Real‐time intraoperative ultrasound biomicroscopy for determining graft orientation during Descemet's membrane endothelial keratoplasty

Purpose To evaluate the intraoperative use of ultrasound biomicroscopy (UBM) during Descemet's membrane endothelial keratoplasty (DMEK) to determine graft's orientation. Methods Prospective interventional study of eight eyes of seven patients who underwent DMEK. Following the identification of correct graft orientation using 'Blue cannula tip' sign during DMEK surgery, UBM was used to ascertain graft's orientation. The rate of successful DMEK graft orientation determined by the UBM was registered and verified postoperatively by anterior segment-optical coherence tomography (OCT). Intra- and postoperative complications, postoperative clearance of the cornea, corrected distance visual acuity and endothelial cell loss were also noted. Results The study included five males and two females aged 54-82 years with corneal oedema due to Pseudophakic bullous keratopathy (n = 5), Fuchs' endothelial dystrophy (n = 2). In all cases, the technique allowed proper determination of the graft's orientation. In one case, 'blue cannula tip' sign showed correct orientation while UBM identified an upside-down graft. The graft was inverted in the anterior chamber using fluid jets, and repeat 'blue cannula tip' sign and UBM examination both showed correct orientation. In all cases, postoperative anterior segment-OCT demonstrated correct graft orientation. Conclusions Use of intraoperative UBM to determine graft orientation during DMEK correlated with proper graft orientation, as was verified postoperatively by anterior segment-OCT. The use of UBM can be particularly helpful in cases of poor graft visibility due to opaque corneal stroma, pigment or blood in the anterior chamber during surgery, or when the blue tint of the graft fades rapidly, which may preclude proper determination of graft's orientation.