New Theory and Efficacy of Corneal Cross Linking ____________________________ J.T. Lin, Ph.D New Vision, Inc. Taiwan 3ya-2013

Summary Historical of CXL Debating issues (safety, Dresden protocol) Dynamic of CXL Kinetic of type-I & type-II (role of oxygen) 5.Minimum corneal thickness 6. Efficacy & optimal protocols * References: (papers by JT Lin): Cornea(8, 2017) PlosOne (7, 2017) Ophthalmology Res (7,2017) IOVS (4,2016); JRS (8,2016) IJO (10,2015).

CXL Milestones (1) Biomechanical studies on KC patient 1980 Biomechanical studies on KC patient 1998 Seiler , University hospital Dresden.and Spoerl starts research on biomechanics of eye tunic. 1994 Improved corneal stability 1995 Evidence of crosslink effect 1996 First experimental result 1997 Therapy test in rabbit First patient treated 1999 enzymatic resistance after CXL

CXL Milestones (2) 2000 First UV LED (370nm) device in market 2002 Study toxic threshold of EC and KC cells 2003 First clinical study published (wollensak et al) First report about epi-on CXL (Pinelli et al) 2006 Stromal demarcation line (Seiler) 2007 Calculation of diffusion of riboflavin (Spoerl) 2008 CXL by confocal laser scanning microscopy (Mazzotta) CXL in endothelial decomp, bullous keratopathy (Ehlers) PACK-CXL (Iseli) First clinical trial in Australia (Wittig-Silva) 2009 Hypoosmolar riboflavin solution for thin corneas(Hafezi) Topography guided PRK and CXL (Kanellopoulous) 2010 Investigation of the riboflavin film (Wollensak) Systemic treatment of keratitis (Makdourni)

CXL Milestones (3) 2011 Iontophoresis for riboflavin application (Vinciguerra) 2012 Acce2018lerated CXL AVEDRO (Celik) 2013 Kinetic model of CXL (oxygen dependent) (Richoz), 2014 Antibacterial efficacy of PACK-CXL (Hafezi) First dynamic model for ribo depletion (Lin) 2015 Laser scan device for focal cross-linking, First CXL UV-pen device (New vision Inc, patented, Lin) High power (18, 45 mW) CXL devices (Mlase, Avedro) 2016 First dynamic theory for CXL type-I efficacy profiles and new criterion for CXL safety (Lin), FDA approval for Avedro KXL (3 mW). Also CFDA approval. 2017 Kinetic model for type-II CXL (Kling & Hafezi). Kinetic model for combined Type-I and –II (Lin) Optimal efficacy and New Protocols (Ln) First animal study for thin and thick corneas (Kling, Hafezi)

Debating issues of CXL: Safety criterion [5.4 J/cm^2, 400 um thickness] (2) Thin corneas (<350 um, safe ?) (4) Dresden (2003) protocol (too much RF drops during CXL) Effective dose (with rib films) (5) Accelerated CXL validation of BR law? (6) Optimal protocol. (fast and efficient)

UV light New dynamic mechanism Experiment setup Power meter B2 solution (0.005%) 10 mm

Measured data * Transmitted light intensity Time (min.) More UV light transmission for t>0 Dynamic spectra of B2 Transmitted light intensity Time (min.) * JT Lin (published in IJLREC, 2013)

Dynamic intensity A(t) = 2.3[ (a-b)C(t) + bCoF +Q] Our new finding (Lin, pub. IBME, 2013) I = Io exp (-Az) A(t) = 2.3[ (a-b)C(t) + bCoF +Q] diffusion F(z)=1-o.5z/D conventional For t=0 only, A=52( 1/cm) for Co=0.1 % A=79 to 41, mean 61 (if F=1) F<1, z=200 um, A = 67 to 43.5 , mean 54 z=400 um, A = 55.5 to 37.8, mean 47 Smaller A, higher Intensity.

Dynamic of Riboflavin concentration (depletion for t >0) Initial (t=0) RF depletion starts from surface (z=0). Time (0 to 120 seconds) Initial (t

CXL Theories developed Conventional theory Schumacher, (2012) Mrochen, Seiler et al (JOVS, 35:726,2012) Assumptions: linear theory, simplified constant concentration (C) Errors: overestimates effective dose (4.0 J/) E* = 5.4J/cm^2 Z*= 400 um (cornea thickness) FIXED parameters Modern theory J.T. Lin (2015) (JRS/2015, JOVS/2016) Nonlinear, dynamic theory of C (z,t) Safety critera [C, D, E’, z] E* = (2.5 – 10.5) J Z* = (200 – 450) um C = 0.1 – 0.3%

CXL safety formulas (Lin, 2016) Safety dose E*=Ed exp(A’z) Ed: endo cell damage threshold (at z=400 um) (2) Minimum Corneal thickness z* = (1/A) ln (E*/Ed) (3) Safety Concentration Co = ln (E*/Ed)/ (2.3mbGz) For Co = 0.1, 0.2, , 0.5% (curves 1, 2 ..5)

kinetic of CXL type-I & Type-II Oxygen is required for type-II, but not absolutely needed in type-I .

kinetic of CXL type-I & Type-II Oxygen is required for type-II, but not absolutely needed in type-I .

CXL Efficacy type-I & Type-II* S1 = sqr [ Co/aI] exp (Az) type-II S2 = (1-b/[O]) Co [ 1 – exp (-apE)] Same dose, s.s. High Intensity, low type-I, Efficacy Faster Oxygen depletion, but same tpe-II efficacy as low intensity. [Q2] profile on surface (z=0) & at z=100 um. For I = 3,9,10, 30,45 mW

Corsslink efficacy (type-I) S = sqr [ (4KCo)/(aI)] exp (Az) Inverse proportional to the UV light intensity (I) proportional to RF Co, and depth (z)

How to optimize CXL , fast and efficient ? High power, faster procedure (small T* ) but higher risk (2) High concentration, deeper CXL depth (3) Longer illumination time, deeper CXL, (4) Higher intensity, faster depletion, but lower efficacy. How to optimize CXL , fast and efficient ? OPTIMAL parameters: 30 mW, 20 sec, 0.1%,

multi-step-method (MSM) Super-position of Efficacy profiles. Depth (z) Define: THE ISSUES: DropF= Frequency of RF drops (during UV exposure) Dresden Proto: DropF = 10 to 15 (too much reduction), Effective dose = 5.4 x0.8= 4. 3 J (b) Modern proto: DropF = 0, low efficacy in high intensity multi-step-method (MSM) Super-position of Efficacy profiles. Eff = 1 –exp [- (S1+ S2 +S3)] Depth (z)

Proposed Optimal CXL Lin-code 3-24 (8,8,8) 9 - 8 (2.5, 2.5, 3.0) multi-step-method (MSM) Hgh effective dose, Fast procedure, High efficacy Lin-code DropF=2, effective dose =4.3 J (or 5.4x0.8) (a) I = 3.0 (mW/cm^2) 3-24 (8,8,8) 0 8 16 24 min. 9 - 8 (2.5, 2.5, 3.0) 18 - 4 (1.3, 1.3, 1.4) 30 – 2.4 (0.8, 0.8, 0.8 Each drop waiting for 1 min. allowing enough diffusion depth.

The new trends Combined techniques: sequential or simultaneous CXL + PRK (2009, same day is better than following day ..) CXL+ LASIK (2011, 2013, more stable, less aberrations) CXL+ femtosecond-flap (less regression, prevent corneal ectasia) CXL+ ICR CXL + CK (3 months, still have regression) CXL+ phakic IOL CXL+ OK (more stable, long term) CXL (on cornea) to correct low myopia; change of corneal front curvature (due to thickness deceasing, K value, K=377/r, drops, r increases) CXL (on sclera) to stop abnormal axial length growth. CXL+ RGP/OK lens CXL (on trabecular meshwork, cell pores 3 x increase, glaucoma, Shang-dong U. Ref: X. Fan. International J ophthalmology 2014,7:157-162

CXL-pen (Lin, patented, 2014) High-power (30-50 mW) Spot size: 4 to 12 mm Scanning mode for customized CXL KC and PACK

IONTOFOR RF device for epi-on enhance PACK-CXL applying an electrical current to increase its mobility across a surface. procedure by reducing the soaking phase from 30 minutes to 5 min. No epithelium removal is needed. 電流刺激儀(法國製造)，增強核黃素在角膜內的滲透深度。 同時也能縮短術前等候時間從30分鐘到5分鐘，特別是應用於epi-on的情況 22