Donor tissue culture conditions and outcome after descemet membrane endothelial keratoplasty

Development of Thermoplastic Polyurethane Films for the Replacement of Corneal Endothelial Function of Transparency Maintenance

Endothelial keratoplasty is the main surgical procedure for treating corneal endothelial dysfunction (CED), which is limited by the global shortage of donor corneas. Herein, we developed and evaluated the modified thermoplastic polyurethane (M-TPU) films with gelatin-glycidyl methacrylate to replace the corneal endothelial function and maintain corneal transparency. The films displayed comparable light transmission characteristics with normal corneas and clinically favorable mechanical properties for surgical manipulation. After surface modification, the hydrophilicity and biocompatibility of M-TPU films were significantly improved. In the rabbit CED model, the M-TPU implants exhibited firm adhesion to the exposed stromal surface. The rabbit corneal transparency and thickness could be restored completely within 1 week of M-TPU film implantation. There was no significant inflammatory reaction and immune rejection during the follow-up of 1 month. Proteomic analysis suggested that the complement inhibition, the increase of mineral absorption, and the decrease of P53 apoptosis signaling pathway and lysine degradation might be beneficial in maintaining the corneal transparency. Overall, our study demonstrated the potential of M-TPU films as artificial implants for the replacement of corneal endothelial function to restore corneal thickness and transparency.

Rate of Endothelial Cell Loss and Graft Survival in Descemet Membrane Endothelial Keratoplasty in Eyes Requiring a Rebubble

PURPOSE

We aimed to compare the rate of 6-month endothelial cell loss (ECL) and 6-month graft survival in eyes that did not require a postoperative rebubble with eyes that did require a postoperative rebubble after Descemet membrane endothelial keratoplasty (DMEK) surgery.

METHODS

A consecutive series of DMEK surgeries performed from September 2013 to March 2020 was retrospectively analyzed. Eyes that did not require a rebubble for graft detachment were compared with eyes with 1 rebubble and eyes with 2 or more rebubbles for 6-month ECL and graft survival. A subanalysis of the rebubble rate for different indications for transplantation was also performed.

RESULTS

One thousand two hundred ninety-eight eyes were included in this study. The 6-month ECL for eyes with no rebubbles, 1 rebubble, and ≥2 rebubbles was 29.3% ± 16.2% (n = 793), 36.4% ± 18.6% (n = 97, P = 0.001), and 50.1% ± 19.6% (n = 28, P < 0.001), respectively. The 6-month graft survival rate for eyes with no rebubbles, 1 rebubble, and ≥2 rebubbles was 99.5%, 97.8% ( P = 0.035), and 81.8% ( P < 0.001), respectively. When compared to the rebubble rate for DMEK for Fuchs dystrophy (156/1165 eyes = 13.4%), the rebubble rates were statistically higher for DMEK for failed penetrating keratoplasty (28.5%, P = 0.021) and pseudophakic bullous keratopathy (28.0%, P = 0.036).

CONCLUSIONS

Eyes undergoing any rebubble procedure in the postoperative period after DMEK have an increased risk of endothelial cell loss and graft failure at 6 months postoperative. DMEK in eyes for failed penetrating keratoplasty and failed DMEK had the highest rebubble rate, with the former reaching statistical significance.

Sutured Descemet Membrane Endothelial Keratoplasty in Patients With Complex Anatomy or Difficulty Positioning

PURPOSE

In Descemet membrane endothelial keratoplasty (DMEK), some patients cannot adhere to postoperative positioning requirements or lack anatomic support for a gas bubble in the anterior chamber. We describe a suturing technique that stabilizes the graft postoperatively without tearing or tenting it.

METHODS

One to two 10-0 nylon sutures with a spatulated needle are used to secure DMEK grafts. Tied with minimal tension, the sutures traverse the corneal stroma at a steep, almost perpendicular angle and approach the graft from the limbus at an angle tangential to the circular graft to prevent vaulting the tissue off the central cornea. We report preoperative and postoperative best spectacle-corrected visual acuity, corneal pachymetry, and anterior segment optical coherence tomography confirming graft attachment in 3 patients.

RESULTS

In case 1 (aphakia, postvitrectomy, and positioning difficulty), pachymetry decreased from 637 μm preoperatively to 495 μm and best spectacle-corrected visual acuity improved from 20/70 to 20/50 at postoperative week 1. In case 2 (aphakia, limited follow-up, and medication adherence), pachymetry decreased from 1106 μm preoperatively to 783 μm at postoperative month 1. In case 3 (tube shunt and loss of gas bubble at 2 hours), slit-lamp examination at postoperative day 1 showed corneal clearing and graft attachment. Pachymetry decreased from over 795 μm preoperatively to 582 μm at postoperative month 1. Anterior segment optical coherence tomography confirmed graft attachment in all patients.

CONCLUSIONS

Single or opposing tangentially oriented sutures can be safely applied to secure DMEK grafts postoperatively in challenging cases.

Double-Scroll Formation by Fluid Column Manipulation in Preloaded DMEK Grafts Prepared From Younger and Older Donor Tissue

PURPOSE

The purpose of this study was to determine whether manipulation of preloaded single-scroll Descemet membrane endothelial keratoplasty (DMEK) grafts within the fluid column of an injector can safely and reliably result in formation of double-scroll DMEK grafts and whether there are differential effects on younger versus older donor tissue.

METHODS

Pairs of DMEK grafts prepared from older (65-80 years) and younger (48-64 years) donors were preloaded into a Straiko modified Jones tube. One member of the pair was manipulated within the fluid column to form a double-scroll graft, and the other remained unmanipulated. Outcomes measured include success rate for double-scroll formation, endothelial cell loss (ECL), and relative scroll width.

RESULTS

Older donor grafts formed double scrolls with a 100% success rate. ECL of older donor manipulated grafts was statistically higher than that of unmanipulated mate grafts (17.4% ± 3.5% vs. 13.0% ± 4.2%, P = 0.03), but was still within the acceptable range for transplant. Younger donor grafts were successfully manipulated into double scrolls with a 67% success rate, and there was no difference in the ECL of manipulated and unmanipulated grafts (15.5% ± 4.4% vs. 13.0% ± 4.5%, P = 0.24). For all grafts and conformations, there was a significant relationship between relative scroll width and ECL ( P < 0.01).

CONCLUSIONS

Fluid column manipulation can be used reliably to form double-scroll DMEK grafts. For younger donor grafts, manipulation yields a double scroll without increasing ECL. For older donor grafts, manipulation results in a minimal, acceptable increase in ECL. Surgeons should weigh the advantage of an easily opened graft against the risk of increased ECL when considering this technique.

Examination of a Modified Graft Preparation Technique to Induce Double-Scroll Formation and Promote the Use of Younger Descemet Membrane Endothelial Keratoplasty Donor Tissue

PURPOSE

The purpose of this study was to determine whether controlled balanced salt solution (BSS) bursts during graft preparation can safely promote formation of a double-scrolled Descemet membrane endothelial keratoplasty (DMEK) graft in younger donor tissue.

METHODS

DMEK grafts prepared from young donor tissue (average age, 55 years; range, 39-66 years) were floated in BSS to spontaneously form scrolls (N = 10 pairs). Controlled BSS bursts were used to promote double-scroll (DS) formation in 1 member of each pair. Grafts were stained, preloaded, and shipped before cell viability analysis. After appropriate training, a less experienced technician performed this technique on 10 additional corneas. Outcomes measured for both technicians include the success rate for obtaining a DS, scroll conformation after shipping, and endothelial cell loss (ECL).

RESULTS

There was no difference in ECL between grafts subjected to additional manipulation compared with unmanipulated mate grafts (observer 1: 15.2% ± 3.3% vs. 15.2% ± 4.4%, P = 0.99; observer 2: 16.3% ± 2.9% vs. 15.9% ± 4.5%, P = 0.8). A technician experienced with this technique had a 90% success rate, whereas a less experienced technician had a 70% success rate. The mean ECL of the 10 grafts manipulated by the less experienced technician was not significantly different from results obtained from the experienced technician (observer 1: 18.5% ± 6.0% vs. 15.2% ± 3.3%, P = 0.15; observer 2: 18.1% ± 5.6% vs. 16.3% ± 2.9%, P = 0.34). Scrolls maintained their conformation during shipping events.

CONCLUSIONS

Double-scroll graft formation using controlled BSS bursts is a reliable technique that can be performed without causing additional damage to DMEK grafts. This technique may make graft unscrolling easier and can promote the use of younger donor tissue for DMEK.

Delivering Endothelial Keratoplasty Grafts: Modern Day Transplant Devices

PURPOSE

To summarize the graft loading, transporting and delivery devices used for endothelial keratoplasty (EK).

METHODS

A literature search of electronic databases was performed.

RESULTS

New techniques and devices have been introduced and implemented to prepare, load, transport and transplant the grafts for EK. The advantages are not only limited to the surgical theatre but also widely spread across the eye banking field. Investigation of advanced materials and designs have been rapidly growing with continuous evolution in the field of eye banking and corneal transplantation. Innovative techniques and modern devices have been evaluated to reduce the endothelial cell loss and increase the precision of the transplant in order to benefit both surgeons and the patients.

CONCLUSIONS

It is extremely important to reduce any potential wastage and optimize the use of every available donor cornea due to the limited availability of healthy cadaveric donor corneas required for transplants. As a result, the use of pre-cut and pre-loaded grafts supplied by the eye banks in calibrated devices have been gaining momentum. Innovation in the field of bioengineering for the development of new devices that facilitate excellent clinical outcomes along with reduction in learning curve has shown promising results.

Rotational alignment of corneal endothelial grafts and risk of graft detachment after Descemet membrane endothelial keratoplasty: a double-masked pseudo-randomized study

PURPOSE

The posterior cornea is rotationally asymmetric, and Descemet membrane endothelial keratoplasty (DMEK) grafts preferentially scroll vertically. This prospective study assessed whether graft attachment after DMEK differed depending on the rotational alignment of the donor graft in the recipient eye.

METHODS

Pseudo-randomization and blinding of the graft orientation in the recipient's eye were possible by procedural separation: (1) The eye bank recorded the position of an orientation marker in the donor cornea; (2) the surgeon preparing the DMEK graft recorded an upside-down marker relative to the eye bank marker; and (3) the surgeon assessed the position of the upside-down marker in the recipient after DMEK. Surgeons were masked towards the eye bank marker. Using mixed-effects models, we assessed graft attachment relative to the rotational alignment of the donor graft.

RESULTS

Postoperatively, the graft was not fully attached in 59 of 179 eyes (33%). A second air fill (rebubbling) was performed in 11%. The graft axis was in line with the recipient cornea axis in 40%, oblique in 28% and orthogonal in 32%. We did not detect an elevated risk of incomplete attachment (odds ratio [OR], 1.16; 95% CI, 0.61-2.20), risk of rebubbling (OR, 1.25; 95% CI, 0.47-3.31) or larger areas of graft detachment in non-aligned grafts compared to aligned grafts.

CONCLUSION

Rotational alignment was not strongly associated with the risk of incomplete graft attachment, although modestly elevated risks cannot be ruled out. Efforts are needed to reduce the need for rebubbling after DMEK and to identify modifiable risk factors for graft detachment.

Implantation of an Artificial Endothelial Layer for Treatment of Chronic Corneal Edema

PURPOSE

The purpose of this study was to describe a novel device that may serve as an alternative to Descemet membrane endothelial keratoplasty (DMEK) for the treatment of chronic corneal edema.

METHODS

The EndoArt (EyeYon Medical, Israel) is a flexible, 50-μm thin artificial endothelial layer that matches the cornea's posterior curvature and functions as a fluid barrier at the posterior stroma, replacing the diseased endothelium. Similar to a DMEK approach, it is implanted into the anterior chamber, carefully positioned on the posterior stroma, and secured using an air-gas mixture. Two patients with chronic corneal edema resulting from endothelial decompensation underwent implantation of the new artificial lamella.

RESULTS

In patient 1, the central corneal thickness (CCT) decreased from 730 μm preoperatively to 593 μm at 1 day postoperatively. In patient 2, the CCT decreased from 761 μm preoperatively to 487 μm at 1 day postoperatively. Both patients reported high satisfaction and an overall brighter visual quality. Although dislocation of the lamella occurred in both cases, the CCT was promptly restored after a repositioning procedure and remained stable at the 17-month follow-up (CCT of 526 and 457 μm for patients 1 and 2, respectively). In contrast to DMEK donor tissue, the artificial lamella is sufficiently robust to allow easy intraocular manipulation without the risk of damaging the implant. It is easily removable and does not require any immunosuppressive treatment because of its nonbiological nature.

CONCLUSIONS

Implantation of the EndoArt led to rapid corneal deturgescence and CCT restoration, presenting a possible option for patients with chronic corneal edema.

Modified procedure for Loading "Flat" DMEK Grafts Into an Injector

PURPOSE

The aim of this study was to determine whether loading a Descemet membrane endothelial keratoplasty (DMEK) graft using a drop-in procedure results in more endothelial cell loss (ECL) than the standard suction procedure.

METHODS

Pairs of donor corneas with equivalent preprocessing endothelium were prepared using the standard protocol of our eye bank. One member of each pair was loaded into an injector using the standard suction protocol. The mate graft was loaded using a drop-in protocol, in which the edge of the graft was gently grasped with a forceps, lifted to the edge of the injector, and dropped inside. Grafts were evaluated for ECL and examined for grab marks or other loading-associated damage.

RESULTS

There was no difference in mean ECL of grafts prepared for DMEK using the standard protocol (20.6% ± 4.5%) compared with that of mate grafts prepared using the drop-in loading protocol (19.5% ± 4.8%, P = 0.59). There was no consistent pattern of damage in the drop-in-loaded grafts, as grab marks or other tissue damage associated with the drop-in loading protocol were not consistently identified by a trained corneal surgeon.

CONCLUSIONS

ECL was not significantly different in grafts prepared using a drop-in loading procedure compared with grafts prepared using the standard suction protocol. The drop-in loading protocol may be particularly useful to surgeons who load their own grafts and eye bank processing technicians who encounter a "flat" DMEK graft that does not scroll or a loosely scrolled DMEK graft.

Does Storage Time Affect the Outcomes of Split Corneal Transplantation to Reduce Corneal Donor Shortage? A Retrospective Study

Split cornea transplantation can reduce the shortage of donor corneas. Therefore, this study aimed to evaluate the effect of split graft storage time on the outcomes of split corneal transplantation through Descemet membrane endothelial keratoplasty (DMEK) and deep anterior lamellar keratoplasty (DALK) surgeries. Split corneal transplantation was performed in 80 eyes using 41 donor corneas. The mean before and after splitting storage times and total storage times were recorded. Donor corneal buttons and split grafts were stored in short-term solution at 4°C. In both surgeries (DMEK and DALK), donor corneas were divided into groups depending on their storage times. Mean postoperative 12th month best corrected visual acuity (BCVA), endothelial cell density (ECD), endothelial cell loss (ECL), central corneal thickness (CCT), refractive spherical equivalent (RSE), refractive astigmatism, and complication rates were compared among the groups. Correlation between storage times and 1-year BCVA, ECL, and complication rates were assessed. Clinical outcomes of the groups 1 year after the surgeries were also compared. DALK and DMEK were performed in 41 and 39 eyes, respectively. Storage times were not correlated with 1-year DMEK outcomes and only weakly correlated with post-DALK ECD, ECL, and RSE values. Except for CCT in those that underwent DALK, the outcomes of DMEK and DALK surgeries with stored and non-stored split grafts were not significantly different (P = .02). The storage times of donor corneas and split grafts do not have any impact on outcomes.

Analysis of Immune Cells on Donor Corneal Endothelium After Corneal Transplantation Using the HRT-Rostock Cornea Module

PURPOSE

The aim of this study was to investigate the immune cells on corneal endothelium of the graft in patients who underwent penetrating keratoplasty (PK), Descemet-stripping endothelial keratoplasty (DSEK), and Descemet membrane endothelial keratoplasty (DMEK).

METHODS

A total of 43 eyes of 43 patients who underwent PK (17 eyes), DSEK (13 eyes), and DMEK (13 eyes) and who did not show any sign of graft rejection were recruited for the study. Patients who underwent cataract surgery (26 eyes) served as controls. Immune cells on the corneal endothelium were examined with laser in vivo confocal microscopy. The associations between the corneal endothelial cell density, type of keratoplasty, aqueous flare, repeated keratoplasty, and time after surgery versus the density of immune cells were investigated.

RESULTS

In vivo confocal microscopy visualized similar numbers of immune cells on the corneal endothelium in the PK, DSEK, and DMEK groups, whereas no immune cells were observed in any of the control patients. The numbers of immune cells tended to be higher in regraft eyes in the PK group (P = 0.00221) and in the DSEK group (P = 0.168) than those in the primary graft eyes. No significant association was found between the density of immune cells and corneal endothelial cell density in the PK, DSEK, and DMEK groups.

CONCLUSIONS

Immune cells were observed to a similar extent in the eyes of PK, DSEK, and DMEK subjects even in the absence of any clinical sign of immune rejection. A further prospective longitudinal study will evaluate the effect of immune cells on long-term graft survival and the risk for graft rejection.

Research Progress of the Application of Hypothermia in the Eye

Hypothermia is widely used in the medical field to protect organs or tissues from damage. Different research fields have different explanations of the protection mechanism of hypothermia. Hypothermia is also widely used in the field of ophthalmology, for example, in the eye bank, the preservation of corneal tissue and the preservation of the eyeball. Low temperature can also be applied to some ophthalmic diseases, such as allergic conjunctivitis, retinal ischemia, and retinal hypoxia. It is used to relieve eye symptoms or reduce tissue damage. Hypothermic techniques have important applications in ophthalmic surgery, such as corneal refractive surgery, vitrectomy surgery, and ciliary body cryotherapy for end-stage glaucoma. Hypothermia can reduce the inflammation of the cornea and protect the retinal tissue. The eyeball is a complex organ, including collagen tissue of the eyeball wall and retinal nerve tissue and retinal blood vessels. The mechanism of low temperature protecting eye tissue is complicated. It is important to understand the mechanism of hypothermia and its applications in ophthalmology. This review introduces the mechanism of hypothermia and its application in the eye banks, eye diseases (allergic conjunctivitis, retinal ischemia, and hypoxia), and eye surgeries (corneal transplant surgery, corneal refractive surgery, and vitrectomy).

Refractive Outcomes After Descemet Membrane Endothelial Keratoplasty + Cataract/Intraocular Lens Triple Procedure: A Fellow Eye Comparison

PURPOSE

Descemet membrane endothelial keratoplasty is often combined with phacoemulsification and intraocular lens implantation (DMEK + cataract/IOL triple procedure) in phakic patients. This procedure results in a refractive shift that is difficult to predict. The aim of this study was to evaluate the hypothesis that the refractive shift in the second eye follows the shift in the first eye.

METHODS

In this retrospective, single-center, consecutive case series, the refractive outcomes of 254 eyes of 127 patients who underwent DMEK + cataract/IOL triple procedure in both eyes for Fuchs endothelial corneal dystrophy have been analyzed. Main outcome measures were spherical equivalent outcome (shift calculations), best spectacle-corrected visual acuity, central corneal thickness, and posterior simulated keratometry.

RESULTS

The mean best spectacle-corrected visual acuity before surgery was 0.51 ± 0.24 and increased to 0.19 ± 0.15 (logMAR) after surgery (P < 0.001). After surgery, a mean hyperopic shift of 0.98 ± 0.89 D was observed. The refractive shift was 1.03 ± 0.93 D and 0.92 ± 1.02 D, in the first and second eyes, respectively (P = 0.435). In a paired analysis, the mean difference of the refractive shift between the first and second eyes was 0.49 ± 0.43 D.

CONCLUSIONS

In our fellow eye comparison, the refractive shift after DMEK + cataract/IOL triple procedure in the second eye was comparable with the shift in the first eye. As a consequence, the refractive outcome of the first eye might serve as a reference for optimizing the refractive target in the second eye. Further studies investigating the influence of corneal parameters on refractive shift are needed for a more predictable lens power selection.

Risk factors for endothelial cell loss after Descemet membrane endothelial keratoplasty (DMEK)

This study aimed to identify the risk factors for endothelial cell density (ECD) loss after Descemet membrane endothelial keratoplasty (DMEK) and analyse whether donor tissues from cold versus organ culture differ in terms of ECD loss after DMEK. Consecutive DMEK cases from a prospective database for Fuchs’ endothelial corneal dystrophy were retrospectively analysed between 2011 and 2016 at the University of Cologne, and the possible risk factors for ECD loss, including patient-related factors, type of tamponade (air or 20% sulphur hexafluoride gas), type of surgery (triple DMEK or DMEK alone), re-bubbling, immune rejection, and donor-related factors were determined. Eight hundred and forty-one eyes were selected. There was no significant difference in the best-corrected visual acuity (logarithm of the minimal angle of resolution) and corneal thickness (P = 0.540 and P = 0.667) between groups. Immune reactions were more common in cold cultures (P = 0.019), but ECD loss (1 year after DMEK) was greater in organ cultures (38.3 ± 0.8%) than in cold cultures (34.7 ± 1.4%) (P = 0.022). Only re-bubbling was significantly associated with ECD loss (P < 0.001). Re-bubbling was found to be a key factor for ECD loss at 1 year after DMEK.

Significant differences between specular microscopy and corneal bank endothelial cell counts - a pilot study

BACKGROUND

It was shown recently that endothelial cell count performed by cornea banks overestimates the real number of endothelial cells. The aim of this study was to investigate the internal quality of preclinical ECD in human donor corneas using two widely used methods for endothelial cell counting, transmitted light microscopy used in organ culture tissue bank and clinically used specular microscopy.

METHODS

Twenty human donor corneas that could not be transplanted were included in this analysis. Differences in evaluating endothelial cell density (ECD) and hexagonal endothelial cell ratio (HEX) between clinical specular microscopy (CSM) and corneal bank transmitted light microscope (CBLM) were evaluated as well as differences between automated and manual cell counts.

RESULTS

Automated CBLM showed a higher ECD of 31.85% compared to automated CSM, while manual CBLM counting is 10.51% higher compared to manual CSM (p < 0.01). Further, higher average ECD values result in a higher difference between CSM and CBLM measurements. The manual CBLM ECDs were significantly higher compared to automated derived ECD from CSM (p < 0.01). However, no systematic bias can be detected when comparing the differences of the measurements with the average ECD measurements of both methods.

CONCLUSION

This preclinical pilot study confirmed a significant higher ECD using transmitted light microscopy in organ culture compared to clinical specular microscopy. This indicates that the early rapid decrease of EC universally observed after surgery might be partly artefactual.

Lower risk of graft dislocation applying organ cultured corneas compared with cold short-term cultured corneas during DSAEK surgery

BACKGROUND

To investigate factors that may affect graft dislocation after uneventful Descemet stripping endothelial keratoplasty (DSAEK), with a special focus on different donor cornea storage conditions.

METHODS

All DSAEK surgeries performed during 6 years in our hospital were retrospectively investigated. Patients with previous intraocular surgeries other than cataract extraction were excluded. Donor data (age, gender, death-to-preservation time, cornea storage conditions, graft storage time, and estimated thickness of the graft) and patient information (age, gender, and indication for surgery) were noted.

RESULTS

A total of 26 dislocations (6.6%) out of 394 DSAEK surgeries were found. The dislocation rate was considerably reduced between 2011 and 2016, due to more experienced surgeons. There was a significantly higher dislocation rate with the use of donor corneas stored in cold storage solution (12.7%) compared with organ culture solution (2.5%) (P < 0.001). During the study period, donor corneas stored in cold storage solution and organ culture solution were applied in 158 (40%) and 236 (60%) cases, respectively. There were no differences in recipient age and gender between patients who received corneas from the two storage systems, indicating a random distribution of grafts. In a multivariate analysis, only operation year (reduced rate over the years) and cold storage solution were statistically significantly associated with graft dislocation.

CONCLUSION

This study suggests that the type of storage solution may have a decisive role in graft dislocation in DSAEK surgery.

Ultrastructural findings in graft failure after Descemet membrane endothelial keratoplasty (DMEK) and new triple procedure

To investigate factors that influence graft failure after Descemet membrane endothelial keratoplasty (DMEK) based on transmission electron microscopy results.Retrospective observational case series.This single center study included 16 eyes of 16 patients with penetrating keratoplasty (n = 14) or repeat DMEK (n = 2) following graft failure after DMEK. The main outcome measures were ultrastructural changes in the explanted graft on transmission electron microscopy, best-corrected visual acuity, and central corneal thickness.The mean preoperative and postoperative best-corrected visual acuity was 1.01 ± 0.54 logMAR and 0.56 ± 0.37 logMAR. The mean central corneal preoperative and postoperative thickness was 667 ± 187 μm and 511 ± 42 μm. Visual acuity and central corneal thickness improved significantly (P = .001/P = .003) after repeat surgery. Electron microscopy showed that 3 of 14 corneas showed upside down transplantation, and 3 corneas had pigmented cells or pigment granules at the Descemet-stroma interface. Further, 9 of 16 specimens showed a posterior collagenous layer deposited onto the Descemet membrane (average thickness 5.1 ± 6.2 μm; ranged 0.65-20 μm); this did not correlate significantly with the time between the original and repeat keratoplasty. Of 16 original grafts, 7 showed ultrastructural anomalies of the Descemet membrane, but one excised cornea showed no Descemet membrane pathologies.The majority of eyes with graft failure after DMEK showed ultrastructural changes in the Descemet membrane. It is crucial to assess donor tissue quality and to conduct graft marking before surgery to avoid immediate or delayed graft failure after DMEK. Nevertheless, repeat keratoplasty provided significant improvement in central corneal thickness and visual acuity.

Corneal endothelial cell dysfunction: etiologies and management

A transparent cornea is essential for the formation of a clear image on the retina. The human cornea is arranged into well-organized layers, and each layer plays a significant role in maintaining the transparency and viability of the tissue. The endothelium has both barrier and pump functions, which are important for the maintenance of corneal clarity. Many etiologies, including Fuchs’ endothelial corneal dystrophy, surgical trauma, and congenital hereditary endothelial dystrophy, lead to endothelial cell dysfunction. The main treatment for corneal decompensation is replacement of the abnormal corneal layers with normal donor tissue. Nowadays, the trend is to perform selective endothelial keratoplasty, including Descemet stripping automated endothelial keratoplasty and Descemet’s membrane endothelial keratoplasty, to manage corneal endothelial dysfunction. This selective approach has several advantages over penetrating keratoplasty, including rapid recovery of visual acuity, less likelihood of graft rejection, and better patient satisfaction. However, the global limitation in the supply of donor corneas is becoming an increasing challenge, necessitating alternatives to reduce this demand. Consequently, in vitro expansion of human corneal endothelial cells is evolving as a sustainable choice. This method is intended to prepare corneal endothelial cells in vitro that can be transferred to the eye. Herein, we describe the etiologies and manifestations of human corneal endothelial cell dysfunction. We also summarize the available options for as well as recent developments in the management of corneal endothelial dysfunction.

Lamellar keratoplasty techniques

Lamellar keratoplasty (LK) has revolutionized corneal graft surgery in several ways. Deep anterior LK (DALK) has eliminated risk of failure due to endothelial rejection. Endothelial keratoplasty (EK) has almost eliminated induced astigmatism and the “weak” graft–host junction as seen with penetrating keratoplasty (PK) and also reduced the risk of endothelial rejection. LK provided new insights into posterior corneal anatomy that led to better understanding and performance of DALK and to the development of another EK procedure, namely pre-Descemet's EK (PDEK). Surgical procedures for LK were further refined based on the improved understanding and are able to deliver better surgical outcomes in terms of structural integrity and long-term patient satisfaction, reducing the need of further surgeries and minimizing patient discomfort. In most specialist centers, anterior lamellar techniques like DALK and EK techniques like Descemet's stripping EK (DSEK) and Descemet's membrane EK (DMEK) have replaced the full-thickness PK where possible. The introduction of microkeratome, femtosecond laser, and PDEK clamp have made LK techniques easier and more predictable and have led to the innovation of another LK procedure, namely Bowman membrane transplant (BMT). In this article, we discuss the evolution of different surgical techniques, their principles, main outcomes, and limitations. To date, experience with BMT is limited, but DALK has become the gold standard for anterior LK. The EK procedures too have undergone a rapid transition from DSEK to DMEK and PDEK emerging as a viable option. Ultrathin-DSEK may still have a role in modern EK.

Clinical Outcomes of Preloaded Descemet Membrane Endothelial Keratoplasty Grafts With Endothelium Tri-Folded Inwards

PURPOSE

To evaluate the initial outcomes and complications of Descemet membrane endothelial keratoplasty (DMEK) using donor tissues tri-folded with the endothelium inwards, preloaded at the Eye Bank, and delivered with bimanual pull-through technique.

DESIGN

Prospective, noncomparative, interventional case series.

METHODS

Setting: Eye bank and tertiary care eye department.

PATIENT POPULATION

Forty-six consecutive eyes of 41 patients with Fuchs endothelial dystrophy with or without cataract operated between November 2016 and March 2017.

INTERVENTION

DMEK tissues prepared with SCUBA technique and punched to a diameter of 8.25 mm were preloaded with the endothelium tri-folded inwards in an intraocular lens (IOL) cartridge with a 2.2-mm opening filled with the same tissue culture medium contained in the vial used for shipment to the surgeon. Standardized DMEK was performed as a single procedure (n = 15) or in combination with phacoemulsification and IOL implantation (n = 31) within 48 hours from preparation using a bimanual pull-through technique.

MAIN OUTCOME MEASURES

Preparation and surgical times, intraoperative and postoperative complications, best spectacle-corrected visual acuity (BSCVA), endothelial cell density (ECD), and graft detachment rate.

RESULTS

Preparation time averaged 26.2 ± 4.1 minutes (range 17-36 minutes), while the surgical time from opening of the stoppers to air fill of the anterior chamber never exceeded 9 minutes (range 3-9 minutes). Surgery was uneventful in all cases. Postoperative complications included graft detachment in 9 of 46 cases (19.6%), successfully managed in all cases by single rebubbling within 6 days from surgery, and glaucoma irresponsive to conservative treatment in 1 of 46 cases (2.1%). In all eyes without comorbidities (35 of 40 eyes) BSCVA was 20/25 (0.097 logMAR) or better as early as 3 months after surgery. Six months postoperatively, ECD was available in 24 of 25 eyes with an endothelial cell loss calculated as a percentage of the preoperative value determined at the eye bank (ranging from 2500 to 2800 cells/mm²) of 29.5% ± 14.8% (range 8.3%-52.1%).

CONCLUSIONS

Delivering a preloaded DMEK tissue, tri-folded with the endothelium inwards, minimizes surgical time and costs without negatively affecting the outcomes of the procedure.

Donor Tissue Preparation for Descemet Membrane Endothelial Keratoplasty: An Updated Review

PURPOSE

To provide an overview of the current literature on donor tissue preparation for Descemet membrane endothelial keratoplasty (DMEK).

METHODS

A comprehensive database search without date restrictions was performed in PubMed and in The Cochrane Library in May, 2017. Keywords included Descemet membrane endothelial keratoplasty, corneal transplantation, graft, harvest, dissection, preparation, endothelial cell, and endothelial cell density. Articles aiming to describe or evaluate a technique for DMEK graft preparation were considered eligible and were included in this review.

RESULTS

A graft dissection technique that provides consistent tissue qualities and a low risk of preparation failure is essential for surgeons and eye banks preparing DMEK tissue. Various techniques have been described aiming to facilitate DMEK graft dissection, including manual dissection, pneumatic dissection, and hydrodissection. All show a trend toward a no-touch technique, for example, without direct physical tissue manipulation during tissue harvesting, as a potential ideal approach to minimize graft damage.

CONCLUSIONS

An overview of the current harvesting techniques available for DMEK may benefit corneal surgeons and eye banks in choosing the best approach for each specific user.

A historical perspective on treatment of fuchs' endothelial dystrophy: We have come a long way

Fuchs' endothelial corneal dystrophy is a hereditary and progressive vision-threatening disease with a high prevalence in our adult population. In the past two decades, endothelial transplantation has dramatically changed the way we treat these patients. Back then, our limited surgical techniques often resulted in less than ideal outcomes. It was unimaginable for our patients to achieve near perfect visual acuity in such a short span of time. Over the years, we have tenaciously refined our surgical techniques to vastly improve patient outcomes, and with the recent advent of Rho-kinase inhibitors, we may even consider delivering a simple injection to our patients in the future. Our purpose is to take a historical perspective on how far we have come in treating this disorder and how rapidly this field will continue to evolve.

Descemet Membrane Endothelial Keratoplasty: Safety and Outcomes: A Report by the American Academy of Ophthalmology

PURPOSE

To review the published literature on the safety and outcomes of Descemet membrane endothelial keratoplasty (DMEK) for the surgical treatment of corneal endothelial dysfunction.

METHODS

Literature searches were last conducted in the PubMed and the Cochrane Library databases most recently in May 2017. The searches, which were limited to English-language abstracts, yielded 1085 articles. The panel reviewed the abstracts, and 47 were determined to be relevant to this assessment.

RESULTS

After DMEK surgery, the mean best-corrected visual acuity (BCVA) ranged from 20/21 to 20/31, with follow-up ranging from 5.7 to 68 months. At 6 months, 37.6% to 85% of eyes achieved BCVA of 20/25 or better and 17% to 67% achieved BCVA of 20/20 or better. Mean endothelial cell (EC) loss was 33% (range, 25%-47%) at 6 months. Overall change in spherical equivalent was +0.43 diopters (D; range, -1.17 to +1.2 D), with minimal induced astigmatism of +0.03 D (range, -0.03 to +1.11 D). The most common complication was partial graft detachment requiring air injection (mean, 28.8%; range, 0.2%-76%). Intraocular pressure elevation was the second most common complication (range, 0%-22%) after DMEK, followed by primary graft failure (mean, 1.7%; range, 0%-12.5%), secondary graft failure (mean, 2.2%; range, 0%-6.3%), and immune rejection (mean, 1.9%; range, 0%-5.9%). Overall graft survival rates after DMEK ranged from 92% to 100% at last follow-up. Best-corrected visual acuity after Descemet's stripping endothelial keratoplasty (DSEK) ranged from 20/34 to 20/66 at 9 months. The most common complications after DSEK were graft detachment (mean, 14%; range, 0%-82%), endothelial rejection (mean, 10%; range, 0%-45%), and primary graft failure (mean, 5%; range, 0%-29%). Mean EC loss after DSEK was 37% at 6 months.

CONCLUSIONS

The evidence reviewed supports DMEK as a safe and effective treatment for endothelial failure. With respect to visual recovery time, visual outcomes, and rejection rates, DMEK seems to be superior to DSEK and to induce less refractive error with similar surgical risks and EC loss compared with DSEK. The rate of air injection and repeat keratoplasty were similar in DMEK and DSEK after the learning curve for DMEK.

A review of the evidence for in vivo corneal endothelial regeneration

Human corneal endothelium has long been thought to be a nonmitotic cell layer with no endogenous reparative potential. Pathologies that damage endothelial function result in corneal decompensation and, if untreated, blindness. The mainstay of treatment involves partial or complete corneal replacement, amounting to 40% of all corneal transplants performed worldwide. We summarize the case reports describing complications postoperatively in the form of (sub)total graft detachment and those resulting in postoperative bare stroma. Complications during cataract and glaucoma surgeries leading to an uncovered posterior cornea are also included. We discuss the newer treatment strategies that are alternatives for current Descemet membrane endothelial keratoplasty and Descemet stripping automated endothelial keratoplasty, including partial grafts and stripping of the diseased cell layer. In more than half of the cases reviewed, corneal transparency returned despite incomplete or no corneal endothelial cell transplantation. We question the existing paradigm concerning corneal endothelial wound healing in vivo. The data support further clinical study to determine the safety of simple descemethorexis in central endothelial pathologies, such as Fuchs endothelial corneal dystrophy, where presence of healthy peripheral cells may allow successful corneal recompensation without the need for donor cells.

Influence of Ultrastructural Corneal Graft Abnormalities on the Outcome of Descemet Membrane Endothelial Keratoplasty

PURPOSE

To investigate if ultrastructural alterations in the Descemet membrane (DM) are correlated with the clinical outcome after Descemet membrane endothelial keratoplasty (DMEK).

DESIGN

Retrospective cohort study.

METHODS

setting: Institutional, single-center.

STUDY POPULATION

One hundred and twelve residual DM specimens obtained after DM stripping.

MAIN OUTCOME MEASURES

Incidence of ultrastructural abnormalities in transmission electron microscopy, graft detachment rate, graft failure rate, best-corrected visual acuity (BCVA), endothelial cell density (ECD), and central corneal thickness (CCT). Examination dates were on the day before DMEK and 1, 3, 6, and 12 months after surgery.

RESULTS

Abnormalities in the ultrastructure of DM were found in 16 of 112 specimens (14%) (abnormal DM group), comprising deposits of long-spacing collagen, fine filaments (proteoglycans), a posterior collagenous layer, pseudoexfoliative material, and guttae. The secondary graft failure rate was significantly higher in the abnormal DM group compared with the normal DM group (P = .001). There was a trend for an increased graft detachment rate in the abnormal DM group (11/16) compared with the normal DM group (42/96) (P = .103). There was no significant difference in mean CCT and ECD after surgery. Mean CCT in the eyes with graft failure in the abnormal DM group at the last follow-up before regrafting was 850 μm, indicating endothelial failure with stromal edema.

CONCLUSION

This study reveals a correlation between ultrastructural alterations of DM in donor corneas and the graft failure rate after DMEK. Thus, graft failure after DMEK not only is determined by surgical trauma and postoperative events but may also be influenced by intrinsic, graft-specific features.

Determinants of visual quality after endothelial keratoplasty

Endothelial keratoplasty is now favored over full-thickness penetrating keratoplasty for corneal decompensation secondary to endothelial dysfunction. Although endothelial keratoplasty has evolved as surgeons strive to improve outcomes, fewer patients than expected achieve best corrected visual acuity of 20/20 despite healthy grafts and no ocular comorbidities. Reasons for this remain unclear, with theories including anterior stromal changes, differences in graft thickness and regularity, induced high-order aberrations, and the nature of the graft-host interface. Newer iterations of endothelial keratoplasty such as thin manual Descemet stripping endothelial keratoplasty, ultrathin automated Descemet stripping endothelial keratoplasty, and Descemet membrane endothelial keratoplasty have achieved rates of 20/20 acuity of approximately 50%, comparable to modern cataract surgery, and it may be that a ceiling exists, particularly in the older age group of patients. Establishing the relative contribution of the factors that determine visual quality following endothelial keratoplasty will help drive further innovation, optimizing visual and patient-reported outcomes while improving surgical efficacy and safety.

Descemet's Stripping Automated Endothelial Keratoplasty versus Descemet's Membrane Endothelial Keratoplasty in the Fellow Eye for Fuchs Endothelial Dystrophy: A Retrospective Study

Aim. To evaluate visual outcome and endothelial cell density (ECD) after Descemet's Membrane Endothelial Keratoplasty (DMEK) in comparison with Descemet's Stripping Automated Endothelial Keratoplasty (DSAEK) in the fellow eye for Fuchs endothelial dystrophy (FED). Design. Single-centre, retrospective case series. Methods. 30 eyes of 30 patients undergoing DMEK, who completed a 1-year follow-up, were compared with 30 fellow eyes which underwent DSAEK for bilateral FED. Main outcome measures studied included Best Corrected Visual Acuity (BCVA) and ECD during a 1-year follow-up period. Results. BCVA improved from 0.78 ± 0.35 logMAR, and 0.73 ± 0.31 logMAR before surgery to 0.22 ± 0.1 logMAR and 0.35 ± 0.12 logMAR 6 months after DMEK and DSEK, respectively (P < 0.001). At one year after surgery, the BCVA was maintained at 0.21 ± 0.12 logMAR and 0.34 ± 0.1 logMAR, respectively, after DMEK and DSAEK. A statistically better visual outcome was observed after DMEK compared to DSAEK (P < 0.05) in fellow eyes. Conclusions. DMEK provided better visual rehabilitation when compared to DSAEK. Nevertheless, there were no significant differences with regard to the ECD within a 1-year follow-up.

Descemet membrane endothelial keratoplasty as treatment for graft failure after descemet stripping automated endothelial keratoplasty

PURPOSE

To investigate the outcome of Descemet membrane endothelial keratoplasty (DMEK) in patients with graft failure after Descemet stripping automated endothelial keratoplasty (DSAEK).

DESIGN

Retrospective cohort study.

METHODS

setting: Institutional.

STUDY POPULATION

Fifteen eyes of 15 patients that underwent DMEK for graft failure with corneal decompensation following DSAEK were analyzed; 15 eyes with primary DMEK for Fuchs corneal dystrophy were included as control group.

MAIN OUTCOME MEASURES

Best-corrected visual acuity (BCVA), endothelial cell density (ECD), central corneal thickness (CCT), and rebubbling rate.

RESULTS

DMEK surgery was successful in all cases of both groups. Mean BCVA (logMAR) before DMEK was 1.27 ± 0.34 in the DMEK after DSAEK group and 1.0 ± 0.40 in the Primary DMEK group. After DMEK, mean BCVA increased significantly to 0.23 ± 0.21 (P = .012, DMEK after DSAEK group) and 0.29 ± 0.23 (P = .042, Primary DMEK group) after 3 months. There were no significant differences in mean BCVA between both groups at each visit. The rebubbling rate was 13% in the DMEK after DSAEK group and 40% in the Primary DMEK group (P = .1). Mean CCT decreased significantly in both groups 1 month after DMEK (P < .05). Mean ECD and change of ECD did not differ significantly between both groups at each visit (P > .05).

CONCLUSION

The results after DMEK as a procedure to treat graft failure after DSAEK were as good as in patients that underwent DMEK as primary intervention to treat advanced Fuchs dystrophy. This indicates that the optical quality can be reestablished by DMEK in patients with failed DSAEK.

Descemet membrane endothelial keratoplasty

Descemet membrane endothelial keratoplasty (DMEK) allows for selective replacement of damaged endothelial cells, using only donor Descemet's membrane with endothelium. However, early adoption by corneal surgeons has been limited (illustrated by graft registry reports: 0.7% all corneal transplants in the USA; 0.4% in Australia for 2011) due to challenges in donor preparation and surgical technique. Recently, innovative donor preparation techniques may improve availability of pre-stripped DMEK donors from eye banks. The refinement of donor insertion and manipulation techniques has also improved outcomes and reduced graft detachment rates-still, the most common postoperative complication following DMEK. Randomised studies are needed to compare clinical practices and surgeon preferences, such as intraoperative use of long-acting gas, early versus late intervention of graft detachments and postoperative steroid management. A review of current literature reveals that most publications to date are reports from similar study cohorts by surgeons who pioneered and advocate this technique. Thus, more long-term clinical studies in other tertiary centres are required in order to confirm if the purported advantages of DMEK such as improved visual outcomes and reduced graft rejection are replicable among most corneal surgeons.

Corneal transplantation: Beyond the horizon

Evolving techniques in keratoplasty have undoubtedly led to thinner corneal grafts. These newer iterations of keratoplasty aim to reduce graft rejections, improve visual acuity and visual rehabilitation. Each technique poses its own advantages and disadvantages; the surgeon should select patients suitable for a particular technique while accounting for their surgical competency given the learning curve associated with these newer techniques. Alternatives to corneal transplant may have a role in addressing the shortages of corneal graft, these bioengineered material and medical treatment still need further studies to demonstrate its clinical applicability.

Influence of the difficulty of graft unfolding and attachment on the outcome in Descemet membrane endothelial keratoplasty

PURPOSE

Descemet membrane endothelial keratoplasty (DMEK) is a standard procedure in patients with endothelial corneal disorders. We investigated the difficulty of unfolding and attaching the graft lamella and its correlation to characteristics of the graft lamella donor, preoperative patient characteristics, and the postoperative outcome.

METHODS

After preparation of the graft lamella, we prospectively graded the unfolding of the graft lamella in 169 consecutive DMEK procedures between September 2012 and August 2013 at the Charité-Universitätsmedizin Berlin with four different grades. Various donor characteristics and preoperative patient characteristics were analyzed and correlated to the grading. Additionally, visual acuity, corneal thickness and endothelial cell density were measured and correlated.

RESULTS

Donor characteristics (age [range, 49 - 79 years], gender, endothelial cell density, total storage time, storage de-swelling time, postmortem time) did not correlate to the grading. Preoperative visual acuity significantly influenced the grade of unfolding and attaching of the graft lamella (p = 0.023), while all other preoperative parameters (age, gender, indication for DMEK, preoperative endothelial cell density and preoperative central corneal thickness) showed no correlation. Visual acuity improved significantly after surgery (p < 0.001, preoperative 0.73 ± 0.43 LogMAR versus 0.31 ±0.28 LogMAR after one month, 0.25 ± 0.29 LogMAR after three months, and 0.21 ± 0.25 LogMAR after six months). Visual acuity did not differ significantly between the grading groups at any time point postoperatively. After 6 months, the mean loss rate of endothelial cell density was 24.7 %. Grading group IV developed significantly higher endothelial loss after one month, after three months and after six months compared to the other groups (p = 0.039, p = 0.008, p = 0.048). Graft detachment requiring an additional intracameral air injection to fix the graft detachment (re-bubbling) occurred in 61 eyes (38.1 %). In eyes graded IV, more re-bubblings were necessary than in all other groups (grade I: 37.0 %; grade II: 44.7 %; grade III: 43.8 %; grade IV: 50.0 %; p = 0.128; df = 3; χ (2) = 5.676).

CONCLUSION

There is no correlation between corneal donor tissue characteristics and the degree of difficulty of unfolding using graft lamella older than 49 years. Therefore, it is not possible to select grafts best suited for DMEK surgery on the basis of donor characteristics when the donor age is above 50 years. Preoperative visual acuity influences the grade of difficulty. The rate of graft detachments and endothelial cell loss increases significantly with a more difficult graft unfolding. The proposed grading system may therefore be relevant for postoperative management.

Superior versus temporal approach in descemet membrane endothelial keratoplasty

PURPOSE

To compare superior vs temporal approach in patients who underwent Descemet membrane endothelial keratoplasty (DMEK).

DESIGN

Monocentric, prospective nonmasked study.

METHODS

A prospective analysis of 53 DMEKs between January and September 2013 was performed at the Charité-Universitätsmedizin Berlin. Only DMEK cases with an incision size of 2.3 mm and with at least 1 month of follow-up were included. The surgically induced astigmatism (SIA), changes in corneal aberrations and in spherical equivalent, visual acuity, endothelial cell density, and complications were evaluated.

RESULTS

Visual acuity improved significantly (0.70 ± 0.39 logMAR vs 0.32 ± 0.31 logMAR after 1 month (n = 48), 0.19 ± 0.15 logMAR after 3 months (n = 46), and 0.16 ± 0.17 logMAR after 6 months (n = 47) (P < .001)) regardless of the approach. SIA was significantly lower after temporal than after superior approach (1.42 ± 0.91 diopters [D] [n = 13] vs 0.81 ± 0.68 D [n = 13], P = .038). Change in total root mean square of all aberrations (RMS) (P = .046) at 6 mm pupil diameter, and change in total RMS (P = .019), third-order aberrations (P = .007), and fourth-order aberrations (P = .041) at 4 mm pupil diameter, demonstrated significantly lower results after temporal compared to superior approach. A higher rate of eyes after temporal approach underwent at least 1 rebubbling (39.1% vs 26.7%, P = .252). The endothelial cell density (P = .053) and the change in spherical equivalent (P = .145) did not differ significantly.

CONCLUSIONS

The temporal approach induces significantly less SIA and corneal aberration. There are no significant differences between superior and temporal approach according to the change in spherical equivalent, visual acuity, and endothelial cell density. The need for rebubbling is higher using the temporal approach.

Clinicopathology of graft detachment after Descemet's membrane endothelial keratoplasty

PURPOSE

To investigate pathomechanisms involved in graft detachment after Descemet's membrane endothelial keratoplasty (DMEK) and its clinical implications.

METHODS

In a prospective case series, 30 eyes with Fuchs' endothelial dystrophy underwent DMEK. Intraoperatively obtained recipients' endothelium-Descemet's membranes (EDMs) were investigated histologically and immunohistochemically. The postoperative donor graft status was categorized as attached or detached. Clinical and morphological parameters were analysed between the study groups.

RESULTS

The detachment rate was 40% (12/30). There was no significant difference in postoperative visual acuity between the groups, but visual recovery was delayed in eyes with initially detached grafts. Gender, age, preoperative central corneal thickness or best corrected visual acuity did not influence the detachment rate. However, separation and disruption of the anterior banded layer (ABL) were frequently observed in patients with graft detachment, and ABL thickness was identified as a significant predictor for graft detachment. The ABL thickness was 2.5 ± 0.9 μm and 3.5 ± 1.6 μm in patients with attached and detached grafts, respectively. Immunohistologically, a deficiency of fibronectin and cytokeratin was observed within the ABL of patients with detached grafts. In contrast, a complete removal of the EDM with residual stromal collagen fragments was observed in patients with adherent grafts.

CONCLUSIONS

Incomplete removal of the EDM, with residual ABL fragments on the recipients' corneal stroma, may be a risk factor for graft detachment after DMEK. The separation and disruption of the ABL might be promoted by a deficiency of matrix proteins, stronger biomechanical properties and a firm adherence to the posterior corneal stroma.

Optimizing outcomes with Descemet's membrane endothelial keratoplasty

PURPOSE OF REVIEW

To review recent advances in posterior lamellar keratoplasty and to describe strategies that enhance the outcome of Descemet's membrane endothelial keratoplasty (DMEK) and should lead to a more widespread use of this technique.

RECENT FINDINGS

DMEK offers significant advantages over Descemet's stripping automated endothelial keratoplasty (DSAEK) such as less immune reaction and better visual acuity because of less higher order aberrations. Donor selection should exclude donors under 50 years because of tissue elasticity; several advanced techniques now allow donor preparation from both cold and organ-cultured tissue in about 99% minimizing the risk of graft loss. Oversizing the area of Descemet's stripping in relationship to graft size enhances graft attachment and use of a standardized approach for graft delivery. Air bubble-driven nontouch unfolding techniques and, possibly, gas tamponade in the anterior chamber further enhance graft attachment and reduce surgery-induced endothelial cell loss. Graft orientation is made earlier by marking, slit beam and optical coherence tomography. Novel understanding of the functional anatomy of Descemet's membrane as well as migration of endothelial cells will allow to further refine DMEK and improve its outcome.

SUMMARY

Although the superiority of DMEK over Descemet's stripping automated endothelial keratoplasty in terms of safety and functionality had been further elucidated, remarkable progress has been made in the recent past regarding tissue preparation, insertion and intraoperative manipulation that will foster the more widespread use of DMEK among corneal surgeons.

Eye-bank preparation of endothelial tissue

PURPOSE OF REVIEW

Eye-bank preparation of endothelial tissue for keratoplasty continues to evolve. Although eye-bank personnel have become comfortable and competent at Descemet's stripping automated endothelial keratoplasty (DSAEK), tissue preparation and tissue transport, optimization of preparation methods continues. Surgeons and eye-bank personnel should be up to date on the research in the field. As surgeons transit to Descemet's membrane endothelial keratoplasty (DMEK), eye banks have risen to the challenge of preparing tissue. Eye banks are refining their DMEK preparation and transport techniques.

RECENT FINDINGS

This article covers refinements to DSAEK tissue preparation, innovations to prepare DMEK tissue, and nuances to improve donor cornea tissue quality.

SUMMARY

As eye bank-supplied corneal tissue is the main source of tissue for many corneal surgeons, it is critical to stay informed about tissue handling and preparation. Ultimately, the surgeon is responsible for the transplantation, so involvement of clinicians in eye-banking practices and advocacy for pursuing meaningful research in this area will benefit clinical patient outcomes.

Evolving indications for Descemet's stripping automated endothelial keratoplasty

PURPOSE OF REVIEW

Recent advances in the field of endothelial transplantation, including increasing acceptance of Descemet's membrane endothelial keratoplasty, may alter the indications for Descemet's stripping automated endothelial keratoplasty, to a procedure reserved for complex endothelial disorders.

RECENT FINDINGS

Recent literature demonstrates that Descemet's membrane endothelial keratoplasty provides better and faster visual outcomes and decreased immunologic rejection compared to Descemet's stripping automated endothelial keratoplasty. However, Descemet's membrane endothelial keratoplasty may be more challenging in the management of a number of more complex endothelial disorders. While the literature on complex Descemet's membrane endothelial keratoplasty is limited, the utility of Descemet's stripping automated endothelial keratoplasty has been validated in the management of endothelial dysfunction in the setting of a number of comorbid conditions including prior penetrating keratoplasty, prior glaucoma surgery, iridocorneal endothelial syndrome, aniridia, aphakia, and anterior chamber intraocular lenses, among others.

SUMMARY

The increasing adoption of Descemet's membrane endothelial keratoplast is changing the practice of endothelial keratoplasty. However, limitations of the Descemet's membrane endothelial keratoplasty procedure have also served to crystallize the essential role of Descemet's stripping automated endothelial keratoplasty in many complex endothelial keratoplasty scenarios. This article will review indications for endothelial keratoplasty, along with the current evidence for Descemet's stripping automated endothelial keratoplasty and Descemet's membrane endothelial keratoplasty in their management.