In 2014 in the United States, patients with corneal endothelial dysfunction were treated with endothelial keratoplasty three times more often than with penetrating keratoplasty (PKP).1 Earlier visual rehabilitation, quicker refractive stability, less induced astigmatism, lower graft rejection rates, and avoidance of doing open-sky surgery are several advantages of Descemet stripping automated endothelial keratoplasty (DSAEK) over PKP.2-7 DSAEK involves first removing the patient’s endothelium and Descemet membrane, then replacing it with a donor corneal graft comprising endothelium, Descemet membrane, and some overlying stroma.8
The visual acuity outcomes with DSAEK are good but not as good as one would expect with all the pristine grafts that we see at the slit lamp after surgery. In one retrospective series of 108 eyes that underwent DSAEK with 3 years of follow-up, the percentage of eyes that achieved a BCVA of 20/40 at 2 years and 3 years was 98.1% and, again, 98.1%. However, the percentage of eyes that achieved a BCVA of 20/20 at 2 years was 34.3% and at 3 years was 47.2%. And these were patients who did not have any known ocular comorbidities, such as age-related macular degeneration or cystoid macular edema.6
Although some studies have concluded that there is no association between graft thickness and postoperative visual acuity,10,11 others have concluded that thinner DSAEK grafts tend to result in better BCVA.12-14 In order to minimize the effect of the donor stroma on postoperative BCVA, many corneal surgeons have turned their attention to ultrathin DSAEK and Descemet membrane endothelial keratoplasty (DMEK).3,9
In 2011, Neff et al14 reported that visual acuity after DSAEK was better with grafts that were thinner than 131 μm postoperatively (this was the median postoperative graft thickness of the 33 eyes included in the study), as measured with anterior segment OCT.14 Although there appears to be no definitive cutoff, DSAEK using grafts thinner than around 130 μm has been called ultrathin DSAEK.
In 2013, Busin et al15 published a prospective study wherein they used a double microkeratome pass technique to prepare ultrathin grafts that had a mean central graft thickness of 78.28 μm. The percentage of eyes that achieved a BCVA of 20/40 or better at 1 year and 2 years was 97% and 100%, respectively. The percentage of eyes that achieved a BCVA of 20/20 or better at 1 year and 2 years was 39% and 49%, respectively. The average BCVA at 1 year was 20/24 and at 2 years was 20/22. The postoperative graft detachment rate was 3.9%, and the endothelial immunologic rejection rate was 2.1%.
In 2002, Melles et al16 introduced DMEK by transplanting a donor graft comprising only Descemet membrane and endothelium. In one prospective study, 41% of eyes (excluding those with ocular comorbidities and those lost to follow-up) had a BCVA of 20/20 or better 1 year after DMEK. The mean BCVA at 1 year was 20/24 (n=81 eyes). The re-bubble rate for graft detachment was 62% (most detachments were partial or peripheral; only one graft detached completely), and the immunologic rejection rate was 5.1% during the first year after DMEK.
In a larger, more recent study,17 41% of eyes (excluding those with ocular comorbidities) had a BCVA of 20/20 or better at 6 months. Graft detachment (of any degree) was noted in 15.8% of eyes. In 2012, Anshu et al18 noted the rate of immunologic rejection to be 0.7% in eyes that underwent DMEK, with a median follow-up of 13 months.18 Some surgeons are using sulfur hexafluoride 20% instead of 100% air as their preferred gas tamponade for DMEK. In one comparative study,19 the re-bubble rate was 2.4% for eyes that underwent DMEK using 20% SF6, compared with 12.8% for eyes that underwent DMEK using 100% air.
Although DSAEK revolutionized the surgical treatment of corneal endothelial disease, the standard of endothelial keratoplasty has transitioned toward thinner donor grafts. Both DMEK and ultrathin DSAEK offer a greater chance of achieving a BCVA of 20/20 more rapidly, and the percentage of eyes achieving this level of vision is quite similar at 1 year after surgery. The endothelial immunologic rejection rate is also quite low for both techniques.
As for the salient differences, DMEK is technically more challenging to learn and perform compared with ultrathin DSAEK. DMEK donor tissue is also more difficult to prepare. The re-bubble rate for DMEK varies widely in the literature and is significantly higher than that of ultrathin DSAEK. Whereas DMEK is not easily accomplished in eyes that are phakic or have aphakia, aniridia, significant iris trauma, an anterior chamber IOL, a trabeculectomy, or a tube shunt, ultrathin DSAEK can be a good option in such eyes.
Regardless of whether more surgeons choose to perform DMEK or ultrathin DSAEK, one thing seems certain: Thinner endothelial grafts are taking over as the new standard in endothelial keratoplasty.
1. 2014 Eye Banking Statistical Report. Eye Bank Association of America. Available at: https://www.restoresight.org/wp-content/uploads/sites/3/2015/03/2014_Statistical_Report-FINAL.pdf. Accessed October 4, 2015.
2. Maier P, Reinhard T, Cursiefen C. Descemet stripping endothelial keratoplasty—rapid recovery of visual acuity. Dtsch Arztebl Int. 2013;110(21):365-371.
3. Busin M, Albé E. Does thickness matter: ultrathin Descemet stripping automated endothelial keratoplasty. Curr Opin Ophthalmol. 2014;25(4):312-318.
4. Chen ES, Terry MA, Shamie N, et al. Descemet-stripping automated endothelial keratoplasty: six-month results in a prospective study of 100 eyes. Cornea. 2008;27:514-520.
5. Koenig SB, Covert DJ, Dupps WJ Jr, Meisler DM. Visual acuity, refractive error, and endothelial cell density six months after Descemet stripping and automated endothelial keratoplasty (DSAEK). Cornea. 2007;26:670-674.
6. Li JY, Terry MA, Goshe J, Davis-Boozer D, Shamie N. Three-year visual acuity outcomes after Descemet’s stripping automated endothelial keratoplasty. Ophthalmology. 2012;119(6):1126-1129.
7. Price MO, Gorovoy M, Price FW Jr, Benetz BA, Menegay HJ, Lass JH. Descemet’s stripping automated endothelial keratoplasty: three-year graft and endothelial cell survival compared with penetrating keratoplasty. Ophthalmology. 2013;120(2):246-251.
8. Terry MA, Chen ES, Shamie N, et al. Endothelial cell loss after Descemet’s stripping endothelial keratoplasty in a large prospective series. Ophthalmology. 2008;115:488.e3-496.e3.
9. Price MO, Price FW Jr. Descemet’s membrane endothelial keratoplasty surgery: update on the evidence and hurdles to acceptance. Curr Opin Ophthalmol. 2013;24(4):329-335.
10. Van Cleynenbreugel H, Remeijer L, Hillenaar T. Descemet stripping automated endothelial keratoplasty: effect of intraoperative lenticule thickness on visual outcome and endothelial cell density. Cornea. 2011;30(11):1195-1200.
11. Shinton AJ, Tsatsos M, Konstantopoulos A, et al. Impact of graft thickness on visual acuity after Descemet’s stripping endothelial keratoplasty. Br J Ophthalmol. 2012;96(2):246-249.
12. Acar BT, Akdemir MO, Acar S. Visual acuity and endothelial cell density with respect to the graft thickness in Descemet’s stripping automated endothelial keratoplasty: one year results. Int J Ophthalmol. 2014;7(6):974-979.
13. Pogorelov P, Cursiefen C, Bachmann BO, Kruse FE. Changes in donor corneal lenticule thickness after Descemet’s stripping automated endothelial keratoplasty (DSAEK) with organ-cultured corneas. Br J Ophthalmol. 2009;93(6):825-829.
14. Neff KD, Biber JM, Holland EJ. Comparison of central corneal graft thickness to visual acuity outcomes in endothelial keratoplasty. Cornea. 2011;30(4):388-391.
15. Busin M, Madi S, Santorum P, Scorcia V, Beltz J. Ultrathin Descemet’s stripping automated endothelial keratoplasty with the microkeratome double-pass technique: two-year outcomes. Ophthalmology. 2013;120(6):1186-1194.
16. Guerra FP, Anshu A, Price MO, Giebel AW, Price FW. Descemet’s membrane endothelial keratoplasty: prospective study of 1-year visual outcomes, graft survival, and endothelial cell loss. Ophthalmology. 2011;118(12):2368-2373.
17. Rodriguez-Calvo-de-Mora M, Quilendrino R, Ham L, et al. Clinical outcome of 500 consecutive cases undergoing Descemet’s membrane endothelial keratoplasty. Ophthalmology.2015;122(3):464-470.
18. Anshu A, Price MO, Price FW Jr. Risk of corneal transplant rejection significantly reduced with Descemet’s membrane endothelial keratoplasty. Ophthalmology. 2012;119(3):536-540.
19. Guell JL, Morral M, Gris O, Elies D, Manero F. Comparison of sulfur hexafluoride 20% versus air tamponade in Descemet membrane endothelial keratoplasty. Ophthalmology. 2015;122(9):1757-1764.