Title: Reply : Safety of posterior-assisted levitation
Abstract: We thank Singh and Stewart for their comments on our article. The anatomy of the vitreous and vitreous base is universally agreed on and when we began performing the PAL procedure, we were concerned about the risk for vitreoretinal trauma. One aim of our paper was to look at the complications experienced and to document the extent to which they occurred. Given the traditional view regarding manipulating objects in the vitreous cavity, we were intrigued by the relatively low rate of complications encountered. While we agree with the authors that the causative break in our patient who experienced an RD could have occurred intraoperatively, we believe that breaks related directly to translational vitreous movements caused by “dragging a needle” through the anterior vitreous are more likely to cause large tears. The fact that during reparative vitrectomy an internal search by the vitreoretinal surgeon failed to reveal the causative break suggests that this was a very small retinal break that became obscured by proliferative epiretinal membranes. The authors cite Christensen and Villumsen1 regarding pseudophakic retinal tears being small and elusive, but it must be remembered that in this context, the pseudophakic breaks could have developed at a later stage following the original surgery. Following uncomplicated cataract surgery, and even more following complicated ones, vitreous syneresis occurs at an accelerated rate. Subsequent posterior vitreous detachments may in themselves be responsible for a significant number of retinal defects. Since the patients in the Christensen and Villumsen series had presumably not had PAL and the RD in our patient appears quite typical of those in the series, it could be argued that this paper also supports the view that our patient experienced a pseudophakic RD unrelated to PAL. In our article, we were careful to point out the potential limitations of PAL. We emphasized that PAL should not be attempted in cases in which the subluxated object could not be directly visualized or for posterior chamber IOLs completely dislocated in the vitreous, since manipulation in this manner could easily cause excessive vitreoretinal trauma. We described patient 4 as a cautionary tale and in our conclusion stated that “[c]areful planning of the point of needle insertion and performing levitation only once in each case minimize vitreous disturbance.” We still think the threshold for referral to a vitreoretinal surgeon should remain low and that unsuccessful attempts at PAL should not prompt the surgeon to persist in this technique. We also pointed out important aspects of the surgical technique to reduce PAL-related vitreoretinal traction. Among these, careful planning of the point of needle entry to enable smooth elevation of the subluxated object in a single motion and not injecting an ophthalmic viscosurgical device for the elevation process were emphasized. Overall pars plana entry of a 25-gauge sharp needle and its movement in a single plane should not be expected to cause more trauma in the vitreous cavity than a standard MVR blade. Although forcible movement of objects entrapped in the vitreous would cause significant vitreoretinal traction, it is likely that the PAL maneuver would be difficult in such situations and the surgeon should therefore abandon the attempt when he/she encounters undue difficulty elevating the lens fragment or IOL. Although we agree with the authors that careful peripheral retinal examination with scleral indentation would help identify most peripheral breaks, we think a significant number may still be missed since the very small breaks typical of a pseudophakic situation do not lend themselves to easy identification with the magnification available on a 20-diopter or 28-diopter IOL during binocular indirect ophthalmoscopy. They may not even be present at the time of examination. According to Christensen and Villumsen,1 22.5% of pseudophakic retinal breaks were not detected in their series. In managing these patients, repeated advice regarding early consultation for the new onset of floaters or visual obscurations may be just as important as a thorough peripheral retinal examination. As with any surgical procedure, we believe that careful patient selection, surgical planning, and surgical technique with the PAL technique are important to provide patients with a relatively safe and noninvasive manner of salvaging an otherwise difficult situation. We await longer term results after PAL that will help in establishing the safety or otherwise of this procedure.