Endothelial keratoplasty involves selective replacement of the diseased host endothelium with a healthy tissue. Because of its advantages over traditional penetrating keratoplasty, it has become the procedure of choice for corneal endothelial disorders. In last two decades the technique of endothelial keratoplasty has underwent tremendous modifications to improve visual outcome and reduce complications. When we think of endothelial keratoplasty, various terms come to our mind like DLEK ,DSEK,DMEK etc. These can be confusing not only for a resident in training but to a general practitioner as well. To improve our understanding in the field of endothelial keratoplasty, we have invited some prominent endothelial keratoplasty surgeons of our country.
Dr. Jagadeesh Kumar Reddy, MS. is the Director (Technical) Sankara Eye Centre, Coimbatore. He has done Fellowship in Cornea and has 30 years of clinical practice. He has performed over 80,000 surgeries and his area of interest is new designs of Intraocular lens, keratoconus- collagen cross-linking, and keratoprosthesis (Synthetic Cornea). He has invented Infocus IOL (Appasamy associates), RIL and PICL (Posterior Iris claw lens) ( excel optics)
Dr. Namrata Sharma completed her postgraduation from Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, and underwent fellowship from Moorfields Eye Hospital in London, UK. Presently she is working as Professor of ophthalmology in Cornea, Cataract, and Refractive surgery services at Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi. She is now the hon. general secretary of All India Ophthalmological Society and regional secretary, Asia-Pacific Academy of Ophthalmology (APAO). She has won multiple international awards such as senior achievement award, American Academy of Ophthalmology ( AAO), International Ophthalmologist Education Award, AAO Best Video awards by ESCRS, RANZCO, and “Best of Show” awards six times by AAO, APAO Leadership award Achievement Award, APAO. She has more than 450 publications in international peer-reviewed journals and has authored 11 books. She has conducted numerous instruction courses at several International and national platforms. She has led many multicentric international trials and RCTs which have changed the clinical practice Cornea.
Dr. Rajesh Fogla DNB, FRCS(Edinburgh), FRCOphth MMed (Ophthalmology) NUS Singapore is the Director Cornea Clinic, and Senior Consultant, Eye Department, Apollo Hospitals, Hyderabad. He is also a visiting Consultant to the Lanka Hospitals, Colombo, Sri Lanka; Al Bahar Hospitals, Kuwait. He is the Past President & Founding member of the Cornea Society of India. He completed post-graduation and fellowship in the cornea from Sankara Nethralaya, Chennai. He worked as a cornea consultant, Sankara Nethralaya, Chennai, INDIA from 1998 – 2005. His areas of interest are lamellar corneal surgery, refractive surgery, ocular surface reconstruction, & infections. He is actively involved in teaching & training and conducted Instruction courses at various international & national meetings. He also conducts fellowship programs, & training courses in Cornea. He has numerous publications in peer-reviewed journals & presented many papers and delivered guest lectures at various national & international meetings. He is the reviewers for International journals - Cornea, Ophthalmology, American Journal of Ophthalmology, Eye, Journal of Cataract & Refractive Surgery, JAMA, IJO
Dr. Samar K Basak, MD, DNB, FRCS, is Director and one of the founder members of Disha Eye Hospitals, Kolkata, India. Disha Eye Hospital is the largest private hospital chain in Eastern India with 14 branches in the state of West Bengal. He looks after Cataract, Cornea and External eye diseases, and Eye Bank services. It has one of the finest independent quality Eye Bank, which retrieves around 1900 eyes and utilizes 1400 cornea annually. Cornea Department of Disha is self-sufficient with all facilities which include – microbiology, OSD clinic, all kind of cornea transplant services including Boston Type 2 keratoprosthesis. He is the recipient of 10 Gold Medal Awards from All India Ophthalmological Society Congress; 8 other Gold Medal oration and prestigious Prof LP Agarwal Oration from All India Institute of Medical Sciences, New Delhi. Internationally, he has received the “Best of Show” Video Award 6 times and Best Poster Award 4 times in the American Academy of Ophthalmology conferences; Best Video Award 2 times in ESCRS and “People’s Choice” Best Video Award in ASCRS-2012. He has received an “Achievement Award” by the AAO in 2008 and by the APAO in 2011; Senior Achievement Award by the AAO in 2015 and Senior Scholar Award by the AAO in 2017. Dr. Basak, an FRCS Examiner since 2008, has written 6 textbooks in Ophthalmology; the most popular one is “Essentials of Ophthalmology” (7th Edition) for the undergraduate MBBS students. He has 41 publications in national and international peer-review journals. He is currently the reviewer of 11 prestigious peer-review journals, including Ophthalmology and Cornea Journal. He is involved with teaching and training program (Phaco/SICS; and DSEK/DMEK/Boston Kpro1 Skill Transfer Course) with ORBIS and SightLife, in India and Southeast Asia regions. He is a bulk Phaco surgeon @2500/year and Keratoplasty (PK/DALK/DSEK/DMEK/Boston KPro) more than 350/year. He is obsessed with DMEK in recent years, performing close to @250/year. In leisure time, he is busy with his unique hobby – “Ophtha-Philately” (Ophthalmology + Philately), collecting and studying ‘Postage stamp only related to ophthalmology’. He has more than 650 stamps in his collection and he has also written a book entitled “Ophtha-Philately”.
eOphtha: In the last couple of decades Endothelial keratoplasty has evolved from DLEK to DSEK/DSAEK and now to DMEK. How important, u think it is to understand these procedures for an anterior segment surgeon?
Dr. J K Reddy:Very important. As each procedure increases patient comfort and visual recovery. Post-operative management also differs and much easier to manage by a general ophthalmologist.
Dr. Namrata Sharma: Deep endothelial lamellar keratoplasty (DLEK) was introduced by Mark Terry in 2003 because there was no specific treatment for those diseases of the cornea which involved the posterior part which includes the descemet’s membrane (DM), endothelium and sometimes the posterior part of the stroma. Since the anterior layers of the cornea was clear , it did not make sense to replace the entire cornea when only part of it is involved in diseases such as Fuchs endothelial dystrophy or PPMD etc. DLEK was a relatively difficult surgery to do and had a learning curve. Very soon the DLEK gave way to Descemet’s Stripping endothelial Keratoplasty (DSEK), Descemet’s Stripping automated endothelial keratoplasty (DSAEK) and Descemet’s membrane endothelial keratoplasty (DMEK). So it is very important to understand each of these procedures by the Cornea surgeons because nowadays corneal surgeries have become more customized so that only the diseased layer of the cornea is replaced with the healthy tissue and rest of the layers which are healthy are left in situ. Since we are not replacing the whole of the cornea but only the diseased layers, the chances of graft rejection is much less as the tissue transplanted is less.
Dr. Rajesh Fogla: In the past two decades, corneal transplantation has witnessed a change from traditional full-thickness penetrating keratoplasty (PK) to selective endothelial keratoplasty (EK) for various endothelial disorders. Absence of incisions & sutures in EK procedures helps maintain a normal corneal topography, with a superior refractive outcome and faster visual rehabilitation compared to PK. As the surgery is performed in a closed chamber with a smaller incision, intraoperative complications associated with open globe surgery in PK are avoided with EK, besides increased tectonic stability. The evolution of EK from DLEK to DMEK has further improved visual outcomes, with reduced risk of endothelial rejection. Therefore it’s important for the anterior segment surgeon to be aware of the current options available to manage various endothelial disorders.
Dr. Samar Basak: For the anterior segment surgeon, it is important to have a basic know-how about the modern corneal transplant procedures. They should know about the wonderful outcomes that are possible with these techniques.
This is practically very important. Often, we get late referrals of post-cataract edema and the primary cataract surgeon has given a bleak prognosis. The patient is pleasantly surprised after the transplant. However, sometimes it becomes very difficult to convince them for the second surgery in spite of good prognosis. So anterior surgeons having knowledge of corneal surgery is important for timely referral and ultimately good outcomes to the patient.
Also, complications will happen. Rather than trying to rescue something beyond someone’s capability, it is better to leave it to the next surgeon. Many times we feel that if the cataract surgeon had not manipulated so much the outcome would be better after the endothelial keratoplasty procedures, such as, DSEK or currently DMEK.
eOphtha: With most corneal surgeons now becoming comfortable with DSEK/DSAEK, How important u think it is to learn DMEK?
Dr. J K Reddy: DMEK is the most recent and advanced technique at present times. A surgeon performing DSAK can easily be further trained to do DMEK. Visual recovery of DMEK is faster and better than DSAK.
Dr. Namrata Sharma: DSEK/DSAEK are very forgiving surgeries because of the fact it does not have a great learning curve and technically it is quite easy to do unlike for DMEK. 10 cases and you are there. DMEK surgery is technically difficult to do and has a relatively longer learning curve. Further, not all cases are fit for DMEK surgery. The advantage of DMEK surgery is that it does not require microkeratome which is expensive as opposed to DSAEK surgery. Furthermore, stringent donor criteria in DMEK of age more than 50 years and non-diabetic donors are difficult to get from the hospital cornea retrieval program (HCRP). This is because as per the statistics of the Eye Bank Association of India, we get donors who are younger in age in the HCRP program as opposed to the voluntary eye donation (VED) program where we get older donors.
If one is not trained in DMEK than in those cases DSAEK may be done as comparable visual acuities may be obtained with DMEK & Ultrathin DSAEK. Having said this, the quality of vision is better with DMEK as compared to DSAEK because the graft is thinner, and hence contrast sensitivity is much better, and higher-order observations are less.
Dr. Rajesh Fogla: DMEK has the advantage of transplanting donor Descemet membrane with healthy endothelial cells via an incision as small as 2mm. Due to the reduced amount of donor tissue transplanted, the risk of endothelial rejection is almost 15 times lower than traditional DSEK / DSAEK. This has a direct impact on the duration or frequency of post-operative topical steroids to prevent endothelial rejection. With a reduced need for steroids, secondary complications of raised intraocular pressure and lens changes can be significantly reduced with DMEK. The corneal anatomy is best restored with DMEK as it does not induce any changes in the posterior corneal curvature, unlike DSEK / DSAEK wherein this change induces a hyperopic refractive shift postoperatively. Hence to have improved refractive outcomes, and longer survival of transplanted donor graft, it's important to make a transition from DSEK / DSAEK to DMEK.
Dr. Samar Basak: The transition to DMEK should ideally be made after the surgeon is comfortable with DSEK/ DSAEK. It is important to have a back-up technique that you are confident in before venturing forth. Learning DMEK is important as it lets you offer better surgery to your patients. There is also a sense of self-improvement in performing the latest surgery. Then there is the professional competition aspect. If you are not doing DMEK, the patient might move to another surgeon who does. All considered, corneal surgeons should slowly transition to DMEK.
eOphtha: What are the indications for which you commonly perform DMEK?
Dr. J K Reddy: Pseudophakic bullous keratopathy, Fuch’s endothelial dystrophy, failed graft.
Dr. Namrata Sharma: Indications of DSAEK and DMEK are different because DSAEK is a more forgiving surgery; it can be done in far more complex cases. The indications for doing DMEK surgeries are Fuchs’ endothelial dystrophy, Pseudophakic Bullous keratopathy, failed therapeutic penetrating keratoplasty, failed DSAEK, congenital hereditary endothelial dystrophy, Posterior polymorphous membrane dystrophy, Iridocorneal endothelial (ICE) syndromes, and Herpetic endothelitis. In a country like ours, therapeutic keratoplasty is generally done using suboptimal grade donor tissue and hence patients may be visually rehabilitated by endothelial keratoplasty rather than replacing the whole graft with full-thickness penetrating keratoplasty.
Hence, indications of DMEK are expanding more so as more modifications are occurring in technique and technology related to DMEK.
Dr. Rajesh Fogla: DMEK is commonly performed for pseudophakic bullous keratopathy following complicated cataract surgery, toxic anterior segment syndrome, Fuchs endothelial dystrophy, and other indications such as aphakic bullous keratopathy, ICE syndrome, edema post-viral endotheliitis, etc.
Dr. Samar Basak: DMEK can be done for most causes of endothelial decompensation/diseases. The indications depend on the surgeon's experience. For beginner surgeon, ideal cases are Fuchs’ dystrophy (Triple-DMEK) and uncomplicated post-cataract surgery edema. Other common indications in my practice are – post HSV keratitis, ICE syndrome, failed graft, and posterior polymorphous corneal dystrophy. Difficult indications and relative contraindications are – the presence of vitreous in AC, aphakia, large iris defects, etc. We have recently published the largest series of DMEK (by a single surgeon from India) in consecutive 600 eyes in the June issue of the Indian Journal of Ophthalmology. In that paper, we have given detailed indications in my practice.
eOphtha: How long you wait for performing DMEK in a case of post-cataract surgery corneal decompensation?
Dr. J K Reddy: 2 to 3 months. Very rarely I perform within a month.
Dr. Namrata Sharma: Generally we wait for around 3 months in cases of post-cataract surgery corneal decompensation. In cases where corneal decompensation have occurred due to TASS, we would like to wait for longer period which may be 6 months as inflammation post-cataract surgery lasts longer and we have also published on this( Kaur M, Titiyal J, Falera R, Arora T, Sharma N. Outcomes of Descemet Stripping Automated Endothelial Keratoplasty in Toxic Anterior Segment Syndrome After Phacoemulsification. Cornea. 2017 Jan;36(1):17-20).
Dr. Rajesh Fogla: At least 8-12 weeks’ time should be given for corneal edema to recover post complicated cataract surgery. If the cornea does not show any signs of recovery during this period then an endothelial replacement surgery can be considered.
Dr. Samar Basak: So first we must rule out other causes of post-cataract corneal edema.
Often, it is due to a detached Descemet membrane which is usually fixed with a simple air Descemetopexy or by intracameral C3F8 injection. An anterior segment OCT is very important to rule out DM detachment in the presence of corneal edema. Sometimes, a retained nuclear fragment is missed, and removing the offending lens fragment immediately can reverse the corneal edema in a few days.
Once we have ruled these out, conventionally we wait for up to 3 months for the edema to resolve. Medical management is continued, and precaution must be taken to avoid a superinfection due to compromised corneal surface. We need to follow-up these patients every 2 weeks to see the result of medical treatment. Often the other eye Specular microscopy actually guides you about the improvement to some extent (Such as, if it is healthy – then wait and watch policy; or if it is suspected Fuchs’ dystrophy, of shows low cell count – usually edema progresses further and then, we need to intervene early. So, if it is worsening; or if the edema is severe from the very beginning (typically after DM being eaten by phaco probe) – in these cases DMEK may be done earlier because the visibility becomes poor.
eOphtha: For a future DMEK surgeon, what are the best resources to learn DMEK?
Dr. J K Reddy: Eye institutes where DMEK is routinely performed.
Dr. Namrata Sharma: There are various resources from where one can learn DMEK surgeries, which include the following:-
- Wet lab DMEK courses conducted by NGOs such as Sight Life, Lion’s international eye bank, etc. These are 3-4 day courses where there are didactic lectures, case selection, wet laboratory training on animal eyes or plastic eyes along with hands-on surgeries where the mentee assists some surgeries and then does surgeries under supervision.
- Short term or long-term courses at various centers in our country like R.P center (AIIMS), LVPEI, Disha Eye Hospital & Research Centre, Sankara Nethralaya, Aravind Eye Hospital, etc.
- Wet Lab Sessions held at various conferences by eminent national and international faculty
- Various models have also been described such as on the onion peel model described by Dr. Vikas Mittal (Mittal V, Mittal R, Singh S, Narang P, Sridhar P.Simulation Model for DMEK Donor Preparation. Cornea. 2018 Sep;37(9):1189-1191).
Dr. Rajesh Fogla: The best option for transition to DMEK is to observe DMEK surgeries with an experienced surgeon, attend a training course, perform wet lab practice, and then finally start DMEK under supervision of a trained surgeon (at least the initial 5-10 cases)
Dr. Samar Basak: Wet lab is the most important resource to learn DMEK. If the surgeon works with an eye bank, use the discarded corneas to learn the main steps of the surgery. Donor peeling practice can be done with any tissue. For donor insertion and unfolding, there are some innovations using an artificial anterior chamber. Watch ‘unedited’ surgical videos repeatedly. YouTube and most ophthalmic society websites have excellent teaching videos. It is easy to get lost with so many different techniques, so choose videos that closely match the surgeon’s own setup. Then spent some time with Masters in their operation theatre, observing the surgeon Live. Watch, Discuss, and Learn. One should have at least 50 DSEK experience prior. And while doing it practically, keep 5 patients in a row in two weeks, and you do mistake and try to correct it/them in the next case immediately, like not after a month or so. Always keep back up tissue, I always say for the first 50 cases. You will get the courage to proceed forward.
eOphtha: In our country with limited availability of good corneal donor tissue, does DMEK offer any advantage over DSEK/DSAEK?
Dr. J K Reddy: Yes very much. DMEK is less expensive than DSAK. The microkeratome related cost and problems are not present in DMEK.
Dr. Namrata Sharma: DMEK offers many advantages over DSEK/DSAEK. The rate of graft rejection in cases of DMEK is much less (1% as opposed to 7%) and the contrast sensitivity is better and higher-order aberrations are also less. DMEK graft is the most physiological graft. Also if you are combining the endothelial keratoplasty surgery with cataract surgery, like in DMEK triple there is no hyperopic shift as compared to the DSAEK triple as there is an addition of stroma with DSAEK procedure.
In our country where tissue availability is a concern single tissue can be utilized for multiple recipients surgeries such as DALK, DMEK and Limbal cell transplant from one Cornea (Vajpayee RB, Sharma N, Jhanji V, Titiyal JS, Tandon R. One donor cornea for 3 recipients: a new concept for corneal transplantation surgery.Arch Ophthalmol. 2007 Apr;125(4):552-4.
Dr. Rajesh Fogla: As the donor DM is used for DMEK, there is an option to use the remaining donor stromal tissue for an anterior lamellar corneal surgery, which improves the utility of the donor tissue.
Dr. Samar Basak: We already know that DMEK has less chance of graft rejection than DSEK which is a big advantage. It also has faster visual rehabilitation and a better quality of vision. These pros outweigh strict tissue criteria. The availability of good donor cornea is perceived as a limitation, however, that is not the case. The tissue damage during DMEK for corneal surgeons familiar with DSEK is less than 1%. With the national corneal distribution system in place, availability is also better now. Again, I shall refer my published papers on DMEK recently – and you will understand this is rather a myth.