Descemet’s membrane endothelial keratoplasty surgery: update on the evidence and hurdles to acceptance. Curr Opin Ophthalmol. 2013;24:329-335. [PMID: 23680758 DOI: 10.1097/icu.0b013e32836229ab]

Assessment of Corneal Graft Outcomes in a Murine Model of Endothelial Keratoplasty

Objectives: In this study, we establish a protocol for evaluating the outcomes of endothelial keratoplasty, including graft survival, rejection, or failure. Additionally, we also evaluate the alloimmune response in graft recipients. Methods: We performed EK using C57BL/6 (allogeneic) and BALB/c (syngeneic) as donors and BALB/c mice as recipients. Slit-lamp examination and optical coherence tomography were performed for clinical evaluations for 16 weeks post-procedure. Criteria for the assessment of corneal opacity were established and the animals were graded weekly. Additionally, we assessed corneal endothelial cell density by harvesting the corneas and staining with zonula occludens-1 (ZO-1). Lastly, lymph nodes were collected, and CD4+ T cells were MACS-sorted and co-cultured with syngeneic or allogeneic antigen-presenting cells (APCs) to assess the IFN-γ expression levels by alloreactive Th1 cells (ELISPOT) in response to the direct (donor) or indirect (host) pathways of sensitization. Results: We observed graft failure in four animals, including irreversible corneal opacity, graft detachment, and anterior synechiae in the first four weeks. The remaining animals were graded between 0 and 5 as per the established criteria. The total and graft corneal thickness and endothelial cell density progressively worsened with a higher grade of corneal opacity. The direct allosensitization of Th1 cells was significantly higher in mice with a higher grade of corneal opacity. At 16 weeks follow-up, the grafts remained stable with low opacity scores in syngeneic EK recipients; however, the opacity scores were higher and variable in allogeneic EK recipients. Conclusions: These findings establish a standardized protocol to assess the graft outcomes in a murine model of EK. Furthermore, we delineate the underlying immunological pathway that contributes to the immune-mediated rejection of grafts in this model.

Clinical Outcomes of Transscleral-Sutured Intraocular Lens Combined With Descemet Membrane Endothelial Keratoplasty

PURPOSE

The aim of the study was to report clinical outcomes of Descemet membrane endothelial keratoplasty (DMEK) combined with transscleral-sutured intraocular lens (IOL) compared with DMEK combined with phacoemulsification and posterior chamber IOL (Phaco-DMEK).

METHODS

A retrospective chart review of all patients who underwent DMEK combined with transscleral-sutured intraocular lens fixation or combined with phacoemulsification for Fuchs endothelial corneal dystrophy from 2016 to 2021 at the Toronto Western Hospital or the Kensington Eye Institute (Toronto, ON, Canada) and had at least 18 months of follow-up was performed. Main outcomes were postoperative distance-corrected visual acuity, rebubbling rate, graft survival rate, and complications.

RESULTS

Twenty-one cases of DMEK combined with transscleral-sutured IOL (DMEK-TSS-IOL) and 44 cases of Phaco-DMEK were evaluated. Twelve eyes (57.15%) had a foldable acrylic 3-piece IOL (AR40E) and 9 (42.85%) had a single-piece polymethylmethacrylate (PMMA) IOL (CZ70BD). LogMAR distance-corrected visual acuity improved significantly from 1.48 ± 0.62 (SD) to 0.86 ± 0.82 ( P = 0.01) 12 months after DMEK-TSS-IOL and from 0.41 ± 0.29 logMAR to 0.11 ± 0.11 logMAR ( P < 0.0001) after Phaco-DMEK. No statistically significant differences were observed in donor ( P = 0.97) or 1-year postoperative endothelial cell density ( P = 0.11) between the groups. Rebubbling was necessary in 33.33% of eyes in DMEK-TSS-IOL compared with 25% of Phaco-DMEK eyes ( P = 0.55). Graft survival rate was 76.19% in the DMEK-TSS-IOL group compared with 90.90% in the Phaco-DMEK group ( P = 0.13).

CONCLUSIONS

Transscleral-sutured IOL combined with DMEK is an option for the management of endothelial diseases in aphakic eyes or those which require IOL exchange for the experienced surgeon. However, when compared with routine Phaco-DMEK, there are higher complication and lower survival rates at 18 months.

NF-κB c-Rel Is a Potential Therapeutic Target for Acute Corneal Transplant Rejection

Purpose

The purpose of this study was to determine the role of nuclear factor kappa B (NF-κB) c-Rel during acute corneal transplant rejection and whether targeting c-Rel can reduce corneal transplant rejection.

Methods

Allogeneic corneal transplantation was performed in wild-type and c-Rel-deficient mice. Corneal graft survival rate, opacity, neovascularization, and edema were evaluated by slit-lamp microscopy. Adeno-associated virus 6 (AAV6) expressing c-Rel-specific small hairpin RNA (AAV6-shRel) and the small-molecule compound pentoxifylline (PTXF) were used to reduce c-Rel expression. Enzyme-linked immunosorbent assay was used to determine the expression of inflammatory cytokines. c-Rel expression was determined by quantitative RT-PCR and western blot. The effect of c-Rel inhibition on corneal transplant rejection was examined using a mouse model of acute allogeneic corneal transplantation. Tear production and corneal sensitivity were measured to determine the potential toxicity of AAV6-shRel and PTXF.

Results

The expression of c-Rel and its inflammatory targets was increased in both mice and patients with corneal transplant rejection. Loss of c-Rel reduced corneal transplant rejection in mouse. Both AAV6-shRel and PTXF were able to downregulate the expression of c-Rel and its inflammatory targets in vitro. Treatment with AAV6-shRel or PTXF reduced corneal transplant rejection in mouse and downregulated the expression of inflammatory cytokines in peripheral blood mononuclear cells from patients with corneal transplant rejection. Treatment with AAV6-shRel or PTXF displayed no side effects on tear production or corneal sensitivity.

Conclusions

Increased expression of c-Rel is a risk factor for acute corneal transplant rejection, and targeting c-Rel can efficiently reduce corneal transplant rejection.

An approach to reduce Descemet's membrane scrolling: Relevance to Descemet's membrane endothelial keratoplasty (DMEK)

Purpose

We aimed to determine whether Descemet's membrane (DM) scrolling occurs primarily along the vertical or horizontal axis and establish whether oval trephination along the axis of least scrolling can reduce the grade of the scroll.

Methods

The longest limbus-to-limbus axis on 28 sclerocorneal discs was taken as the horizontal axis. The horizontal (n = 7) or (right angles to it) vertical (n = 6) axis was marked on DM before peeling it off. The direction and grade of scrolling was observed. Narrow strips (3-4 mm wide) were then cut along the two axes (n = 4 each) and the scrolling pattern was observed. Ellipses (7 × 9 mm) of DM were punched along the two axes (n = 6 each) and the scrolls graded. Immunofluorescent staining for elastin on horizontal and vertical tissue sections from three DM samples was performed. The intensity and thickness of elastin staining were measured.

Results

Twenty-four (85.72%) DM samples showed scrolling along the horizontal axis, none showed scrolling along the vertical axis, and four (14.28%) samples showed a spiral scroll, regardless of which axis was marked (grade 3.7 and 3.6). Vertically oval discs showed significantly reduced scrolling (grade 1.2) compared to horizontally oval discs (grade 3.5). Narrow strips of DM showed a similar scrolling pattern. Immunohistology showed no difference in any of the parameters examined along the two axes or from the center to the periphery.

Conclusion

DM scrolls primarily along the horizontal axis. Vertically oval DM samples show minimal scrolling, which can be an advantage in DMEK. Differential scrolling is not determined by the distribution of elastin.

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.

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.

Yogurt Technique for Descemet Membrane Endothelial Keratoplasty Graft Preparation: Early Clinical Outcomes

PURPOSE

The aim of this study was to evaluate the efficacy and safety of the Yogurt technique for Descemet membrane endothelial keratoplasty (DMEK) graft preparation.

METHODS

This study included patients who underwent DMEK combined or not with phacoemulsification surgery using donor tissues prepared by a surgeon with the DMEK Tzamalis disposable punch at 2 referral hospitals between October 2019 and June 2021. Primary outcomes were duration of graft preparation, surgeon grading of graft quality, and endothelial cell density measured at 1 and 6 months after surgery. Secondary outcomes were best-corrected visual acuity (BCVA) measured at 1 and 6 months postoperatively and DMEK intraoperative and postoperative complications.

RESULTS

Forty-nine patients were included in this study. The mean DMEK graft preparation time was 7.2 ± 1.4 minutes. Donor grafts were rated good in 67.3% of cases (33 of 49), sufficient in 24.5% (12 of 49), and poor in 8.2% (4 of 49). Donor mean endothelial cell density was 2580 ± 155 preoperatively, which were reduced to 2269 ± 191 ( P < 0.000) and 1697 ± 142 ( P < 0.0001) at 1 and 6 months, respectively. No significant difference was found in graft preparation outcome ( P = 0.543). The preoperative BCVA was 0.65 ± 0.44 logMAR, which improved to 0.31 ± 0.43 logMAR ( P < 0.0001) and 0.12 ± 0.14 logMAR ( P < 0.0001) at 1 and 6 months after surgery, respectively.

CONCLUSIONS

This study shows that the DMEK Tzamalis punch can be used as an effective and safe method for DMEK graft preparation with a shallow learning curve that allows it to be successfully performed by relatively inexperienced surgeons.

IOL Power Calculation in Eyes Undergoing Combined Descemet Membrane Endothelial Keratoplasty and Cataract Surgery

PURPOSE

To assess the accuracy of different corneal powers for intraocular (IOL) power calculation in combined Descemet membrane endothelial keratoplasty (DMEK) and cataract surgery and investigate whether preoperative parameters correlate to the prediction error (PE).

METHODS

This prospective case series involved patients with Fuchs endothelial dystrophy receiving combined DMEK and cataract surgery. Preoperatively, patients underwent optical biometry and anterior segment OCT (AS-OCT). AS-OCT measurements were repeated 6 months postoperatively, when final refraction was assessed. The PE was calculated using the preoperative average keratometry (K_ave) measured by the optical biometer and User Group for Laser Interference Biometry (ULIB) constants. It was also calculated, after constant optimization, using the preoperative K_ave from both devices and the total corneal power (TCP) measured by AS-OCT, as well as the postoperative K_ave and TCP measured by AS-OCT.

RESULTS

ULIB constants resulted in the highest hyperopic PE (P < .0001). Constant optimization improved the results, because the PE was zeroed out and the absolute PEs decreased. No significant difference was found among the Barrett Universal II, Emmetropia Verifying Optical 2.0, Haigis, Hoffer Q, Holladay 1, Kane, and SRK/T formulas. Further improvement was achieved with the postoperative K_ave and TCP, although the accuracy remained moderate. The PE based on preoperative corneal measurements was correlated to the amount of corneal flattening; the latter could be predicted by multiple linear regression accounting for anterior and posterior corneal radii (P = .0002) and was correlated to the preoperative anterior/posterior ratio.

CONCLUSIONS

Constant optimization is beneficial for combined DMEK and phacoemulsification. Predicting postoperative corneal flattening may improve the results of IOL power accuracy. [J Refract Surg. 2022;38(7):435-442.].

Evolution of corneal transplantation techniques and their indications in a French corneal transplant unit in 2000–2020

Purpose

This retrospective cohort study assessed the evolution of corneal transplantation and its indications in the last 21 years (2000–2020) in a specialized ophthalmology department in a tertiary referral center in France.

Methods

The surgical techniques and indications, patient age and sex, and postoperative best-corrected visual acuity (BCVA) 6 months after keratoplasty were extracted.

Results

In total, 1042 eyes underwent keratoplasty in 2000–2020. Annual numbers of corneal transplantations increased by 2.2-fold. Penetrating keratoplasty (PKP) was the sole technique for the first 11 years. Descemet stripping automated endothelial keratoplasty (DSAEK) and Descemet membrane endothelial keratoplasty (DMEK) were introduced in 2011 and 2014, respectively. Cases of both quickly increased, accounting for 28% and 41% of cases in 2015–2020, respectively. Eventually, DSAEK and DMEK were respectively used for most pseudophakic bullous keratopathy (PBK) and all Fuchs endothelial cell dystrophy (FECD) cases. PKP cases declined to 27%. Deep anterior lamellar keratoplasty (DALK) was rare (3% of all cases). These changes associated with rises in PBK and particularly FECD cases, and a strong decline in keratoconus, causing FECD, PBK, and keratoconus to move from being the 4^th, 1^st, and 3^rd most common indications to the 1^st, 2^nd, and 6^th, respectively. On average, BCVA improved by 0.1–0.3 logMAR. Patient age dropped steadily over time. Female predominance was observed.

Conclusions

The invention of DSAEK and then DMEK precipitated an enormous change in clinical practice and a large expansion of keratoplasty to new indications. This study confirms and extends previous findings in other countries.

Tissue engineered scaffolds for corneal endothelial regeneration: a material's perspective

Currently, the treatment of corneal diseases caused by damage to the corneal endothelium requires a donor cornea. Because of their limited availability (1 donor cornea for 70 patients in need), researchers are investigating alternative approaches that are independent of donor tissue. One of them includes the development of a tissue engineered scaffold onto which corneal endothelial cells are seeded. In order to function as a suitable substrate, some of its essential properties including thickness, permeability, transparency and mechanical strength should meet certain demands. Additionally, the membrane should be biocompatible and allow the formation of a functional endothelium on the surface. Many materials have already been investigated in this regard including natural, semi-synthetic and synthetic polymers. In the current review, we present an overview of their characteristics and provide a critical view on the methods exploited for material characterization. Next, also the suitability of scaffolds to serve their purpose is discussed along with an overview of natural tissues (e.g. amniotic membrane and lens capsule) previously investigated for this application. Eventually, we propose a consistent approach to be exploited ideally for membrane characterization in future research. This will allow a scientifically sound comparison of materials and membranes investigated by different research groups, hence benefitting research towards the creation of a suitable/optimal tissue engineered endothelial graft.

Thickness Measurement of Endothelium-Descemet Membrane in Descemt Membrane Detachment Patients Using High-Definition Optical Coherence Tomography

Purpose: (1) To measure the corneal endothelium-Descemet membrane (EDM) layer thickness in Descemet membrane detachment (DMD) patients in vivo using high-definition optical coherence tomography (HD-OCT), and to investigate its correlation with age. (2) To explore whether the detachment time will affect the EDM thickness. (3) To explore whether the EDM thickness of cornea with DMD was different from that without DMD. Participants: Patients with DMD were divided into three groups. Group 1 included twenty-three patients whose Descemet membrane (DM) was partial or complete detached from the corneal stroma after various ocular surgeries. Group 2 included eight patients from group 1 who underwent twice HD-OCT examination on different days before the DM reattached to the stroma. Group 3 included nine patients from group 1 who had clear grayscale boundary between the DM and stroma in HD-OCT images after DM reattachment. Methods: All patients underwent HD-OCT and EDM thickness was measured using Image -Pro Plus 6.0. In Group 1, regression analyses were used to evaluate the correlation between EDM thickness and age, and the thickness difference between the ≤50-year-old group and the >50-year-old group was analyzed by independent sample t-test. In Group 2, paired samples t-test was used to check whether detachment time would affect EDM thickness. In Group 3, paired samples t-test was used to check whether the EDM thickness of cornea with DMD was different from that without DMD. p < 0.05 was considered significant. Results: In Group 1, the EDM thickness measured on the first post-operative day was 27.8 ± 3.6 μm, and a positive correlation was found between EDM thickness and age (r = 0.619, p < 0.05). The EDM thickness of ≤50-year-old group and >50-year-old group were 23.9 ± 3.2 and 29.2 ± 2.6 μm, and there was a significant difference between the two groups (p = 0.001). In Group 2, the first measurement of EDM thickness was 27.5 ± 4.0 μm, the second measurement was 27.6 ± 4.2 μm, the interval between the two measurements was 2.1 ± 1.6 days, and there was no significant difference between the two measurements (p = 0.328). In Group 3, the EDM thickness with DM detachment was 28.3 ± 3.5 μm, with DM reattachment was 23.4 ± 2.4 μm, there was a significant difference between the two measurements (p = 0.002). Conclusions: The EDM thickness in the state of DMD is thicker than its actual thickness in normal cornea, and EDM thickness of the >50-year-old group is much thicker than that of the ≤50-year-old group.

Outcomes of Pseudophakic, Phakic, and Triple DMEK

PURPOSE

To evaluate the outcome of phakic and pseudophakic eyes treated by Descemet membrane endothelial keratoplasty (DMEK) versus DMEK combined with cataract surgery (triple DMEK).

METHODS

Retrospective cohort study based on the prospective Cologne DMEK data base. This study is a single-center analysis of 62 eyes undergoing phakic (age mean ± SD 52 ± 6.43), 518 eyes undergoing pseudophakic (73.5 ± 8.57), and 557 eyes undergoing triple DMEK (67.93 ± 8.57). Outcome measures were changes in best spectacle-corrected visual acuity (BSCVA), central corneal thickness, endothelial cell density (ECD), rebubbling rates within the first year after surgery, and the need for cataract surgery within the first 2 years after phakic DMEK.

RESULTS

The preoperative BSCVA (mean ± SD; logarithm of the minimum angle of resolution) was 0.30 ± 0.22 in the phakic, 0.63 ± 0.45 in the pseudophakic, and 0.44 ± 0.30 in the triple DMEK group (P < 0.001), which changed to 0.09 ± 0.12, 0.14 ± 0.1, and 0.1 ± 0.1 (P < 0.001) 1 year after surgery, respectively. There was no difference in central corneal thickness (P = 0.929) and endothelial cell density (P = 0.606) 1 year postoperatively. Rebubbling rates in DMEK using SF6 20% for anterior chamber tamponade were not significantly different (P = 0.839). After phakic DMEK, 40% of eyes underwent cataract surgery within the second year. However, there was a high loss to follow-up in this group.

CONCLUSIONS

Phakic and triple DMEK procedures tend to have a better 1-year BSCVA than pseudophakic DMEK, with no differences in all other parameters analyzed. However, patients from the pseudophakic DMEK group were older and already had worse BSCVA before surgery.

Tips, Tricks, and Guides in Descemet Membrane Endothelial Keratoplasty Learning Curve

Lamellar keratoplasty is fast becoming the most popular form of corneal transplantation. The adoption of Descemet membrane endothelial keratoplasty (DMEK) in the management of Fuchs endothelial dystrophy and pseudophakic bullous keratopathy is partly responsible for this shift in the paradigm of management of corneal pathology. The learning curve of DMEK, however, has been proven to be much steeper than previous endothelial keratoplasty procedures. To ease the procedure, experts have proposed multiple innovative techniques from tissue preparation to graft unfolding to aid the more novice surgeon. Here, we collate and share tips and tricks from our collective experiences to support the learning curve and outcomes in DMEK for both the novice and more experienced corneal transplant surgeons.

Younger Donor Tissue in Descemet Membrane Endothelial Keratoplasty Surgery: Clinical Outcomes

PURPOSE

To determine whether using younger donor tissue for Descemet membrane endothelial keratoplasty (DMEK) surgery influences clinical outcomes.

METHODS

Scroll tightness, unscrolling time, rebubble rate, and preoperative and 3- and 6-month postoperative endothelial cell density (ECD) and endothelial cell loss (ECL) were compared for 661 DMEK grafts prepared from younger (aged younger than 50 yrs, n = 81) and older donors (aged 50 yrs or older, n = 580) with Student t test, χ2 test, or Mann-Whitney U test.

RESULTS

There was no difference in overall unscrolling time (younger donors: 3.1 ± 3.1 min, older donor: 2.9 ± 2.7 min, P = 0.503). Experienced faculty surgeons, compared with fellows, had a significantly lower unscrolling times for both younger donors (2.4 ± 2.3 vs. 4.6 ± 3.9 min, P = 0.002) and older donors (2.5 ± 2.1 vs. 3.7 ± 3.3 min, P <0.001). Rebubble rates were not statistically different between younger (12.3%) and older donors (15.0%, P = 0.527). Three-month ECD was higher in grafts from younger compared with that in those from older donors (2138 ± 442 vs. 1974 ± 470 cells/mm2, P = 0.024). Six-month ECD was similar for younger (1972 ± 509 cells/mm2) and older donors (1947 ± 460 cells/mm2, P = 0.585). There was no difference in 3- or 6-month ECL comparing younger (3-mo: 24.3% ± 13.4%; 6-mo: 31.1% ± 15.2%) with older donors (3-mo: 25.9% ± 15.5%, P = 0.489; 6-mo: 27.8% ± 15.1%, P = 0.231).

CONCLUSIONS

DMEK grafts prepared from younger donors exhibited similar unscrolling times, rebubble rates, and 3- and 6-month ECL compared with older donors. Experienced surgeons might begin to accept DMEK grafts from younger donors with confidence.

The "Yogurt" Technique for Descemet Membrane Endothelial Keratoplasty Graft Preparation: A Novel Quick and Safe Method for Both Inexperienced and Senior Surgeons

PURPOSE

To describe and evaluate the efficacy and safety of a novel technique to prepare Descemet membrane endothelial keratoplasty (DMEK) donor grafts using a newly designed partial-thickness hinge punch.

METHODS

The novel punch has a circular guarded blade missing 1 clock hour, creating an uncut hinge on the donor cornea. In addition, 2 straight cuts are made by the punch perpendicular to the edge of trephination toward the trabecular meshwork in the hinge area. After the donor corneoscleral rim is positioned endothelial side up, a partial-thickness trephination is performed avoiding any rotational movements. Descemet membrane is lifted from Schwalbe line in the hinge area, and DMEK graft is peeled after desired marking without further preparation.

RESULTS

Three surgeons of different experience levels on DMEK (senior/independent/fellow) initially applied the new technique in 18 research corneas, divided into equal groups. Two failures in graft preparation were noted, defined as radial tears extending ≥0.5 mm. The mean preparation time was 6.21 ± 1.45 minutes. No statistically significant differences were noted in success rate, duration, and endothelial cell loss (ECL) between surgeons (P > 0.05). ECL was evaluated as an average of 5 readings on randomly selected graft areas, not including graft periphery. Fifteen additional research corneas were stripped by 1 single user in an eye bank setting. No tissue loss was recorded, whereas ECL and mortality rate remained unaffected after preparation (P = 0.64 and P = 0.72, respectively).

CONCLUSIONS

This new DMEK graft preparation technique, simulating the opening of a yogurt cup, seems to be a safe and an efficient method, providing shorter preparation time and low failure rates independent of surgeon's experience level.

Comparing the effect of three Descemet membrane endothelial keratoplasty injectors on endothelial damage of grafts

Purpose:

Various injectors are commercially available for Descemet membrane endothelial keratoplasty (DMEK) but not all injectors have been studied for endothelial damage of grafts. The aim of the study was to compare endothelial damage in pre-stripped DMEK tissue from three clinically used injector devices: the modified Jones tube, the STAAR intraocular (IOL) injector, and the Geuder glass cannula in a laboratory setting.

Methods:

Twenty-four human donor corneas were used for this study, eight for each study arm. Each endothelial graft was pre-stripped, trephined to 8.0 mm diameter, then loaded into either the modified Jones tube, the STAAR IOL injector, or the Geuder glass cannula by an eye bank technician who had no prior experience with any of the injectors. Grafts were then ejected, stained with Calcein acetoxymethyl (AM), and quantitatively analyzed using FIJI image software. The primary outcome was the percent of endothelial damage from injector loading and injection. Donor demographics were analyzed using Fisher’s exact test. The percentage of endothelial cell loss was compared across groups using the Kruskal–Wallis test.

Results:

The mean percent of endothelial damage from after injection of the graft was 37.8% (±SD 12.2%) for the modified Jones tube, 37.0% (±SD 13.9%) for the STAAR IOL injector, and 23.5% (±SD 5.1%) for the Geuder cannula (P = 0.008).

Conclusion:

DMEK injectors contribute to intraoperative endothelial damage of transplanted grafts. The Geuder glass cannula may offer increased ease of use and less endothelial damage compared to the modified Jones tube or STAAR IOL injector for the novice user in early cases.

Cost-effectiveness analysis of preloaded versus non-preloaded Descemet membrane endothelial keratoplasty for the treatment of Fuchs endothelial corneal dystrophy in an academic centre

AIMS

To determine the cost-effectiveness of preloaded Descemet membrane endothelial keratoplasty (pDMEK) versus non-preloaded DMEK (n-pDMEK) for the treatment of Fuchs endothelial corneal dystrophy (FECD).

METHODS

From a societal and healthcare perspective, this retrospective cost-effectiveness analysis analysed a cohort of 58 patients with FECD receiving pDMEK (n=38) or n-pDMEK (n=30) from 2016 to 2018 in the Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, USA. Exclusion criteria were previous ocular surgeries (other than uncomplicated cataract surgery), including other keratoplasty procedures, ocular pathological conditions as glaucoma, amblyopia, laser treatments, or any retinal or corneal disease. The main outcome parameters were the incremental cost-utility ratio (ICUR) and net monetary benefit (NMB).

RESULTS

pDMEK was less costly compared with n-pDMEK (healthcare: $13 886 vs $15 329; societal: $20 805 vs $22 262), with a slighter greater utility (QALY 0.6682 vs QALY 0.6640) over a time horizon of 15 years. pDMEK offered a slightly higher clinical effectiveness (+0.0042 QALY/patient) at a lower cost (healthcare: -$1444 per patient; societal: -$1457 per patient) in improving visual acuity in this cohort of patients with FECD. pDMEK achieved a favourable ICUR and NMB compared with n-pDMEK. Based on sensitivity analyses performed, the economic model was robust.

CONCLUSIONS

From the societal and healthcare perspective, pDMEK was less costly and generated comparable utility values relative to n-pDMEK. Therefore, pDMEK appears to be cost-effective and cost saving with respect to n-pDMEK. Further long-term follow-up data are needed to confirm these findings.

Endothelial Cell Loss After Descemet's Membrane Endothelial Keratoplasty for Fuchs' Endothelial Dystrophy: DMEK Compared to Triple DMEK

PURPOSE

This study compared the outcomes after Descemet's membrane endothelial keratoplasty (DMEK) in pseudophakic patients with the outcomes after DMEK combined with cataract surgery (triple-DMEK) in patients with Fuchs' endothelial dystrophy (FED).

DESIGN

Retrospective, single-institution, interventional, consecutive case series.

METHODS

Outcomes of 114 DMEKs in patients with FED at a minimum of 1-year follow-up were reviewed. A total of 34 eyes (29 patients) were pseudophakic and underwent only DMEK (DMEK-only), and 80 eyes (56 patients) underwent triple-DMEK. Main outcome measurements included endothelial cell loss (ECL), best-corrected visual acuity (BCVA), central corneal thickness (CCT), and complications.

RESULTS

At 1 month, ECL was 25% (±16%) and 35% (±15%) in DMEK-only and triple-DMEK groups, respectively. At 1 year, ECL was 33% (±13%) and 41% (±16%) in DMEK-only and triple-DMEK groups, respectively. There was statistically significantly less ECL after DMEK-only than after triple-DMEK at both 1 month (95% confidence interval [CI]: 1.67-15.02; P = .016) and 1 year (95% CI: 1.06-14.07; P = .034). CCT was significantly lower after DMEK-only than after triple-DMEK at 1 month but not at 1 year. BCVA was excellent and similar in the 2 groups. There were no cases of graft failure. Graft rejection and rebubbling rates were similar in DMEK-only and triple-DMEK groups: rejection occured in 8.8% and 8.75% of cases respectively (P = .50), and rebubbling in 2.9% and 2.5% respectively (P = .44).

CONCLUSIONS

Both the DMEK-only and the triple-DMEK groups had low rebubbling rates and good visual outcomes, but the combined triple-DMEK procedure resulted in significantly greater loss of endothelial cells than DMEK-only surgery at both 1 month and 1 year.

One-Year Clinical Outcomes of Preloaded Descemet Membrane Endothelial Keratoplasty Versus Non-Preloaded Descemet Membrane Endothelial Keratoplasty

PURPOSE

To compare the one-year outcomes of preloaded Descemet membrane endothelial keratoplasty (pDMEK) and non-preloaded DMEK (n-pDMEK) in patients with Fuchs endothelial corneal dystrophy (FECD).

METHODS

This retrospective comparative cohort study consecutively included 68 eyes with Fuchs endothelial corneal dystrophy who underwent either pDMEK (n = 38) or n-pDMEK (n = 30) performed by cornea fellows with an experienced surgeon between 2016 and 2018 at the Massachusetts Eye and Ear Infirmary. Exclusion criteria were previous surgery (other than uncomplicated cataract surgery) and any documented evidence of macular or other corneal diseases. Corrected distance visual acuity (CDVA), central corneal thickness, intraocular pressure, patient characteristics, postprocessing endothelial cell count, donor graft data, and complications were compared.

RESULTS

CDVA showed similar results for pDMEK (0.12 ± 0.11 logarithm of the minimal angle of resolution [LogMAR]) and n-pDMEK (0.13 ± 0.13 LogMAR) (P = 0.827). Sixty-six percent of the pDMEK eyes and 57% of the n-pDMEK eyes achieved a VA of ≥0.1 LogMAR, and 95% and 97%, respectively, achieved a CDVA ≥0.3 LogMAR. The preoperative central corneal thickness of pDMEK and n-pDMEK (644 ± 62.2 μm, 660.5 ± 56.2 μm) decreased significantly after surgery (525.1 ± 43.6 μm, 526.5 ± 45.2 μm, P < 0.001), with no difference between groups (P = 0.840). The postprocessing endothelial cell count did not differ between pDMEK (2959.2 ± 182.9 cells/mm2) and n-pDMEK (2939.3 ± 278.7 cells/mm2) (P = 0.484). Complication rates were comparable with just the rebubbling performed in a minor procedure room showing a lower rate for pDMEK (13.16%) compared with n-pDMEK (33.33%) (P < 0.045).

CONCLUSIONS

One-year clinical outcomes were similar between pDMEK and n-pDMEK procedures, rendering eye bank-prepared pDMEK tissues a useful tool in the treatment of endothelial dysfunction.

Descemet membrane endothelial keratoplasty and corneal biomechanics

OBJECTIVE

To study the behaviour of the biomechanical properties of the cornea in DMEK (Descemet membrane endothelial keratoplasty).

METHOD

Prospective longitudinal observational study. 21 pre and post-DMEK eyes. 3-month follow-up with the dynamic Scheimpflug Analyzer (Corvis ST, Oculus; Wetzlar, Germany). The following parameters were measured: IOPnc: non-corrected intraocular pressure (IOP), IOPb: IOP corrected by biomechanics, maximum deflection amplitude (DefA), CCT: central corneal pachymetry, flattening speed 1 and 2, peak distance, HC deformation amplitude: deformation amplitude in maximum concavity, integrated inverse concave radius, DAR 1 and 2: deformation amplitude at 1mm and 2mm from the corneal apex, respectively. ARTh: Ambrosial pachymetric ratio, SP1: stiffness parameter, CBI: Corvis Biomechanical index and the maximum inverse radius. Pre-operative and post-operative measurements were performed with a 3-month follow-up and compared with a paired sample t-test.

RESULTS

There was a significant decrease in the IOPnc of 1.54±3mmHg (p<0.05), a significant increase in the post-surgical IOPb of 3.79±3.18mmHg (p<0.001), a significant pachymetric decrease of 164.4±91.35μm (p<0.001) after the intervention. All dynamic parameters of the Scheimpflug analyzer changed significantly after surgery (p<0.05), except the ARTh and IWC variables.

CONCLUSIONS

Variables indicate a decrease in corneal strength post-DMEK, with an increase in IOPb, at least the first 3 months after surgery. This finding is especially relevant in the follow-up of patients with coexisting glaucoma.

Perceived difficulties and barriers to uptake of Descemet's membrane endothelial keratoplasty among surgeons

Purpose: To determine barriers related to implementation of Descemet's membrane endothelial keratoplasty (DMEK) among corneal surgeons.

Methods: This was a multicenter survey study of all corneal surgeons who participated in a DMEK wet lab organized by the Netherlands Institute for Innovative Ocular Surgery. Data related to barriers limiting uptake of DMEK surgery, self-perceived levels of competence, and difficulty with different steps of DMEK surgery were analyzed.

Results: The survey response rate was 31% (22 of 72). The most common barrier to uptake of DMEK surgery identified was anxiety related to incorrect insertion of the tissue and the need to regraft (64%, 14 of 22), followed by anxiety related to tissue preparation (50%, eleven of 22). Surgeons also felt anxious regarding the possibility of rebubbling with initial DMEK (41%, nine of 22). Steps related to DMEK graft (76%) preparation, tissue insertion (41%), and graft unfolding (72%) were identified as the most difficult steps to learn by the respondents.

Conclusion: The DMEK learning curve, especially for the novice surgeon, may be shortened by seeking educational resources, including wet labs and surgical videos. Eye banks may facilitate adoption of DMEK by making validated DMEK tissue more accessible to surgeons globally.

Comparative analysis of biomechanical parameters of the corneas following Descemet membrane endothelial keratoplasty and contralateral healthy corneas

PURPOSE

To compare the biomechanical properties of the unilateral operated corneas in patients who had undergone Descemet membrane endothelial keratoplasty (DMEK) for pseudophakic bullous keratopathy (PBK) with those of the contralateral normal corneas.

METHODS

This was a retrospective cohort study conducted at university hospitals (Department of Ophthalmology, Rabin Medical Center, Petach Tikva, Israel, and S. Fyodorov Eye Microsurgery State Institution, Moscow, Russia). Forty eyes of 20 patients who underwent DMEK for unilateral PBK 3.5 to 36 months ago and with normal fellow eyes were included in the study. An ocular response analyzer was used to measure the corneal biomechanical properties in the operated and normal fellow eyes. The main outcome measures were corneal hysteresis (CH) and corneal resistance factor (CRF).

RESULTS

The mean CH (8.4 ± 1.5 mmHg vs. 8.2 ± 1.5 mmHg, P = 0.707) and the mean CRF (8.7 ± 1.6 mmHg vs. 8.3 ± 1.6 mmHg, P = 0.419) values did not show any statistically significant difference between the operated and the normal fellow eyes.

CONCLUSIONS

In our study, the corneas that underwent DMEK for PBK showed normal values for biomechanical parameters. These findings support the previous studies that have reported near complete visual, functional, and ultra-structural rehabilitation of the corneas following DMEK.

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.

Descemet Membrane Endothelial Keratoplasty with Irregular-Edged Graft: A Salvage Method for Large Radial Graft Tears

Large radial tears of donor Descemet membrane (DM) during the preparation of Descemet membrane endothelial keratoplasty (DMEK) grafts can make the trephination stage impossible because of small graft diameter. This results in irregular-edged grafts. In this study, we report two pseudophakic bullous keratopathy patients who underwent DMEK surgery with irregular-edged Descemet membrane (DM) grafts. Main outcome measures were preoperative and postoperative 1-, 3-, and 6-month best corrected visual acuity (BCVA), endothelial cell density (ECD) and central corneal thickness (CCT). Intraoperative and early postoperative complications were also evaluated. Both irregular-edged grafts were successfully implanted into the anterior chamber, unfolded, and attached to the posterior corneal stroma. Patients’ BCVA at 6 months was 1.0 (Snellen equivalent: 20/20) and 0.6 (Snellen equivalent: 20/32) respectively. Decrease in ECD at the last visit was 27% and 25%. CCT decreased from 723 μm and 850 μm to 530 μm and 523 μm, respectively. No intraoperative complications occurred except for the large radial Descemet membrane graft tears that developed during donor DM stripping. None of the cases needed a rebubbling procedure postoperatively. We have demonstrated that irregular-edged DM grafts can be successfully implanted for DMEK surgery with good clinical outcomes.

Component corneal surgery: An update

Several decades ago, penetrating keratoplasty was a challenge to corneal surgeons. Constant effort by the corneal surgeon to improve the outcomes as well as utilization of the available resources has led to a revolutionary change in the field of keratoplasty. All these efforts have led to the evolution of techniques that allow a corneal surgeon to disease-specific transplant of individual layers of corneal “so-called component corneal surgery” depending on the layer of cornea affected. This has led to an improvement in corneal graft survival as well as a better utilization of corneal tissues. This article reviews the currently available literature on component corneal surgeries and provides an update on the available techniques.

CTG18.1 repeat expansion may reduce TCF4 gene expression in corneal endothelial cells of German patients with Fuchs' dystrophy

PURPOSE

It was the aim of this investigation to elucidate the functional effects of CTG18.1 trinucleotide repeat expansion and the polymorphism rs613872 in the transcription factor 4 (TCF4) in corneas of patients affected by Fuchs' endothelial corneal dystrophy (FECD).

METHODS

Sixty-one unrelated German patients with FECD and 113 unaffected controls were investigated and genotyped for the CTG18.1 locus by triplet primed PCR (TP-PCR) and the rs613872 polymorphism via Sanger sequencing and by employing genomic DNA from peripheral blood leucocytes. DNA and RNA retrieved from human corneal endothelial explants were examined for alterations in the gene expression of TCF4, ZEB1, E-cadherin, N-cadherin, as well as the CTG18.1 locus.

RESULTS

The CTG18.1 trinucleotide repeat expansion (>50 repeats) was detected in the peripheral blood in 77% of affected FECD patients and 11.5% of the healthy volunteers. Applying the TP-PCR method, the length of CTG18.1 repeat expansions correlates in the blood and corneal cells. We noted that the CTG18.1 trinucleotide repeat expansion was associated with reduced TCF4 and ZEB1 gene expression, especially in the explanted corneal endothelial cells. While E-cadherin gene expression was not detected in any corneal endothelial cells, expression of CDH2 (N-cadherin) was detected in FECD-affected endothelium and in our controls.

CONCLUSIONS

The CTG18.1 repeat expansion may reduce gene expression of TCF4 and ZEB1, suggesting that a mechanism triggering a loss of function may contribute to FECD. The correlation of CTG18.1 repeat expansion from blood and the cornea may represent the first step toward investigating the potential relevance of testing the blood of cornea donors to minimize the risk of transplanting grafts potentially affected with FECD.

Rebubbling in Descemet Membrane Endothelial Keratoplasty: Influence of Pressure and Duration of the Intracameral Air Tamponade

PURPOSE

To explore the impact of intracameral air tamponade pressure and duration on graft attachment and rebubbling rates.

DESIGN

A prospective, interventional, nonrandomized study.

METHODS

setting: Department of Ophthalmology, Charité - Universitätsmedizin Berlin.

STUDY POPULATION

One hundred seventeen patients who underwent Descemet membrane endothelial keratoplasty (DMEK).

OBSERVATION

Intraocular pressure (IOP) at the end of the surgery, immediately after filling the anterior chamber with air, categorized into low (<10 mm Hg), normal (10-20 mm Hg), and high (>20 mm Hg), and the time until partial removal of the air.

MAIN OUTCOME MEASURES

Rebubbling rates and endothelial cell density over a 3-month follow-up period analyzed by a multivariable Cox regression model and an analysis of covariance model.

RESULTS

Thirty-two patients required a rebubbling (27% [95% CI 19%-35%]). Nine patients required more than 1 rebubbling (7% [95% CI 3%-12%]). Compared with normal IOP, lower (HR 8.98 [95% CI 1.07-75.41]) and higher IOP (HR 10.63 [95% CI 1.44-78.27]) increased the risk of requiring a rebubbling (P = .006). Independent of the IOP, an air tamponade duration beyond 2 hours reduced the risk of rebubbling (HR 0.36 [95% CI 0.18-0.71, P = .003]). One month after surgery, the mean endothelial cell loss was 13% (95% CI 2%-25%) and 23% (95% CI 17%-29%) in the group with air tamponade duration of below and above 2 hours, respectively (P = .126). At 3 months after surgery, it was 31% (95% CI 17%-42%) and 42% (95% CI 32%-52%) in the respective groups (P = .229).

CONCLUSIONS

A postsurgical air tamponade of at least 2 hours with an IOP within the physiological range could help to reduce rebubbling rates.

The effect of air, SF6 and C3F8 on immortalized human corneal endothelial cells

PURPOSE

While anterior chamber air bubbles aid attachment during posterior lamellar surgery only for few days, these periods can be prolonged with gases in non-expanding concentrations. To test the effects of different gas compositions on immortalized human corneal endothelial cells (HCEC-12), we utilized Transwell inserts with semipermeable membranes as an artificial anterior chamber model.

METHODS

Human corneal endothelial cells (HCEC-12) were cultured on Transwell inserts for 24 hr, then flipped, burdened and sunk with titanium rings in medium (M1), as well as filled with 2 ml of air (A), 20% sulphur hexafluoride (SF6) (S), or 12% C3F8 (C). After gas exposition for 24, 48 and 120 hr, cells were evaluated by live/dead staining, cell viability assay and Ki67 immunohistochemistry.

RESULTS

Proliferation was significantly reduced (Ki67-positive fraction; M1, 14.8 ± 2.0%; A, 7.9 ± 1.4%; S, 8.1 ± 1.3%; C, 9.9 ± 2.3%; p-values; A, S, C versus M1 < 0.01), the total cell number decreased and the percentage of dead cells increased under gas exposition, independently of the type of gas (120 hr cell count/2.25 cm² : M1 = 660.8 ± 57.0 cells; A = 125.5 ± 17.4 cells, S = 123.5 ± 17.0 cells, C = 118.8 ± 16.6 cells; p-value: M versus A/S/C < 0.001; 120 hr dead cells: M = 2.6 ± 1.0%, A = 8.4 ± 2.7%, S = 9.5 ± 3.2%, C = 11.3 ± 3.1%; p-value: M1 versus A/S/C < 0.01). Medium (M1)-control also proved significantly higher cell viability values in comparison with the gases, which did not differ significantly among them (120 hr luminescence: M1 = 1752.2 ± 91.4, A = 433.0 ± 30.3, S = 507.8 ± 23.3, C = 523.8 ± 20.3; p-value: M1 versus A/S/C < 0.01).

CONCLUSIONS

Gas exposition led to a reduction in proliferation and an increase in cell death in HCEC-12, independently of the gas composition.

[Influence of 20 % sulfur hexafluoride (SF6) on human corneal endothelial cells : An in vitro study]

BACKGROUND

In posterior lamellar keratoplasties, such as Descemet membrane endothelial keratoplasty (DMEK) and Descemet's stripping automated endothelial keratoplasty (DSAEK) an air bubble is left inside the anterior chamber to promote graft attachment during the early postoperative period. In the case of insufficient graft adhesion a renewed intracameral air injection is often necessary. The use of sulfur hexafluoride diluted with air (SF6 20 %) as an alternative to pure air may further enhance graft attachment and reduce the rebubbling rate. The effect of SF6 20 % on corneal endothelium is currently unclear and was therefore examined in vitro.

MATERIAL AND METHODS

For this study 12 human corneoscleral discs were mounted in artificial anterior chambers, the systems were continuously filled with culture medium and the anterior chambers with air (n = 5) or SF6 20 % (n = 7) as tamponade. After 6 days of storage in the incubator endothelial cell density, toxicity on endothelial cells and corneal thickness were evaluated.

RESULTS

There were no significant differences in endothelial cell loss (p = 1.000), endothelial cell count (p = 0.648), toxicity on endothelial cells (p = 0.048) and central corneal thickness (p = 0.905) between the two groups after 1 week. The level of significance was defined as p ≤ 0.05 and adjusted to p ≤ 0.0056 according to the Bonferroni correction for multiple testing.

CONCLUSION

The use of SF6 20 % as tamponade in the anterior chamber for posterior lamellar keratoplasty can be proposed as a safe alternative to pure air filling related to endothelial cell loss. Increased toxic effects on the corneal endothelium by SF6 20 % were not detected in this study; however, further prospective clinical trials are needed to examine the long-term effects in humans.

Midterm Results of Descemet Membrane Endothelial Keratoplasty: 4 to 7 Years Clinical Outcome

PURPOSE

To evaluate the midterm outcomes of Descemet membrane endothelial keratoplasty (DMEK) up to 4-7 years postoperatively.

DESIGN

Retrospective, consecutive interventional case series.

METHODS

A total of 250 consecutive eyes of 209 patients who underwent DMEK at our institute and had potentially at least 4 years of follow-up. Main outcome measures were best-corrected visual acuity (BCVA), endothelial cell density (ECD), central corneal thickness (CCT), graft survival rate, and postoperative complications.

RESULTS

At 6 months postoperatively, 73% of the eyes reached a BCVA of ≥20/25 (0.8) and 44% ≥20/20 (1.0), and remained stable up to 7 years (P = .7114). ECD dropped by 33.9% in the first 6 months, and then declined by a yearly rate of 9.0%. CCT did not show a significant change after 6 months up to 7 years (P = .8447). The cumulative graft survival rate at 4 and 7 years was 0.96 (95% confidence interval [0.93, 0.99]). Rebubbling procedures were performed in 4.4% of eyes, all within the first 6 postoperative months. Repeat transplantations were performed in 15.2% of cases to manage greater than one third graft detachment (11.6%), primary graft failure (1.6%), or secondary graft failure (2.0%), with the majority (79%) of repeat transplantations performed within the first year. After 6 months, the main complications were allograft rejection (2.4%) and secondary graft failure (2.0%).

CONCLUSIONS

The visual acuity level achieved at 6 months after DMEK may remain stable up to at least 4-7 years; ECD shows a constant, slow decrease; and complications after the first 6 months occur in <5% of cases.

Descemet membrane adhesion strength is greater in diabetics with advanced disease compared to healthy donor corneas

Descemet membrane endothelial keratoplasty (DMEK) is an increasingly popular surgical procedure for treating ocular diseases that require a corneal transplant. Previous studies have found that tissue tearing during surgical preparation is more likely elevated in eyes from donors with a history of diabetes mellitus. To quantify these potential differences, we established an experimental technique for quantifying the force required to separate the endothelium-Descemet membrane complex (EDM) from stroma in human donor corneal tissue, and we assessed differences in adhesion strength between diabetic and non-diabetic donor corneas. Transplant suitable corneas were obtained from 23 donors 50-75 years old with an average preservation to assay time of 11.5 days. Corneas were classified from a medical records review as non-diabetic (ND, n = 9), diabetic without evidence of advanced disease (NAD, n = 8), or diabetic with evidence of advanced disease (AD, n = 10). Corneas were sectioned into 3 mm wide strips and the EDM peeled from the stroma. Using the force-extension data obtained from mechanical peel testing, EDM elastic peel tension (T_E), elastic stiffness (S_E), average delamination tension (T_D), and maximum tension (T_MAX) were calculated. Mean T_E, S_E, T_D, and T_MAX values for ND corneas were 0.78 ± 0.07 mN/mm, 0.37 ± 0.05 mN/mm/mm, 0.78 ± 0.08 mN/mm, and 0.94 ± 0.17 mN/mm, respectively. NAD values did not differ significantly. However, AD values for T_E (1.01 ± 0.18 mN/mm), T_D (1.09 ± 0.21 mN/mm), and T_MAX (1.37 ± 0.24 mN/mm) were greater than ND and NAD corneas (P < 0.05). S_E did not differ significantly between groups. These findings provide proof of the concept that chronic hyperglycemia from diabetes mellitus results in a phenotypically more adhesive interface between Descemet membrane and the posterior stroma in donor corneal tissue. Results of this study provide a foundation for further investigations into the impact of diabetes on the posterior cornea, eye banking, and keratoplasty.

Generation and Feasibility Assessment of a New Vehicle for Cell-Based Therapy for Treating Corneal Endothelial Dysfunction

The corneal endothelium maintains corneal transparency by its pump and barrier functions; consequently, its decompensation due to any pathological reason causes severe vision loss due to corneal haziness. Corneal transplantation is the only therapeutic choice for treating corneal endothelial dysfunction, but associated problems, such as a shortages of donor corneas, the difficulty of the surgical procedure, and graft failure, still need to be resolved. Regenerative medicine is attractive to researchers as a means of providing innovative therapies for corneal endothelial dysfunction, as it now does for other diseases. We previously demonstrated the successful regeneration of corneal endothelium in animal models by injecting cultured corneal endothelial cells (CECs) in combination with a Rho kinase (ROCK) inhibitor. The purpose of the present study was to optimize the vehicle for clinical use in cell-based therapy. Our screening of cell culture media revealed that RELAR medium promoted CEC adhesion. We then modified RELAR medium by removing hormones, growth factors, and potentially toxic materials to generate a cell therapy vehicle (CTV) composed of amino acid, salts, glucose, and vitamins. Injection of CECs in CTV enabled efficient engraftment and regeneration of the corneal endothelium in the rabbit corneal endothelial dysfunction model, with restoration of a transparent cornea. The CECs retained >85% viability after a 24 hour preservation as a cell suspension in CTV at 4°C and maintained their potency to regenerate the corneal endothelium in vivo. The vehicle developed here is clinically applicable for cell-based therapy aimed at treating the corneal endothelium. Our strategy involves the generation of vehicle from a culture medium appropriate for a given cell type by removing materials that are not favorable for clinical use.

Scrolling Characteristics of Pre-Descemet Endothelial Keratoplasty Tissue: An Ex Vivo Study

PURPOSE

To evaluate the scrolling propensity of pre-Descemet endothelial keratoplasty (PDEK) tissue and to compare it with each component of the PDEK tissue, namely the pre-Descemet layer (Dua's layer [PDL]) and the Descemet membrane (DM).

DESIGN

Experimental laboratory investigation.

METHODS

Fourteen human donor sclerocorneal discs in which a type 1 big bubble was obtained by stromal injection of air were studied. The wall of the type 1 big bubble was excised and its grade of scrolling noted. The components of the wall (ie, the DM and PDL) were then separated and the scrolling of each was individually graded. Statistical comparison of the grade of scrolling of each layer and correlation with age was carried out; 25-μm slices of anterior and posterior stroma obtained with the femtosecond laser from 4 control samples were used for comparison. The main outcome measure was the grade of scrolling of PDEK tissue in comparison with PDL and DM.

RESULTS

Mean donor age was 67 years. The mean grade of the scroll formed by PDEK tissue was1.6 compared to 0.64 for PDL alone and 3.6 for DM alone. The difference was statistically significant. No correlation between donor age and degree of scrolling for any of the tissues tested was found.

CONCLUSION

PDEK tissue scrolls less than DM. PDL scrolls the least. This demonstrates that PDL tissue splints the DM and reduces its scrolling in PDEK. This feature has relevance to tissue preparation, handling, and unscrolling in the eye during endothelial keratoplasty.

Corneal tissue interactions of a new 345 nm ultraviolet femtosecond laser

PURPOSE

To assess the suitability of a new 345 nm ultraviolet (UV) femtosecond laser for refractive surgery.

SETTING

Department of Ophthalmology, University of Erlangen-Nürnberg, Erlangen, Germany.

DESIGN

Experimental study.

METHODS

Twenty-five porcine corneas were used for stromal flap or lamellar bed creation (stromal depth, 150 μm) and 15 rabbit corneas for lamellar bed creation near the endothelium. Ultraviolet femtosecond laser cutting-line morphology, gas formation, and keratocyte death rate were evaluated using light and electron microscopy and compared with a standard infrared (IR) femtosecond laser. Endothelial cell survival was examined after application of a laser cut near the endothelium.

RESULTS

Flaps created by the UV laser were lifted easily. Gas formation was reduced 4.2-fold compared with the IR laser (P = .001). The keratocyte death rate near the interface was almost doubled; however, the death zone was confined to a region within 38 μm ± 10 (SD) along the cutting line. Histologically and ultrastructurally, a distinct and continuous cutting line was not found after UV femtosecond laser application if flap lifting was omitted and standard energy parameters were used. Instead, a regular pattern of vertical striations, presumably representing self-focusing induced regions of optical tissue breakdown, were identified. Lamellar bed creation with standard energy parameters 50 μm from the endothelium rendered the endothelial cells intact and viable.

CONCLUSION

The new 345 nm femtosecond laser is a candidate for pending in vivo trials and future high-precision flap creation, intrastromal lenticule extraction, and ultrathin Descemet-stripping endothelial keratoplasty.

FINANCIAL DISCLOSURES

Mr. Klenke and Ms. Skerl were paid employees of Wavelight GmbH when the study was performed. Dr. Seiler is a scientific consultant to Wavelight GmbH. No other author has a financial or proprietary interest in any material or method mentioned.

Impact of the radius of the injector system on the cell viability in descemet membrane endothelial keratoplasty: an ex vivo experimental study

PURPOSE

To evaluate the impact of the radius of the injector system on the viability of the endothelial cells in Descemet membrane endothelial keratoplasty (DMEK).

METHODS

Descemet membranes (DMs) of 30 corneoscleral rims were used in a paired design and divided into three groups (A, B, C). The right corneas were used as control (without shooting through the injector after DM preparation) and the left cornea for simulation of the implantation step (shooting through a glass injector of different radii). The injector in Group A had a diameter of 0.5 mm, group B 0.9 mm and group C 1.4 mm. Prior to preparation, endothelial cell count was measured and endothelial cell quality assessed. Quantification of potential damage was achieved by staining with a viability bioassay (calcein acetoxymethyl and ethidium homodimer-1) and DAPI. Apoptosis was evaluated by TUNEL (terminal dUTP nick-end labelling) staining.

RESULTS

The average percentage of the endothelial cell death ratios was 4.9 ± 3.3% in group A (n = 5), 3.7 ± 3.7% in group B (n = 5) and 3.9 ± 3.6% in group C (n = 5) with no significant difference compared to the control. The average percentage of apoptotic endothelial cells was 0.05 ± 0.05%, 0.60 ± 0.53% and 0.15 ± 0.26% in groups A, B and C, respectively, with no significant difference compared to the control.

CONCLUSIONS

Prepared grafts for transplantation in DMEK procedures may be injected through a smaller sized injector system of up to 0.5 mm with no significant increase in cell loss. Clinical studies are necessary to draw a final conclusion.

Intraoperative OCT-Assisted DMEK: 14 Consecutive Cases

PURPOSE

To describe the utility of a new intraoperative optical coherence tomographer (OCT) to evaluate endothelio-Descemet graft orientation during Descemet membrane endothelial keratoplasty (DMEK) procedures.

METHODS

Prospective, observational, and single-center pilot case series including 14 eyes of 14 patients consecutively scheduled for DMEK surgery. After injecting the graft into the anterior chamber, the graft orientation was assessed with the help of anterior segment OCT. The surgical time and unfolding time were measured. The postoperative measurements included best-corrected visual acuity, central pachymetry, and specular microscopy at 1 month.

RESULTS

Using the OCT images, it was possible to evaluate the graft orientation in all cases. The mean unfolding time was 6.1 ± 3.0 minutes, the mean best-corrected visual acuity was 0.3 ± 0.3 logarithm of the minimum angle of resolution, the mean decrease in central pachymetry was 213 ± 177 μm, and the mean central endothelial cell count was 1906 ± 319 cells per square millimeter.

CONCLUSIONS

Live intraoperative OCT is useful to visualize and assess graft orientation in DMEK surgery. It enables faster graft positioning with less graft manipulation in the presence of severe corneal edema.