Bowman’s layer grafting

Intrastromal implantation of Bowman’s membrane graft in eyes with moderate and advanced progressive keratoconus can result in an immediate flattening of the corneal curvature that is sustained over the longer term, according to Isabel Dapena MD, The Netherlands Institute for Innovative Ocular Surgery, Rotterdam, The Netherlands. “Bowman’s layer intrastromal grafting does not compromise the corneal surface and has a lower risk for complications than penetrating keratoplasty or deep anterior lamellar keratoplasty and theoretically diminishes the risk for allograft rejection,” Dr Dapena told the 38th Congress of the ESCRS. The technique involves obtaining the complete Bowman’s layer from donor corneas and creating a scleral pocket through a scleral tunnel at 50% depth with a lamellar spatula. The donor Bowman’s membrane is then inserted in the pocket with a glide and with the injection of liquid carefully unfolding the membrane with a cannula, she explained. Dr Dapena presented the results obtained in a series of 35 keratoconus cases who underwent Bowman’s layer intrastromal implantation. The patients had a mean age of 32 years, a Kmax greater than 69 in 26 of the patients and thin corneas with a mean thinnest pachymetry of 349 microns. They included 26 advanced keratoconus cases and nine moderate cases. Immediately after surgery there was an important flattening of the cornea maintained largely unchanged throughout a follow-up of seven-to-eight years, she noted. There was an average flattening of the cone of 5.0D. In addition, the best spectacle-corrected visual acuity improved slightly and the vision with contact lenses remained stable. Complications included corneal hydrops in five eyes (14%), which occurred between four and seven years postoperatively. Four of those with hydrops occurred among the advanced keratoconus cases and one occurred in a moderate keratoconus case. In addition, five eyes (14%) showed continued corneal steepening, three of which occurred among the advanced cases and two of which occurred among the moderate cases. “This technique achieved flattening of cornea curvature and stabilisation of progressive keratoconus in 83 and 63% of cases at five and eight years, respectively, with preservation of the visual acuity. It may postpone or even completely avoid the need for deep anterior lamellar keratoplasty or penetrating keratoplasty,” Dr Dapena added. She noted that she and her associates have also achieved good results of a new technique, Bowman’s layer onlay grafting, in a series of five patients with progressive advanced keratoconus. The new technique has the advantage of being a completely extraocular approach without risk for micro-perforation in very thin corneas.