DSEK Versus DMEK – A
Prospective Study. Dr. Vijayalakshmi Prabhu,
P16693, Dr. K S Siddharthan, Dr. Jagadeesh KumarReddy K
DSEK versus DMEK – A prospective study
Purpose :
To evaluate visual acuity and endothelial cell density after Descemet Stripping Endothelial Keratoplasty (DSEK) in comparison with Descemet Membrane Endothelial Keratoplasty (DMEK).
Design:
Non-randomised, prospective study.
Methods :
17 eyes of 17 patients undergoing DSEK, who completed a 1-year follow-up, were compared with 17 eyes of 17 patients undergoing DMEK for Fuch’s endothelial dystrophy, Phakic / Pseudophakic Bullous Keratopathy. Main outcome measures included Best-Corrected Visual Acuity (in logarithm of the minimal angle of resolution – logMAR units) and Endothelial Cell Density(ECD) within a 1-year follow-up.
Results :
BCVA increased from 1.41 ± 0.38 logMAR and 1.40 ± 0.33 logMAR pre-op to 0.37 ± 0.11 logMAR & 0.23 ± 0.17 logMAR at 6 months post-op (p<0.05), and to 0.18 ± 0.12 logMAR & 0.09 ± 0.15 logMAR 1 year after DSEK and DMEK (p<0.05),respectively. ECD decreased from 2422 ± 163 cells/mm2 and 2463 ± 180 cells/mm2 pre-op to 1684 ± 152 cells/mm2 & 1559 ± 141 cells/mm2 1 year after DSEK and DMEK(p<0.05) respectively.
Conclusion :
DMEK provided faster visual rehabilitation when compared to DSEK.
Introduction
Keratoplasty is considered as the most successful organ transplantation technique worldwide. The first successful penetrating keratoplasty was performed by Edward Konrad Zirm in 1906 1. Penetrating keratoplasty involves surgical removal of diseased or damaged cornea from the host and replacement with a full-thickness donor cornea. The major goals of penetrating keratoplasty are to improve visual acuity, to maintain the integrity of the eye and to treat various infections. The drawbacks of full thickness corneal surgery have been well recognized and include unpredictable refractive outcomes, permanent weakening of the eye, suture related complications, vulnerability to trauma, prolonged visual rehabilitation, corneal graft rejection, and ultimately graft failure.
Arthur Von Hippel performed the first successful lamellar keratoplasty (LK) for visual impairment in 1886 2. The basic principle of LK is to replace only that part of cornea that is diseased and leave the recipient’s normal anatomic layers intact .The advantage of this technique is that there is only least amount of resection. LK procedures performed in the anterior or posterior domain of the human cornea are referred to as anterior lamellar keratoplasty (ALK) and posterior lamellar keratoplasty (PLK) respectively. The dividing boundary line between ALK and PLK (Descemet’s stripping endothelial keratoplasty [DSEK], Descemet’s stripping automated endothelial keratoplasty [DSAEK] and Descemet’s membrane endothelial keratoplasty [DMEK]) is the Descemet’s membrane.
Endothelial keratoplasty (EK) is an exciting development in the field of corneal transplantation that allows selective replacement of diseased endothelium. The current success of EK is attributable to the pioneering work of Melles, who introduced the concept of posterior lamellar keratoplasty (PLK).3,4 Terry et al popularized the procedure as Deep Lamellar Endothelial Keratoplasty ( DLEK) 5,6. Price et al developed a procedure in which there is lamellar dissection of stroma, descemet membrane and endothelium and termed it as Descemet’s Stripping Endothelial Keratoplasty (DSEK) 7.
A variant of DSEK where microtome assisted donor dissection was described by Gorovoy and termed as Descemet’s stripping automated endothelial keratoplasty (DSAEK)8. With DSAEK, the corneal clarity is restored within a short period of time but the resulting stromal interface haze may be a limiting factor for final visual acuity. Many authors have attributed this limitation to problems with the recipient-donor stromal interaction like initial keratocyte apoptosis and a later hyperactivity and stromal regeneration as seen on histopathology. There is also proteoglycan deposition in the interface. It leads to formation of interface haze, thus limiting the visual potential to 20/30 or less in many patients and reduces the contrast sensitivity.
To overcome this in 2006, Melles made further refinement in endothelial keratoplasty where the graft consists only of descemet membrane and endothelial cells and coined as Descemet’s Membrane Endothelial Keratoplasty (DMEK) 9.Thus the recipient cornea retains its optical quality with no interface and majority of these patients attain 20/20 vision. McCauley et al by using a microkeratome modified this technique and termed as Descemet’s Membrane Automated Endothelial Keratoplasty(DMAEK) 10.
The intraocular complications such as expulsive hemorrhage, cataract, glaucoma are much avoided in lamellar keratoplasty. The incidence of graft rejection and wound dehiscence are also much less when compared with penetrating keratoplasty.
Main parameters that define the success of a surgical technique for corneal replacement are the functional outcome as well as endothelial cell survival. Many studies have shown that DSAEK and DMEK offer significant advantages over PK with regard to postoperative visual outcome and postoperative astigmatism, as well as providing faster functional rehabilitation.11-14 PK might be better when compared with DSAEK or DMEK, with respect to endothelial cell survival in the early postoperative period.15,16 However, mid-term results show comparable endothelial cell survival between PK and DSAEK or DMEK.17-21.A study evaluating outcomes of DMEK in comparison with DSEK has not yet been carried out in the Indian population.
Hence, this study aims to evaluate the visual outcome and endothelial cell density in patients undergoing DSEK in comparison with those undergoing DMEK at a tertiary eye centre in South India. Results of the study can be extrapolated to the general population. Providing faster and complete rehabilitation through these newer techniques would therefore benefit the patients, in particular and the society, at large.
Recipient characteristics
Table 1 and figure 1 Age distribution
| Age Distribution | ||||
| Study Group | ||||
| Age | DMEK | DSEK | Total | (%) |
| < 40 years | 2 | 2 | 4 | 12% |
| 41 – 50 | 2 | 3 | 5 | 15% |
| 51 – 60 | 2 | 2 | 4 | 12% |
| 61 – 70 | 7 | 6 | 13 | 38% |
| > 70 years | 4 | 4 | 8 | 24% |
| Total | 17 | 17 | 34 | 100% |
Table 2 and Figure 2 Diagnosis
| Study Group | |||
| Indication | DMEK | DSEK | Total |
| PBK | 13 | 16 | 29 |
| FED | 4 | 1 | 5 |
| Total | 17 | 17 | 34 |
DMEK = Descemet Membrane Endothelial Keratoplasty; DSEK = Descemet Stripping Endothelial Keratoplasty
Methods
The study commenced after obtaining the Institutional Ethics Committee and the Scientific Committee approval.
Patients:
17 eyes of 17 patients undergoing DSEK between January 2014 and January 2015, who completed a 1-year follow-up, were included in this study. These patients were compared with 17 eyes of 17 patients undergoing DMEK between January 2014 and January 2015, after having been matched with the DSEK patients, with respect to diagnosis and donor characteristics. Indications for surgery were Fuch’s endothelial dystrophy( n = 1 and n = 4 for DSEK and DMEK, respectively) and PBK (n = 16 and n = 13 for DSEK and DMEK, respectively). Patients with other ocular pathologies were not included in this study. All patients received a graft prepared from a corneoscleral button that had been stored in Cornisol (Aurolab, 1, Sivagangai Main road, Veerapanjan, Madurai – 625020, India) at 4° C (short-term cultured graft) in co-ordination with our eye bank.
Corneal donor tissue:
All patients received corneal grafts from our eye bank. All grafts were short-term cultured in Cornisol at 4 ° C. All donor corneas with endothelial cell density more than 2000 cells/mm2 were used in this study. The corneas were taken from donors aged between 40 and 65 yrs. Published data by Laaser and associates22 suggests that donor tissue culture conditions have no significant effect on visual outcome and endothelial cell survival.
Surgery:
All surgeries were performed by 2 surgeons under regional/peribulbar anaesthesia. Donor preparation was performed immediately prior to transplantation. Donor preparation was successful in all DMEK/DSEK cases, without any loss of corneoscleral buttons.
DMEK :
After mounting the corneoscleral button on a teflon block , the endothelium was marked by gentle touch with a 7.5 to 8.5 mm trephine (depending on the required graft size) and stained with 0.06% trypan blue for 60 seconds. The groove of the endothelium and Descemet’s membrane graft was deepened by Sinskey hook. The edge of DMEK graft was first lifted with a Sinskey hook and then grasped with 2 forceps . By simultaneous centripetal movement of the 2 forceps, the graft was completely detached. Due to the elastic properties of Descemet’s membrane, the endothelium-Descemet’s membrane (EDM) roll was formed spontaneously with endothelial side outside. The graft was then taken into a intraocular lens catridge (Technis 2.2 mm AMO) connected to a 1 ml syringe with a silicon tubing .The host corneal epithelium is marked with a corresponding sized trephine marker. A 3 mm clear corneal incision was made in the patient’s cornea. The patient’s EDM was removed under air using an inverted Sinskey hook inside the trephine marking. A sideport was made for the ease of injecting air during the procedure. The graft was injected into the anterior chamber .The EDM was positioned centrally and unfolded by applying intermittent pressure to outer corneal surface. By enlarging the air bubble, the EDM was then flattened out on the surface of the iris and then air was completely removed, resulting in shallowing of the anterior chamber. Air was injected underneath the graft until the anterior chamber was completely filled with air, which was left in place for at least 3 hours following the procedure. If pupillary block was noted then air release was done or the air was left in-situ for 1 day. Any complications during the procedure were noted.
DSEK :
The preparation of donor corneal lenticules was performed using the manual dissection technique. Ultrasonic pachymetry was done to assess corneal thickness. A limbal incision was made at a predetermined depth of approximately 500 µm. Air was used in the anterior chamber maintainer to facilitate a complete limbus-to-limbus corneal pocket, using corneal crescent knife. The corneal lenticule was mounted on a teflon block with the endothelial side-up, followed by trephination with a 8-mm trephine. Transfer of the graft into the patient’s eye was achieved by using the Busins glide (Abbott Medical Optics Inc., 1700E, St.Andrew Place, Santa Ana, CA – 92705, USA) through a 3.2 mm nasal clear cornea tunnel. After marking the epithelium with a 9-mm marker, the patient’s EDM was removed under air using an reverse Sinskey hook inside the 9-mm marking. The graft was delivered to the patient’s eye using the standardized pull-through technique by Busin23 . The graft was placed on the plate and pulled into the funnel-shaped part of the Busins glide using a micro-incision forceps. The Busin glide was then inverted and positioned at the nasal clear cornea tunnel. On the temporal side, a microincision forceps was inserted to pull the graft into the anterior chamber, allowing it to unfold spontaneously. Air was injected underneath the graft until the anterior chamber was completely filled with air, which was left in place for 3 hours following the procedure. Any complications during the procedure were noted.
Main outcome measures
Main outcome measures included best corrected visual acuity (BCVA, logMAR) and
endothelial cell density (ECD) within 1-year follow up. The endothelial cell density was measured using Endothelium Specular Microscope (TOMEY EM-3000) . The corneal graft changes were also noted like detachment of the graft, corneal edema using slit lamp. (Topcon-SlIE,Topconcorp,JAPAN).
A failed graft was identified based on its clarity which was determined by Descemet membrane folds and Descemet Membrane Detachment (DMD) which reduced the visual outcome and/or necessitating secondary intervention.
Statistical evaluation was performed. The differences in quantitative variables between groups were assessed by means of the unpaired t test. Comparsion between groups was made by the Non parameteric Mann-Whitney test. ANOVA was used to assess the quantitative variables. Turkey’s post hoc test was performed. A chi square test was used to assess differences in categoric variables between groups. A p value of <0.05 using a two-tailed test was taken as being of significance for all statistical tests.
Results
Visual outcome:
Patients with other ocular comorbidity, besides Fuch’s endothelial dystrophy/ PBK were not included in this study. All DSEK patients (n=17) and DMEK patients (n=17) completed a 1-year follow-up.
The mean of logMAR in DSEK group at post-operative 1 month follow-up was 0.672+/-0.18 (p<0.01), 3 months follow-up was 0.524+/-0.21 (p<0.001), 6 months follow-up was 0.373+/-0.11 (p<0.001)and 1 year follow-up was 0.185+/-0.12 (p<0.001) respectively. The increase in mean BCVA was statistically significant.
Table 3 and Figure 3 Mean log MAR in DSEK group
| Mean of logMAR in DSEK group | ||||
| Mean | SD | sig | ||
| DSEK | Pre | 1.413 | 0.384 | |
| Day1 | 1.198 | 0.363 | >0.05 | |
| Day3 | 1.094 | 0.286 | <0.05 | |
| 1 week | 1.030 | 0.309 | <0.05 | |
| 1 Month | 0.672 | 0.185 | <0.01 | |
| 3 Month | 0.524 | 0.206 | <0.001 | |
| 6 Month | 0.373 | 0.114 | <0.001 | |
| 1 Year | 0.185 | 0.124 | <0.001 | |
The mean of logMAR in DMEK group at post-operative 1 month follow-up was 0.401+/-0.14(p<0.01), 3 months follow-up was 0.299+/-0.12 (p<0.001), 6 months follow-up was 0.234+/-0.17 (p<0.001) and 1 year follow-up was 0.087+/-0.15 (p<0.001) respectively. The increase in mean BCVA was statistically significant.
Table 4 and Figure 4 Mean logMAR in DMEK group
| Mean of logMAR in DMEK group | ||||
| Mean | SD | sig | ||
| DMEK | Pre-op | 1.401 | 0.331 | |
| Day1 | 0.997 | 0.385 | <0.05 | |
| Day3 | 0.930 | 0.420 | <0.05 | |
| 1 week | 0.846 | 0.525 | <0.05 | |
| 1 Month | 0.401 | 0.144 | <0.01 | |
| 3 Month | 0.299 | 0.124 | <0.001 | |
| 6 Month | 0.234 | 0.168 | <0.001 | |
| 1 Year | 0.087 | 0.153 | <0.001 | |
A total of 94% eyes in DSEK group and 92% eyes in DMEK group achieved a BCVA of <0.5 at the end of 1 year.
Endothelial cell density :
The mean of ECD in DSEK group at post-operative 1 month follow-up was 2199+/-195 cells/mm2(p<0.05), 3 months follow-up was 2089+/-187 cells/mm2(p<0.001), 6 months follow-up was 1902+/-186 cells/mm2(p<0.001) and 1 year follow-up was 1684+/-152 cells/mm2(p<0.001) respectively. The decrease in ECD was statistically significant.
Table 5 and Figure 5 Mean ECD in the DSEK group
| Mean ECD in DSEK group | |||||
| Mean | SD | sig | Mean difference | ||
| DSEK | Pre-op | 2422 | 163 | ||
| 1 Month | 2199 | 195 | <0.05 | 223.007* | |
| 3 Month | 2089 | 187 | <0.001 | 332.570* | |
| 6 Month | 1902 | 186 | <0.001 | 520.132* | |
| 1 Year | 1684 | 152 | <0.001 | 738.007* | |
The mean of ECD in DMEK group at post-operative 1 month follow-up was 2207+/-173 cells/2(p<0.01), 3 months follow-up was 2036+/-177 cells/mm2(p<0.001), 6 months follow-up was 1866+/-207 cells/mm2(p<0.001) and 1 year follow-up was 1559+/-141 cells/mm2(p<0.001) respectively. The decrease in ECD was statistically significant.
Table 6 and Figure 6 Mean ECD in the DMEK group
| Mean ECD in DMEK group | |||||
| Mean | SD | Sig | Mean Difference | ||
| DMEK | Pre-op | 2463 | 180 | ||
| 1 Month | 2207 | 173 | <0.01 | 242.416* | |
| 3 Month | 2036 | 177 | <0.001 | 406.845* | |
| 6 Month | 1866 | 207 | <0.001 | 570.845* | |
| 1 Year | 1559 | 141 | <0.001 | 867.845* | |
The mean endothelial cell loss at the end of 1 year in the DSEK group was 31.50% and in the DMEK group was 36.01%. Statistical significance was observed between the groups in ECD at the end of 1 year (p<0.05).
DISCUSSION
When DSEK was introduced first by Price and Price in 2005, it was observed that the technique maintained the anatomical integrity of the cornea and provided faster visual recovery for the patients.7 Subsequently, in 2006, DMEK was introduced by Melles24 when it was observed that the new procedure would provide quick visual rehabilitation to the patients without affecting the endothelial cell survival. The usage of PK for patients with corneal endothelial disorders has rapidly declined since then.
DSEK is a surgical technique which is widely practised these days. DMEK is a surgical technique which is carried out to a limited extent because of problems encountered during the donor preparation and uncurling of the DM in the anterior chamber.
Currently, DSEK remains the surgical procedure of choice for treating corneal endothelial disorders. It is a widely accepted fact that DSEK allows for a good donor preparation and easier manipulation of the graft in the anterior chamber because of the higher stability of the thicker graft. Also, the availability of the new graft insertion devices for DSEK23,25 makes it a more frequently performed procedure in comparison with DMEK. However, the thickness of the posterior stroma in DSEK, although decreasing with time26 seems to affect the visual outcome. The poorer visual acuity in DSEK has been attributed to the presence of stroma which seems to cause posterior astigmatism, a hyperopic shift26-29 or atleast higher-order optical aberrations30. Thus, DMEK, where the donor graft does not have a posterior stroma is thought to provide a better functional outcome.
In our study, a total of 34 patients were included of which 17 patients had undergone DMEK and 17 patients had undergone DSEK respectively.
In the DMEK group, 13 were PBK patients and 4 were FED patients. 11 patients were males and 6 patients were females. The age of patients ranged from 32 to 83 years with a mean age of 61.7+/-13.8 years.
In the DSEK group, 16 were PBK patients and 1 was FED patient. 9 patients were males and 8 patients were females. The age of patients ranged from 35 to 84 years with a mean age of 60.5+/-13.5 years.
Visual outcome
In our study, six months after surgery, 85% of patients after DMEK had a vision better than 0.5 and 50% of patients after DSEK had a vision better than 0.5. The DMEK group showed better BCVA than the DSEK group at the 6-month time point : 0.23+/-0.17 logMAR and 0.37+/-0.11 logMAR for DMEK and DSEK, respectively. This is comparable to the findings in Goldich Y et al31 study and Tourtas T et al32 studies.
At 1 year follow-up period, in our study, 92% of patients in the DMEK group and 94% of patients in the DSEK group had vision better than 0.5 as compared to previously published data by Ham and associates13 and Droustas and associates,33who reported a visual acuity of 20/40 or better in 95% and 96% of patients, respectively, and a visual acuity of 20/25 or better in 75% and 74% of patients, respectively, 6 months after surgery. Price34 et al observed a visual acuity of 20/40 or better in 94% of patients and a visual acuity of 20/25 or better in 63% of patients 3 months after surgery. Theofilas32 et al observed a visual acuity of 20/40 or better in 95% and 43% of patients, 6 months after DMEK and DSAEK, respectively. Also they observed that 50% and 6% of patients reached a BCVA of 20/25 or better, 6 months after DSAEK and DMEK, respectively. The percentage of visual acuity of 20/40 or better 6 months after DSAEK has been observed to vary between 80% and 97%.35-37
In our study, the mean BCVA was 0.09+/-0.15 logMAR and 0.18+/-0.12 logMAR 1 year after DMEK and DSEK, respectively as compared to the mean BCVA of 0.11±0.13 logMAR and 0.20±0.13 logMAR 6 months after DMEK and DSAEK, respectively in Terry MA et al38 study.
Endothelial cell density
Another factor of paramount importance which decides the success of a posterior lamellar keratoplasty is endothelial cell survival. The mean ECD before surgery was 2463+/-180 cells/mm2 and 2422+/-163 cells/mm2 in the DMEK and DSEK groups, respectively. The mean ECD at 1 year follow-up period was 1559+/-141 cells/mm2 and 1684+/-152 cells/mm2 in the DMEK and DSEK groups, respectively. The mean ECD difference was 867 cells/mm2 and 738 cells/mm2 at 1 year after DMEK and DSEK respectively.
In our study, the endothelial cell loss in the patients, after DMEK and DSEK, were 36.01% and 31.50% respectively, 1 year after surgery. Endothelial cell loss at 6-month follow-up period was 25.9±14.0% after DSAEK and 27.9±16.0% after DMEK in Terry MA et al35 study. Theofilas and associates32 reported an endothelial cell loss of 41% in the DMEK group and an endothelial cell loss of 39% in the DSEK group at 6-month post-operative period.
Endothelial cell loss was 32%+/-20% after DMEK in 38 eyes that reached the 6-month examination in Price et al study.34 The average 6-month endothelial cell loss after DMEK in three series was 32%.15,34,39 The endothelial cell loss at 1 year was 36 ± 20% with most of the loss being observed during the first 3 months after surgery: 31 ± 18% (range, 3%-77%) in Guerra et al study40.Additionally, Ham et al reported an endothelial cell loss of 34% and 42% after DMEK , in a subset of patients that had completed 2 and 3 years of follow-up, respectively.41
The low endothelial cell density in our DMEK patients may be attributable to increased endothelial cell loss caused during donor preparation and manipulation of the Descemet Membrane in the anterior chamber during the surgery.
Complications
Descemet Membrane was not attached in 4 patients and graft edema was seen in 1 patient in the DMEK group. Graft edema was seen in 1 patient in the DSEK group. As a part of treatment of these complications, 3 patients underwent Penetrating Keratoplasty and 1 patient underwent DSEK. 1 patient underwent intracameral air injection which was successful. In the DSEK group, 1 patient underwent DMEK as repeat procedure. In our study, in the DMEK group, a total of 4 patients had graft detachment which constitutes about 23% as compared to 19 (21%) cases out of 87 patients in Droutsas K et al study.33 In our study, 24% of the cases in DMEK group failed which is comparable to the failure rate of 20% after DMEK procedure in Ham L et al study.13 In DMEK, Price et al reported a primary graft failure rate of 8% in an initial series of 60 eyes34 and Dapena et al reported 11 primary failures (9.2%) in their consecutive series of 120 eyes.42
The cause for graft failure in our study was primary failure. Primary graft failure defines an initial lack of endothelial function, with the graft failing to clear as expected and may be attributed to primary donor endothelial dysfunction from suboptimal quality or surgical trauma to the endothelium at the time of transplantation.
This technique is relatively new and standardising the DMEK surgical technique, would make the technique, safe and very effective. Also, the adhesive property of the donor graft used in DMEK needs to be evaluated. The failure rate is expected to go down with refinement in surgical techniques and better instrumentation. Long-term data with more number of patients are needed to understand long-term endothelial cell loss and graft survival with this procedure.
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