The risk for plaque tilt was greatest for posterior tumors near the fovea and optic disc, which are well known to have a higher local failure rate.2,4,6,9,15 Notched plaques were used for juxtapapillary tumors in which the posterior tumor margin was located less than 1.5 mm from the disc, thus explaining the association between notched plaques and plaque tilt. Plaque localization is more difficult for tumors located posteriorly near the disc and fovea, where surgical access and visualization are constrained by the orbital anatomy. In addition, it can be difficult to achieve close apposition of the plaque to the sclera owing to obstruction by the optic nerve sheath, inferior oblique muscle, and posterior ciliary vessels and nerves.10- 12,16 These difficulties could explain the higher failure rate for posterior tumors in centers where ultrasonographic localization is not routinely performed.2,4,6,9,15 However, we show in this study that posterior location is a risk factor for plaque tilt (and possibly local failure) even when intraoperative ultrasonography at plaque insertion has confirmed correct plaque localization. The same anatomical structures that hamper accurate plaque localization can become congested and edematous while the plaque is in place, displacing the plaque from the scleral surface. Consequently, we now routinely perform intraoperative ultrasonography at plaque removal, and if significant tilt is observed, the plaque can be left in longer or adjuvant transpupillary thermotherapy can be performed.