Overall clinical outcomes of Descemet membrane endothelial keratoplasty in 600 consecutive eyes: A large retrospective case series

Healing the Cornea: Exploring the Therapeutic Solutions Offered by MSCs and MSC-derived EVs

Affecting a large proportion of the population worldwide, corneal disorders constitute a concerning health hazard associated to compromised eyesight or blindness for most severe cases. In the last decades, mesenchymal stem/stromal cells (MSCs) demonstrated promising abilities in improving symptoms associated to corneal diseases or alleviating these affections, especially through their anti-inflammatory, immunomodulatory and pro-regenerative properties. More recently, MSC therapeutic potential was shown to be mediated by the molecules they release, and particularly by their extracellular vesicles (EVs; MSC-EVs). Consequently, using MSC-EVs emerged as a pioneering strategy to mitigate the risks related to cell therapy while providing MSC therapeutic benefits. Despite the promises given by MSC- and MSC-EV-based approaches, many improvements are considered to optimize the therapeutic significance of these therapies. This review aspires to provide a comprehensive and detailed overview of current knowledge on corneal therapies involving MSCs and MSC-EVs, the strategies currently under evaluation, and the gaps remaining to be addressed for clinical implementation. From encapsulating MSCs or their EVs into biomaterials to enhance the ocular retention time to loading MSC-EVs with therapeutic drugs, a wide range of ground-breaking strategies are currently contemplated to lead to the safest and most effective treatments. Promising research initiatives also include diverse gene therapies and the targeting of specific cell types through the modification of the EV surface, paving the way for future therapeutic innovations. As one of the most important challenges, MSC-EV large-scale production strategies are extensively investigated and offer a wide array of possibilities to meet the needs of clinical applications.

Machine learning based endothelial cell image analysis of patients undergoing descemet membrane endothelial keratoplasty surgery

OBJECTIVES

In this study, we developed a machine learning approach for postoperative corneal endothelial cell images of patients who underwent Descemet's membrane keratoplasty (DMEK).

METHODS

An AlexNet model is proposed and validated throughout the study for endothelial cell segmentation and cell location determination. The 506 images of postoperative corneal endothelial cells were analyzed. Endothelial cell detection, segmentation, and determining of its polygonal structure were identified. The proposed model is based on the training of an R-CNN to locate endothelial cells. Next, by determining the ridges separating adjacent cells, the density and hexagonality rates of DMEK patients are calculated.

RESULTS

The proposed method reached accuracy and F1 score rates of 86.15 % and 0.857, respectively, which indicates that it can reliably replace the manual detection of cells in vivo confocal microscopy (IVCM). The AUC score of 0.764 from the proposed segmentation method suggests a satisfactory outcome.

CONCLUSIONS

A model focused on segmenting endothelial cells can be employed to assess the health of the endothelium in DMEK patients.

Non-invasive endothelial cell density measurement of in toto pre-stripped DMEK-roll - impact of pre- and intraoperative endothelial cell loss on postoperative midterm clinical outcome

BACKGROUND/OBJECTIVES

To measure the endothelial cell density (ECD) of the in toto pre-stripped endothelial Descemet membrane lamellae (EDML) and to describe the impact of pre- and intraoperative endothelial cell loss (ECL) on postoperative midterm clinical outcome.

SUBJECTS/METHODS

The ECD of 56 Corneoscleral Donor Discs (CDD) was first measured with an inverted specular microscope (t0pre). The measurement was then repeated non-invasively after the preparation of the EDML (t0post). DMEK was performed the next day using these grafts. Follow-up examinations took place 6 weeks, 6 months and 1 year postoperatively where the ECD was assessed. In addition, the impact of ECL 1 (during preparation) and ECL 2 (during surgery) on the ECD, visual acuity (VA) and pachymetry at 6 months and 1 year was investigated.

RESULTS

The average ECD (in cells/mm²) at time points t0pre, t0post, 6 weeks, 6 months & 1 year was 2584 ± 200, 2355 ± 207, 1366 ± 345, 1091 ± 564 and 939 ± 352. The average logMAR VA and pachymetry (in µm) was 0.50 ± 0.27 and 597 ± 63, 0.23 ± 0.17 and 535 ± 54, 0.16 ± 0.12 and 535 ± 54, 0.06 ± 0.08 and 512 ± 37, respectively The ECL 1 (9% on average) had no significant impact on the main outcome measures after 6 months and 1 year (p > 0.11). The ECL 2 correlated significantly with the ECD and the pachymetry at 1 year postop (p < 0.02).

CONCLUSION

Our results indicate that the non-invasive ECD measurement of the prestripped EDML roll before its transplantation is feasible. Despite significantly decreasing ECD up to 6 months postoperatively, visual acuity further improved and thickness further decreased up to 1 year postoperatively.

Comparison of Pre-Descemet Endothelial Keratoplasty and Descemet Membrane Endothelial Keratoplasty in Endothelial Decompensation

PURPOSE

The purpose of this study was to compare the outcomes of pre-Descemet endothelial keratoplasty (PDEK) and Descemet membrane endothelial keratoplasty (DMEK) in cases of endothelial decompensation.

METHODS

This was a prospective, randomized, interventional study conducted at a tertiary eye hospital in North India. Thirty eyes of 28 patients with corneal decompensation were randomly subjected to PDEK (n = 15 eyes) and DMEK (n = 15 eyes). Preoperative demographic details, surgical indications, uncorrected distance visual acuity, corrected distance visual acuity, contrast sensitivity, anterior and posterior segment details, intraocular pressure, central corneal thickness, endothelial cell count, and corneal aberrometry tracing on wavefront analysis were recorded. Patients were followed up for 6 months postsurgery. Visual and graft survival outcomes were assessed.

RESULTS

Intraoperatively, a surgeon reported better ease of preparation and intracameral handling with PDEK grafts. Both groups showed comparable improvement in visual acuity, contrast, and high-order aberrations. A decrease in central corneal thickness was significantly higher in DMEK (196 ± 26 vs. 140 ± 14 μm) patients. DMEK grafts were significantly thinner than PDEK grafts at the 6-month follow-up (16 ± 2.17 vs. 27.2 ± 1.93 μm). Endothelial cell loss (35% in DMEK vs. 33.4% in PDEK, P = 0.48) and rise of intraocular pressure (from 15.33 ± 2.85 mm Hg to 15.53 ± 2.2 mm Hg in the DMEK group vs. from 14.6 ± 1.99 mm Hg to 16.2 ± 1.43 mm Hg in the PDEK group) were comparable. Rebubbling rates were higher in the DMEK group (3/15, 20%) compared with the PDEK group (1/15, 6.66%; P = 0.165).

CONCLUSIONS

DMEK and PDEK were comparable for both quantitative and qualitative visual outcomes and anatomically for graft survival at the 6-month follow-up.

Risk Factors for Descemet Membrane Endothelial Keratoplasty Rejection: Current Perspectives- Systematic Review

Descemet membrane endothelial keratoplasty (DMEK) is a corneal endothelial transplantation procedure with selective removal of a patient's defective Descemet membrane and endothelium. It is replaced with a healthy donor Descemet membrane and endothelium without a stromal component. Corneal graft rejection can be at the level of epithelium, stroma as well endothelium. DMEK graft rejection is relatively less common than rejection with DSAEK or penetrating keratoplasty, and a good outcome may be achieved with prompt management. The clinical picture of DMEK rejection is usually similar to endothelial rejection in Descemet Stripping Endothelial Keratoplasty (DSEK/DSAEK), which generally manifests as pain, redness, reduction in visual acuity, stromal edema, endothelial rejection line, keratic precipitates at the back of the cornea and corneal neovascularization. However, more subtle forms of rejection or immune reactions are more common in DMEK compared to DSAEK eyes. Early clinical diagnosis, prompt intervention, and meticulous management safeguard visual acuity and graft survival in these cases. Intensive topical steroids form the mainstay in the management of DMEK rejection. Sometimes, oral or intravenous steroids or other systemic immunomodulators may be required. DMEK graft failure can be primary or secondary, and failure usually requires a second procedure in the form of repeat DMEK or DSEK or penetrating keratoplasty (PKP). A detailed literature search was performed using search engines such as Google Scholar, PubMed, and Google books, and a comprehensive review on DMEK rejection was found to be lacking. This review is a comprehensive update on the risk factors, pathophysiology, primary and secondary graft failure, recent advances in diagnosis, prevention of rejection, and updates in the management of DMEK rejection. The review also discusses the differential diagnosis of DMEK failure and rejection, prognosis, and future perspectives considering DMEK failure and rejection.

Recent and Evolving Therapies in the Management of Endothelial Diseases

Corneal endothelium is the innermost layer of the cornea which has both barrier and pump function and very important to maintain cornea clarity. Unlike epithelium, endothelium does not have regenerative potential; hence, endothelial damage or dysfunction could lead to corneal edema and visual impairment. Advanced corneal transplantation which involves selective replacement of dysfunctional endothelium has led to improved and faster visual rehabilitation. But in recent times, alternative therapies in the management of corneal edema and endothelial diseases have been reported. In this review, we aim to give a comprehensive review of various strategies for the management of corneal endothelial dysfunction in order to give treatment which is precisely tailored for each individual patient. A review of all peer-reviewed publications on novel strategies for the management of endothelial dysfunction was performed. The various approaches to the management of endothelial dysfunction are compared and discussed. Shortage of human donor corneas globally is fuelling the search for keratoplasty alternatives. Corneal endothelial dysfunction can be caused following surgery, laser or corneal endothelial dystrophies which could be amenable to treatment with pharmacological, biological intervention and reverse the endothelial dysfunction in the early stages of endothelial failure. Pharmacological and surgical intervention are helpful in cases of good peripheral endothelial cell reserve, and advanced cases of endothelial cell dysfunction can be targeted with cell culture therapies, gene therapy and artificial implant. Treatment strategies which target endothelial dysfunction, especially FECD in its early stages, and gene therapy are rapidly evolving. Therapies which delay endothelial keratoplasty also are evolving like DSO and need more studies of long-term follow-up and patient selection criteria.

Impact of vaccination on keratoplasty

PURPOSE OF REVIEW

Corneal graft rejection has been reported after coronavirus disease 2019 (COVID-19) vaccination. The purpose of this review is to evaluate the literature regarding corneal graft rejection after vaccination, including rejection rates and risk factors. We aim to create a framework to identify patients who are at higher risk for graft rejection and may warrant consideration of prophylactic interventions.

RECENT FINDINGS

Graft rejection has been reported following administration of mRNA, viral vector, and inactivated whole-virion COVID-19 vaccines. Most cases had additional risk factors associated with rejection. Vaccination increases circulation of proinflammatory cytokines, CD4+ and CD8+ T-cell responses, and antispike neutralizing antibody, all of which may contribute to graft rejection. Two prospective studies have found no relationship between recent vaccination and rejection but 20% of cornea specialists report to have seen a vaccine-associated rejection and 22% recommend delaying vaccination in certain circumstances. Many specialists recommend prophylactic topical corticosteroids before and after vaccination to mitigate rejection risk but there is no evidence to support this practice on a wider scale.

SUMMARY

Our framework identified 96.8% of penetrating keratoplasty patients with vaccine-associated rejection as higher risk. Further research is needed in order to develop evidence-based guidelines.

“Endothelium-Out” and “Endothelium-In” Descemet Membrane Endothelial Keratoplasty (DMEK) Graft Insertion Techniques: A Systematic Review With Meta-Analysis

Background

We evaluated the visual outcomes and complications of “endothelium-out” and “endothelium-in” Descemet membrane endothelial keratoplasty (DMEK) graft insertion techniques.

Materials and Methods

Electronic searches were conducted in CENTRAL, Cochrane databases, PubMed, EMBASE, ClinicalTrials.gov. Study designs included clinical trials, comparative observational studies, and large case series (≥25 eyes). PRISMA guidelines were used for abstracting data and synthesis. Random-effects models were employed for meta-analyses.

Results

21,323 eyes (95 studies) were included. Eighty-six studies reported on “endothelium-out” techniques; eight studies reported on “endothelium-in” techniques. One study compared “endothelium-out” to “endothelium-in” techniques. Eighteen “endothelium-out” studies reported that 42.5–85% of eyes achieved best-corrected visual acuity (BCVA) ≥20/25 at 6 months; pooled proportion of eyes achieving BCVA ≥20/25 at 6 months was 58.7% (95% CI 49.4–67.7%,15 studies). Three “endothelium-in” studies reported that 44.7–87.5% of eyes achieved BCVA of ≥20/25 at 6 months; pooled proportion of eyes achieving BCVA ≥20/25 at 6 months was 62.4% (95% CI 33.9–86.9%). Pooled mean endothelial cell loss was lower in the “endothelium-in” studies (28.1 ± 1.3%, 7 studies) compared to “endothelium-out” studies (36.3 ± 6.9%,10 studies) at 6 months (p = 0.018). Graft re-bubbling rates were higher in the “endothelium-out” studies (26.2%, 95% CI 21.9–30.9%, 74 studies) compared to “endothelium-in” studies (16.5%, 95% CI 8.5–26.4%, 6 studies), although statistical significance was not reached (p = 0.440). Primary graft failure rates were comparable between the two groups (p = 0.552). Quality of evidence was considered low and significant heterogeneity existed amongst the studies.

Conclusion

Reported rates of endothelial cell loss were lower in “endothelium-in” DMEK studies at 6 months compared to “endothelium-out” studies. Outcomes of “endothelium-in” techniques were otherwise comparable to those reported in “endothelium-out” studies. Given the technical challenges encountered in “endothelium-out” procedures, surgeons may consider “endothelium-in” techniques designed for easier intra-operative DMEK graft unfolding. “Endothelium-in” studies evaluating outcomes at longer time points are required before conclusive comparisons between the two techniques can be drawn.

Preventive treatment of allograft rejection after endothelial keratoplasty: A systematic review and meta-analysis

PURPOSE

To evaluate the efficacy of preventive treatment against allograft rejection after endothelial keratoplasty (EK), we conducted a systematic review and meta-analysis.

METHOD

PubMed, Cochrane Library, Embase and ScienceDirect databases were searched until May 2021. We computed a random-effect meta-analysis on graft rejection rate stratified by the intervention (i.e. Descemet membrane EK (DMEK) and Descemet stripping (Automated) EK (DS(A)EK) or ultrathin (UT)-DSAEK), and postoperative treatment. Meta-regressions were performed to compare intervention, treatment and influence of putative confusion factors.

RESULTS

We included 49 studies and 12 893 EK (6867 DMEK and 6026 DS(A)EK/UT-DSAEK). Topical steroids were merged in two efficacy regimens: standard steroids (prednisolone acetate 1% or dexamethasone 0.1%) and soft steroids (fluorometholone 0.1% or loteprednol etabonate 0.5%). Globally, DMEK had a lower graft rejection rate than DS(A)EK/UT-DSAEK (coefficient - 3.3, 95 CI, -4.60 to -1.90; p < 0.001). No significant differences were observed between standard and soft steroids to prevent graft rejection after DMEK. After EK, the rate of ocular hypertension was 20% (95 CI, 14 to 26%) with the use of standard steroids and 7% (5 to 9%) with soft steroids. Comparisons of treatments were not feasible in DS(A)EK/UT-DSAEK due to a lack of studies.

CONCLUSIONS

Descemet membrane endothelial keratoplasty (DMEK) has less risk of graft rejection compared with DS(A)EK/UT-DSAEK. Furthermore, soft steroids seemed to be a valuable alternative to standard steroids to prevent graft rejection after DMEK, involving a safe profile against ocular hypertension. Further studies are needed to compare other drugs in the prevention of graft rejection after EK.

Outcomes of Descemet Membrane Endothelial Keratoplasty in Bangkok, Thailand

Purpose

To investigate the medium-term clinical outcomes and risk factors for primary graft failure after Descemet membrane endothelial keratoplasty (DMEK) in Thai patients.

Patients and Methods

This is a single-center retrospective cohort study. Sixty-two eyes of 62 patients who underwent DMEK at Ramathibodi Hospital, Bangkok, Thailand, with a minimum of 24-month follow-up were recruited. Preoperative donor and recipient characteristics, intraoperative data, and postoperative outcomes including best-corrected visual acuity (BCVA), graft clarity, endothelial cell density (ECD), central corneal thickness (CCT), and complications were evaluated at 1, 3, 6, 12, and 24 months after surgery.

Results

The mean age of the patients was 67.2 ± 9.9 years, and 52% were female. The mean follow-up time was 37.5 ± 11.0 months. The most common indications for DMEK were Fuchs' endothelial corneal dystrophy (FECD) (53.2%) and pseudophakic bullous keratopathy (PBK) (17.7%). Nearly half of patients had triple-DMEK. The median preoperative BCVA was 20/400. Postoperative BCVA of ≥ 20/40 was reached in 37.1% and of ≥ 20/20 in 6.5% after 1 month which increased to 54.8% and 17.7% after 3 months; and to 67.7% and 27.4% after 24 months. Endothelial cell loss (ECL) at 3, 6, 12, and 24 months was 30.5%, 33.8%, 44.4%, and 45.9%, respectively. Graft diameter was the single factor, showing a significant relationship with postoperative ECD. Most frequent postoperative complications included graft detachment (22.6%), increased IOP/glaucoma (17.7%), and primary graft failure (16.1%). In univariate analysis, death-to-operation time and the diagnosis of PBK were significantly associated with the occurrence of primary graft failure.

Conclusion

DMEK is a safe, effective, and feasible treatment for endothelial failure in Asian eyes. Careful case selection, use of relatively fresh donor tissues, and appropriate surgical techniques can prevent primary graft failure and facilitate optimal outcomes following surgery.

Recent indications of endothelial keratoplasty at a tertiary eye care center in South India

PURPOSE

To describe the patient demographics and recent clinical indications of endothelial keratoplasty (EK) in patients presenting to a tertiary eye care center in India.

METHODS

This cross-sectional hospital-based study included 2,182 patients who underwent EK between Jan 2016 and Dec 2019 (4 years period). The data were collected using an electronic medical record system.

RESULTS

Overall, 2,632 eyes of 2,182 patients underwent EK during the study period. Median age was 62 (IQR: 48-70) years and adults (94.45%) comprised most of the cohort. More commonly, the patients were male (55.59%) and from the higher socioeconomic strata (67.51%). The corneal signs included corneal edema (70.93%), corneal scarring (29.60%), corneal vascularization (16%) and guttae (12.88%). The major indications of EK were post-cataract surgery corneal edema in 1331 (50.57%) patients, endothelial dystrophy in 537 (20.4%) patients, failed graft in 535 (20.33%) patients causing a vision impairment of > 20/400-20/1200 in about a half (45.55%) of the patients. Descemet stripping endothelial keratoplasty (DSEK) and Descemet membrane endothelial keratoplasty (DMEK) were performed in 2075 (78.84%) and 557(21.16%) patients, respectively.

CONCLUSION

EK is commonly performed during the sixth decade of life and in males. The most performed procedure is DSEK. The commonest indication was post-cataract surgery corneal edema.

Corneal oedema with in situ implantable collamer lens: a challenging scenario for descemet membrane endothelial keratoplasty

A 27-year-old woman had foggy vision and photophobia since 10 months after implantation of implantable collamer lens (ICL STAAR Surgical AG, Nidau, Switzerland) with evidence of corneal decompensation and no cataract formation. Descemet membrane endothelial keratoplasty in phakic eyes is challenging, considering presence of posterior chamber phakic intraocular lens (IOL), decreasing the space available in anterior chamber to manoeuvre the graft. Need of inferior peripheral iridotomy in presence of central hole technology in ICL depends on the dynamics of full chamber air bubble. At 8 months, vision had improved to 20/20 and normal IOP with well-attached graft, stable phakic IOL and clear lens.

Descemet Membrane Endothelial Keratoplasty and Bowman Layer Transplantation: An Anatomic Review and Historical Survey

For nearly a century, the definitive treatment of many corneal dystrophies and ectactic disorders was limited to penetrating keratoplasty, but over the past 2 decades, a surge of surgical innovation has propelled the treatment of many corneal diseases to more targeted approaches with significantly better visual outcomes. Anterior stromal diseases were first changed through endothelial-sparing techniques, such as deep anterior lamellar keratoplasty, but have more recently transitioned to stromal-sparing approaches. Ultraviolet corneal crosslinking strengthens the cornea and halts progression of keratoconus in >90% of cases. Intracorneal ring segment and corneal allogenic ring segment implantation offer methods to flatten ectatic corneas. However, Bowman layer transplantation - inlay and more recently onlay techniques - has shown promise for treating advanced keratoconus and preventing keratoplasty. The advent of endothelial keratoplasty radically changed the treatment of corneal endothelial dysfunction, and Descemet membrane endothelial keratoplasty specifically offers an average postoperative visual acuity of 20/25 (0.8) with only 8.8% of grafts requiring retransplantation in the first 5 years. Here, we review the rapid innovations for surgical treatment of corneal diseases, spanning from endothelial keratoplasty and endothelial regeneration to anterior lamellar keratoplasty and stromal augmentation, highlighting key steps which may be moving us closer to a "postkeratoplasty" world.

Pre-Descemet's endothelial keratoplasty: a simple, Descemet's membrane scoring technique for successful graft preparation

PURPOSE

Pre-Descemet's endothelial keratoplasty (PDEK) donor tissue preparation involves the intrastromal injection of air to create a type 1 big bubble (BB) and avoidance of the creation of a type 2 BB. The purpose of this study was to design and test a technique to consistently creates a type 1 BB without risk of creating a type 2 BB.

METHODS

A prospective matched study with 64 human donor sclerocorneal discs, which were not suitable for corneal transplantation, was conducted. The corneas were divided into two groups, of which 32 were subjected to the standard technique of preparing the PDEK donor tissue (group 1, control) and 32 new technique, where in the donor Descemet's membrane was scored with a Sinskey hook. Frequency of occurrence of different types of BB was compared and statistically analysed.

RESULTS

With the standard technique (group 1), type 1 BB occurred in 53.1%, type 2 BB in 34.4% and mixed BB in 12.5% of samples. With the scoring technique (group 2), a type 1 BB occurred in 100% of the samples. No type 2 or mixed BB occurred in any case in group 2. The difference in creation of a type 1BB between the two groups was statistically significant (p=0.00).

CONCLUSION

The scoring technique is a simple, inexpensive and reproducible option to consistently achieve a type 1 BB to prepare PDEK graft tissue. The next step would be to study the clinical outcomes of PDEK performed with tissue obtained by the scoring technique.