Femtosecond Laser Assisted Deep Anterior Lamellar Keratoplasty (FS-DALK)

1. Femtosecond Laser AssistedDeep Anterior Lamellar Keratoplasty(FS-DALK) FaridKarimian M.D. Department of Ophthalmology Labbafinejad Medical Center October 2012 www.iranophthalex.com

2. Overview • DALK replaces anterior Corneal stromal Lamella • Directly placed same thickness donor over Pre-Descemet and Endothelium • Rational for DALK: • Reduced risk of intraoperative complications • Preserving recipient (Host) endothelium • Transplantation of Epithelium and Stroma (only) • Potentially clear interface with reducing Haze • Reducing risk of immunologic Rejection • Limitations of “Anwar Big-Bubble” Technique: • Steep learning Curve • Prolonged operation time ( in the beginning ) • Risk of intraoperative corneal perforation

3. Indications • FS-DALK indications similar to Manual DALK • Optical and Tectonic indications: • Pathologies involving anterior and deep corneal stroma in presence of Healthy Endothelium • Reis-Buckler of Bowman’s layer • Stromal dystrophies not-involving Endothelium • Ectatic corneal disorders and Keratoconus • Post-Refractive Surgery Keratectasia

4. Femtosecond Laser • FS-Laser Abilities; • Performs precise, pre-programmed Corneal incision • Accurate “shape” and “Depth” • Customized graft edges and lamella • Stepped incisions increase surface area: improve apposition and alignment leading to faster wound healing • Overall it is a “Laser knife”

5. Surgical Technique • Anesthesia: • Anterior LK: Topical • DALK: General or Local • FS-Laser Type: • All types of New Generation machines • Same laser parameters for both Donor and Recipient • Donor Cornea Preparation: • Preserved Corneoscleral donor over Artificial chamber • Well pressurized whole globe

6. Different Side-Cuts and Configurations • Zigzag shape • Mushroom shape: Larger outer diameter Lower astigmatism • Top-hat: Best wound stability • Christmas tree shape • Traditional • Decagonal : More precise depth, No torque rotation Better suture placement

7. Recipient Preparation- Step 1 • Recipient is prepared first • Central cornea marking • Side cut formation: Zigzag configuration • 3 consecutive steps: • Step 1: • Anterior side cut: 30 deg. Angled, 25 deg. Arc length and 6.0 mm diameter • Depth: 50 µ above thinnest point Pachymetry (According to Scheimpflug imaging) • Energy: Maximum of energy minus 0.2 µJ • Side-cut spot separation: 3 µm • Side-cut layer separation: 3µm • Depth in contact Glass: -200µm

8. Step 2 • Recipient lamellar cut • Diameter: 9.5 mm • Depth in Cornea: 100µm above the thinnest corneal pachy point • Lamellar cut intersects with (previous) channel created • Diameter : anterior< posterior zigzag lamella • 100µm

9. Step 3 • Side-cut Zigzag lamella: • Diameters: anterior: 8.1mm, Posterior: 9.0mm • Target thickness: 100µm above thinnest corneal pachy • Two constant values: 80µ ( stromal Thickness over DM ) + • 20µ ( DM and Endothelium complex ) • = 100µ( total stromal endothelial bed )

10. Donor Disc Preparation • Postoperative increase of 120 µ is routinely planned • T-factor = 20µ ( DM and Endothelial thickness complex)+ intended increase calculated to achieve an appropriate postoppachymetry ~ 140µ • Donor Depth: Recipient lamellar cut depth + T-factor • Laser Energy: 1.8 µJ • Tangential spot separation: 5µm • Radial spot separation: 5µm • Again Zigzag lamella is prepared in Donor cornea

11. Air Bubble formation • Recipient Lamella removal • Air injection: • Air injection cannula • Fogla cannula ( B&L ) is flat needle with hole facing down at tip site • Route of injection: previous created channel • Channel may need dissection in thin keratoconic cornea • Air injection: forceful to achieve big bubble over DM • Procedure continues as Classic Big bubble technique

12. Advantages of FS-DALK • Precision of Depth • Configuration and customization of side-cuts • Stronger wound strength and more stable • Higher success for bubble formation ( 85% vs 65% ) • Earlier wound stabilization: Earlier suture removal • Reduction of surgeon learning curve

13. Advantages of FS-DALK 7- Easier air injection in deep stroma ( 50 µ over DM ): more smooth injection 8 - Faster visual recovery and less induced astigmatism

14. Disadvantages of FS-DALK • High Expenses and instrument costs • Space and facilities: needs 2 suite • FS-Machine dependent • Higher quality of Donor • Donor lamella preparation: More Difficult • More dependent on precise Pachymetry

15. Complications of FS-DALK • Incomplete Lamellar Preparation: • Donor Lamella: Corneal edema, haziness, Corneal arcus • Recipient Lamella: Scar, opacities/ improper laser setting for deep cornea • Inadvertent AC Penetration: Errors in Pachymetry • Conversion to PKP: Due to DM rupture • Other complications similar to Manual DALK

16. Summary • FS-DALK is a new technique of Keratoplasty which applies the Precision and advantages of Femtosecond Laser to achieve higher success and better results with lower risks in performing DALK • At present time high expenses and lower accessibility of Femtosecond machine limits its widespread application THANK YOU FOR YOUR KIND ATTENTION