In chapter 4, a technique is described for posterior lamellar keratoplaty, in which a 7.0 to 7.5 mm diameter posterior lamellar disc is transplanted through a 9 mm sclero-corneal pocket incision. Although the results of the technique may compare favourably to those after a penetrating keratoplasty, it may still have some disadvantages.

The first disadvantage is that a 9 mm scleral incision requires suturing at the end of the surgery. This may again induce some with-the-rule astigmatism, and the placement and removal of the sutures require additional surgical time. Also, although the donor tissue is not in direct contact with the sutures, the presence of sutures in the vicinity of the transplant may still give a higher risk of allograft rejection. Eliminating sutures from the procedure was therefore given high priority, to avoid all suture-related complications.

A second disadvantage is that the intra-corneal trephine used to excise a recipient posterior lamellar disc, obscures the view of the underlying structures during surgery, for example the crystalline lens. The trephine may be a relatively large instrument for the space available in the anterior chamber, and damage to the crystalline lens would not be inconceivable, especially with vitreous pressure during surgery. In our series, a touch of the crystalline lens could not occur, because the procedure was performed only on pseudophakic eyes.

To overcome these disadvantages, the technique was modified, so that the entire procedure could be performed through a 5.0 mm, self-sealing scleral tunnel incision. The method of dissection and obtaining a deep stromal depth is similar to that described in Chapter 2 and 4, and in the DALK course. A posterior lamellar disc is than excised using a custom made, scissor-like instrument, and the donor tissue is implanted with a custom made inserter (see Video 2 - on Cd-rom only).

Please note that the instruments shown on the video are not the currently used prototype instruments, but images of the latter instruments are not yet available.

Figure 5.1: Drawings of the surgical procedure. Source: NRC Handelsblad. Wim Kohler/Roland Blokhuizen, September 8 2001. 

Figure 5.2: Slit-lamp photographs of the same eye one week and one month after posterior lamellar keratoplasty. The posterior transplant (arrows), 8.5 mm in diameter, is in position with complete apposition of the donor-to-host tissues at the stromal interface. At 12 oclock, the outline of the 5.0 mm scleral tunnel incision (arrowheads) is visible through which the posterior lamellar disc was transplanted. At one month, the visual acuity was 0.7.