Peripheral optimized CXL and high power Theo Seiler

Peripheral optimized CXL and high power Theo Seiler Institut für Refraktive und Ophthalmo-Chirurgie (IROC ) and University of Zürich Seite 1

PMD thinnest point steepest point Seite 2

PMD vs KC PMD thinnest pachymetry / μm KC 700 500 300 Seite 3 0 0. 5 1 radial distance to apex / mm 2

PMD Seite 4

PMD Seite 5

CXL In the majority of the keratectasia cases the weakest point of the cornea that needs CXL most is 1 to 3 mm away from the center Seite 6

study OCT 1 month post CXL, 10 eyes, inhomogeneity of the beam in curve th 1 relative depth in % 100 90 th 80 th 1 70 mav 60 50 0 Seite 7 0 1 2 radial distance / mm 3

proposal In order to create a homogeneous CXL-effect also in the periphery of the cornea irradiation with a top hat-profile is not good enough. 3 mm away from the center the light intensity needs to be increased by at least 25% Seite 8

profile UV-X 2000 Avedro I 0 UV-X 1000 8 mm Seite 9 4 mm 0 4 mm 8 mm

profile Crosslinking profile of the UV-X 2000 Seite 10

CXL-types volume-type 0μm 30 min 3. 00 m. W/cm² surface-type 9 min 10. 00 m. W/cm² 100μm 200μm 300μm 400μm 500μm 600μm Seite 11 0. 1% 0. 5% 30 min 2 min

CXL-types Pseudo-Bowmans Seite 12

CXL-types Seite 13

CXL-types volume-type CXL-depth 250 to 330 μm Seite 14

CXL-types Applications volume-type (homogeneous riboflavin, low power) • infectious keratitis • melting diseases • keratoconus ? Applications surface-type riboflavin gradient, high power) • refractive laser surgery • customized CXL Seite 15 (high

conclusion 1. In the majority of the cases a peripheral CXL is mandatory 2. Second generation CXL lightsources need an optimized beam profile 3. The surface-type CXL works only if the central irradiance guarantees an illumination time of 10 min and less Seite 16