The value of DSAEK

DSAEK in monocular patient S/P glaucoma filtering surgery 
with iris coloboma and zonulysis. Courtesy of Sadeer B Hannush MD . Although more corneal transplant surgeons are switching to Descemet’s membrane endothelial keratoplasty (DMEK) for the reported benefits of quicker healing, better visual outcomes, lower risk of rejection and glaucoma, and lower dependence on long-term corticosteroids, older procedures such as Descemet’s stripping automated endothelial keratoplasty (DSAEK) still have a valuable role to play for certain indications, according to Sadeer B Hannush MD. “Despite the emergence of DMEK or pre-Descemet’s endothelial keratoplasty (PDEK) as some surgeons’ endothelial keratoplasty procedures of choice for the indication of endothelial dysfunction, these procedures may not be ideal in the setting of certain comorbidities,” said Dr Hannush. This is especially true if the surgeon is not experienced in performing DMEK, he noted. CHALLENGING Dr Hannush, Wills Eye Hospital, Philadelphia, Pennsylvania, USA, himself an experienced DMEK surgeon, said that hypotony, unicameral eyes (with easy communication between the anterior and posterior segments), and conditions preventing adequate tamponade make DMEK cases particularly challenging. DSAEK, on the other hand, may give the surgeon a better chance of bringing these cases to a successful conclusion. Likewise, instances where the surgeon anticipates more difficulty than usual in unscrolling the DMEK graft, such as eyes with deep anterior chambers and those with prior vitrectomies, may also potentially benefit from DSAEK procedures, he said, since in these instances no special technique modifications are necessary to complete DSAEK, which may not be the case in DMEK. There are various circumstances in which the aforementioned conditions may occur, said Dr Hannush, including but not limited to the presence of aphakia, iris colobomata or zonular dehiscence, aniridia, eyes with anterior chamber intraocular lenses (IOLs), and eyes with iris- or scleral-fixated IOLs. “In cases where the surgeon 
anticipates IOL exchange (unicameral eye), or in the presence of a filtering procedure like trabeculectomy or tube shunt, DSAEK may be considered as the endothelial keratoplasty procedure of choice,” he added. Dr Hannush said his preference is to use thin grafts, below 100 microns, for DSAEK. “Size does matter when it comes to graft thickness. A thinner endothelial graft is advantageous, not just because of the properties of the graft itself, but also the reduced likelihood of variability in thickness across the cornea when you 
use a thinner graft, leading to better optical quality and enhanced visual acuity,” he said. To prepare the grafts, the full-thickness donor corneal tissue is mounted, endothelial side down, on an artificial anterior chamber and approximately two-thirds to four-fifths of the anterior stroma is removed using a microkeratome with 300- or 350-micron cutting heads, and varying the pressure in the anterior chamber and the speed of the pass to achieve a 100-micron or less lamellar graft, said Dr Hannush. He highlighted the utility of DSAEK in difficult cases with the example of a patient with an anterior chamber implant and chronic pseudophakic corneal and macular oedema. “After explanting the anterior chamber IOL, a three-piece acrylic posterior chamber implant is fixated to the sclera by insertion of the haptics into scleral tunnels and the use of fibrin sealant. Once Descemet’s membrane has been stripped from the host, the DSAEK endothelial graft is positioned behind the host stroma and tamponaded into position with an air bubble,” he said. There is little concern in this scenario over the graft migrating posteriorly around the sclerally-fixated IOL, 
which might have been the case with 
a DMEK graft. Sadeer B Hannush: sbhannush@gmail.com