The main disadvantages of EK include the potential for wasting donor tissue (due to poor harvesting, which is minimized with eye bank–prepared tissue), increased risk of primary graft failure during surgical learning curve, and the need for additional surgical interventions postoperatively (re-injection of air, or rebubbling). Reduced postoperative visual acuity is another potential drawback and is discussed separately in the following subsection.
Potential for reduced postoperative visual acuity
Coexisting corneal pathology such as basement membrane changes or subepithelial fibrosis may cause surface irregularity that limits vision after DSEK or DMEK. In some cases, debridement or superficial keratectomy may be necessary. Another possible cause of decreased vision after EK is light scattering due to preexisting long-standing corneal edema. An evaluation of patients with Fuchs corneal dystrophy who underwent DSEK revealed that the corneal light scattering associated with anterior stromal haze improved significantly after surgery but was still increased compared with that in a normal cornea 24 months after the procedure.
Figure 15-15 Iris prolapse following blunt trauma after Descemet stripping endothelial keratoplasty (DSEK).
(Courtesy of Robert W. Weisenthal, MD.)
A review of the literature on DSEK outcomes found that the average best-corrected Snellen visual acuity (BCSVA) ranged from 20/34 to 20/66. Also, an American Academy of Ophthalmology (AAO) Preferred Practice Pattern guideline reported that in a review of studies, a best spectacle-corrected visual acuity of 20/40 or better was achieved at 1 year in 38%–90% of patients after DSEK compared with 97% of patients after DMEK; further, 39%–47% of patients had 20/20 vision after DMEK (see Table 15-8). A number of studies have compared DMEK and DSEK, and all concluded that DMEK provided more rapid recovery of visual acuity and a better final visual outcome. The difference in visual outcome between DSEK and DMEK may be related to the alteration of the posterior corneal curvature that occurs with DSEK. This alteration is due to the unevenness and thickness of the donor tissue and the irregularity of the interface between the donor stromal tissue and the host Descemet membrane. This is in contrast to the nearly normal anatomical restoration of the cornea achieved with DMEK, which is due to the extremely thin graft tissue used and the exceedingly smooth interface created between the host Descemet membrane and transplanted Descemet membrane and endothelium in DMEK.
Nevertheless, for many surgeons, DSEK is still the procedure of choice for routine EK, because manipulation and placement of tissue are easier with this technique. DSEK is particularly useful in patients with disorganized anterior segments, those with sutured posterior chamber or anterior chamber IOLs, and in patients who have undergone tube shunt implantation or other glaucoma procedures. In an effort to improve the visual outcome after DSEK, some surgeons advocate using thinner donor grafts (between 90 and 120 μm), a variation called ultrathin DSEK. However, Wacker et al, in a meta-analysis of 23 series, found that there may be a weak correlation but overall insufficient evidence to conclude that graft thickness is clinically important with respect to BCVA after DSEK. These same investigators have also shown that visual acuity after DSEK continues to improve over a 5-year period, with more than half of the patients seeing better than 20/25 at 5 years, which they believe was a result of ongoing remodeling of the cornea reducing corneal haze and aberrations.
American Academy of Ophthalmology Cornea/External Disease Panel. Preferred Practice Pattern Guidelines. Corneal Edema and Opacification. San Francisco: American Academy of Ophthalmology; 2013. Available at www.aao.org/ppp.
Baratz KH, McLaren JW, Maguire LJ, Patel SV. Corneal haze determined by confocal microscopy 2 years after Descemet stripping with endothelial keratoplasty for Fuchs corneal dystrophy. Arch Ophthalmol. 2012;130(7):868–874.
Dickman MM, Kruit PJ, Remeijer L, et al. A randomized multicenter clinical trial of ultrathin Descemet stripping automated endothelial keratoplasty (DSAEK) versus DSAEK. Ophthalmology. 2016;123(11):2276–2284.
Hamzaoglu EC, Straiko MD, Mayko ZM, Sáles CS, Terry MA. The first 100 eyes of standardized Descemet stripping automated endothelial keratoplasty versus standardized Descemet membrane endothelial keratoplasty. Ophthalmology. 2015;122(11):2193–2199.
Roberts HW, Mukherjee A, Aichner H, Rajan MS. Visual outcomes and graft thickness in microthin DSAEK—one year results. Cornea. 2015;34(11):1345–1350.
Rudolph M, Laaser K, Bachmann BO, Cursiefen C, Epstein D, Kruse FE. Corneal higher-order aberrations after Descemet’s membrane endothelial keratoplasty. Ophthalmology. 2012; 119(3):528–539.
Tourtas T, Laaser K, Bachmann BO, Cursiefen C, Kruse FE. Descemet membrane endothelial keratoplasty versus Descemet stripping automated endothelial keratoplasty. Am J Ophthalmol. 2012;153(6):1082–1090.
Wacker K, Baratz KH, Maguire LJ, McLaren JW, Patel SV. Descemet stripping endothelial keratoplasty for Fuchs’ corneal endothelial dystrophy: five-year results of a prospective study. Ophthalmology. 2016;123(1):154–160.
Wacker K, Bourne WM, Patel SV. Effect of graft thickness on visual acuity after Descemet stripping endothelial keratoplasty: a systematic review and meta-analysis. Am J Ophthalmol. 2016;163:18–28.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.