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Novel approach to keratoconus

New Bowman’s layer grafting technique shows promise

Roibeard O’hEineachain

Posted: Thursday, December 3, 2020

Placing a donor Bowman’s layer graft on to a thin keratoconic cornea can result in an immediate flattening of the corneal curvature and stabilisation or improvement in patients’ visual acuity, according to Isabel Dapena MD, The Netherlands Institute for Innovative Ocular Surgery, Rotterdam, The Netherlands.

“In progressive keratoconus, the Bowman’s layer onlay technique has potential as a means of flattening the corneal surface, halting progression and postponing more invasive keratoplasty techniques while also maintaining preoperative contact lens visual acuity,” Dr Dapena told the 24th ESCRS Winter Meeting in Marrakech, Morocco.

The new surgical technique involves first removing the epithelium and then placing a Bowman’s membrane graft on to the stroma and stretching it so that there are no folds. Afterwards it is covered with a bandage contact lens, she explained.

Dr Dapena and her associates performed Bowman’s layer onlay grafting in five patients with advanced progressive keratoconus, including one case that had undergone corneal cross-linking (CXL) immediately previously. The remaining four patients were unsuitable candidates for CXL.

She noted that all the surgeries were performed successfully and with an immediate postoperative flattening of the corneal curvature in all eyes. In addition, all eyes were completely re-epithelialised with a well-integrated graft by two-to-three weeks postoperatively. In one eye with a particularly steep cornea there was a partial dislocation of the Bowman’s layer graft. It was repositioned and sutured over with amniotic membrane tissue.

At one-to-six months follow-up, the average Kmax decreased from 74.9D preoperatively to 69.1D, but there were no changes in posterior corneal values. Furthermore, at six months, best spectacle-corrected visual acuity (BSCVA) had improved by at least two lines in three of five patients and best contact lens-corrected visual acuity remained unchanged. Patients also expressed high satisfaction with the procedure.

HIGH PATIENT SATISFACTION
Dr Dapena noted that the new Bowman’s layer onlay technique may help address the need that exists for treatment of eyes with progressive keratoconus and thin corneas. Such eyes are often unsuitable candidates for procedures like corneal cross-linking and intracorneal ring segments.

The onlay technique is based on the hypothesis that keratoconus results from a disruption of Bowman’s layer. The results so far are similar to those of the Bowman’s layer intrastromal inlay technique, also developed at the Rotterdam Institute.

“This onlay technique is theoretically much better because it is a completely extraocular approach and there is no risk for micro-perforation, allowing the treatment for a much larger group of patients,” Dr Dapena added.