Descemet membrane endothelial keratoplasty (DMEK) is a corneal surgical technique which selectively replaces the damaged posterior part of the cornea with a healthy donor graft retaining the rest of the tissue intact. There is a need to validate and standardize the donor tissue before grafting due to certain issues that can lead to consequences such as graft failure due to poor endothelial cell count, higher mortality, detachment of the graft, or increased surgical expenses, time, and effort. Thus, prospective potential surgeons and eye banks should now aim at developing new improved surgical techniques in order to prepare the best suited, validated, precut, preloaded, and easy to transplant tissue to reduce pre- and postsurgical complications. This could be achieved by defining parameters like graft thickness, accepted mortality threshold of the endothelial cells, and behavior of grafts during preservation and transportation along with using more sophisticated instruments like microkeratome and femtosecond lasers for graft preparation. Thus, a rapport between the eye banks and the surgeons along with the advanced instruments can overcome this challenge to find the best possible solution for endothelial keratoplasty (EK). 1. Introduction The cornea is the anterior part of the eye globe. It is an avascular tissue which is directly exposed to the external environment. It focuses the image by refracting the light to the retina through a lens. Hence, it should be clear and well maintained for optimal visibility [1]. The cornea acts as a shield against external dust or microbes and prevents them to enter the eye globe. Damage or disturbance to the cornea due to scar, foreign bodies, or other diseases or disorders can lead to poor visibility. Cornea is made up of six layers which are responsible for the organization of the corneal cellular matrix which in turn is important for guiding the light to the retina. The corneal layers are the epithelium, basement membrane, Bowman’s layer, stroma, Descemet’s membrane, and endothelium (Figure 1) [1]. Each layer has its own specificity, but when corneal transplantation especially penetrating keratoplasty (PK)/endothelial keratoplasty (EK) is considered, the endothelium has a more important role to play as it does not have the capacity to regenerate and hence should be left viable and undisturbed. Endothelial damage or poor viable cell count is assumed to be majorly responsible for graft rejection [2]. Figure 1: Different layers of a corneal tissue and types of surgeries that involve specific layers. DALK replaces the
References
[1]
T. Nishida, “Cornea,” in Cornea: Fundamentals, Diagnosis and Management, J. Krachmer, M. Mannis, and E. Holland, Eds., vol. 1, pp. 3–26, Elsevier-Mosby, Philadelphia, Pa, USA, 2005.
[2]
M. Parekh, G. Salvalaio, S. Ferrari, et al., “Effect of post-mortem time on the quality of the donor cornea during preservation and after transplantation,” Cornea, vol. 32, no. 6, pp. 842–846, 2013.
[3]
F. W. Price, W. E. Whitson, and R. G. Marks, “Progression of visual acuity after penetrating keratoplasty,” Ophthalmology, vol. 98, no. 8, pp. 1177–1185, 1991.
[4]
G. W. Zaidman and S. Goldman, “A prospective study on the implantation of anterior chamber intraocular lenses during keratoplasty for pseudophakic and aphakic bullous keratopathy,” Ophthalmology, vol. 97, no. 6, pp. 757–762, 1990.
[5]
K. D. Neff, J. M. Biber, and E. J. Holland, “Comparison of central corneal graft thickness to visual acuity outcomes in endothelial keratoplasty,” Cornea, vol. 30, no. 4, pp. 388–391, 2011.
[6]
T. Donald and A. Arundhati, “Anterior lamellar keratoplasty: “Back to the Future”-a review,” Clinical and Experimental Ophthalmology, vol. 38, no. 2, pp. 118–127, 2010.
[7]
S. Shimmura and K. Tsubota, “Deep anterior lamellar keratoplasty,” Current Opinion in Ophthalmology, vol. 17, no. 4, pp. 349–355, 2006.
[8]
F. Trimarchi, E. Poppi, C. Klersy, and C. Piacentini, “Deep lamellar keratoplasty,” Ophthalmologica, vol. 215, no. 6, pp. 389–393, 2001.
[9]
J. Shimazaki, S. Shimmura, M. Ishioka, and K. Tsubota, “Randomized clinical trial of deep lamellar keratoplasty vs penetrating keratoplasty,” American Journal of Ophthalmology, vol. 134, no. 2, pp. 159–165, 2002.
[10]
W. J. Reinhart, D. C. Musch, D. S. Jacobs, W. B. Lee, S. C. Kaufman, and R. M. Shtein, “Deep anterior lamellar keratoplasty as an alternative to penetrating keratoplasty: a report by the American academy of ophthalmology,” Ophthalmology, vol. 118, no. 1, pp. 209–218, 2011.
[11]
I. Dapena, K. Moutsouris, K. Droutsas, L. Ham, K. Van Dijk, and G. R. J. Melles, “Standardized “no-touch” technique for descemet membrane endothelial keratoplasty,” Archives of Ophthalmology, vol. 129, no. 1, pp. 88–94, 2011.
[12]
E. A. Groeneveld-van Beek, J. T. Lie, J. van der Wees, M. Bruinsma, and G. Melles, “Standardized “no-touch” donor tissue preparation for DALK and DMEK: harvesting undamaged anterior and posterior transplants from the same donor cornea,” Acta Ophthalmologica, vol. 91, no. 2, pp. 145–150, 2012.
[13]
M. Busin, V. Scorcia, A. K. Patel, G. Salvalaio, and D. Ponzin, “Pneumatic dissection and storage of donor endothelial tissue for Descemet's membrane endothelial keratoplasty: a novel technique,” Ophthalmology, vol. 117, no. 8, pp. 1517–1520, 2010.
[14]
H. D. McKee, L. C. Irion, F. M. Carley, V. Jhanji, and A. K. Brahma, “Donor preparation using pneumatic dissection in endothelial keratoplasty: DMEK or DSEK?” Cornea, vol. 31, no. 7, pp. 798–800, 2012.
[15]
S. Sikder, D. Ward, and A. S. Jun, “A surgical technique for donor tissue harvesting for descemet membrane endothelial keratoplasty,” Cornea, vol. 30, no. 1, pp. 91–94, 2011.
[16]
P. Studeny, A. Farkas, M. Vokrojova, P. Liskova, and K. Jirsova, “Descemet membrane endothelial keratoplasty with a stromal rim (DMEK-S),” British Journal of Ophthalmology, vol. 94, no. 7, pp. 909–914, 2010.
[17]
N. Ghaznawi and E. S. Chen, “Descemet's stripping automated endothelial keratoplasty: innovations in surgical technique,” Current Opinion in Ophthalmology, vol. 21, no. 4, pp. 283–287, 2010.
[18]
H. Mehta, “Newer trends in lamellar keratoplasty,” Journal of the Bombay Ophthalmologists’ Association, vol. 14, no. 2, pp. 19–24, 2005.
[19]
M. A. Sarayba, T. S. Ignacio, P. S. Binder, and D. B. Tran, “Comparative study of stromal bed quality by using mechanical, IntraLase femtosecond laser 15- and 30-kHz microkeratomes,” Cornea, vol. 26, no. 4, pp. 446–451, 2007.
[20]
M. A. Sarayba, T. S. Ignacio, D. B. Tran, and P. S. Binder, “A 60 kHz IntraLase femtosecond laser creates a smoother LASIK stromal bed surface compared to a zyoptix XP mechanical microkeratome in human donor eyes,” Journal of Refractive Surgery, vol. 23, no. 4, pp. 331–337, 2007.
[21]
Y. J. Jones, K. M. Goins, J. E. Sutphin, R. Mullins, and J. M. Skeie, “Comparison of the femtosecond laser (IntraLase) versus manual microkeratome (Moria ALTK) in dissection of the donor in endothelial keratoplasty: initial study in eye bank eyes,” Cornea, vol. 27, no. 1, pp. 88–93, 2008.
[22]
P. S. Binder, “Flap dimensions created with the IntraLase FS laser,” Journal of Cataract and Refractive Surgery, vol. 30, no. 1, pp. 26–32, 2004.
[23]
L. T. Nordan, S. G. Slade, R. N. Baker, C. Suarez, T. Juhasz, and R. Kurtz, “Femtosecond laser flap creation for laser in situ keratomileusis: six-month follow-up of initial U.S. clinical series,” Journal of Refractive Surgery, vol. 19, no. 1, pp. 8–14, 2003.
[24]
I. Ratkay-Traub, T. Juhasz, C. Horvath et al., “Ultra-short pulse (femtosecond) laser surgery: initial use in LASIK flap creation,” Ophthalmology Clinics of North America, vol. 14, no. 2, pp. 347–355, 2001.
[25]
R. Antoine, B. Abdelkader, G. Virginie et al., “Interface quality of endothelial keratoplasty buttons obtained with optimised FS laser settings,” British Journal of Ophthalmology, vol. 96, no. 1, pp. 122–127, 2012.
[26]
Y. Y. Y. Cheng, E. Pels, and R. M. M. A. Nuijts, “Femtosecond-laser-assisted Descemet's stripping endothelial keratoplasty,” Journal of Cataract and Refractive Surgery, vol. 33, no. 1, pp. 152–155, 2007.
[27]
C. Monterosso, A. Fasolo, L. Caretti, G. Monterosso, L. Buratto, and E. B？hm, “Sixty-kilohertz femtosecond laser-assisted endothelial keratoplasty: clinical results and stromal bed quality evaluation,” Cornea, vol. 30, no. 2, pp. 189–193, 2011.
[28]
Y. Y. Y. Cheng, S. J. Kang, H. E. Grossniklaus et al., “Histologic evaluation of human posterior lamellar discs for femtosecond laser descemet's stripping endothelial keratoplasty,” Cornea, vol. 28, no. 1, pp. 73–79, 2009.
[29]
Y. Y. Y. Cheng, J. S. A. G. Schouten, N. G. Tahzib et al., “Efficacy and safety of femtosecond laser-assisted corneal endothelial keratoplasty: a randomized multicenter clinical trial,” Transplantation, vol. 88, no. 11, pp. 1294–1302, 2009.
[30]
J. S. Mehta, R. Shilbayeh, Y. M. Por, H. Cajucom-Uy, R. W. Beuerman, and D. T. Tan, “Femtosecond laser creation of donor cornea buttons for Descemet-stripping endothelial keratoplasty,” Journal of Cataract and Refractive Surgery, vol. 34, no. 11, pp. 1970–1975, 2008.
[31]
S. H. Yoo, G. D. Kymionis, A. Koreishi et al., “FS laser-assisted sutureless anterior lamellar keratoplasty,” Ophthalmology, vol. 115, no. 8, pp. 1303–1307, 2008.
[32]
C. Kent, “Laser Transplants: Are We There Yet?—although FS lasers excel in some respects, it's not clear that they're ready to become the gold standard,” http://www.revophth.com/content/d/cover_focus/c/29946/.
[33]
D. A. Peyrot, F. Aptel, C. Crotti et al., “Effect of incident light wavelength and corneal edema on light scattering and penetration: laboratory study of human corneas,” Journal of Refractive Surgery, vol. 26, no. 10, pp. 786–795, 2010.
[34]
J. L. Bourges, A. Rousseau, J. J. Saragiussi, G. Renard, and F. Behar-Cohen, “Creating endothelial lenticules with FSe laser: the double layer technique,” Acta Ophthalmologica, vol. 89, no. s248, 2011.
[35]
O. Suwan-Apichon, J. M. G. Reyes, N. B. Griffin, J. Barker, P. Gore, and R. S. Chuck, “Microkeratome versus femtosecond laser predissection of corneal grafts for anterior and posterior lamellar keratoplasty,” Cornea, vol. 25, no. 8, pp. 966–968, 2006.
[36]
S. Sikder and R. W. Snyder, “Femtosecond laser preparation of donor tissue from the endothelial side,” Cornea, vol. 25, no. 4, pp. 416–422, 2006.
[37]
W. Bethke, “The Evolution of the FS Laser—what began as a high-tech device for cutting a LASIK flap has developed into a versatile tool for reshaping the cornea,” http://www.revophth.com/content/d/refractive_surgery/c/22763/.
M. Busin, “Tools and techniques Ultra-thin DSAEK,” ASCRS Eye world. The newsmagazine of the American Society of cataract and refractive surgery, http://eyeworld.org/article.php?sid=6198.
[40]
M. Busin, A. K. Patel, V. Scorcia, and D. Ponzin, “Microkeratome-assisted preparation of ultrathin grafts for descemet stripping automated endothelial keratoplasty,” Investigative Ophthalmology & Visual Science, vol. 53, no. 1, pp. 521–524, 2012.
[41]
S. S. Chaurasia, R. Champakalakshmi, A. Li, et al., “Effect of fibrin glue on the biomechanical properties of human Descemet's membrane,” PLoS ONE, vol. 7, no. 5, Article ID e37456, 2012.
[42]
C. Micheal Chen and B. H. Jeng, “Comparative cost analysis of surgeon-cut versus eye bank cut dnor cornea tissue for endothelial keratoplasty,” Investigative Ophthalmology & Visual Science, vol. 53, E-Abstract 25, 2012.
[43]
T. Bayyoud, D. R？ck, J. Hofmann, K. Bartz-Schmidt, and E. Yoeruek, “Precut technique for Descemet’s Membrane Endothelial Keratoplasty, preparation and storage in organ culture,” Klinische Monatsbl？tter für Augenheilkunde, vol. 229, no. 6, pp. 621–623, 2012.
