, λ = wavelength, n= the refractive index. M = E (1- σ)/(1+σ)(1-2σ) Elastic modulus (M ) is related to Young s modulus Randall J, Vaughan JM. Proc R Soc Lond B Biol Sci. 1982;214: Scarcelli G, Kim P, Yun SH. Biophys J. 2011;101: Scarcelli G, Kling S, Quijano E, Pineda R, Marcos S,and Yun SH. Invest Ophthalmol Vis Sci. 2013;54: ) Avedro Benchtop Brillouin-Scattering System EMCCD camera 780-nm band filter Alignment laser - fixation marker nm ~35 mw Fourier lens FiberDock 1 P-M M-VIPA Achromatic lens Spectrograph SpF Second OB Dichroic Mirror Future LED SMF FiberDock 2 RB D2 cell 780-nm ASE cleanup filter <25 mw limit 30 mw RB absorption cell SpF First OB /4 Object stage Alignment mirror 1 Future Dichroic Alignment mirror 2 Future fiber movingplatform connector PBS Future Telescope Alignment via QWP reflection SMF /4 outer surface is the alignment 0.25%R 22

23 System Sensitivity a) 1 sec exposure with new optical system b) c) Fig. 5. Spectral orders 1, 2, m of Brillouin and Rayleigh scattering lines at 1-second exposure: a) water; b) methanol; c) PMMA; A1/S1 anti-stokes/stokes Brillouin scattering components of 1 st order; R1 Rayleigh scattering, 1 st order. 10- s exposure: A1 R1 S1 A2 R2 S2 a) 10 microsecond exposure with new optical system b) c) Fig. 6. Spectrums of Brillouin and Rayleigh scattering lines of Fig. 5 recorded at 10-microsecond single-pixel exposure. 45 Avedro Laboratory Data, 1/2015 Brillouin Spectroscopy in Cross-Linking Scarcelli et al measured differences in treated and untreated porcine corneas that are in agreement with Avedro laboratory findings for the same dose They also demonstrated that Brillouin Spectroscopy could show effect as a function of depth, and was sensitive enough to detect differences between cross-linking protocols 5.4 J/cm 2 Scarcelli G, Kling S, Quijano E, Pineda R, Marcos S,and Yun SH. Invest Ophthalmol Vis Sci. 2013;54: ) 46 23

24 Brillouin Spectra of Live Human Eye Without Contact Lens With Contact Lens 47 Distance does not change (Brillouin Frequency Shift) Frequency is relatively constant in stroma as subject moves in and out Distance changes (Brillouin Frequency Shift) Frequency changes between Contact lens and stroma as subject moves in and out Brillouin Spectroscopy: Clinical System in Development Potential Applications: Measure Effect of Cross Linking Early Diagnosis of Ectasia Pre-Op Screening of Refractive Patients Assessment of other tissues PiXL treatment planning using individual biomechanical properties Future Applications: More Accurate IOP Measurement Assessment of Other Tissues Lens, Lamina, Retina? 48 24

25 Biomechanical Customization of PiXL Treatment Design Corneal Tomography Biomechanical Properties Customized PiXL Treatment Plan PiXL for Post-Cataract Myopia Case Example 52 year old Female Pseudophakia OD Refraction OD: x 180 BCVA 20/20, UCVA 20/200 25

26 PiXL For Post-Cataract Myopia Case Example: 9 Month Post-op 9 Months Pre-OP sphere UCVA: 20/25 BCVA: 20/20 Case from: Dr. Pavel Stodulka PiXL The Future of Refractive Correction Post- IOL tune-ups Post- refractive surgery enhancements ( SMILE) Low myopia All patients with keratoconus.. and this is just the beginning. 26

27 Thank you Osama Ibrahim 27