Laser Assisted Procedures in Penetrating Keratoplasty
Condition: Keratoconus; Corneal Dystrophies; Corneal Opacity
MeSH terms: Keratoconus; Corneal Dystrophies, Hereditary; Corneal Opacity
Study type: Interventional

Summary: 
      Laser- assisted procedures in penetrating keratoplasty (PK) are proposed to improve the
      surgical outcomes: minimally invasive procedures, improved biomechanical stability of the
      transplanted flap, reduction of rejection risks, reduction of inflammation, reduction of
      infections risk, faster healing process.

      In order to achieve these goals, two different lasers were used during PK surgery:

        -  a femtosecond laser to cut an anvil shaped profile

        -  a diode laser to weld the surgical wound
    

Detailed description: 
      The femtosecond laser is used to cut an anvil-shaped laser incision used in PK. This design
      has the purpose to create a more structurally stable and predictable wound configuration with
      the aim of a faster recovery of vision and higher optical quality, compared with the
      conventional blade trephination and the most common laser-cut patterns. The "anvil" profile
      is designed as described in the followings. Donor and recipient corneal trephination are
      performed using a 150 kHz FS laser (iFS150TM, IntralaseTM FS Laser, Abbott Medical Optics
      -AMO, Santa Ana, CA, USA). As concerned iFS150 settings, we refer to the following technical
      parameters: in the donor graft, the outer and inner diameters of the ring lamellar cut at 350
      µm in depth were set at 8.5 mm and 6.6 mm, respectively; the anterior-side cut started with
      an angle of 135° at a diameter of 7.7 mm, while the straight posterior side cut diameter was
      6.7 mm. In the recipient eye, the diameters were designed to be 0.2 mm shorter (8.3 mm outer
      diameter, 6.4 mm inner diameter, 7.5 mm anterior side cut and 6.5 mm posterior side cut).
      After completion of the trephination, the corneal button was gently lifted from the host and
      the donor graft was secured in place on the recipient bed by means of 10-0 nylon cardinal
      sutures, which were removed after the final 16-running 10-0 nylon suture was completed. A
      similar FS-laser cut procedure producing a 0.2 mm-narrower corneal bed -diameter is performed
      on the patient's recipient eye. After completion of the trephination, the corneal button is
      lifted gently from the host and the donor graft is secured into place with 10-0 nylon
      cardinal sutures, that are removed as a running 10-0 nylon suture is placed.

      The particular "anvil" shape of the graft provides a larger contact surface in between donor
      and recipient cornea, which enables an effective application of the diode laser welding
      technique of corneal wounds we have previously set up in cataract and PK applications
      (Menabuoni et al. 2007, Rossi et al. 2008). This laser-assisted suturing technique is based
      on the photothermal activation of the stromal collagen, providing an immediate sealing of the
      surgical wound and a good stabilization of the graft. Once the donor graft was sutured in its
      final position, diode laser welding was performed. A sterile saturated water solution of 10%
      w/v Indocyanine Green (ICG) (Pulsion Medical System AG, Munich, Germany) was prepared and
      applied to the walls of the surgical wound at the donor-recipient interface. A mild
      photothermal effect was induced by means of a near infrared diode laser (Mod. WELD 800,
      El.En., Calenzano, FI, Italy) that emitted at 810 nm. The laser light was delivered through a
      300-micron core diameter optical fiber that was mounted on a handpiece and used "as a pencil"
      by the surgeon under a surgical microscope. In a slow, continuous/fluid motion, the surgeon
      moved the fiber tip along the wound edge at a distance of 1.5 mm from the external surface of
      the cornea. The power radiation emitted was a 60 mW continuous wave, which resulted in an 8
      W/cm2 power density on the tissue surface. The laser welding treatment time was set at 130s.

      Thanks two the combine laser assisted procedures, the possible reduction of suture materials
      allows a faster and improved the healing process, with minimal inflammation and reaction.
      Thus the combination of FS laser trephination with the diode laser welding technique may
      provide extremely precise, and minimally invasive surgical procedures in PK.
    

Intervention name(s): Penetrating keratoplasty; Femtosecond laser; Diode laser
Intervention type(s): Procedure; Device; Device
Intervention description(s): Femtosecond laser sculptured anvil graft. Laser welding of the flap in its final position. 12 months follow up study; A commercial femtosecond laser to cut a particular shaped graft; Low power, near infrared diode laser for welding the surgical wound
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: anvil-shaped corneal graft; penetrating keratoplasty; femtosecond laser; laser welding